Merapi

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  • Last Known Eruption
  • 7.542°S
  • 110.442°E

  • 2968 m
    9735 ft

  • 263250
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Most Recent Weekly Report: 9 July-15 July 2014


PVMBG reported that during 4-10 July seismicity at Merapi fluctuated at normal levels. Deformation measurements showed general inflation. Solfatara plumes rose 450 m above the summit on 4 July. The Alert Level remained at 1 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


Most Recent Bulletin Report: May 2011 (BGVN 36:05)


Recovery; intermittent activity; damaging lahars

A VEI 4 (Volcanic Explosivity Index) eruption began at Merapi volcano on 26 October 2010. Within the last 100 years, this volcano had not produced such large-magnitude explosions (Surono and others, in review; Andreastuti and others, 2011). The eruption and secondary events affected areas in all directions around the volcano; pyroclastic flows reached 4 km to the N, 11.5 km to the W, 7 km to the E, and ~15 km to the S, and explosive bombs reached 4 km from the summit in all directions (Jousset, 2010). These events included explosive central vent eruptions that caused significant changes in the summit morphology (figure 48) and according to Act Forum Indonesia, triggered evacuations of communities within a 20 km radius of the summit. In BGVN 36:1/2 we reported on preliminary damage assessments that included significant fatalities and damaged infrastructure.

Figure 48. A photo comparison of Merapi's morphological changes on 23 March 2010 and 16 March 2011. Viewed from the S flank, these photos focus on the summit dome. Non-juvenile material was excavated during two episodes of explosive activity. During 26-29 October ~1.4 x 106 m3 was excavated from the crater and from 4-5 November ~10 x 106 m3 was removed (Surono and others, in review). Photo courtesy of the Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPK") from their report covering 14-20 March 2011.

The explosive events of 2010 represent a break in Merapi's iconic style of activity (Surono and others, in review). "Merapian" is a term often assigned to volcanic events characterized by hot pyroclastic block flows generated during the collapse of growing viscous lava domes (Schmincke, 2004). Standard eruptive activity at Merapi includes "continuous degassing and extrusion of andesitic lava domes whose collapses generate block avalanches and gravitational pyroclastic flows" (Allard and others, 2011).

At least 17 VEI = 2 events have occurred since the catastrophic 15 April 1872 eruption (Siebert and others, 2010). While explosive activity is characteristic of past behavior, assessments of data from 2010 confirm that the 26 October eruptive sequence did not begin with lava extrusion (typical of past eruptions). Instead, intense explosions initiated activity that lasted for ~5 weeks (Surono and others, in review).

During the Merapi special session at the EGU General Assembly held in April 2011, Andreastuti and others (2011) concluded that "the rate of magma extrusion [during the peak of Merapi's 2010 activity] was as much as 17-to 21-times higher [than] the 2006 eruption and the distance of pyroclastic flows in the same drainage (Gendol River) reached 15 km in 2010 and only 7 km in 2006."

This assessment and others (e.g. Alder and others, 2011) linked the highly explosive eruptions of October-November 2010 to elevated and variable gas emissions.

On 4 December 2010, after 40 days of maintaining the highest alert, the Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) downgraded the hazard Alert Level from 4 to 3 ("Awas," Red Alert to "Siaga," Watch). The Alert Level was reduced again on 19 January 2011 from 3 to 2 (to "Waspada," Advisory). The Alert Level remained at Level 2 into June 2011.

In this report we review the recovery efforts, Merapi's intermittent activity, and the long-term lahar crisis from March to June 2011. We also include a review of intervals of gas geochemistry data recorded prior to the 26 October 2010 disaster that recently became available.

Recovery efforts. Since October 2010, of the ~300,000 people evacuated, 11,000 were still displaced as of January 2011 (Jakarta Post and IRIN). Authorities had set up nine camps within the city of Yogyakarta and ~70 camps were located farther away within Central Java. On 2 May 2011 the head of Badan Nasional Penanggulangan Bencana (BNPB), Indonesia's National Disaster Management Agency, reported: "With almost all the displaced having moved to temporary shelters, our focus now is how to rebuild communities affected by the disaster" (IRIN, 2011).

In May 2011 the Indonesian government sought international aid (including the International Red Cross and United Nations) and international non-governmental organizations were working in Indonesia for relief efforts. The Jakarta Post reported on 12 May 2011 that Australia had agreed to help Indonesia establish a Disaster Relief Center for disaster management training; the location will be in Sentul, West Java and will serve members of the Association of Southeast Asian Nations (ten countries currently belong to ASEAN). BNPB had called upon the World Bank to begin a Risk Transfer scheme, allowing the local government to focus aid specifically on reconstruction programs.

According to reports from the Jakarta Globe in April 2011, the recent disaster and long history of volcanism at Merapi prompted the Indonesian government to implement an extensive recovery plan for the Yogyakarta province. They prioritized the development of spatial planning maps, expansion of the Merapi National Park, large-scale reforestation (approximately 1,300 hectares), and allocation of 1.35 trillion Rupiah ($155 million) to improve housing, infrastructure, social efforts, and economic stimulation plans. New mapping in the province will reassign land-use and designate relocation sites for former residents. In general, residential areas lying within 10 km of the summit will remain off limits (Sayudi and others, 2010). The Jakarta Post noted these maps also highlight where reforestation will occur. Impacts were substantial to Merapi National Park which lost up to 2,800 hectares out of 6,410 hectares of forest due to the recent eruptions. The Volcano Technical Research Center (BPPTK) reassessed zones in the Sleman region, the area hardest hit by volcanic activity, and will release a map indicating hazard zones. "[These maps] will show which areas are safe, unsafe and suitable for habitation," stated Sleman administration spokeswoman Endah Sri Widiastuti (Jakarta Post).

A controversial location within the 10 km exclusion zone is the village of Kinahrejo, the former home of spiritual leader Mbah Maridjan, called the guardian of Merapi. Working with a team of 17 respected community members, he preserved traditional ceremonies and local culture for Merapi residents. Pyroclastic flows covered the village on 26 October 2010, taking the life of the guardian and other inhabitants who did not evacuate.

The new guardian is Mbah Maridjian's son, Asihono (his new name: Mas Lurah Suraksosihono). During Merapi's disastrous eruptions of October and November, Asihono cooperated with the local government and agencies including the Volcanology and Geological Disaster Mitigation Agency (PVMBG) and BPPTK. On 4 April 2011 Sultan Hamengku Buwono X elected Asihono from a group of eight candidates. In an interview with Jakarta Globe on 5 April 2011, the new guardian explained: "I'm not just going to take a cultural approach based on the dreams or guidance from the spirits, but I will also coordinate with the authorities to protect human life and the environment on Mount Merapi and anticipate the fall of victims to future eruptions."

New dome growth. Seismicity was variable and intermittent explosions were observed at Merapi at least every month through June 2011 since the main eruptive events of October and November 2010. This activity kept local residents vigilant and caused some alarm when incandescence suddenly appeared on Merapi's summit on 25 March and 13 April (figure 49). On these two occasions, a bright glow on the crater's E side was recorded on closed circuit television (CCTV).

Figure 49. Bright incandescence visible on the E side of Merapi's crater was observed at 1940 on 25 March 2011. Courtesy of Volcano Technical Research Center (BPPTK Activity Report 21-27 March 2011).

The point of incandescence was a location of concentrated degassing. In the aftermath of the eruption in 2010, fumaroles became well established and BPPTK intends to resume gas monitoring. They reported that a new dome was growing in the crater: "The final phase is usually marked by eruption of lava dome growth. However, we won't lower the [alert] status as long as the condition of Merapi is still volatile," reported Subandriyo of BPPTK on 11 April 2011 (Kompas News). Since 19 January 2011, the Alert Level was at 2, Advisory.

Gas monitoring. From ultraviolet correlation spectrometer (COSPEC) measurements, BPPTK reported continuous SO2 emissions for both 1992 through early 2009 (BPPTK, 2011b) and January 2005-January 2010 (figure 50). Other data resulted from sampling with Giggenbach bottles; a method of condensate retrieval requiring evacuated alkaline-solution-filled bottles (Williams-Jones and Rymer, 2000). Gas species such as CO2, SO2, H2S, and HCL were analyzed during June 2003-June 2010 (figure 51).

Figure 50. Merapi SO2 fluxes measured from January 2005 to roughly April 2009 using COSPEC (sulfur dioxide in metric tons per day). The curve shown displays an undisclosed averaging function on the data. Modified from BPPTK, 2011a.
Figure 51. Gas sampling at Merapi's Woro Crater (a location map is posted in BGVN 32:02) conducted during June 2003-January 2011. Results from Giggenbach bottle collection and lab analysis for gas species are plotted on log scales. Right-hand vertical axis corresponds to upper (blue) data and trendlines. Left-hand vertical axis corresponds to the lower (black) data trendlines and data. Original concentration units were undisclosed (but Bulletin editors hope to clarify these units in later discussions on Merapi). Modified from BPPTK, 2011a.

SO2 ranged from ~75 metric tons/day (t/d) to ~285 t/d and appeared to peak mid-year in 2005 and 2006 (figure 50). A sudden decrease of 50 t/d in January 2007 preceded an increasing trend that ended in mid-2008. These fluxes also had fewer sustained peaks around March 2008 and declined until the available record ends around March 2009.

The SO2 peak of ~200 t/d generally correlated with the 2005 mid-year episode of elevated seismicity that prompted the BPPTK (at that time called the Directorate of Volcanology and Geological Hazard Mitigation, "DVGHM") to raise the Alert Level from Normal to Advisory (from 1 to 2). However, there were no additional reports of plumes or increased dome activity then (BGVN 32:02).

In 2006, the Alert Level was raised to the highest level on 13 May due to intense dome growth and earthquake activity (BGVN 31:05), a time when SO2 reached ~225 t/d.

According to information recorded in Bulletin reports, the abrupt decrease of SO2 in late 2006-early 2007 did not appear to correlate with significant volcanism in that time interval. The gradual increasing-and-decreasing trend in SO2 flux from 2007 until the end of the record was marked by rare ash plumes (e.g. 19 March 2007, 9 Aug 2007, and 19 May 2008), and modest dome growth (BGVN 32:02). Bulletin reports also noted incandescence and ashfall had continued during 23 May-29 May 2007. MODVOLC thermal anomalies became rare after 5 September 2006 (BGVN 33:10).

Intermittent activity during 18 April-1 May 2011. Unrest at Merapi since the 2010 crisis was characterized by intermittent increases in seismicity as observed from 18 to 24 April 2011 (figure 52). Over the course of that week, rockfall signals doubled from the previous observation period and 39 multiphase events were recorded.

Figure 52. Histograms from September 2010 to June 2011 summarize the number of seismic events from four categories is summarized for Merapi. Events shown are rockfalls; MP, multiphase (shallow source, dominant frequency ~1.5 Hz); VA, deep volcano-tectonic earthquakes, 2.5-5 km below the summit; VB, shallow volcano-tectonic earthquakes, less than ~1.5 km below the summit. Tremor episodes were infrequent and thus excluded. Courtesy of BPPTK (Activity Report 6-12 June 2011). (A figure in BGVN 36:1/2 presented representative samples of these various waveforms.)

BPPTK also reported that ground deformation was variable throughout this time period as EDM (Electronic Distance Meter) measurements were recorded across the summit. Measurements made on 18 April 2011 compared with those recorded on 25 April 2011 from the monitoring post of Selo showed the following changes: a difference in distance amounting to +8 mm (R1) and a change in movement amounting to 0.1 mm per day.

Measurements carried out on 18 April 2011 compared to those of 24 April 2011 from Jrakah monitoring post indicated the following changes: a difference in distance amounting to -4 mm (R1) with a change in movement amounting to 0.5 mm per day, and a difference in distance of +6 mm (R2) with a movement of 0.7 mm per day.

Plumes of ash and gas reached an altitude of ~800 m on 24 and 25 April. Communities near Merapi's flanks reported ashfall on 29 April, 30 April, and 1 May 2011. (BPPTK Activity Report 25 April-1 May 2011).

Ongoing hazards. The recent weekly report by BPPTK (20 March to 12 June 2011), described plumes of gas and ash that occurred regularly. As measured from above the summit, the average height of these plumes was ~500 m; a maximum height of 900 m was recorded on 20 April. The tallest plume was accompanied by a ramping up of earthquakes and the regular occurrence of lahars, some hot enough to steam while racing through river drainages (figure 53).

Figure 53. On 21 March 2011 and 14 April 2011 steaming lahars descended Merapi's flanks. This photo was taken on 14 April 2011from a CCTV camera installed in Pencar village, less than 20 km S of Merapi in the Desa Bimomartani region. Note Merapi volcano in upper right-hand area of the photo. Courtesy of BPPTK (Activity Report discussing 11-17 April 2011).

A large amount of volcanic ash fell from Merapi's explosive eruptions in 2010; this has aggravated slope stability and led to increased lahar hazards. In an interview on 11 April 2011 for Kompas News, Subandriyo, the Head of the BPPTK explained that "only about 30 percent" of the material that fell on Merapi's flanks has been remobilized by erosion. "Therefore, the threat of [lahars] will occur two to three years ahead."

As of June 2011, 15 major lahars had occurred since November 2010. The worst occurred on 23 January 2011 along the eroded banks of the Putih river. The major highway between Magelang and Yogyakarta was cut off when a 60 m wide section of blacktop was torn away by torrential mudflows. As a result, hundreds of homes within 12 different villages near the river were inundated forcing 5,000 people to flee. There were three fatalities.

Major infrastructure was also affected; 52 levees were damaged and 14 bridges were destroyed. Intense lahar damage was also reported along the SE rivers: Blongkeng, Batang, Progo, Code, and Gendol.

References. Allard, P., Métrich, N., and Sabroux, J.-C., 2011, Volatile and magma supply to standard eruptive 549 activity at Merapi volcano, Indonesia. EGU General Assembly 2011, Geophysical 550 Research Abstracts 13, EGU 2011-13522 (2011).

Andreastuti, S., Costa, F., Pallister, J.,Sumarti., S., Subandini, S., Heriwaseso, A., Kurniadi, Y. , Petrology and pre-eruptive conditions of the 2010 Merapi magma. EGU General Assembly 2011, Geophysical 550 Research Abstracts 13, EGU2011-5150 (2011).

BPPTK, Volcano Technical Research Center, 2011a, Geochemistry of Merapi. (URL: http://www.merapi.bgl.esdm.go.id/aktivitas_merapi.php?page=aktivitas-merapi&subpage=geokimia)BPPTK, Volcano Technical Research Center, 2011b, Monitoring of Geochemical and Temperature of Merapi. (URL: http://www.merapi.bgl.esdm.go.id/pages.php?page=geokimia-dan-suhu)

Schmincke, H.-U, 2004, Volcanism, Berlin:Springer, 324 pp.

Jousset, P., 12/6/10, Centennial Eruption at Merapi volcano: October/November 2010, MIAVITA, European Commission. (URL: http://miavita.brgm.fr/Documents/MIAVITA-Merapi-eruption.pdf)

Sayudi, D.S., Nurnaning, A., Juliani, DJ., Muzani, M.; 2010, "Peta Kawasan Rawan Bencana Gunungapi Merapi, Jawa Tengah Dan Daerah Istimewa Yogyakarta 2010," (The map of the Rawan Bencana Gunungapi Merapi Region, Central Java: Yogyakarta Special District 2010), Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPTK"). (URL: http://www.merapi.bgl.esdm.go.id/peta/2011/04/KRBGMerapi2010FINALcopyright_78a74b.jpg)

Siebert L., Simkin T., and Kimberly P., 2010, Volcanoes of the World, 3rd edition, University of California Press, Berkeley, 558 p.

Surono, Jousset, P., Pallister, J., Boichu, M., Buongiorno, M.F., Budisantoso, A., Costa, F., Andreastuti, S., Prata, F., Schneider, D., Clarisse, L., Humaida, H., Sumarti, S., Bignami, C., Griswold, J., Carn, S., Oppenheimer, C., (in review), 100-year explosive eruption of Java's Merapi volcano, Journal of Volcanology and Geothermal Research.

Williams-Jones, G. and Rymer, H., 2000, Hazards of Volcanic Gases, in Sigurdsson, H., ed., Encyclopedia of Volcanoes: San Diego, California, Academic Press, p. 997-1004.

Information Contacts: Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPTK"), (URL: http://www.merapi.bgl.esdm.go.id/index.php); Badan Nasional Penanggulangan Bencana (BNPB- Indonesian National Disaster Management Agency), (URL: http://dibi.bnpb.go.id); Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://portal.vsi.esdm.go.id/joomla/); IRIN News (URL: http://www.IRINnews.org); Jakarta Globe (URL: http://www.thejakartaglobe.com); The Jakarta Post (URL: http://www.thejakartapost.com); KompasNews, Jakarta, Indonesia (URL: http://www.Kompas.com); Mitigate and Assess risk from Volcanic Impact on Terrain and human Activities project (MIAVITA), (URL: http://miavita.brgm.fr/default.aspx); Act Forum Indonesia (URL: http://www.actalliance.org/); Relief Web (URL: http://www.reliefweb.int).

Index of Weekly Reports


2014: March | April | May | June | July
2013: July | November
2011: January | March | September
2010: September | October | November | December
2008: May
2007: March | May | August
2006: March | April | May | June | July | August
2005: July
2002: January | February | March | April | May | June | July | August | September
2001: January | February | March | April | May | July | August | September | October | November | December
2000: November

Weekly Reports


9 July-15 July 2014

PVMBG reported that during 4-10 July seismicity at Merapi fluctuated at normal levels. Deformation measurements showed general inflation. Solfatara plumes rose 450 m above the summit on 4 July. The Alert Level remained at 1 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


4 June-10 June 2014

PVMBG reported that during 30 May-5 June seismicity at Merapi fluctuated at normal levels and declined as compared to the previous two weeks. Deformation measurements showed no significant changes. Solfatara plumes rose 400 m and drifted W on 31 May. The Alert Level remained at 1 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


28 May-3 June 2014

PVMBG reported that during 16-22 May seismicity at Merapi fluctuated at normal levels and deformation measurements showed no significant changes. Solfatara plumes rose 300 m and drifted W on 27 May. The Alert Level remained at 1 (on a scale of 1-4) on 23 May.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


21 May-27 May 2014

PVMBG reported that seismicity at Merapi decreased during 16-22 May, as compared to the previous week. No deformation was detected. The Alert Level was lowered to 1 (on a scale of 1-4) on 23 May.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


14 May-20 May 2014

PVMBG reported that seismicity at Merapi decreased during 9-15 May, as compared to the previous week. Thumping noises continued to be reported from multiple observation posts, and on 12 May fumarolic plumes rose 350 m. The Alert Level remained at 2 (on a scale of 1-4) on 29 April.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


7 May-13 May 2014

PVMBG reported that during 2-8 May white plumes rose as high as 650 m above Merapi. Thumping noises continued to be reported from multiple observation posts. Seismicity fluctuated but remained above background levels. The Alert Level remained at 2 (on a scale of 1-4) on 29 April.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


30 April-6 May 2014

PVMBG reported that during 20-29 April seismicity at Merapi increased and thumping sounds were heard within an 8 km radius. On 25 April white fumarolic plumes rose 450 m and drifted W. The Alert Level was raised to 2 (on a scale of 1-4) on 29 April.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


23 April-29 April 2014

PVMBG reported that field observations of Merapi conducted two days after the explosion on 20 April revealed that a fracture in the dome had widened 70 m to the W, and new material had been deposited in the W part of the crater. The Alert Level remained at 1 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


16 April-22 April 2014

PVMBG reported that Merapi observers at the Ngepos post noted white plumes rising 300 m above the lava dome on 15 April. Seismicity increased during 18-20 April. During 0426-0440 on 20 April an explosion occurred and rumbling was heard in areas as far as 8 km away. Ash plumes were observed from some observations posts, but foggy conditions prevented views from others. Based on satellite images and wind data, the Darwin VAAC reported that an ash plume rose to an altitude of 10.7 km (35,000 ft) a.s.l. and drifted 260 km WNW. PVMBG noted that ashfall was reported in areas within 15 km S, SW, and W. The Alert Level remained at 1 (on a scale of 1-4).

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC)


26 March-1 April 2014

PVMBG reported explosions from Merapi on 9 March. An explosion detected at 0654 was followed by a plume observed on CCTV from Pasarbubar that drifted W. Two Explosions were also recorded at 0655. At 0708 a volcanic earthquake occurred and CCTV in Market Bubar recorded brown plumes that rose 1.5 km above the crater. At 0730 ash fell in the villages of Umbulharjo (30 km S), Kepuharjo, Sidorejo (27 km NNE), and Balerante (6 km SSE). During 14-20 March dense gas plumes rose 600 m. Seismicity was at normal levels. The Alert Level remained at 1 (on a scale of 1-4).

Based on analysis of satellite images, the Darwin VAAC reported that on 27 March an ash plume rose to an altitude of 9.8 km (32,000 ft) a.s.l. and drifted SE. The VAAC noted that an eruption occurred around 0630, confirmed by a news article. Ash had dissipated the next day. Another news article noted that the increased activity lasted only four minutes, from 0112 to 0116, and that ashfall occurred on the S and SE flanks.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); The Jakarta Post; The Jakarta Post


13 November-19 November 2013

According to news articles, a phreatic eruption at Merapi on 18 November produced an ash plume that rose 2 km above the crater and caused ashfall in areas as far as 60 km E. About 600 families from the Glagaharjo village gathered at evacuation assembly points, while others on the W flank evacuated then returned to their homes hours later.

Source: Jakarta Post


17 July-23 July 2013

Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian (BPPTK) reported that at 0415 on 22 July a booming sound from Merapi was followed by a rising plume observed from multiple observation posts. Ashfall was reported in areas S, including Kaliurang and Balerante. The Alert Level remained at 1 (on a scale from 0-4).

According to news articles, the eruption lasted until about 0530, and generated a dense black plume that rose 1 km. A booming sound was heard 30 km away. Ashfall affected the district of Deles, Tlogowatu, Kemalang, Balerante, Klaten, and Jawa Tengah. Hundreds of residents evacuated but returned to their homes later that day.

Sources: Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian (BPPTK); Bernama; Associated Press


7 September-13 September 2011

CVGHM reported that during 29 August-4 September white solfatara plumes rose at most 350 m above Merapi and drifted W. On 4 September small avalanches traveled 700 m SW. The Alert Level remained at 2 (on a scale of 1-4). Based on a pilot observation, the Darwin VAAC reported that on 8 September an ash plume rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted almost 30 km N.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC)


16 March-22 March 2011

According to news articles, on 21 March a lahar traveled through the village of Sleman, approximately 20 km SW of Merapi, burying 21 homes in addition to vehicles and livestock. At least 200 residents were evacuated.

Source: The Jakarta Post


2 March-8 March 2011

CVGHM reported that gas plumes rose from Merapi during 28 February-6 March. The highest plume which rose 100 m and drifted E was observed on 5 March from the Babadan post on the NW flank. The number of multi-phase (MP) earthquakes was slightly lower compared to the previous week. The Alert Level remained at 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


19 January-25 January 2011

CVGHM reported that the Alert Level for Merapi was lowered to 2 (on a scale of 1-4) on 9 January. During 10-16 January seismicity had decreased compared to the previous week. Gas plumes rose from the crater; on 11 January gas plumes rose to a maximum height of 80 m above the crater. On 12 January avalanches descended the Krasak drainage, traveling 1.5 km SW. Lahars and high water during 15-23 January damaged infrastructure and caused temporary road closures. On 22 January plumes rose 175 m above the crater and drifted E.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


5 January-11 January 2011

According to a news article, lahars on Merapi's flanks that occurred on 3 and 9 January caused damage to houses, farms, and infrastructure in multiple villages in the Magelang district, 26 km WNW of Merapi. One death and one injury were reported. On 9 January, the Red Cross evacuated people trapped in their homes in the Sirihan village. An estimated 3,000 people live in the flooded area, but the number of people evacuated was unknown.

Source: IRIN News


1 December-7 December 2010

CVGHM reported that activity at Merapi declined during 1-3 December. Seismic data showed a decrease in the number of earthquakes as well as amplitude of the events. Deformation measurements did not show any significant changes. Although fog often prevented visual observations or views through webcams, gas plumes were seen rising 500 m above the crater and drifting W. Sulfur dioxide plumes were no longer detected in satellite imagery. CVGHM noted that lahar deposits were seen in multiple drainages and that several bridges had been recently damaged by lahar activity. On 4 December, the Alert Level was lowered to 3 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


24 November-30 November 2010

CVGHM reported that avalanches on Merapi's flanks were detected by the seismic network during 25-30 November. Although fog often prevented observations, white and brown plumes rising 100 m above the crater drifted SW on 25 November, and brownish plumes rose 300 m above the crater on 27 November. During 27-30 November, white plumes rose 100-800 m above the crater and drifted W, SW, N, and E. Incandescence from the crater was observed through cameras installed at the Merapi museum. According to news articles, a lahar in the Code River that runs through Yogyakarta, 30 km SSW, flooded streets and damaged bridges, and caused about 1,000 residents to evacuate. The Alert Level remained at 4, the highest level, on a scale of 1-4.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); BNO News


17 November-23 November 2010

CVGHM reported that on 15 November no pyroclastic flows descended Merapi's flanks and few avalanches were detected compared to the previous day. During 16-18 November, the number of seismic signals and the number of avalanches both continued to decrease. Although fog often prevented observations, a gas-and-ash plume was observed rising 1.5 km above the crater and drifting SW. A steam plume rose 250 m above the crater and drifted W. On 18 November a pyroclastic flow occurred with low intensity. Lahar deposits were seen in multiple drainages. CVGHM noted areas that remained within a 10-20 km danger zone. On 21 November one pyroclastic flow was detected and five were recorded the next day. During 21-23 November avalanches continued to occur. Lahars traveling S on 23 November carried material up to 100 cm in diameter. According to news articles, the Yogyakarta airport resumed operations on 20 November. The death toll from the eruption reached 322 and more than 130,000 people continued to live in temporary shelters.

Based on analysis of satellite imagery, the Darwin VAAC reported that during 16-21 November ash plumes rose to altitudes of 4.6-6.1 km (15,000-20,000 ft) a.s.l. and drifted 55-165 km W and NW.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); Agence France-Presse (AFP); Agence France-Presse (AFP)


10 November-16 November 2010

CVGHM reported that during 10-11 November seismicity from Merapi along with the number of avalanches and pyroclastic flows decreased compared to the previous two days. Lahar deposits were seen in multiple drainages around Merapi at a maximum distance of 16.5 km from the summit.

On 10 November, plumes generally rose 800 m above the crater, but at about 2200 a brownish plume rose to a height of 1.5 km. Heavy ashfall was reported in areas to the WSW and WNW. A 3.5-km-long pyroclastic flow and a 200-m-long avalanche both traveled S in the Gendol drainage. Incandescence from the crater was observed through a closed-circuit television (CCTV) system installed at the Merapi museum. On 11 November, roaring was followed by light ashfall at the Ketep observation post. Plumes, brownish-black at times, rose 800 m above the crater and drifted W and NW. Avalanches again traveled S in the Gendol drainage. One pyroclastic flow was observed through the CCTV traveling 3 km S. A brownish plume rose 1.5 km above the crater. The Alert Level remained at 4 (on a scale of 1-4).

Based on analysis of satellite imagery, the Darwin VAAC reported that during 12-14 November ash plumes drifted 185-280 km SW at an altitude of 7.6 km (25,000 ft) a.s.l. High-altitude sulfur dioxide clouds detected over the Indian Ocean possibly contained ash. In the latter part of 14 November and during 15-16 November, ash plumes rose to altitude of 6.1-7.6 km (20,000-25,000 ft) a.s.l. and drifted 110-130 km S, SW, and W. The sulfur dioxide concentration in the high-level clouds had decreased; the clouds were not thought to contain ash.

During 14-15 November, news articles stated that the death toll from the eruption was over 250, and the Yogyakarta airport had remained closed. About 390,000 residents also began to return home after the "danger zones" were reduced in some areas due to decreased activity during the previous few days.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); Associated Press; RTT News; The Jakarta Post


3 November-9 November 2010

CVGHM reported that during 3-8 November the eruption from Merapi continued at a high level, characterized by incandescent avalanches from the lava dome, pyroclastic flows, ash plumes, and occasional explosions. Visual observations were often difficult due to inclement weather and gas-and-ash plumes from the eruption. On 7 November, a news article stated that since the eruption began on 26 October approximately156 people have died and more that 200,000 people have been displaced.

On 3 November observers stationed at multiple posts reported ash plumes from pyroclastic flows. One pyroclastic flow traveled 10 km, prompting CVGHM to extend the hazard zone to a 15-km-radius and recommend evacuations from several more communities. Another pyroclastic flow traveled 9 km SE later that day. The Darwin VAAC reported that an ash plume rose to an altitude of 18.3 km (60,000 ft) a.s.l. and drifted 110 km W. Ground observers noted a significant eruption, but could not confirm the plume altitude. On 4 November an ash-and-gas plume rose to an altitude of 11 km (36,100 ft) a.s.l., and pyroclastic flows descended the NW, NNW, and N flanks as far as 3 km. Based on analyses of satellite imagery, the Darwin VAAC reported that ash plumes rose to altitudes of 10.7-11.9 km (35,000-39,000 ft) a.s.l. and drifted W. On 5 November, rumbling sounds were heard in areas 30 km away. Pyroclastic flows continued to descend the flanks. Ash fell in Yogyakarta, 30 km SSW, and "sand"-sized tephra fell within 15 km. CVGHM recommended evacuations from several more towns within a 20-km radius.

Activity remained very intense on 6 November. Pyroclastic flows descended the flanks; one traveled 4 km W. Incandescent avalanches traveled 2 km down multiple drainages to the SSE, S, and SSW. Ash plumes rose to an altitude of 7 km (23,000 ft) a.s.l. Flashes from the lava dome were reported from observations posts and incandescent material was ejected above the crater. A subsequent pyroclastic flow sent an ash plume to an altitude of 6 km (19,700 ft) a.s.l. that drifted W, N, and E. Throughout the day, ashfall was heavy on Merapi's flanks, and was observed in surrounding areas including Selo (6 km NNW) and Magelang (26 km WNW). In Muntilan (18 km WSW) tephra and ash depths reached 4 cm. On 5 and 6 November, the Darwin VAAC reported that ash plumes observed in satellite imagery rose to an altitude of 16.8 km (55,000 ft) a.s.l. News articles stated that three airlines cancelled flights to Jakarta due to the ash-induced aviation hazard.

On 7 November, the number of seismic signals indicating pyroclastic flows increased from the previous day. An explosion was heard and ash plumes rose 6 km and drifted W. Lightning was seen from Yogyakarta and ash fell within 10 km. Pyroclastic flows traveled 5 km and lava avalanches moved 600 m S and SW. High-altitude ash plumes drifted SW. According to the Darwin VAAC, during 7-8 November satellite imagery revealed ash plumes drifting 165-220 km W and SW at an altitude of 7.6 km (25,000 ft) a.s.l. On 8 November an SO2 cloud was seen over the Indian Ocean at altitudes of 12.2-15.2 km (40,000-50,000 ft) a.s.l. The airport in Yogyakarta closed. CVGHM reported that incandescent avalanches were sometimes seen through a closed-circuit television system. Ash plumes rose to an altitude of 4.5 km (14,800 ft) a.s.l. and drifted NE.

On 9 November CVGHM noted a reduction in intensity of activity from Merapi; one pyroclastic flow occurred in a 6-hour period. Rumbling sounds were accompanied by an ash plume that rose to an altitude of 4.5 km (14,800 ft) a.s.l. and lava-dome incandescence. Ashfall was reported in Selo and lava avalanches traveled 800 m SSE.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); CNN; Daily Mail; Jakarta Globe


27 October-2 November 2010

According to the Darwin VAAC, ground-based reports indicated an eruption from Merapi on 28 October. Cloud cover prevented satellite observations. CVGHM reported that two pyroclastic flows occurred on 30 October. According to a news article, ash fell in Yogyakarta, 30 km SSW, causing low visibility. CVGHM noted four pyroclastic flows the next day.

On 1 November an eruption began mid-morning with a low-frequency earthquake and avalanches. About seven pyroclastic flows occurred during the next few hours, traveling SSE a maximum distance of 4 km. A gas-and-ash plume rose 1.5 km above the crater and drifted E and N. CVGHM recommended that evacuees from several communities within a 10-km radius should continue to stay in shelters or safe areas. The Darwin VAAC reported that a possible eruption on 1 November produced an ash plume that rose to an altitude of 6.1 km (20,000 ft) a.s.l., according to ground-based reports, analyses of satellite imagery, and web camera views. On 2 November an ash plume was seen in satellite imagery drifting 75 km N at an altitude of 6.1 km (20,000 ft) a.s.l. News outlets noted diversions and cancellations of flights in and out of the Solo (40 km E) and Yogyakarta airports. The Alert Level remained at 4 (on a scale of 1-4).

CVGHM reported 26 pyroclastic flows on 2 November. A mid-day report on 3 November stated that 38 pyroclastic flows occurred during the first 12 hours of the day. An observer from the Kaliurang post saw 19 of those 38 flows travel 4 km S. Plumes from the pyroclastic flows rose 1.2 km, although dense fog made visual observations difficult. Ashfall was noted in some nearby areas.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); CNN; BBC News


20 October-26 October 2010

CVGHM reported that from the end of September to 20 October the rate of inflation at Merapi was 0.6 cm per day. On 21 October the rate increased to 10.5 cm per day, and incidents of incandescence from the lava dome increased. CVGHM raised the Alert Level to 3 (on a scale of 1-4). The rate of inflation increased sharply on 24 October to a rate of 42 cm per day. The next day, CVGHM raised the Alert Level to 4, and recommended immediate evacuation for several communities (news reports estimated 11,000-19,000 people) within a 10-km radius.

An eruption began at about 1700 on 26 October that was characterized by explosions along with pyroclastic flows that traveled WSW and SE. CVGHM reported that multiple pyroclastic flows occurred until 1854, when the pyroclastic flow activity started to subside. Most of the pyroclastic flows lasted 2 to 9 minutes, except for two that lasted 33 minutes each. Booming noises were heard, and incandescence from the crater was seen from the Selo observation post to the N. An ash plume was also observed rising 1.5 km above the crater.

According to news articles, officials noted that about 15,000 people had not yet evacuated, even though several minor eruptions had already occurred prior to 26 October. Reports on 27 October noted that about 25 people died and several were injured.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Associated Press; Associated Press; Jakarta Globe; BBC News


22 September-28 September 2010

CVGHM reported that a pattern of increasing seismicity from Merapi began in to emerge in early September. Observers at Babadan (7 km W) and Kaliurang (8 km S) heard an avalanche on 12 September. On 13 September white plumes rose 800 m above the crater. Inflation, detected since March, increased from background levels of 0.1 to 0.3 mm per day to a rate of 11 mm per day on 16 September. On 19 September earthquakes continued to be numerous, and the next day CVGHM raised the Alert Level to 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


14 May-20 May 2008

Based on a pilot observation, the Darwin VAAC reported that an ash plume from Merapi rose to an altitude of 11.6 km (38,000 ft) a.s.l. on 19 May. Ash was not identified on satellite imagery.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)


8 August-14 August 2007

Based on a pilot observation, the Darwin VAAC reported that an ash plume from Merapi rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted W on 9 August. Ash was not identified on satellite imagery.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)


23 May-29 May 2007

According to a news article, "hot clouds" and incandescent material from Merapi traveled a distance of 1 km SE down the Gendol River on 23 May. People in the nearby village of Muntilan, about 16 km W, reported "hot clouds" and ashfall.

Source: Antara News


14 March-20 March 2007

Based on pilot reports, the Darwin VAAC reported that an eruption plume from Merapi reached an altitude of 6.1 km (20,000 ft) a.s.l. and drifted NE on 19 March.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)


2 August-8 August 2006

Based on pilot reports, the Darwin VAAC reported that eruption plumes from Merapi on 2 and 3 August reached altitudes of ~6.1 km (~20,000 ft) a.s.l. and drifted W. According to CVGHM, during 2-4 August rockfalls traveled 1 km SE toward the Gendol river and gas plumes reached a maximum of 400 m above the summit (10,900 ft a.s.l.). On 3 August, the Alert Level was lowered to 2 (on a scale of 1-4).

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC)


26 July-1 August 2006

Incandescent rock avalanches from Merapi were observed almost daily during 26 July-1 August, advancing at a maximum distance of 2 km SE toward the Gendol River. On 29 July, gas plumes reached maximum heights of 430 m above the summit (11,000 ft a.s.l.). Pyroclastic flows were not observed during the reporting period. The Alert Level remained at 3 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


19 July-25 July 2006

During 19-25 July, gas plumes at Merapi reached maximum heights of 400 m above the summit (11,000 ft a.s.l.). Lava flows were observed daily, advancing at a maximum distance of 1.5 km SE toward the Gendol River. Pyroclastic flows were not observed during the reporting period. The Alert Level remained at 3 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


12 July-18 July 2006

During 12-18 July, lava flows at Merapi were observed and reached a maximum distance of 2 km SE along the Gendol River. Gas plumes were also observed daily and reached heights of 1 km above the crater (12,800 ft a.s.l.). On 17 July, CVGHM reported that the Alert Level was lowered one level to 3 (on a scale of 1-4) in all remaining areas previously at Alert Level 4 (S slopes). Pyroclastic flows were not observed during the reporting period.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


5 July-11 July 2006

Gas plumes were observed during 5-11 July at Merapi and reached a maximum height of 1.2 km above the summit (3,600 ft a.s.l.) on 6 July. Due to a decrease in activity, on 10 July the Alert Level was lowered one level to 3 (on a scale of 1-4) in all areas except the S slope.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Agence France-Presse (AFP)


28 June-4 July 2006

According to CVGHM, pyroclastic flows and rockfalls at Merapi decreased in frequency and intensity during 28 June-4 July. Pyroclastic flows were observed during 28-30 June and reached a maximum distance of 3 km SE along the Gendol River. Gas plumes were observed during 28 June-1 July and reached a maximum height of 1 km above the summit (12,800 ft a.s.l.) on 28 June.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


21 June-27 June 2006

During 21-25 June, seismic signals at Merapi indicated almost daily occurrence of rockfalls and pyroclastic flows. Due to inclement weather, pyroclastic flows were only observed on 24 June and reached a maximum distance of 4 km SE along the Gendol River and 2.5 km SW along the Krasak River. Gas plumes were observed during 22-25 June and reached a maximum height of 1.5 km above the summit (14,600 ft a.s.l.) on 24 June.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


14 June-20 June 2006

Gas plumes were emitted from Merapi on 14 and 15 June and reached a maximum height of 900 m above the summit (12,500 ft a.s.l.). On 14 June, a dome-collapse event, lasting approximately 3.5 hours, produced pyroclastic flows that reached a maximum distance of 7 km SE along the Gendol River. Two people assisting with evacuation efforts were trapped an underground shelter in Kaliadem village and died, the first fatalities of the current eruption. On 15 June, pyroclastic flows reached a maximum distance of 4.5 km SE along the Gendol River. According to news reports, pyroclastic flows continued during 16-19 June as a new dome grew. On 19 June, water shortages were reported. The Alert Level remained at 4, the highest level.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Deutsche Presse-Agentur; The Jakarta Post; Reuters; Associated Press


7 June-13 June 2006

On 8 June, according to a CVGHM report, the lava-dome growth rate at Merapi was an estimated 100 thousand cubic meters per day and the estimated volume was approximately 4 million cubic meters. An estimated volume loss of 400 thousand cubic meters on 4 June was due to a partial dome collapse of the S part of the Geger Buaya crater wall (constructed from 1910 lava flows).

Gas plumes were observed almost daily during 7-13 June and reached a maximum height of 1.2 km above the summit (13,600 ft a.s.l.) on 10 June. During 8-10 June, the Darwin VAAC reported that small ash plumes were visible on satellite imagery and minor ashfall was reported to the S at the Merapi Volcano Observatory and in Yogyakarta, about 32 km (19.9 miles) away. On 8 June a pyroclastic flow, lasting 12 minutes, reached a maximum distance of 5 km SE toward the Gendol River, the predominate travel direction since the 27 May earthquake (M 6.2). According to a news report, the 8 June event prompted approximately 15,500 people to evacuate from the Sleman district to the S and the Magelang district to the W. On 13 June, the Alert Level was lowered from 4 to 3 but renewed pyroclastic-flow activity the next day again prompted a return to Alert Level 4, the highest level.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); Associated Press; Reuters; AFX News


31 May-6 June 2006

The Alert Level at Merapi remained at 4, the highest level, during 31 May to 6 June. Sulfur-dioxide plumes were observed daily during this period and reached a height of 1.3 km above the summit (13,900 ft a.s.l.) on 1 June. According to the Darwin VAAC, low-level emissions were visible on satellite imagery on 1 and 6 June. Multiple pyroclastic flows reached a maximum distance of 4 km SE toward the Gendol River and 3.5 km SW toward the Krasak and Boyong Rivers. CVGHM reported on 31 May that lava avalanches moved towards the W for the first time during the recent eruption.

According to a volcanologist in Yogyakarta, lava-flow distances and lava-dome volume had both approximately doubled since the 27 May M 6.2 earthquake. The lava-dome volume was estimated at 4 million cubic meters. On 6 June, groups living near the base of the volcano began to move into temporary shelters. Activities remain restricted within a 7 km radius from the volcano's summit and within 300 m of the banks of Krasak/Bebeng, Bedog, and Boyong Rivers to the SW, and Gendol River to the SE.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); Associated Press; Agence France-Presse (AFP)


24 May-30 May 2006

The Alert Level at Merapi remained at 4, the highest level, during 24-30 May. On 24-25 May, lava flows were observed moving SW towards the Krasak River and SE towards the Gendol River. According to news reports, on 27 May an M 6.3 earthquake that killed about 5,400 resulted in a three-fold increase in activity at Merapi. According to CVGHM, an M 5.9 earthquake coincided with pyroclastic flows of unknown origin that extended 3.8 km SW toward the Krasak River. During 28-30 May, multiple pyroclastic flows reached a maximum of 3 km SE toward the Gendol River and 4 km SW toward the Krasak and Boyong Rivers. Gas plumes reached a height above the volcano of 500 m (11,300 ft a.s.l.) on 25 May, 1,200 m (13,600 ft a.s.l.) on 26 May, 100 m (10,000 ft a.s.l.) on 29 May, and 900 m (12,600 ft a.s.l.) on 30 May.

Residents remained evacuated from villages within a 7 km radius from the volcano's summit and within 300 m of the banks of Krasak/Bebeng, Bedog, and Boyong Rivers to the SW, and Gendol River to the SE.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); The Canadian Press


17 May-23 May 2006

The Alert Level at Merapi remained at 4, the highest level, during 17-22 May. Incandescence and sulfur-dioxide plumes were observed. Pyroclastic flows to the SW and SE reached 4 km on 19 May and 3 km on 20 May. On 22 May, the lava dome volume was estimated at ~ 2.3 million cubic meters. The Darwin VAAC reported that low-level emissions continued during 18-19 and 23 May. CVGHM recommended that residents who live in valleys on the NNW flanks near Sat, Lamat, Senowo, Trising, and Apu Rivers and on the SE flank near Woro River be allowed to return to their homes. Residents remained evacuated from villages within a 7 km radius from the volcano's summit and within 300 m of the banks of the Krasak/Bebeng, Bedog, and Boyong Rivers to the SW, and the Gendol River to the SE.

According to news reports, an eruption producing a cloud of hot gas and ash was witnessed on 17 May. Witnesses said the size of the plume was smaller than ash-and-gas plumes on 15 May. On 18 May, a representative for Merapi from the Center for Volcanological Research and Technology Development (part of CVGHM), reported new ashfall.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); Associated Press; Agence France-Presse (AFP); Reuters


10 May-16 May 2006

CVGHM reported that on 11 May, gas plumes rose to ~600 m above Merapi (or 11,600 ft a.s.l.). Avalanches of incandescent material extended 200 m SE towards the Gendol River, and 1.5 km SW towards the Krasak River. Several small incandescent avalanches of volcanic material were visible from observatory posts. The new lava dome at the volcano's summit had grown to fill the gap between the 2001 lava flows and the 1997 lava flows on the W side of the summit. The lava dome reached a height above that of the 1997 lava flows. Seismicity was dominated by multi-phase earthquakes and signals associated with avalanches. On 13 May at 0940, the Alert Level was raised from 3 to 4, the highest level.

The Darwin VAAC reported that on 11 May an ash plume was visible on satellite imagery below 3.7 km (12,000 ft) a.s.l. An ash plume at an unknown height was visible on satellite imagery on 15 May.

According to news reports, after the Alert Level was raised to 4 on 13 May, about 4,500 people living near the volcano were evacuated. Intense activity occurred on 15 May, with pyroclastic flows traveling as far as 4 km to the W. By 16 May a total of about 22,000 people were evacuated; according to figures posted at the district disaster task force center about 16,870 people were evacuated from three districts in Central Java Province, and more than 5,600 others were evacuated from the Slemen district, a part of Yogyakarta Province. Activity decreased on 16 May. On 17 May pyroclastic flows traveled as far as 3 km. Local volcanologists reported that the lava dome continued to grow, but at a slower rate than during previous days.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); Associated Press; Agence France-Presse (AFP); Reuters


3 May-9 May 2006

CVGHM reported that on 6 May, gas plumes rose to 800 m above Merapi (or 12,300 ft a.s.l.) and 18 incandescent avalanches of volcanic material were observed. On 7 May, 26 incandescent avalanches that extended about 100 m were seen during the morning. Incandescence was seen at the summit ten times. On 6 and 7 May, the lava dome continued to grow and seismicity was dominated by multi-phase earthquakes. Shallow volcanic earthquakes and signals from landslides and rockfalls were also recorded. On 8 May, the Darwin VAAC reported that CVGHM warned of a plume rising to ~3.7 km (12,000 ft) a.s.l. No ash was visible on satellite imagery. Merapi remained at Alert Level 3 (on a scale of 1-4), as it has since 12 April.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC)


26 April-2 May 2006

On 28 April, CVGHM observed a lava flow from Merapi traveling ~1.5 km SW to the Lamat River. On the 28th, seismicity was dominated by multiphase earthquakes. Signals from landslides, rockfalls, and low-frequency events were also recorded. According to news reports, around 27 April nearly 2,000 villagers were evacuated from Sidorejo and Tegalmulyo villages on the volcano's flanks. On the 27th, small amounts of ash fell in Gemer village about 5 km from Merapi's summit. Merapi remained at Alert Level 3 (on a scale of 1-4).

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Xinhua; Reuters


19 April-25 April 2006

During 21-25 April seismicity at Merapi remained at high levels, with several seismic signals recorded that were associated with rockfalls. The sulfur-dioxide flux from the volcano was 175 metric tons on 22 April. On 22 and 23 April, fumarolic emissions reached a maximum height of 400 m above the volcano (or 11,000 ft a.s.l.). On the 25th, two rockslides from lava-flow fronts were heard from nearby observatories. According to news reports, about 600 of the approximately 14,000 people living near the volcano had been evacuated by the 24th. Merapi remained at Alert Level 3 (on a scale of 1-4).

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Reuters; Associated Press


12 April-18 April 2006

According to CVGHM, volcanic activity began to increase at Merapi on 11 April, and on 12 April at 1500 they raised the Alert level from 2 to 3 (on a scale of 1-4). They reported that an eruption could occur at any time and no one was permitted within 8 km of the summit. According to news reports, authorities informed people living in villages near the volcano to be prepared for possible evacuations.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Associated Press; Reuters


5 April-11 April 2006

According to a news article, authorities banned mountain climbing on 10 April at Merapi due to increased activity. There were reports that the amount of tremor had increased and that lava was seen flowing near Pasar Bubar village, ~350 m from the volcano's crater.

Source: Deutsche Presse-Agentur


15 March-21 March 2006

Increased seismicity at Merapi led CVGHM to raise the Alert Level from 1 to 2 (on a scale of 1-4) around 20 March. According to a news articles, small earthquakes were recorded at the volcano on 19 March and more than 200 were recorded during the week. Around 10,000 residents near the volcano were warned to prepare for possible evacuations if activity escalates.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Agence France-Presse (AFP)


6 July-12 July 2005

An increase in the number of volcanic earthquakes at Merapi during 7-11 July led DVGHM to increase the Alert Level at the volcano to 2 (on a scale of 1-4) on 9 July.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


4 September-10 September 2002

During 26 August-1 September, observers saw incandescent lava avalanches travel predominately down Merapi's SW flank into the upstream portions of the Sat, Lamat, and Senowo rivers. The avalanches reached a maximum run-out distance of ~2.5 km. Seismicity was dominated by 311 lava avalanches. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


28 August-3 September 2002

During 19-25 August, observers saw 16 incandescent lava avalanches travel predominately down Merapi's SW flank into the upstream portions of the Sat, Lamat, and Senowo rivers. The avalanches reached a maximum run-out distance of ~2.5 km. Seismicity was dominated by 187 lava avalanches. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


21 August-27 August 2002

During 5-18 August, incandescent lava avalanches traveled predominately down Merapi's SW flank into the upstream portions of the Sat, Lamat, and Senowo rivers. The avalanches reached a maximum run-out distance of ~2.5 km. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


31 July-6 August 2002

During 29 July-4 August, incandescent lava avalanches traveled predominately down Merapi's SW flank into the upstream portions of the Sat, Lamat, Senowo, and Bebeng rivers. The avalanches reached a maximum run-out distance of ~2.6 km. A thin white plume rose ~400 m above the summit. Seismicity was dominated by signals from 237 lava avalanches. No pyroclastic flows were reported. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


24 July-30 July 2002

During 15-21 July, incandescent lava avalanches traveled predominately down Merapi's SW flank into the upstream portions of the Sat, Lamat, Senowo, and Bebeng rivers. The avalanches reached a maximum run-out distance of ~2.5 km. Seismicity was dominated by signals from 201 lava avalanches. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


17 July-23 July 2002

During 8-14 July, incandescent lava avalanches traveled predominately down Merapi's SW flank into the upstream portions of Sat, Lamat, Senowo, and Bebeng rivers. The avalanches reached a maximum run-out distance of ~2.5 km. Seismicity was dominated by signals from 180 lava avalanches. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


10 July-16 July 2002

During 1-7 July, observers noted 60 incandescent lava avalanches traveling predominately down Merapi's SW flank into the upstream portions of Sat, Lamat, Senowo, and Bebeng rivers. The avalanches reached a maximum run-out distance of ~2.6 km. On 2 July two pyroclastic flows traveled toward the upstream portion of Sat River, reaching a maximum run-out distance of 0.5 km. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


3 July-9 July 2002

During 24-30 June, observers noted 68 incandescent lava avalanches flowing predominately down Merapi's SW flank into the upstream portions of the Sat, Lamat, and Senowo rivers. The avalanches reached a maximum run-out distance of ~2.5 km. Seismicity appeared to decrease in comparison to the previous week and no low-frequency earthquakes were recorded. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


26 June-2 July 2002

During 17-23 June, observers noted 65 incandescent lava avalanches flowing predominately down Merapi's SW flank into the upstream portions of the Sat, Lamat, and Senowo rivers. The avalanches reached a maximum run-out distance of ~2.5 km. Seismicity decreased in comparison to the previous week. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


19 June-25 June 2002

During 10-16 June, incandescent lava avalanches flowed predominately down Merapi's SW flank to the upstream portions of the Sat, Lamat, and Senowo rivers to a maximum run-out distance of ~2.5 km. Seismicity decreased in comparison to the previous week. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


12 June-18 June 2002

VSI reported that activity at Merapi was generally decreasing. During 3-9 June, incandescent lava avalanches flowed predominately down Merapi's SW flank to the upstream portions of the Sat, Lamat, and Senowo rivers to a maximum run-out distance of ~2.5 km. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


5 June-11 June 2002

During 27 May-2 June, seismicity generally decreased at Merapi in comparison to the previous week. Incandescent lava avalanches flowed predominately down Merapi's SW flank to the upstream portions of the Sat, Lamat, and Senowo rivers to a maximum run-out distance of ~2.5 km. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


29 May-4 June 2002

During 22 April-26 May incandescent lava avalanches flowed down Merapi's flanks, predominately SW to the upstream portions of the Sat, Lamat, and Senowo rivers. They reached a maximum run-out distance of ~2.75 km. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


24 April-30 April 2002

During 15-21 April, several incandescent lava avalanches were observed traveling down Merapi's flanks, predominately SW to the upstream portions of the Lamat, Sat, and Senowo rivers, reaching a maximum run-out distance of ~2.5 km. Two minor pyroclastic flows traveled up to 1.8 km on 14 April. Seismicity decreased in comparison to the previous week, SO2 emission rates were average, and the lava dome showed no signs of deformation. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


27 March-2 April 2002

During 18-24 March, several incandescent lava avalanches were observed traveling down Merapi's flanks, predominately SW to the upstream portions of the Lamat, Sat, and Senowo rivers and partly in a more southerly direction towards Bebeng River. The maximum run-out distance was ~2.5 km. No pyroclastic flows occurred during the report period. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


20 March-26 March 2002

During 11-17 March, 69 incandescent lava avalanches were observed traveling down Merapi's flanks, predominately SW to the upstream portions of the Lamat, Sat, and Senowo rivers and partly in a more southerly direction towards Bebeng River. The maximum run-out distance was ~2.5 km. No pyroclastic flows occurred during the report period. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


27 February-5 March 2002

During 25 February-3 March 88 incandescent lava avalanches were observed traveling down Merapi's flanks, predominately SW to the upstream portions of the Lamat, Sat, and Senowo rivers and partly in a more southerly direction towards Bebeng River. The maximum run-out distance was ~2.5 km. Four minor pyroclastic flows were observed during the report period; three occurred on 25 February and one on 3 March. The flows travelled SSW as far as 1 km to the upstream portion of the Bebeng River. Seismicity at the volcano was similar to the previous week. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


20 February-26 February 2002

During 18-24 February there were 67 incandescent lava avalanches observed traveling down Merapi's flanks, predominately WSW to the upstream portions of the Lamat and Senowo rivers and partly SW toward the Sat and Bebeng rivers. The maximum run-out distance was ~2.2 km. One minor pyroclastic flow was observed; it traveled 2.2 km down the Senowo River. Seismicity was dominated by avalanche earthquakes (607), which slightly increased in comparison to the previous week (600). Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


13 February-19 February 2002

During 11-17 February there were 65 incandescent lava avalanches observed traveling down Merapi's flanks, predominately WSW to the upstream portions of Lamat and Senowo rivers and partly SW toward the Sat and Bebeng rivers. The maximum run-out distance was ~2.5 km. During the report period, six minor pyroclastic flows travelled up to 2.5 km to the upstream portions of the Lamat and Senowo rivers. According to news reports, Volcanology Development and Investigation Agency staff stated that intense rain during the current rainy season could cause landslides around the volcano's crater. Merapi remained at Alert Level 2 (on a scale of 1-4).

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); The Jakarta Post; The Jakarta Post


6 February-12 February 2002

During 28 January-3 February 194 lava avalanches were observed traveling down Merapi's flanks, predominately SW toward the upstream portions of the Sat and Bebeng rivers, and partly WSW to the Lamat and Senowo rivers. The maximum run-out distance was ~2.7 km. There were no major observed changes in seismicity; 855 lava avalanche signals dominated the seismicity. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


30 January-5 February 2002

During 21-27 January, 979 lava avalanches traveled down Merapi's flanks, predominately SW toward the upstream portions of the Sat and Bebeng rivers, and partly WSW to the Lamat and Senowo rivers. The maximum run-out distance was ~2.75 km. Several small pyroclastic flows travelled up to ~1.5 km to the upstream portions of the Sat and Bebeng rivers; two on the 23rd, one on the 24th, and two on the 25th. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


16 January-22 January 2002

During 14-20 January lava avalanches continued to travel down the flanks of Merapi, predominately SW toward the upstream portions of Sat and Bebeng rivers, and partly WSW to the Lamat and Senowo rivers. The maximum run-out distance was ~2.75 km. On 17 January, five small pyroclastic flows traveled 1.2 km to the upstream portions of the Sat and Bebeng rivers. Seismicity increased compared to the previous week and was dominated by 853 lava avalanches. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


9 January-15 January 2002

During 7-13 January lava avalanches continued to travel down the flanks of Merapi, predominately SW toward the upstream portions of the Sat and Bebeng rivers and partly WSW to the Lamat and Senowo rivers. The maximum run-out distance was about 2.5 km. On 7 January a small pyroclastic flow traveled ~2 km to the upstream portion of Bebeng River. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


26 December-1 January 2002

Visual observations during 17-20 December revealed that 109 lava avalanches travelled predominately toward the upstream portion of the Sat River, and to a lesser extent to the Lamat and Senowo rivers. The maximum run-out distance was ~2.5 km. A pyroclastic flow on 18 December travelled ~1 km to the upstream portion of the Bebeng River. During the report period, seismicity was dominated by avalanche earthquakes that were similar in frequency and magnitude to those of previous weeks. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


28 November-4 December 2001

During 19 November- 2 December VSI personnel observed 90 incandescent lava avalanches traveling SW, predominately to the upstream portion of the Sat River, and to a lesser extent to the Lamat and Senowo rivers. The maximum run-out distance was 2.5 km. During the report period, seismicity was dominated by avalanche earthquakes that were similar in frequency and magnitude to those of the previous week. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


14 November-20 November 2001

During 5-18 November VSI personnel observed 192 incandescent lava avalanches traveling SW, predominately to the upstream portion of the Sat River, and to a lesser extent to the Lamat and Senowo rivers. The maximum run-out distance was 3 km. During the report period, seismicity was dominated by avalanche earthquakes. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


31 October-6 November 2001

During 22-28 October, VSI personnel observed 121 incandescent lava avalanches traveling SW predominately to the upstream portion of the Sat River, and to a lesser extent to the Lamat and Senow rivers. The maximum run-out distance was 2.75 km. On 24 October four minor pyroclastic flows were observed travelling a maximum distance of 2 km to the upstream portions of the Sat and Senowo rivers. Seismicity was dominated by avalanche earthquakes similar in magnitude and frequency to earthquakes the previous week. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


24 October-30 October 2001

During 15-21 October, VSI personnel observed 103 incandescent lava avalanches traveling SW predominately to the upstream portion of the Sat River, and to a lesser extent to the Lamat and Senow rivers. The maximum run-out distance was 2.75 km. Seismic activity was dominated by avalanche earthquakes similar in magnitude and frequency to earthquakes the previous week. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


17 October-23 October 2001

During 8-14 October, VSI personnel observed 53 incandescent lava avalanches traveling SW predominately to the upstream portion of the Sat River, and to a lesser extent to the Lamat and Senow rivers to a maximum run-out distance of ~2 km. On 8 October at 1729 a minor pyroclastic flow traveled ~2 km down the Sat River. Seismicity was dominated by 692 lava avalanche events. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


3 October-9 October 2001

During 1-7 October 59 incandescent lava avalanches were observed travelling SW. The avalanches predominately traveled to the upstream portions of the Sat River, and to a lesser extent down the Lamat and Senowo rivers to a maximum run-out distance of 2.5 km. Seismicity was dominated by approximately the same number and intensity of avalanche earthquakes as the previous week. An average of 80 tons per day of SO2 was measured. The Alert Level remained at 2.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


26 September-2 October 2001

During 17-30 September incandescent lava avalanches traveled SW primarily down the Lamat, Senowo, and Bebeng rivers to a maximum run-out distance of 2.5 km. During 17-23 September 51 lava avalanches were observed. Temperatures at Gendol Crater increased from 590-595 ºC the previous week to 602-617 ºC during 17-23 September and to 598-618 ºC during 24-30 September. Avalanche earthquakes, which dominated the seismicity, increased in comparison to the previous week.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


19 September-25 September 2001

According to VSI, during 10-16 September volcanic activity at Merapi decreased in comparison to the previous week. Incandescent lava avalanches continued to travel SW as far as 2.5 km to reach the upstream portions of the Lamat and Senowo rivers. Seismographs recorded 588 lava-avalanche events during the report period. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


29 August-4 September 2001

During 13-26 August approximately 380 lava avalanches were observed travelling SW, extending a maximum distance of 2.8 km mainly down the Sat and Lamat rivers, and to a lesser extent towards the Senowo and Bebeng rivers. Seismic activity consisted primarily of avalanche earthquakes, as it had for the previous 2 weeks. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


22 August-28 August 2001

During 30 July-12 August lava avalanches traveled towards the SW, extending a maximum distance of 2.8 km down the Sat, Senowo, Lamat, and Bebeng Rivers. Seismic activity was dominated by avalanche earthquakes. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


18 July-24 July 2001

During 9-15 July volcanic activity at Merapi was similar to the previous week. A total of 52 lava avalanches traveled SW to a maximum distance of 2.5 km down the Sat, Senowo, and Lamat rivers. Emissions from low-pressure fumaroles rose to 755 m above the summit. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


11 July-17 July 2001

During 2-8 July low-pressure emissions from fumaroles rose 700 m above the volcano. During the same interval lava avalanches traveled SW to a maximum distance of 2.5 km into the upper reaches of the Sat, Senowo, and Lamat rivers. The volcano was at Alert Level 2.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


2 May-8 May 2001

Activity at Merapi increased during 23-29 April, with reports of several medium-sized pyroclastic flows. Four pyroclastic flows were observed traveling into the upper reaches of the Sat, Senowo, Lamat, and Bebeng rivers, with a maximum runout distance of 1.8 km in the Sat River. Lava avalanches traveled up to 2.5 km down the Sat River. Superficial earthquakes continued to dominate the seismicity. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


25 April-1 May 2001

During 16-23 April lava avalanches continued to flow down the Sat, Senowo, Lamat, and Bebeng rivers, with a maximum runout distance of 2 km. Fumaroles emitted gas that rose up to 500 m above the summit. Seismic activity continued to be dominated by avalanche earthquakes. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


18 April-24 April 2001

VSI reported that during 9-15 April lava avalanches continued to fill the upstream areas of the Sat, Senowo, Lamat, and Bebeng rivers, with a maximum runout distance of 2 km in the Sat River. In addition, eleven pyroclastic flows entered the Sat and Lamat rivers, reaching as far as 3 km. Avalanche earthquakes continued to dominate the seismicity, but their amplitude and frequency decreased in comparison to the previous week. An observer reported that on 13 April a small amount of ash fell around the Babadan Post Observatory ~7 km W of the volcano. Merapi remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


11 April-17 April 2001

Visual and instrumental monitoring by VSI personnel during 2-9 April revealed that volcanic activity continued at Merapi. Lava avalanches continued to enter upstream areas of the Sat, Senowo, Lamat, and Bebeng rivers, with a maximum runout distance of 2.5 km in the Sat River. An observer reported that ten pyroclastic flows traveled down the Sat, Senowo, and Bebeng rivers, reaching as far as 2.3 km in the Sat River. Fumaroles emitted steam and gas up to 950 m above the volcano's summit. Both the number and amplitude of earthquakes was high, but less than previously recorded. Seismic activity was dominated by avalanche earthquakes. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


21 March-27 March 2001

Visual and instrumental monitoring by VSI personnel through 18 March revealed that volcanic activity continued at Merapi. Hot lava avalanches continued to enter the Sat, Senowo, Bebeng, and Lamat rivers, with a maximum runout distance of 3 km in the Sat River. Pyroclastic flows traveled up to 1 km down the Sat, Senowo, and Bebeng rivers. Superficial earthquakes dominated the seismicity, though the number and amplitude decreased from the previous week. Observations during a summit visit on 17 March revealed that high-pressure fumaroles remained on most of the dome's surface. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


14 March-20 March 2001

Visual and instrumental monitoring by VSI personnel revealed that volcanic activity continued at Merapi. Hot lava avalanches continued to enter the Sat, Senowo, Bebeng, and Lamat rivers, with a maximum runout distance of 2.5 km in the Sat River. Pyroclastic flows traveled up to 2.75 km down the Sat, Senowo, and Bebeng rivers. Superficial earthquakes dominated the seismicity, though fewer occurred than in the previous week. Observations on 10 March revealed that high-pressure fumaroles appeared on most of the dome's surface. The volcano remained at Alert Level 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


7 March-13 March 2001

Visual and instrumental monitoring conducted by VSI personnel revealed that volcanic activity at Merapi had decreased; therefore on 7 March the Alert Level was reduced from 3 to 2 (on a scale of 1-4). During 27 February- 5 March, volcanic activity was dominated by an average of 100 lava avalanches per day. The avalanche material traveled to the SW, entering the Sat and Senowo rivers with runout distances of 2.3-2.5 km. On 6 March a pyroclastic flow deposited material up to 1.5 km down the Sat River.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


28 February-6 March 2001

Based on reports from the VSI, the Darwin VAAC stated that the Alert Level at Merapi was downgraded on 25 February from 4, the highest level, to 3.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)


21 February-27 February 2001

Based on reports from the VSI, the Darwin VAAC stated that during 15-21 February volcanic activity decreased at Merapi. According to the Meteorological and Geophysical Agency of Indonesia, during 11-18 February daily ash emissions rose up to ~150 m above the summit. The volcano remained at Alert Level 4, the highest level.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)


14 February-20 February 2001

VSI reported that after the large 10 February eruption volcanic activity decreased in intensity. Lava avalanches and pyroclastic flows continued, but were smaller than they were the previous week. During 10 to 13 February pyroclastic flows entered the Sat, Lamat, Senowo, and Bebeng rivers to a maximum runout distance of 2-3 km, in comparison to ~4.5 km the previous week. After 13 February lava avalanches and pyroclastic flows traveled 1.5-2.5 km to the WSW and lasted 1-2 hours. According to the VSI, high temperatures around Merapi indicate that magma is near the surface. The W and S sides of "lava dome 2001" grew and covered "lava dome 1997" to the S. Several fumaroles appeared to mark a fracture along the area where the 10 February eruption occurred. Fractures formed in a similar matter prior to the November 1994 eruption. The volcano remained at Alert Level 4, the highest level.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC)


7 February-13 February 2001

Intense and dangerous volcanic activity continued at Merapi with hot lava avalanches, near-continuous pyroclastic flows, and an eruption on 10 February that deposited ash on many cities out to 60 km E of the volcano. During 30 January to 5 February, continuous hot lava avalanches and pyroclastic flows traveled down the SW flank of the volcano along the Sat, Senowo, and Bebeng rivers to a maximum runout distance of ~4.5 km. Lava avalanches also traveled down the Lamat River, a drainage that avalanches had not previously traveled down during the current period of volcanic activity. Approximately 25 pyroclastic flows occurred daily. Ash associated with the pyroclastic flows fell around Merapi. During 0430 to 0630 on 3 February heavy rain mixed with ash and produced minor lahars. On 6 February the dome was reported as being 1 million cubic meters in volume and growing at 45 cubic meters per day.

Pyroclastic-flow activity began at 2100 on 9 February and lasted up to 1 hour. At 0200 on 10 February, a medium-sized pyroclastic flow lasted for ~30 minutes. At 0330 the same day "lava dome 1998," which was under the new lava dome ("lava dome 2001"), partially collapsed. The collapse triggered a large and continuous pyroclastic flow that lasted as long as 2.5 hours. The pyroclastic flow traveled up to 7 km SW of the summit towards the Sat River, and 4.5 WSW to the Lamat River. The resultant ash cloud rose up to 5-8 km above the summit, spread ~60 km towards the E, and deposited ash on the towns of Klaten, Solo, Sukoharjo, and Boyolali. The greatest ash thickness was ~1 cm, reported within a 5 km radius around the volcano. At 0530 the Alert Level at the volcano was raised from 3 to 4, the highest level. News articles reported that ~12,000 residents near the volcano were evacuated on 10 February, though many people returned to their property the next day despite the evacuation order. By 11 February, lava dome 2001 was estimated to be 1.4 million cubic meters in volume and unstable, especially after the 10 February collapse of "lava dome 1998."

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); ABC News - Australian Broadcasting Corporation; Associated Press


31 January-6 February 2001

The VSI reported that activity continued to increase during 23 January-1 February. At 0000 on 27 January an eruption produced continuous pyroclastic flows and molten lava avalanches that lasted as long as 2 hours. The eruption also produced a thick ash plume that rose 2 km above the volcano's summit and was accompanied by a strong sulfurous smell. On 28 January, "lava dome 2001" partially collapsed, resulting in pyroclastic flows and molten lava avalanches that occurred at 2-5 minute intervals. The avalanche and pyroclastic-flow material traveled down the Sat and Bebeng rivers to the SW, and Senowo River to the W. The maximum runout distance of 4.5 km occurred in the Sat River. Ash fell in 5 districts within a 15-20 km radius around the volcano; Dukun, Srumbung, Salam, Ngluwar, and Muntilan. On 31 January, pyroclastic flows continuously entered the Sat River, and to a lesser extent the Senowo and Bebeng rivers. The maximum runout distance was ~3.5 km. Again, ash fell on the towns within a ~15 km radius around the volcano. Visual observations and photographic analysis revealed that the dome became higher and larger than it was during the previous report period, and that there was a new active point at the summit that may have been a fumarole or a hot spot. The volcano remained at Alert Level 3 (on a scale of 1-4).

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Associated Press; Agence France-Presse (AFP)


24 January-30 January 2001

An Associated Press article from 25 January reported that ash mixed with rain fell on the village of Deres on the flanks of the volcano. Activity reportedly increased slightly on 25 January.

Source: Associated Press


17 January-23 January 2001

The VSI reported that during 16-22 January visual and instrumental monitoring revealed a continued increase of volcanic activity at Merapi. Activity consisted of several pyroclastic flows, small ash eruptions, glowing lava flows, lava avalanches, and an increase in seismicity, especially in avalanche and multi-phase earthquakes. More than 20 pyroclastic flows per day traveled continuously to the Sat (upstream of River Putih), Senowo, and Bebeng rivers. The number of glowing lava avalanches also increased since last reported, with more than 150 events per day observed. The avalanches traveled down to the Sat, Senowo, and Bebeng rivers extending as far as 3,500 m. The new lava dome, "lava dome 2001," grew at the volcano's summit over the preexisting "lava dome 1998." The Darwin VAAC reported that an ash cloud that was not visible on satellite imagery reached 500 m above the summit on 19 January. The VSI reported that during the report period ash fell in the towns of Babadan, Ngepos, and Kaliurang. An average of 95 tons/day of SO2 was measured. The volcano remained at Alert Level 3 (on a scale of 1-4).

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Darwin Volcanic Ash Advisory Centre (VAAC); Associated Press


10 January-16 January 2001

The VSI report for 9-15 January noted that activity increased at Merapi, prompting the hazard status to be raised to Alert Level 3 at 0600 on 10 January. Observers frequently noted a weak white plume that rose 500 m above the summit. Glowing lava avalanches continued into the upstream areas of the Sat, Lamat, and Senowo rivers to a runout distance of 2,000 m. On 14 January there were 29 pyroclastic-flow events, which filled the Sat, Lamat, and Senowo rivers out to a maximum distance of ~4,000 m. During this week there were continuous glowing lava avalanches and pyroclastic flows at intervals of 30-60 minutes. The Associated Press reported on 11 January that authorities had ordered people living around the mountain to be on high alert and prepare to leave at short notice.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM); Associated Press


29 November-5 December 2000

During 21-27 November small explosions occurred at Merapi, with the largest producing an ash plume that rose up to 800 m above the summit. Seismicity was high and dominated by multi-phase earthquakes. The volcano remained at Alert Level 2 (ranging from 1 to 4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


15 November-21 November 2000

The VSI reported that during the week small explosions produced ash plumes that rose up to 430 m above Merapi's summit. High rains during 7 to 13 November caused landslides to occur in the upstream portion of Boyong river, Kaliurang. The river is on the S flank of Merapi and extends ~28 km map distance from the summit. The landslides killed one person and more landslides or lahars are expected during the current rainy season. The volcano is at Alert Level 2 (ranging from 1 to 4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)


Index of Bulletin Reports


Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

01/1969 (CSLP 04-69) Nuee ardentes travel down SW-flank valleys; more dome growth

02/1969 (CSLP 04-69) Lava avalanches cause extensive damage, leaving many homeless

10/1972 (CSLP 67-72) Summit explosion on 6 October

03/1976 (NSEB 01:06) Increases in seismicity, lava dome height, and incandescent spots on dome

11/1976 (NSEB 01:14) Ash clouds rising 3 km; nuées ardentes down the SW flank

03/1977 (NSEB 02:03) Lava dome growth continues; frequent avalanches

08/1978 (SEAN 03:08) 980°C fumaroles on N flank; increased seismicity

09/1978 (SEAN 03:09) Fumarole temperatures and gas analyses

07/1979 (SEAN 04:07) Hot avalanches decline; dome growth continues

01/1980 (SEAN 05:01) Dome growth continues

02/1981 (SEAN 06:02) Lava dome growth; hot avalanches

12/1981 (SEAN 06:12) Sixty percent of the summit dome destroyed; hot avalanches

01/1982 (SEAN 07:01) Heavy ashfall

06/1984 (SEAN 09:06) Explosions, nuées ardentes, lahars; 1,000 evacuated

10/1986 (SEAN 11:10) Rockfall seismicity suggests increased lava dome growth

11/1986 (SEAN 11:11) Summit lava dome growth

12/1986 (SEAN 11:12) Lava flow from October-November dome advances onto SW flank

02/1987 (SEAN 12:02) Rockfall seismicity ends; dome growth probably stops

04/1987 (SEAN 12:04) Lava dome, largest since 1973, appears stable

08/1987 (SEAN 12:08) Lava dome growth, but nuées ardentes de avalanche stop

12/1987 (SEAN 12:12) No lava dome growth from August to November

05/1989 (SEAN 14:05) Large summit dome; fumaroles to 800°C; lahar alert

11/1989 (SEAN 14:11) Large lava dome growing slowly in summit crater

07/1990 (BGVN 15:07) Slight increase in seismicity; lava dome volume stable

03/1991 (BGVN 16:03) Slight increase in seismicity; no apparent dome growth

04/1991 (BGVN 16:04) High-temperature fumaroles; no changes evident to summit dome

05/1991 (BGVN 16:05) Continued seismicity but lava dome unchanged

06/1991 (BGVN 16:06) Gas plumes and seismicity

11/1991 (BGVN 16:11) Degassing but no apparent lava dome growth

11/1991 (BGVN 17:03) Deformation data from 1988-90; seismicity 1990-91

12/1991 (BGVN 16:12) Hot material moves down flanks

01/1992 (BGVN 17:01) Ash ejection; hot flows destroy crops

02/1992 (BGVN 17:02) Lava dome growth and pyroclastic flows

03/1992 (BGVN 17:03) Continued lava extrusion; small rockfalls and avalanche-generated pyroclastic flows

04/1992 (BGVN 17:04) Continued lava dome growth and rockfalls

07/1992 (BGVN 17:07) Growing lava dome spawns avalanches; summit gas data

10/1992 (BGVN 17:10) Pyroclastic flows follow earthquakes and rainfall; gas data

11/1992 (BGVN 17:11) Pyroclastic flows from growing summit lava dome

01/1993 (BGVN 18:01) Pyroclastic flows from growing summit lava dome; highest plume rises 1500 m

01/1994 (BGVN 19:01) Avalanches decrease; and seismic spectra for tremor and avalanches

03/1994 (BGVN 19:03) Hazard status up: sharp increases in pyroclastic flows, glowing rock falls, and tilt

07/1994 (BGVN 19:07) Increased deformation precedes a nuee ardente

08/1994 (BGVN 19:08) Two new broad-band seismometers detect long-period pulses and tremor

10/1994 (BGVN 19:10) Pyroclastic flows on 22 November kill at least 41 people on the SSW flank

12/1994 (BGVN 19:12) Pyroclastic flows continue through 7 December

02/1995 (BGVN 20:02) Seismic data associated with the 22 November 1994 dome collapse

10/1995 (BGVN 20:10) Pyroclastic flows travel down two river drainages

01/1996 (BGVN 21:01) Increased seismicity related to lava avalanches and rockfalls

08/1996 (BGVN 21:08) Increasing eruptive activity prompts preparations for evacuation

10/1996 (BGVN 21:10) Peak in volcanism on 31 October results in over 15 pyroclastic flows

06/1997 (BGVN 22:06) Pyroclastic flows and vigorous plumes noted in first half of 1997

12/1997 (BGVN 22:12) Intermediate hazard status posted during September 1997

07/1998 (BGVN 23:07) Increasing activity culminates in mid-July pyroclastic flows

08/1998 (BGVN 23:08) Details of July eruptions, new monitoring equipment

05/1999 (BGVN 24:05) Frequent lahars, lava avalanches, and pyroclastic flows during March-May

11/2000 (BGVN 25:11) Consistent gas plume; lava avalanches and landslide; new lava dome and fractures

12/2000 (BGVN 25:12) Dome failure and growth during January 2001; over 30 pyroclastic flows

01/2001 (BGVN 26:01) Failure of 1998 lava dome on 10 February causes major eruption

07/2001 (BGVN 26:07) Volcanism continues at decreased intensity; Alert reduced from 4 to 2

10/2001 (BGVN 26:10) Dome collapses and lava avalanches August-November; two unconfirmed deaths

02/2002 (BGVN 27:02) Heightened lava dome activity from August 2001 through at least February 2002

06/2002 (BGVN 27:06) Pyroclastic flows and lava avalanches occur during February-June 2002

09/2002 (BGVN 27:09) Frequent lava avalanches; plumes up to 550 m above summit

03/2003 (BGVN 28:03) Infrared satellite data show continuous activity through mid-January 2002

05/2006 (BGVN 31:05) Mid-2006 brings multiple pyroclastic flows that kill two, and travel up to 7 km

06/2006 (BGVN 31:06) Fewer pyroclastic flows during July; ASTER thermal data

02/2007 (BGVN 32:02) March-July 2006 volcanic crisis; May earthquake killed ~5,800

10/2008 (BGVN 33:10) Lava dome growth with intermittent ash plumes and rock avalanches

02/2011 (BGVN 36:01) Eruption started 26 October 2010; 386 deaths, more than 300,000 evacuated

05/2011 (BGVN 36:05) Recovery; intermittent activity; damaging lahars




Bulletin Reports

All information contained in these reports is preliminary and subject to change.


01/1969 (CSLP 04-69) Nuee ardentes travel down SW-flank valleys; more dome growth

Card 0331 (10 January 1969) Eruption destroys 60 homes; three people missing

Sixty homes have been destroyed and at least three persons are missing in a volcanic eruption in Indonesia. Lava flowed down the mountainside into the town of Magerang and the village of Muntilam. A larger eruption is predicted.

Card 0332 (13 January 1969) Nuee ardentes travel 11-12 km down SW flank river valleys

Djajadi Hadikusumo provided the following report dated 9 January. "Activity of Merapi volcano increased since 8 January. From 0230 on nuee ardente d'avalanches, accompanied by lightning, continuously went down into rivers of Blongkeng, Batang, Bebeng, and Krasak (SW slope) reaching a distance of about 11 or 12 km from the summit, approximately until the village of Nganggrung on the SW slope, situated inside the prohibited zone. All of 'lava 1967' tumbled down and on its place now glare could be observed. The seismograph at Plawangan Observatory (~5.5 km S of the summit) still records volcanic tremors in high amount. At this observatory the ash layer was 2 cm thick."

Card 0333 (13 January 1969) New lava emerges at location of 8 January dome collapse

K. Fredriksson provided the following report by telephone 13 January concerning conversations with D. Hadikusumo on 11 January. Seismic acitivity has calmed down. Mt. Merapi covered by cloud since 8 January. Paroxysm on 8 January at 0230 hours. Nuee ardente of avalanche to village of Pakel, 13 km SW. Main direction of avalanche to the rivers Blongkeng and Bebeng. New lava emerged on the same spot where the lava dome has collapsed. Evacuation of people taking place in Magelang area and around the villages of Kamongan and Djombang.

Card 0334 (14 January 1969) Volcanic materials extend 13 km W of the summit

Mt. Merapi . . . is currently producing nuee ardente blasts in the direction of the Borobudur Temples near Muntilan, 35 km NW of Jogdjakarta. The status of the temples and archaeological sites is not known but volcano blasts of incandescent lava materials were ejected from the Merapi volcano in a westerly direction up to a distance of 13 km from the summit toward the towns of Magelang, Kamongan, and Djombang.

Card 0343-0344 (20 January 1969) Minor lava avalanches from new dome

The following was received from Kurt Fredriksson in Djakarta on 20 January 1969. "Herjono took me to the still hot ash flow area around Kaligesik as high as considered safe. I photographed and collected a few samples. Climbed to the Blawangan Observation Station at 1,290 m altitude. During night and early morning observed and photographed several lava avalanches. Good conditions between 0200 and 0800. The lava avalanches appear to consist of blocks or clusters of blocks, incandescent, which break loose from the growing lava dome at various places and tumble down 1-2 km or 400-500 m below summit. The material apparently accumulates in certain places and gives rise to secondary steam explosions. At approximately 0730 rather strong disturbance was observed on seismograph, not felt however, followed in few minutes by emission of dark smoke in SW of crater above new lava dome. Most steam, white continuous, seems otherwise to originate in N side of summit crater. Shock could have been caused by collapse?

"Major phase pf eruption is over. Lava avalanches from new dome appear minor. The ash flow deposit ~10 m. In the Kaligesik area (sampled) and still hot (secondary steam explosions) indicates that this is more like real 'nuee ardente' type than Mt. Mayon. No welding ocurs and channel higher up on steep slope appears to be swept clean like at Mayon."

Information Contacts: Card 0331 (10 January 1969) George Beauchamp, U.S.A.I.D. Disaster Relief.
Card 0332 (13 January 1969) Djajadi Hadikusumo, Geological Survey of Indonesia.
Card 0333 (13 January 1969) Kurt Fredriksson, Smithsonian Institution.
Card 0334 (14 January 1969) American Embassy, Djakarta, Indonesia.
Card 0343-0344 (20 January 1969) Kurt Fredriksson, Smithsonian Institution.

02/1969 (CSLP 04-69) Lava avalanches cause extensive damage, leaving many homeless

Card 0370-0371 (05 February 1969) January avalanches leave 2,000 people homeless

13 January 1969. Latest reports from Java said that up until Wednesday afternoon the volcano was still emitting hot air which went down the Blongkeng and Batang rivers along a stretch of 7.5 km. An observation post at Krindjing reported major and minor avalanches and ash rains to the accompaniment of thunder and lightning. Observation posts in Jogjakarta said activites of Merapi had increased in violence on 9 January. Hot air spouted from the summit of the volcano, reaching a distance of about 12 kilometers. Three officials at the Plawang post, nearest to Merapi, were said to be in excellent condition despite violent seismic activities, rains and ash rains.

Reports of the Jogjakarta municipality said thus far a total of about 180 houses had been seriously damaged. The interior of some of the houses was filled with mud, at several points as thick as 1.5 m. Most of the houses were located along the bank of the Tjode river in the center of Jogjakarta. At present a total of about 2,000 citizens have been rendered homeless. The majority came from the Prawiro dirdjan, Sajidan, Djeties, and Bintara villages. Meanwhile, drinking water supplies in Jogjakarta have now been reduced by ~50% as a result of damages to some of the vital local installations. Likewise, streets in the vicinity of the Sjuhada Mosque were cracked at several points.

Card 0372 (05 February 1969) New lava emission on 25 January; serious road damage

25 January 1969. Merapi started emitting new lava again recently after having been quiet for some time according to the latest reports of the volcanological station. The lava was estimated at 250 m in length and 150 m in width. It is called the 1969 lava.

27 January 1969. Traffic communications between Magelang and Jogjakarta have been cut off since 22 January due to serious road damages along a stretch of 200 m linking Muntilan and Tempel. Torrential rains in the vicinity of the Merapi volcano last Wednesday flooded several rivers which later swept away rocks, pebbles and sand, rendering serious damages to roads linking Muntilan and Tempel. A market in the Tulan subregency was inundated by swollen waters of the rivers. Meanwhile panic has gripped villagers at Srumbung, Dukuh, Salam, and Muntilan.

Card 0407 (17 February 1969) Three known victims of the January avalanches, but 3,800 refugees

"The eruption which took place in the summit region recently, on the night of 7-8 January 1969, resulted in avalanches of the lava dome reaching distances of 13 km down the crater rim. Since 11 January a lava flow has come down in the vicinity of Geger Buaja in the direction of Jogjakarta. Until now there are only three registered victims of the kampongs Gimbal and Ngangrang, however the number of refugees in the Jogjakarta region amounts to about 3,800 people. It seems that the activity of the volcano has quieted down since 25 January."

Information Contacts: Card 0370-0371 (05 February 1969) Otto Soemarwoto, Antara News Agency, The Djakarta Times, Djakarta, Indonesia.
Card 0372 (05 February 1969) Otto Soemarwoto, Antara News Agency, The Djakarta Times, Djakarta, Indonesia.
Card 0407 (17 February 1969) G.A. De Neve, Universtas Padjadjaran, Bandung, Indonesia.

10/1972 (CSLP 67-72) Summit explosion on 6 October

Card 1468 (18 October 1972) Summit explosion on 6 October

Babadan Volcano Observatory, some 4.2 km WNW of Mt. Merapi summit.

06 October 1972. 0720: Strong emission of whitish smoke in the upper part of Batang breach. 0729: Gas explosions; ash cloud rose to 3,000 m above summit. 0730: Rumblings of avalanches which went down into Batang River (SW) 3km distant; rock falls (of explosion) went into Trising and Apu rivers (NW). 0742: Shower of large-grain sand at the observatory; also in Telogolele village some 7 km distance from summit. 0745: Sand shower stopped; thin sand deposit at the observatory.

Some volcanic quakes were recorded about 3.5 minutes before the explosion took place and thereafter tremors of avalanches were recorded for about 8 minutes. After this Mt. Merapi was hidden by clouds. All other observatories around the volcano were unable to observe the activity due to thick clouds; only rumblings could be heard. The center of activity was located in the upper part of "1969 lava" in the Batang breach. A small part of the upper part thereof was blown off in the eruption cloud. During the following week no abnormal phenomena were observed (up to 11 October).

Information Contacts: Djajadi Hadikusumo, Geological Survey of Indonesia.

03/1976 (NSEB 01:06) Increases in seismicity, lava dome height, and incandescent spots on dome

Activity increased in February compared to the previous month. The number of volcanic earthquakes increased, the lava dome grew higher, and red glares were observed at 2 points on the dome. The number of glowing avalanches decreased from January, however, and there was only one nuée ardente, on 4 February, that traveled about 750 m SW into the Batang River.

On 5 March at 1503, reddish white smoke emitted with strong gas pressure was observed to about 350 m above the summit. The volcano was hidden behind clouds. On 6 March, small avalanches took place continuously from 0135 until 0348, then the volcano was covered by clouds. At 1702, three avalanches were observed. From 1733 on, bigger nuées ardentes took place, interspersed with minor ones, until 13 March (table 1).

Table 1. Daily number of nuées ardentes and maximum distances traveled from the vent, 6-13 March 1976.

    1976     LARGE   SMALL    MAXIMUM DISTANCE (km)

    06 Mar     10      19            4
    07 Mar     17      16            5.5
    08 Mar      5       2            3.5
    09 Mar      5       6            6
    10 Mar      1       4            2.75
    11 Mar      1       9            5.5
    12 Mar      -       6            1.5
    13 Mar      -       3            1.5

From the evening of 8 March until the evening of 9 March, when the volcano became visible from the Ngepos Volcano Observatory 11 km SW of the summit, it could be observed that the lower part of the lava dome, estimated to be about 400,000 m3, or almost 1/3 of its volume (1.4 x 106 m3), had slid away. During the events on 6 and 7 March nuées ardentes moved SW, entering a tributary of the Batang River and continuing much further down stream into the rivers Sat, Blongkeng, and Bebeng. The prevailing wind blew E, depositing finer volcanic products on the E and SE flanks to a maximum distance of 37.5 km. Thickest ash falls were on the ESE flank. At 6 km from the summit the deposit apparently measured 5 mm and temporarily panicked the villagers.

Nuées ardentes caused forest fires on the upper SW flank near the tributaries of the rivers Sat, Blongkeng, and Bebeng. Roughly 580,000 m3 of ash were deposited on the E flank, and around 300,000 m3 of avalanche material were deposited on the upper SW flank.

Information Contacts: D. Hadikusumo, Volcanology Division, GSI.

11/1976 (NSEB 01:14) Ash clouds rising 3 km; nuées ardentes down the SW flank

Merapi was unusually active on 6 and 7 November, emitting 3,000-m ash clouds, and nuées ardentes that moved 2.5 km down the SW flank. No casualties or serious property damage were reported. The new dome, which began growing after the March activity, had an estimated volume of 20,000 m3 in June.

Information Contacts: D. Hadikusumo, Volcanology Division, GSI; D. Shackelford, Villa Park, CA; UPI.

03/1977 (NSEB 02:03) Lava dome growth continues; frequent avalanches

The new lava dome, had increased in volume from about 2 x 103 m3 in June, 1976 to about 2.5 x l06 m3 in late February, 1977. Avalanches continued to occur at intervals of 15 minutes or more; sometimes, but not every day, nuées ardentes accompanied the avalanches, especially after a heavy rainfall.

Information Contacts: J. Matahelumual, Volcanology Division, GSI; D. Shackelford, Villa Park, CA.

08/1978 (SEAN 03:08) 980°C fumaroles on N flank; increased seismicity

Merapi was visited by Haroun Tazieff in July. No eruption was occurring, but seismicity was increasing, and fumarole temperatures on the N flank reached 980°C, as compared to 400-500°C during previous periods of quiescence.

Information Contacts: H. Tazieff, CNRS, Gif-sur-Yvette; P. Jezek, SI.

09/1978 (SEAN 03:09) Fumarole temperatures and gas analyses

Franois Le Guern and Haroun Tazieff provided the following fumarole temperatures and gas compositions (table 2), obtained during their July visit to Merapi. Gases were analyzed with a field gas chromatograph.

Table 2.Fumarole temperatures (maximum and analyzed with a gas chromatograph) and gas compositions (in volume %) at Merapi, July 1978. "Crater" is the crater near the active dome. Courtesy of Franois LeGuern and Haroun Tazieff.

    Location     Gendol(1) Gendol(2) Gendol(3)  Crater  Woro

    Max Temp °C    820        -         -        901     760
    Anal Temp °C   720       720       819       744     580
    CH4            0.013     0.017    <0.001     0.06     -
    CO2            3.28      4.02      4.57      5.26    3.21
    H2O           94.37     93.08     93.71     90.75   94.27
    H2S            0.24      0.30      0.47      1.15    0.12
    SO2            0.25      0.31      0.51      1.14    0.06
    H2             1.12      1.36      0.56      1.46     Tr
    O2+Ar          0.15      0.19      0.005     0.02     Tr
    N              0.55      0.68      0.13      0.12    2.34
    CO             0.03      0.03      0.01      0.02    0.02

Information Contacts: F. LeGuern and H. Tazieff, CNRS, Gif-sur-Yvette.

07/1979 (SEAN 04:07) Hot avalanches decline; dome growth continues

Newspaper reports state that hot avalanches from the lava dome decreased in frequency during May, after as many as 40/day had occurred in April. The May avalanches traveled as much as 1.75 km. Growth continued at the new dome, which first appeared in January 1979 and now covers the remnants of the 1973 and 1978 domes.

Information Contacts: Kompas, Jakarta; M. Krafft, Cernay.

01/1980 (SEAN 05:01) Dome growth continues

Lava dome extrusion continued through 1979 from a SW flank vent ~200 m below the summit. A lobe of lava extending a short distance down the upper SW flank gave the dome an asymmetrical form and occasionally spawned nuées ardentes d'avalanche. The last significant nuée ardente traveled ~6 km in August 1979, but remained within the forbidden zone, where human access is prohibited. The maximum thickness of the active dome was ~100 m in October. In November, VSI estimated its volume at 1.14 x 106 m3 and its extrusion rate at ~105 m3/month.

Information Contacts: A. Sudradjat and L. Pardyanto, VSI.

02/1981 (SEAN 06:02) Lava dome growth; hot avalanches

The lava dome that began to emerge at the summit in 1979 was still growing in February and had reached an altitude of 2947 m. Lava fragments from the E and central part of the cone had moved 2.0 km toward the Batang River, and 250-500 m farther in December. Personnel at the Ngepos Observatory have counted 34 larger and 468 smaller lava avalanches in recent months; the time interval was not reported. Nuées ardentes d'avalanche occurred in November and December but were confined to the summit area. Two Minakami A-type earthquakes, the first in several months, were recently recorded by the seismograph at the Babadan Observatory (4 km from the summit). No important lahars have occurred along the Putih, Bebeng, and Krasak Rivers since the beginning of this year's rainy season.

Further Reference. Tazieff, H., 1983, Monitoring and interpretation of activity on Mt. Merapi, Indonesia, 1977-80: a practical example, Civil Defense, in Tazieff, H. and Sabroux, J.C. (eds.): Forecasting Volcanic Events, Elsevier, Amsterdam, p. 485-494.

Information Contacts: A. Sudradjat and L. Pardyanto, VSI.

12/1981 (SEAN 06:12) Sixty percent of the summit dome destroyed; hot avalanches

Landsliding on the summit lava dome 29 November was followed by a nuée ardente d'avalanche that flowed 3-4 km down the Batang River valley. Ash fell 15-20 km to the NW. An avalanche of incandescent lava from the dome set fire to 15 hectares of tropical mixed forest. On 1 December approximately 3/5 of the lava dome slid down the upper flank, flooding the Krasak and Batang Rivers and adding 1.2 x 106 m3 to the deposits from previous debris flows. As of early December, there were about 6.9 x 106 m3 of unstable material in the summit area. Authorities feared that monsoon rains could cause large cold lahars, and officials of Magelang District, W of Merapi, remained on constant alert in early December. AFP reported that the volcano continued to emit ash in mid-December.

A tripartite electro-seismometer at Babadan Observatory and two single-detector seismographs near the volcano recorded continuous trains of tremors and very shallow earthquakes that may have been landslide events. Continuous records of magnetic values showed no significant changes. No sharp variations in CO2 and H2S emissions were detected. Tilt measurements showed deformation of 10-20 µrad, within the normal variation.

Information Contacts: A. Sudradjat, VSI; AFP; Jakarta DRS.

01/1982 (SEAN 07:01) Heavy ashfall

Heavy ashfall that began 6 February damaged crops and halted traffic in the nearby Boyolai region, according to a press report dated 8 February.

Information Contacts: AFP.

06/1984 (SEAN 09:06) Explosions, nuées ardentes, lahars; 1,000 evacuated

The quoted material is a report from Adjat Sudradjat.

"Merapi erupted 15 June between 0215 and 0600, accompanied by nuées ardentes that extended 7 km down rivers (the Batang, Bebeng, and Krasak) on the SW side of the volcano. An eruption plume rose to 6 km height and caused ashfall in Muntilan, Ambarawa, and Semarang, approximately 60 km N of the volcano. The eruption was accompanied by detonations. The first explosion was followed by a milder eruption producing a plume to 2 km height and a nuée ardente to 6 km distance at noon. The frequency of nues ardentes progressively decreased until the morning of 16 June. No eruptions were observed the following day. Lahar material estimated to exceed 4 x 106 m3 along the Bedeng, Krasak, and Putih Rivers may threaten Magelang city (population about 125,000)."

An image from the NOAA 7 polar orbiting satellite on 15 June at 1441 showed a hazy area that did not seem to be weather-related extending from 7°S to 5°S and from 110°E to the edge of the image at 106°E. The hazy area did not extend back to Merapi, nor was any tephra emission apparent at the volcano. No evidence of activity could be seen on the image returned the next day at about the same time.

Newspapers reported ashfalls at Magelang (30 km NW of Merapi) and Salatiga (35 km NE of the volcano). Visibility near Salatiga was limited to 10 m and more than a cm of ash covered roads, slowing traffic. More than 2 cm of ash fell at Solo (45 km E of the volcano) and ashfall was reported at Cilacap, on the coast 160 km SW of Merapi.

"Seismographs detected a progressive increase in seismicity from 4 counts/day on 8 June to 59 on 12 June. A warning was issued 13 June, and the evacuation of 1000 persons from forbidden zone section VI (Kemiren village) was immediately implemented. The tong-tong warning system was tested again to be sure that it was operational. The eruption was preceded by an intense lava avalanche on 13 June that caused a nuée ardente d'avalanche (nuée ardente of Merapi type)."

"As of 22 June, no volcanic A-type earthquakes had been recorded. The dominant seismicity has been continuous tremors, very shallow volcanic earthquakes, and avalanche events with multiphase signatures. Judging from this evidence, two possibilities are: (1) the 15 June eruption is the final phase of the 1969-1984 lava dome growth (effusive stage-see below); or (2) the 15 June eruption is evidence of the gas phase of a new cycle. Both possibilities would show quiescence of A-type earthquakes. The rate of dome growth, which was reported to have sharply increased 20-21 June, may tend to support the latter hypothesis if it continues."

"After the 1969 gas explosion, Merapi continued to build a lava dome in its summit crater. Since the orifice is not symmetrical, the lava dome becomes unstable as it grows, and portions slide away, producing avalanches and nuées ardentes d'avalanche. The maximum growth of the dome was 3.6 x 106 m3 and the rate of growth was seemingly constant at about 0.1 x 106 m3/month. Intensive sliding usually occurs in rainy seasons, in November annually, and removes 20-30% of the dome's total volume. The lava blocks that slide away from the dome may originate lahars, affecting a large area of the SW sector of the volcano."

Further References. Bardintzeff, J.M., 1984, Merapi volcano (Java) and Merapi-type nuée ardente: BV, v. 47, p. 433-46.

Zen, M.T., Siswowidjoyo, S., Djoharman, L., and Harto, S., 1980, Type and characteristics of the Merapi eruption: Buletin Dept. Teknik Geologi, Inst. Teknologi Bandung, v. I, p. 34-46.

Information Contacts: A. Sudradjat, VSI; M. Matson, NOAA/NESDIS; Jakarta Times.

10/1986 (SEAN 11:10) Rockfall seismicity suggests increased lava dome growth

Between 13 and 17 October, seismographs recorded numerous local rockfall events at rates that reached 300-400/day on the 15th and 16th, suggesting possible increased growth of the lava dome. No A- or B-type shocks were detected. Seismicity declined to background after 17 October. Geologists climbed the volcano 15 October. Heavy steaming was occurring from the lava dome, but rates of SO2 emission had declined slightly to 70 t/d, from typical rates of 100-200 t/d. Temperatures at Woro and Gendol fumaroles remained at ~600 and 800°C.

Information Contacts: I. Bahar, MVO; T. Casadevall, VSI.

11/1986 (SEAN 11:11) Summit lava dome growth

Renewed growth of the summit lava dome began in early October and continued into November. As of mid-Nov, the lava dome volume was 3 x 106 m3. Several hundred rockfalls/day have been occurring since mid-Oct.

Information Contacts: VSI; ANS.

12/1986 (SEAN 11:12) Lava flow from October-November dome advances onto SW flank

Aerial observations 6-7 January revealed no evidence of major new dome growth since Oct-Nov 1986. The volume of the summit crater lava dome was > 4 x 106 m3. From the SW base of the Oct-Nov dome, a lava flow extended through the breach in the crater wall onto the volcano's SW flank, where it continued to advance slowly. Incandescent rockfalls from the toe of the flow, and from the area where the flow emerged from the dome, were observed at night in early January. The number of earthquakes has declined since peaking in late October and early November.

Information Contacts: VSI.

02/1987 (SEAN 12:02) Rockfall seismicity ends; dome growth probably stops

Seismic instruments recorded a significant decrease in the number of rockfall events in late January and early February, suggesting that growth of the October-November lobe of the lava dome had ceased. Rockfall seismicity remained weak through early March.

Information Contacts: VSI.

04/1987 (SEAN 12:04) Lava dome, largest since 1973, appears stable

Merapi was inspected on 9 May. The September 1986-January 1987 lava dome remained stable and was not growing [but see 12:8]. A robust whitish gas plume containing SO2 continued to be emitted from fumaroles on the E side of the lava dome and from the Gendol and Woro fumarole fields. The volume of the new lava dome measured on 9 May was slightly in excess of 4 x 106 m3, the largest since 1973. No rockfall avalanches were noted during April, although several earthquakes/day were recorded.

Information Contacts: T. Casadevall, USGS & VSI.

08/1987 (SEAN 12:08) Lava dome growth, but nuées ardentes de avalanche stop

Comparison of photographs taken during visits to the summit in May, July, and on 8 August, showed that the lava dome continued to increase in volume. Most of the growth seems to have occurred by addition of material to the top of the dome and in its NE sector. No perceptible new growth has occurred on the SW part of the dome. . . .

Information Contacts: VSI.

12/1987 (SEAN 12:12) No lava dome growth from August to November

The volcano was visited by a VSI/USGS team on 19 November. Comparison of photos taken in August and November indicated no significant additional growth of the lava dome.

Information Contacts: VSI.

05/1989 (SEAN 14:05) Large summit dome; fumaroles to 800°C; lahar alert

The volume of the summit lava dome has remained constant since January at ~6.4 x 106 m3. Two active solfataric vents fed a plume that rose to as much as 500 m above the summit. May 1989 temperatures at the vents were [813°C] (Gendol) and [575°C] (Woro). The number of earthquakes recorded . . . near Merapi [is shown in table 3]. No lahars occurred in February, although rainfall was increasing on the volcano's NW sector (while decreasing on the SW sector). An increased lahar alert notification has been released, especially for areas along SW-sector river valleys (K. Putih, K. Blongkeng, K. Krasak).

Information Contacts: VSI.

11/1989 (SEAN 14:11) Large lava dome growing slowly in summit crater

The slowly growing lava dome in the summit crater reached 6.6 x 106 m3 by late 1989, a size described as "critical" for the collapse-prone dome. A white plume rose as much as 250 m from the crater's solfatara field, but under little pressure. COSPEC measurements showed an average SO2 flux of 73 t/d, up slightly from August. No lahar occurred during September, but alert status has been increased with the coming rainy season. Seismicity generally increased in September from August values (table 3). No A-type events were recorded.

Table 3. Seismicity recorded at Merapi, January-February and August-September 1989.

    Month   Collapse   Multiphase volcanic   B-type   Tectonic
    Jan      416           11                 2         70
    Feb      208           24                 0         65
    Mar-Jul                   NO DATA
    Aug      430           50                 2         64
    Sep      609           34                 2        279

Information Contacts: VSI.

07/1990 (BGVN 15:07) Slight increase in seismicity; lava dome volume stable

The number of volcanic earthquakes at Merapi increased slightly during July, with six recorded events/week, compared to 4-5/week in June. During the first week of August, five earthquakes were recorded. Earthquakes associated with collapse episodes on the lava dome were recorded an average of 32 times/week. More than 36 volcanic events were recorded during a swarm in the 24 hours beginning 4 August at 0000. The volume of the lava dome was stable at 6.8 x 106 m3, up from 6.6 x 106 m3 in late 1989. Fumarole temperatures on the dome were measured at 555 and 820°C.

Information Contacts: VSI.

03/1991 (BGVN 16:03) Slight increase in seismicity; no apparent dome growth

Seismic activity increased slightly in early March, from two events/week to an average of 9/week. A swarm of small-amplitude (plus three large-amplitude) shallow volcanic earthquakes occurred on 10 March. The lava dome volume was stable at 6.8 x 106 m3, the same as reported in August 1990 (15:07).

Information Contacts: W. Modjo, VSI; AP.

04/1991 (BGVN 16:04) High-temperature fumaroles; no changes evident to summit dome

No changes were visible at the summit dome, whose volume remained at ~6.8 x 106 m3. Diffuse to dense gas plumes rose to 450 m above the summit. Temperatures of 832 and 543°C were measured at the dome's Gendol and Woro solfataras, respectively. The temperature measured through cracks in the 1956 lava was 86°C on 20 April. There was no significant change in seismicity, although the weekly number of volcanic earthquakes briefly rose to 17 during the second week in April from the long-term average of 1-4. One multiphase event and 3-10 tectonic earthquakes were recorded/week.

Information Contacts: W. Modjo, VSI.

05/1991 (BGVN 16:05) Continued seismicity but lava dome unchanged

Seismic activity remained unchanged, with three volcanic earthquakes recorded during the first week in May, and seven during the last week in May. No changes were visible at the summit dome.

Information Contacts: W. Modjo, VSI.

06/1991 (BGVN 16:06) Gas plumes and seismicity

Diffuse to dense gas plumes rose 475 m in June, with SO2 fluxes averaging 80 t/d. The weekly number of volcanic earthquakes fluctuated, briefly rising to 33 during the third week in June, of which 28 were recorded on the 22nd. Three volcanic earthquakes were recorded below the crater at 3.0-3.5 km depth. An average of two multiphase events and 10-12 tectonic earthquakes were recorded weekly.

Information Contacts: W. Modjo, VSI.

11/1991 (BGVN 16:11) Degassing but no apparent lava dome growth

The volume of the lava dome apparently remained stable at 6.8 x 106 m3, and the temperature of the nearby solfatara was 806°C in early December, about the same as in November. Degassing continued, with the vapor column reaching 300 m height. December COSPEC measurements yielded SO2 emission rates of 73 t/d during the first week and 87 t/d the second week. Average plume velocity was 0.9-3.4 m/second. December is generally a rainy month at Merapi, and geologists were closely monitoring lahar hazards. Moderate seismicity continued to be recorded by nearby instruments (table 4).

Table 4.Local seismicity at Merapi during the first two weeks of December 1991. Courtesy of VSI.

    Dec 91   Volcanic   Multiphase volcanic   Avalanche   Tectonic
    Week 1      3           5                    10          13
    Week 2     13           4                     6           4

Information Contacts: VSI; UPI.

11/1991 (BGVN 17:03) Deformation data from 1988-90; seismicity 1990-91

[The following seismicity and deformation data were excerpted from 17:3] Comparison of distance measurements across the summit in June-July 1988 and September 1990, during to shortly after the later stages of the previous dome-building eruption, showed expansions that reached nearly 1 m (figure 1). Seismic data from 1990-91 show a strong increase in B-type events during the August 1990 crisis. B-type seismicity remained at increased levels through 1991 (figure 2).

Figure 1. Distance changes (in mm) at Merapi, between measurements in June-July 1988 and September 1990. Data collected by B. Voight, K. Young, and staff of the Merapi Volcano Observatory. Courtesy of B. Voight.
Figure 2. Monthly number of volcanic earthquakes (bars) and the inverse of seismic energy release (calculated after Voight, 1988), at Merapi, 1990-91. Courtesy of B. Voight.

Reference: Voight, B., 1988, A model for prediction of volcanic eruptions: Nature, v. 332, p. 125-130.

Information Contacts: B. Voight, Pennsylvania State Univ.

12/1991 (BGVN 16:12) Hot material moves down flanks

The press reported that hot "lava" began moving down Merapi's flanks on 21 January at about midnight. There were unconfirmed descriptions of damage to plantations in one area, but officials reported no evacuations.

Information Contacts: UPI.

01/1992 (BGVN 17:01) Ash ejection; hot flows destroy crops

At about midnight on 21 January, an eruption reportedly began with explosive ash ejection. Accompanying flows of hot "lava" traveled 1.5 km down the flanks of the volcano, destroying rice fields and other crops. A Space Shuttle photograph taken at 0700 on 24 January showed a steam plume, and apparent dusty deposits on the summit area and to the SE. Press information indicated that the volcano continued to erupt on 7 February, with reports of ashfall to ~30 km and additional hot "lava" flows. The estimated 5,000 residents living within a 14-km radius of the volcano were warned by local authorities to be ready to evacuate at any time.

Information Contacts: C. Evans, NASA-SSEOP; UPI; The Jakarta Post.

02/1992 (BGVN 17:02) Lava dome growth and pyroclastic flows

The following supersedes [16:12 and 17:1].

Increased seismicity preceded the start of summit-area lava extrusion that was first observed on 20 January. Deep (A type, 3.1-3.7 km depth) and shallow (B type, <2 km depth) volcanic earthquakes were recorded between mid-Dec 1991 and the first week of January 1992. A growing number of avalanche or rockfall events were detected, with weekly totals that increased from 4 (30 Dec-5 January) to 17 (6-12 January) to 49 (13-19 January). Although rumbling from rockfalls was audible, the summit remained cloud-covered, preventing direct observations.

Glowing rockfalls were first seen on 20 January between 1800 and 2000, emerging from a narrow opening between the NW crater rim (formed by the 1957 lava dome) and the 1984 dome. The rockfalls initially traveled an estimated 125 m from the summit, but they extended farther with time, to ~1,500 m on 31 January (figures 3 and 4). A new lava dome was covering the NW part of the 1984 dome when geologists from the MVO climbed the volcano on 31 January. The 1992 lava was ~50 m higher than the 1984 dome.

Figure 3. Sketch map of Merapi's 1992 lava dome, and the distribution of avalanche-generated, pyroclastic-flow deposits as of 18 February. Courtesy of MVO.
Figure 4. View of Merapi at 0630 on 3 March 1992, drawn by Sadjiman from Jurangjero, ~ 8 km WSW of the summit. Courtesy of MVO.

The first avalanche-generated pyroclastic flow occurred on 31 January at 1535, and three more were detected the next day (table 5).

Table 5. Number of avalanche-generated pyroclastic flows at Merapi, 31 January-2 March 1992. Courtesy of MVO.

    1992    Pyroclastic   Distance from
             Flows        summit (m)

    31 Jan       1              800
    01 Feb       3            850-900
    02 Feb       3          up to 4000
    04 Feb       9            800-1500
    05 Feb       7          up to 1500
    06 Feb       2          up to 2000
    07 Feb       6          up to 3500
    10 Feb       3           1000-1750
    12 Feb       1              800
    17 Feb      20           1500-2500
    18 Feb       3           1500-2000
    20 Feb       5            600-1000
    21 Feb       1             1750
    25 Feb       1              800
    29 Feb       1             2000
    01 Mar       1             2000

The most vigorous pyroclastic-flow activity was on 2 February, when 33 were observed between 1220 and 2221, extending a maximum of 4 km from the summit. These were accompanied by small explosions that were heard 4 km NW of the summit (at Babadan Observatory). Ash rose to 2,600 m above the summit. Sulfur odors were also noted. Volcanic earthquakes were very rare during the eruption.

Pyroclastic-flow intensity then decreased; none have occurred since 2 March, but the lava dome continued to grow as of mid-March. Glowing rockfalls were nearly continuous (>1,000/day since 2 March), but relatively small, extending <2,000 m from the summit, all toward the W. Although the activity occurred during the rainy season (October-April), the 1992 deposits have not been a significant source of rain-generated lahars.

Four alert levels have been established by VSI at Merapi: 1) Notifies residents of increased activity and the need for awareness and caution: 2) More serious precursors require increased awareness; local authorities are requested to prepare for hazard prevention and evacuation: 3) All persons living in the danger zone must pack valuables and items that would supply basic needs during an evacuation: 4) Evacuation required because of explosive eruption and the approach of pyroclastic flows toward inhabited areas.

During the 1992 eruption, Alert Level 1 was announced on 24 January, increasing to Level 2 on 1 February at 2215, and to Level 3 the next day at 1430. As the eruption intensity decreased, the alert level was lowered to 2 on 12 February and to 1 on 2 March.

Information Contacts: S. Bronto, MVO.

03/1992 (BGVN 17:03) Continued lava extrusion; small rockfalls and avalanche-generated pyroclastic flows

Glowing rockfalls continued from Merapi's 1992 dome. They were channeled into the headwaters of rivers on the NW (Senowo), W (Putih), and SW (Bebeng) flanks, extending 300-2,000 m from the dome. The number of rockfalls and multiphase earthquakes generally decreased after late February, although they still dominated seismic records (figure 5). Occasional avalanche-generated pyroclastic flows remained relatively small and traveled a maximum of 2,000 m downslope. The plume was low (to 550 m height), relatively thin, and white. The average SO2 flux measured by COSPEC (figure 6) was 324 t/d through mid-April, with individual measurements ranging from 32 to 419 t/d, the highest on 2 April. As of mid-April, Merapi remained at a Level-1 Alert (see 17:2 for details of the alert system), with summit climbs by the public prohibited.

Figure 5. Merapi's daily number of glowing rockfalls, multiphase earthquakes, and pyroclastic flow events, with amplitudes x durations of glowing rockfalls, January-April 1992. Courtesy of MVO.
Figure 6. Daily average SO2 flux measured by COSPEC at Merapi, December 1991-early April 1992. Courtesy of MVO.

[1988 and 1990-91 seismicity and deformation data were moved to follow 15:7]

Information Contacts: B. Voight, Pennsylvania State Univ.

04/1992 (BGVN 17:04) Continued lava dome growth and rockfalls

Dome growth continued through early May, reaching an estimated volume of 4 x 106 m3. Combined rockfall and pyroclastic-flow volumes were estimated to be <106 m3. The 1992 dome covered the remnant of the 1957 lava dome that had formed the NW crater rim, causing a shift in the primary direction of glowing rockfalls from W to NW, down the upper Senowo River valley. No pyroclastic flows have been observed since mid-Apr (17:03).

Information Contacts: S. Bronto, MVO.

07/1992 (BGVN 17:07) Growing lava dome spawns avalanches; summit gas data

The volume of the lava dome at the end of July was calculated at ~10.5 x 106 m3, of which 2.8 x 106 m3 were pyroclastic-flow and avalanche deposits. Glow from rockfalls tended to become less bright in late July, but the distance traveled by avalanches remained relatively constant, at up to 1,500 m (to the WNW). Gases at the Gendol solfatara field, in the S part of the summit crater, were sampled for analysis (table 6).

Table 6.Gas concentrations (in volume %) and temperatures (in °C) measured at Merapi's Gendol solfatara field, May-December 1992. Courtesy of S. Bronto.

    Gas    06 May  27 Jun  09 Jul  23 Jul  08 Sep  22 Oct  3 Dec
    H2     0.63    1.19    1.33    1.72    1.03    1.09    0.91
    O2+Ar  0.015   0.05    0.09    3.05    0.04    0.02    0.005
    N2     0.11    0.27    0.77   28.23    0.27    0.15    0.23
    CO     0.03    0.04    0.06    0.09    0.05    0.05    0.06
    CO2    4.57    8.48   11.17   29.09    4.46    3.21    4.48
    SO2    0.79    1.57    1.77   10.86    0.71    2.20    0.95
    H2S    0.44    1.35    1.10    1.66    0.32    0.40    1.08
    HCl    0.11    0.29    0.42    6.37    0.17    0.40    0.51
    H2O   93.31   86.76   83.29   18.95   92.96   92.18   91.76
    Temp   802     818     820     813     816     807     824

Information Contacts: S. Bronto, MVO.

10/1992 (BGVN 17:10) Pyroclastic flows follow earthquakes and rainfall; gas data

Gas at the Gendol solfatara field, on the S part of the summit, has been sampled since May 1992 (table 6). The gas analysis from 23 July shows a sharp increase in O2 + Ar, N2, CO2, SO2, and HCl, and a decrease in H2O. Concentrations had returned to previous values by the 8 September sampling. VSI geologists noted that the increase in volcanic gases may have been related to pyroclastic flows generated by dome collapse. Blue sublimates were observed around the Gendol G.13 solfatara field during fieldwork at the summit on 8 September.

Shallow earthquakes (1.8 km depth) occurred beneath Merapi on 26 August at 1314 and 1325, with magnitudes of 1.1 and 1.5, respectively. Pyroclastic flows started at 1331, 1335, and 1341, flowing 2.5 km WNW down the upper Senowo River. Volcano observation stations at Selo (~5 km NNE) and Babadan (~4.5 km NW) reported 21 and 14 mm of rainfall, respectively, in the 2 hours before the pyroclastic flows. There were additional smaller pyroclastic flows on 28 August at 1715, 1909, and 1929. Geologists believe that the pyroclastic flows may correlate with rainfall, volcanic gas activity, and seismicity.

Information Contacts: S. Bronto, MVO.

11/1992 (BGVN 17:11) Pyroclastic flows from growing summit lava dome

The growing 1992 lava dome continued to generate incandescent pyroclastic flows. These advanced down the SW-W flank (along the upper Senowo, Sat, and Bebeng Rivers) to a maximum of 1 km from the base of the dome. White vapor rose 450 m above the dome's summit. SO2 emission measured by COSPEC (from Plawangan Observatory) was 120-230 t/d. No lahars were reported, although rainfall recorded at five volcano observatories around Merapi totaled 160-191 mm/week (in 10-17 episodes/week totaling 1,082-1,580 minutes) during the period ending in early December. No A- or B-type earthquakes have been detected at Merapi for the past 3 months. Multiphase events occurred at rates of 40-50/week, and avalanche tremors at 966-1,108 times a week.

Information Contacts: W. Modjo, VSI.

01/1993 (BGVN 18:01) Pyroclastic flows from growing summit lava dome; highest plume rises 1500 m

Incandescent pyroclastic flows generated by the growing 1992 lava dome continued to advance down the Bebang river in late 1992 and early 1993. Some of the larger rockfalls overflowed into the Bedog and Boyong rivers on the S flank. Pyroclastic flows were visually observed between the end of December and 6 February 1993. On 3 February, the longest pyroclastic flow of this period travelled 4 km WNW down the Senowo and Sat rivers, and the highest plume, rising 1,500 m, occurred at 2200-2206. Rainfall recorded between 1515 and 2310 that same day at five volcano observatories around Merapi totalled 58-94 mm. There has been no increase in seismicity of volcanic gas concentrations (table 6). Blue sublimates are no longer seen around the G.13 solfatara field.

Information Contacts: S. Bronto, MVO.

01/1994 (BGVN 19:01) Avalanches decrease; and seismic spectra for tremor and avalanches

Seismic and visual activity have decreased since the beginning of 1993. In the interval from May-Nov VSI staff reported only 3-10 avalanches/month, as compared to 10 avalanches/day during dome growth in 1992 and early 1993. Some specific cases of tremor, and tremor with avalanche, are depicted on figures 7 and 8.

Figure 7. Three-component seismic record for Merapi during a large tremor (top). Recorded at Klathakan on 3 June 1993, starting at 1542. Three-component maximum entropy spectral analysis for the seismic record above (bottom). Courtesy of A. Brodscholl and K. Brotopuspito, GMU.
Figure 8. Three-component seismic record for Merapi during a tremor and coincident avalanche down the W flank (top). Recorded at Klathakan on 3 June 1993, starting at 1430. Three-component maximum entropy spectral analysis for the seismic record above (bottom). Courtesy of A. Brodscholl and K.S. Brotopuspito, GMU.

About a week after the rainy season began at the end of November 1993, both the tremor rate and the volume of released gas increased. In early December the amplitudes of volcanic tremor rose to 2-3x higher than in previous months.

As of November the VSI supported seven seismic receiver stations at Merapi and the Geophysical Laboratory of GMU supported three. Most of the stations consisted of a vertical-component seismograph with a 1.0 Hz natural frequency. Starting in April 1993 GMU also studied Merapi using a portable 3-component system with a 0.2 Hz cut-off frequency. The portable system collected good quality data at two sites on Merapi: a) Klathakan, 1.8 km WNW of the summit between 1,200-1,300 m elevation (in the interval 1240-1600, 3 June 1993) and b) At Puncak, 0.5 km N of the summit (in the interval 0730-1530, 14 October 1993).

At Puncak, particle analysis on multiple tremor records revealed azimuths that ranged WSW-SW, occasionally swinging to ESE. From these results researchers suggested two possible tremor sources may lie at depth beneath the summit region: one offset slightly toward the W, another toward the E.

At Klathan the seismic record included intervals with tremor and little other noise (figure 7, top). The seismic record also included an interval of tremor coincident with an avalanche, which tumbled and bounced down the W flanks (figure 8, top). These two different signal sources were characterized using spectral response (figures 7 and 8, bottom); both produced spectra with a broad peak centered near 6 Hz. The broad 6 Hz peak is largest for the case of the tremor. But the case of the coincident tremor and avalanche yielded substantial peaks in the low-frequency range (centered near 0.25 Hz and at or below 0.1 Hz).

On the broad 6-Hz peaks the three components differ slightly, particularly with respect to individual spikes on the peaks. For the case of the tremor without the avalanche (figure 7, bottom), the spikes often correspond between the vertical and N-S horizontal (approximately radial), but the spikes of these components often differ from those on the E-W horizontal (approximately tangential). For the case of the tremor and avalanche, the largest spikes occur mainly to the low-frequency side of the broad peak (figure 8, bottom).

These results suggest that for some cases at Merapi an avalanche accompanied by tremor can be discriminated from tremor alone by looking at the low-frequency content of the signal. Other cases, such as typical earthquakes at Merapi, are not discussed here, but it is conceivable that advancing avalanches can be detected seismically as one means of early warning.

Information Contacts: A. Brodscholl and K. Brotopuspito, GMU; S. Bronto, MVO.

03/1994 (BGVN 19:03) Hazard status up: sharp increases in pyroclastic flows, glowing rock falls, and tilt

The number of pyroclastic flows, glowing rock falls, and tilt increased sharply in the past several months (table 7). Both pyroclastic flows and rockfalls with substantial incandescent components traveled as far as 1.8 km (more typically, 0.5-1.0 km) down the SW slopes. In March, the number of these falls increased 1,550-fold over the background value at an undisclosed time (table 7).

Table 7. Merapi activity during 1 November 1993-23 March 1994. Pyroclastic flows have a background level ("bkgd.") of ~60-120 flows/month. In 1994 they ranged from 5-47x the background level. The background level for rockfalls was undisclosed. The RSAM curve refers to a measure of seismic power output.

                  1993            1994
                  Nov     Dec     Jan     Feb    1-23 Mar
 
    Pyroclastic   bkgd. bkgd.  5x      9x       47x
    Flows
    Rockfalls     297x    409x    599x    827x    1,550x
 
    SO2 flux (metric tons/day)
    Variation    31-188  41-108  37-151  64-162   65-197
    Average        91      66      81      73      123

    RSAM
    bkgd.       ~13     ~14     ~16     ~17      ~16
    max.        ~13    1@~22    ~18     ~18     2@>24

Tiltmeters were installed in November 1992 on the crater rim near the contact with the 1992 dome. Beginning in July 1993 they showed a consistent outward rotation of ~5 µrad/day, achieving a change of 1,200 µrad overall through the end of March 1994. A measure of seismic power output (RSAM) also showed cumulative increases during November 1993-Mar 1994, indicating heightened seismic activity (table 7). During this interval the SO2 flux data were less compelling, but also showed both overall and generally progressive increases in the smallest values measured for any one interval (table 7).

Based on these monitoring data VSI proposed a shift in the hazard status, from "Normal Activity" to "First Alert Level."

Information Contacts: W. Tjetjep and R. Sukhyar, VSI; S. Bronto, MVO; UPI.

07/1994 (BGVN 19:07) Increased deformation precedes a nuee ardente

A nuée ardente erupted around 1400 on 16 July 1994, an event preceded by a clear increase in tilt several days before the eruption. Figure 9 shows tilt measurements during the interval 1-18 July. One set of measurements came from a site on Merapi's summit (Goa Jepang, ~2,900 m elevation); the other set of measurements came from a cave on Merapi's S flank (~1,000 m elevation).

Figure 9. Tilt at Merapi recorded at both the summit and in a cave on the S flank, 1-18 July 1994 Courtesy of Arnold Brodscholl.

The daily temperature variation in the cave is <1°C, suggesting little influence from temperature there (left-hand scale). The daily record of tilt varied significantly less at the cave site (typically <100 µrad) than at the summit site (typically ~150 µrad), an observation consistent with the more stable temperature in the cave.

Tilt began increasing at both sites roughly five days prior to the eruption. During this interval the tilt at both sites correlated consistently overall, and moderately at the finer-scale. Tilt ceased to track consistently near the end of the eruption, when the flank site underwent a dramatic decrease, a turn-around that began prior to the end of the eruption. Summit tilt measurements in January 1993 were similar to those presented here but then measurements at the cave site were a rarity, leaving the increased tilt without confirmation.

Information Contacts: A. Brodscholl, GMU; Subandryo, VSI; B. Voight, Pennsylvania State Univ.

08/1994 (BGVN 19:08) Two new broad-band seismometers detect long-period pulses and tremor

Two STS2 broad-band seismometers were deployed on 27-29 July by collaborators of the Geophysical Laboratory of GMU and Martin Beisser of GFZ-Potsdam. The researchers investigated signal coherency at different points on the volcano to find suitable sites for a multi-station seismic array that will make permanent records at a 50-Hz sampling rate. The researchers measured Merapi seismicity at a base station located at Klathakan (1.8 km WNW of the summit between 1,200-1,300 m elev), the site of a seismic station for the last eight years. The second station was mobile and GPS-equipped; however, for the following comparisons and discussion the mobile site remained 400 m N of the base station.

Figure 10 shows amplitude data for three components of volcanic shock from the mobile station. The volcanic shock event that began at 1750 and 37 seconds on 27 July is here termed Event A. Figure 11 shows the arriving signals and allows for a visual comparison of the coherency in the vertical component (top two plots), and two orthogonal horizontal components (lower four plots). From visual inspection, the best coherency appeared in the vertical-component data. Some other types of events received appeared to show less coherency between the two sites.

Figure 10. A seismic event on Merapi received at the mobile station showing 3-component amplitude data. The event shown began at 1750 and 37 seconds on 27 July 1994 and is termed "Event A." Courtesy of A. Brodscholl.
Figure 11. The first five seconds of Event A on Merapi (27 July 1994) as received at the broadband base and mobile stations (400-m separation). The records show considerable coherency. Courtesy of A. Brodscholl.

Figure 12 shows three components of a previously undetected tremor type, a tremor preceded by or superimposed on a long-period pulse. On the record, the interval of greatest short-period amplitude came after the pulse's maximum. Examples of this kind of tremor were seen three times in 12 hours. Whether these events are common on Merapi and elsewhere still remains uncertain.

Figure 12. Merapi seismic record from the mobile station showing an example of tremor coming after the maximum of a long-period pulse. These pulses and temporally associated tremors were seen three times in a 12-hour period and were not previously detected. Courtesy of A. Brodscholl.

[The reported low-frequency signal was later found to be caused by instrumental problems not recognized at the time of submission.]

Information Contacts: M. Beisser, GFZ-Potsdam, Germany; A. Brodscholl, GMU.

10/1994 (BGVN 19:10) Pyroclastic flows on 22 November kill at least 41 people on the SSW flank

Collapse of the active summit dome on 22 November produced pyroclastic block-and-ash flows and glowing surges that traveled SSW up to 7.5 km from the summit (figure 13). As of 28 November, 41 people had died and another 43 were at hospitals in serious condition. All of the victims lived in areas near the banks of the Boyong River. That river flows off Merapi's S flanks and, at ~28 km map distance from the summit, passes through the city of Yogyakarta (population ~50,000). The threats to areas on Merapi's S flank were noted in February 1994, when rockfalls were first observed and reported along the Boyong River. Every month since March, the possibility of SW-flank destruction had been mentioned in Berita Merapi (Merapi News) informing local governments, including Sleman Regency (where this disaster took place), of hazards posed by nuées ardentes. Rockfalls from the dome have recently traveled down the Boyong and other rivers for distances of 500-1,500 m.

Figure 13. Deposits of the Merapi eruption of 22 November 1994 shown on a 500-m-contour base map of the SW quadrant with the primary drainages and some towns labeled. Courtesy of Sukhyar, MVO.

The eruption was preceded by low-frequency earthquakes on 20 October. Multiphase seismic events and rockfalls continued to be recorded at normal levels, with occasional low-frequency events, but one tremor episode occurred on 3 November. On 4 November this change in seismic behavior was reported to the Chief of Regencies. During 21-22 November, a team from MVO climbed to the summit to observe dome development and to install an extensometer station to measure the offset along cracks.

The first nuée ardente was recorded instrumentally at 1014 on 22 November, and was observed visually from the Plawangan, Ngepos, Babadan, and Jrakah observation posts. The team at the summit saw a vertical plume that originated from a location somewhere on the S part of the dome.

The intensity of the nuées ardentes increased at 1020, prompting the observer at Plawangan to send a warning to the forestry officer at Kaliurang (figure 13), a well-known tourist resort. The officer then yelled a warning to the local people. Five minutes later (1025) MVO instructed all observation posts and radio stations of the Regional Task Force that the alert status had been raised to the highest level (Level 4), and that evacuations should begin. At 1045 the observer at Plawangan sent a message to the Chief of Pakem District, but he was already in the field, probably because he had heard the previous warning. Another evacuation warning was radioed to regional task forces at 1100. By 1215 the first victim had been discovered. The Plawangan observation post was abandoned at 1508 and the personnel temporarily moved to Kaliurang. The nuées ardentes had diminished by 1720 that evening.

A NOAA/NESDIS volcano hazards alert stated that at 1346 on 22 November a plume rose to ~10 km. At that time winds aloft were toward the W at 18 km/hour. These same points were repeated in an aviation safety alert (NOTAM).

A UNDHA report on 23 November stated that 25 of 40 employees building a water treatment facility were still missing, while 15 were found dead. Evacuees totalled 6,026 from the neighboring villages in the subdistrict of Pakem. Evacuation and emergency response measures had been undertaken by the local authorities and community members. The UNDHA reported that local volcanology officials advised authorities and local people to remain on alert for seven days.

A 23 November Tokyo Kyodo broadcast (in English) reported "Indonesia's team for disaster safety in Yogjakarta said ash rain has reached Temanggung, ~45 km NW of Merapi." A UPI news report stated that, on the morning of 23 November, an official of the natural disasters office in Sleman said that 118 people were in three hospitals suffering from serious burns. The report further stated that "hundreds of homes have collapsed and thousands of cattle were buried by ash." On 26 November UPI reported that >4,700 people remained in evacuation centers.

According to press accounts and other information collected by the U.S. Embassy and issued on 23 and 25 November, most of the casualties occurred when superheated gases swept through two small villages (Desa Purwobinangun and Desa Hargobinangun in the Sleman district). The eruption ignited ~500 hectares of rainforest near Kaliurang, which press reports said had been damaged by ashfall. Embassy reports on 25 November stated that an estimated 34-200 people were still missing (there had been no communication with some affected villages on the slopes of the volcano). Well over 500 injured persons had been treated at local hospitals. The 25 November Embassy report said that "Local authorities are now concerned about an accumulation of volcanic material [on Merapi's flanks]. It is feared that the approaching rainy season could dislodge this material (estimated in the range of 11 million m3) causing dangerous [mudflows] in the villages below. City officials in Yogyakarta . . . are reported to be constructing a third catchment dam to regulate volcanic material entering the Code river, which runs through the city."

A 23 November Reuters press report stated that "The official Antara news agency said that despite warnings, local people were reluctant to leave the area, regarding the volcano as sacred and likely to offer some supernatural signs if it were to cause a major disaster."

Information Contacts: Sukhyar, MVO; SAB; UNDHA; AP; Reuters; UPI; ANS.

12/1994 (BGVN 19:12) Pyroclastic flows continue through 7 December

Collapse of the active summit dome on 22 November sent pyroclastic flows down the SW flank (19:10), overrunning several villages. Although no eruption column was described by VSI observers, aviation warnings on the 22nd stated that ash rose to 10 km; satellite analysis the next day indicated that the plume was a low-level feature well below 6 km. As of 7 December, the UNDHA had confirmed 58 deaths; an Antara news report on 19 December placed the number at 60. Indonesian and Japanese medical teams conducted life-saving plastic surgery on 22 critically injured burn victims.

Continuing small eruptions through 7 December sent pyroclastic flows up to 1.5 km down the Boyong River. An estimated 1 x 106 m3 of pyroclastic sediment has been deposited along the Boyong River, while another 12 x 106 m3 remains on the slopes near the crater. Geochemical analysis in late November indicated increased SO2 emissions of up to 44 t/d.

Most of the >6,000 evacuees were allowed to return home in early December. However, local authorities decided that 2,700 evacuees from five villages within 5 km of the summit in Sleman District (Turgo, Kinahredjo, Kaliadem, Tritis, and Ngandong) would be resettled locally. Although pyroclastic flows had damaged the spring-water source that supplies clean water to the Kaliurang Hill Resort, part of it was reopened on 19 December; the W part was not reopened because it was still considered dangerous.

Residents along the Code River (15,000 people in 11 villages) in Yogyakarta were alerted to the possibility of evacuation, because heavy rainfall in the Boyong River drainage could trigger cold lahars. Existing lahar control works and sabo dams have been constructed on the W side of the volcano in the Magelang District. The Boyong River has only two sabo dams with a capacity of 400,000 m3. The Indonesian government plans to construct three sabo dams of 350,000 m3 capacity each, downstream from the Boyong River.

Information Contacts: UNDHA; Reuters; ANS; BOM Darwin, Australia.

02/1995 (BGVN 20:02) Seismic data associated with the 22 November 1994 dome collapse

Workers at the GMU Geophysical Laboratory and Martin Beisser of GFZ-Potsdam recorded seismic data during the [summit lava dome] collapse from their station at Klathakan, 1.8 km WNW of the summit. Their broad-band seismic instrument showed the associated disturbance beginning on 22 November at 1007 and 32 seconds (radial-component data shown on figure 14). So far as the GMU and GFZ workers know, the wide dynamic range of their broad-band instrument preserved the event with a minimal amount of high-amplitude signal "clipping." Also, in their interpretation, the collapse and seismic disturbance began simultaneously. In other words, the initial displacement at the beginning of the seismic record is thought to correspond to the arrival of signals from the inception of the collapse.

Figure 14. Seismic record for the Merapi 22 November 1994 dome collapse. The component shown is horizontal, radial to the edifice; amplitude scale is arbitrary. The data were recorded on a data logger connected to a Streckeisen STS2 seismometer (with a 50 Hz sampling rate, a 8.33 mHz to 50 Hz linear response, and a 32-bit analog-to-digital converter). Courtesy of A. Brodscholl and K. Brotopuspito.

The collapse-related seismic event lasted for almost an hour (figure 14). The initial signals were set against a moderately quiet background, and maximum amplitude generally increased with time. Highest-amplitude signals were received ~40 minutes after the event began. These largest signals had amplitudes that reached approximately 30 mm/second, whereas at the beginning of the collapse the maximum amplitudes were only ~0.05 mm/second. Thus, on the seismic records, amplitudes ultimately grew to 600x as large as the initial signals.

The eruption and collapse also appear in a 200-hour time window showing measured seismic amplitude in specified wavelengths (figure 15). The figure was prepared using signal processing techniques, which for the high frequency (0.1-1.0 Hz) data involved significant averaging of the maximum values (to once an hour). These depictions show that one or two noteworthy seismic disturbances took place at ~150 and 180 hours prior to the collapse (cause unknown). Compared to the other seismic disturbances on these records, the collapse and eruption induced larger amplitude and much more sustained signals. The post-collapse signals were also followed by an interval of at least 10 hours of elevated background (most noticeable in the 1-12 Hz range).

Figure 15. Radial component of the Merapi 22 November 1994 dome collapse showing a seismic amplitude (arbitrary scale) versus time for stated wavelength ranges. The inception of the collapse lies at the zero point of the time scale. Courtesy of A. Brodscholl and K. Brotopuspito.

Using the available data, the investigators failed to find any clearly related premonitory seismic signals for the collapse. Sufficient collateral data (for example, teleseismic and meteorological data) might help constrain detected collapse and eruption earthquakes, or shed light on the cause of the pre-collapse seismic disturbances.

Since our last report (19:12), continued dome building occurred at Merapi. On 5 January another collapse brought 1 x 106 m3 of debris downslope. This collapse produced a small pyroclastic flow on the S slope.

Information Contacts: A. Brodscholl and K. Brotopuspito, GMU; M. Beisser, GFZ-Potsdam, Germany; W. Tjetjep, VSI.

10/1995 (BGVN 20:10) Pyroclastic flows travel down two river drainages

During August-October 1995 pyroclastic flows ("glowing avalanches") continued flowing down the Boyong River; others entered the Krasak River and reached ~1-1.5 km from the source. Seismic activity was dominated by multiphase and lava-avalanche (rockfall) earthquakes. The number of multiphase earthquakes increased in October to 793 events, compared to 186 in September. Earthquakes associated with lava avalanches or rock falls gradually decreased from 1,195 events in August to 806 in September and 605 in October (figure 16). Shallow volcanic (B-type) earthquakes (~1 km depth) were recorded on 25 October and a deep volcanic (A-type) earthquake (2.7 km depth) was detected on 30 October. Observations in October indicated an inflation associated with 40 µrad of tilt. Measurement of SO2 by COSPEC indicated that the emission rate during October fluctuated between 18 and 112 t/d (average 63).

Figure 16. Seismicity at Merapi, June-October 1995. Courtesy of VSI.

Information Contacts: W. Tjetjep, VSI.

01/1996 (BGVN 21:01) Increased seismicity related to lava avalanches and rockfalls

During November-December 1995 glowing avalanches down the Boyong, Krasak, and Bebeng rivers reached up to 2.5 km from the source. Seismic activity was dominated by multiphase earthquakes, low-frequency earthquakes, and lava avalanches (rockfalls). The number of multiphase earthquakes decreased from 924 in November to 152 in December; low-frequency earthquakes also decreased from 74 in November to 42 in December. Seismicity associated with lava avalanches and rock falls increased from 816 events in November to 1,078 in December (figure 17). A deep volcanic earthquake (A- type) and two tremor events were recorded in November, three shallow volcanic earthquakes (B-type) occurred in December.

Figure 17. Monthly number of rockfall, multiphase, and low-frequency earthquakes at Merapi, June-December 1995. Courtesy of VSI.

Inflation increased since 17 November from 2.5 to 10.8 µrad/day. Tilt data collected at two stations in the summit area during November and December indicated inflation of 60 and 320 µrad, respectively. The geomagnetic intensity in early December was -14.5 nTs; it then decreased to -1.5 nTs by the end of the month. The emission rate of SO2 during November fluctuated between 27 and 275 t/d, averaging 95 t/d, and the plume velocity was ~3.2-3.5 m/s. In December the emission rate decreased to 70 t/d, fluctuating between 18 and 156 t/d; plume speed was slightly higher at 3.3-3.6 m/s.

Information Contacts: Wimpy S. Tjetjep (Director), Volcanological Survey of Indonesia (VSI), Jalan Diponegoro 57, Bandung, Indonesia; Steve O'Meara, PO Box 218, Volcano, HI 96785, USA .

08/1996 (BGVN 21:08) Increasing eruptive activity prompts preparations for evacuation

A news report in early August noted that emission of thick clouds from the crater had increased significantly. Emitted clouds and "glowing lavas" reportedly blackened the peak of the mountain. Villagers living on the slope of Merapi were apparently told to make preparations for possible evacuation.

On 13 September a pilot report from Qantas Airlines stated that an ash cloud had been observed above Merapi to ~6 km altitude. In a communication with the Darwin Volcanic Ash Advisory Center, the Merapi Volcano Observatory reported no significant change in the eruptive status, consisting of small ash clouds being produced. No plume was evident on satellite imagery.

Information Contacts: Xinhua News Agency, 5 Sharp Street West, Wanchai, Hong Kong; Bureau of Meteorology, Northern Territory Regional Office, P.O. Box 735, Darwin NT 0801, Australia.

10/1996 (BGVN 21:10) Peak in volcanism on 31 October results in over 15 pyroclastic flows

Sometime between 1417 and 1930 on 9 August, a pyroclastic flow traveled 3.5 km from the summit down the SSW flank, reaching the upper parts of the Krasak and Boyong rivers. No casualties were reported, and neither A- nor B-type volcanic earthquakes were recorded.

During September white plumes rose above the summit solfarata field. From the second week of September, multiphase volcanic earthquakes, which are dominant at Merapi, rose sharply to 1,398 events/day. This seismic increase accompanied growth of the lava dome. After the 9 August pyroclastic flow, the volume of the remaining lava dome was ~100,000 m3. The dome volume was estimated at 4.5 x 105 and 7.5 x 105 m3 on 24 September and 11 October, respectively, based on Celestron photographs. The growth rate of the lava dome was estimated at 17,050 m3/day on 11 October, much higher than usual (3,000-5,000 m3/day).

Multiphase earthquakes again increased with 3,804 events registered on 24 October. These earthquakes showed harmonic patterns, which had never been recorded before at Merapi. At 1533 on 24 October, four pyroclastic flows descended toward the upper reaches of the Krasak and Boyong rivers, and traveled a maximum of 2.5 km from the summit. No casualties were reported.

Between 0000 and 1800 on 27 October, multiphase earthquakes suddenly decreased with only 32 events recorded. However, multiphase earthquakes increased again on 30 October with 693 events during a period of six hours. From Celestron photographs on 29 October, it was estimated that the lava dome was 11 x 105 m3 in volume with a daily growth of 17,500 m3. The height of the dome also increased from 42 to 48 m during 11-29 October. At 1813 on 28 October, a pyroclastic flow descended into the upper part of the Krasak River, and the next day (0133 and 1633 on 29 October) two more pyroclastic flows followed. At 0714 on 30 October one pyroclastic flow was observed to move down toward the upper part of the Sat River from the 1992 lava dome. The tiltmeter at Station 2 indicated increasing deformation (>310 µrad) from 9 August to late October, consistent with increasing seismic and eruptive activity.

Volcanic activity reached a peak on 31 October. At 1544 a series of pyroclastic flows began to be observed. They traveled from the summit to the upper reaches of the Bebeng, Krasak, Boyong, and Kuning rivers. From 1544 to 1650, seventeen pyroclastic flows were recorded. The biggest ones occurred at 1637 and 1640, respectively, with a maximum runout of 3 km. Between 1718 and 2117, dense clouds hampered direct observations, but seismic information indicated nine small pyroclastic flows. During 2125-2155 thin ashfall (0.5 mm in thickness) was reported at Babadan Observatory (4 km W of Merapi). From 2130 to 2352 seven pyroclastic flows descended into the Krasak, Bebeng, and Boyong rivers, with a maximum runout of 3 km.

Pyroclastic flows decreased the next day (1 November) and ceased on 2 November. Five pyroclastic flows were observed to travel 1 km from the summit between 0000 and 0514 on 1 November. From 2 November, the lava dome showed no signs of significant growth, and the number and released energy of multiphase earthquakes also declined. However, rock-fall avalanches slowly increased.

Information Contacts: Mas Atje Purbawinata, Director, Merapi Volcano Observatory, Jalan Cendana 15, Yogyakarta 55166, Indonesia; Wimpy S. Tjetjep, Director, Volcanological Survey of Indonesia, Jalan Diponegoro 57, Bandung 40122, Indonesia (Email: vsimvo@ibm.net).

06/1997 (BGVN 22:06) Pyroclastic flows and vigorous plumes noted in first half of 1997

The Societe Volcanologique de Geneve (SVG) reported that on 11 January a member of the Volcanological Survey of Indonesia (VSI) noticed the emplacement of ~ 400,000 m3 of material on the dome. On 14 January, at 0930 the first of many pyroclastic flows was observed. During the following 10 hours 81 pyroclastic flows ran down the flanks, reaching as far as 4 km. Tremors and volcano-tectonic earthquakes were recorded. On 17 January a strong explosion threw a 4,000-m-high column above the crater and another pyroclastic flow raced down the slopes at 1040.

The National Coordinating Board for Disaster Management (BAKORNAS PB) of the Indonesian Government later announced that an eruption took place at 1035 on 17 January. Heavy rains on 17 and 18 January in surrounding areas could have caused mudflows. Reuters reported that about 5,000 people living near Merapi were evacuated from their villages after the volcano started spewing burning ash and hot lava. By 18 January the volcanic activity started decreasing. On 24 January the volcano began spewing hot clouds again; many of the evacuees returned home despite the warnings. According to local newspapers, six people were missing, several were injured, and many had been blinded by the heat clouds, but none were dead. Damage included hundreds of hectares of crops burned.

SVG also reported that a new crater had formed within the 1992 lavas and the early- 1997 lavas. A new dome was growing inside this crater; its volume was estimated to be 160,000 m3. On 22 March and 29 June 1997 Qantas flights over Merapi reported ash at ~ 6.1 and 10 km altitude, respectively. In both cases, however, satellite imagery failed to confirm the plumes because of high clouds.

From 12 to 15 April a field party from the European Volcanological Society (SVE) observed the volcano, from Kaliungarang village, ~6 km from the dome; later they moved to closer positions. They reported pyroclastic flows and rockfalls with frequencies of 5-10 events/hour; the longest runout distances were 2 km from the summit. Of these rockfalls, only a few were made of incandescent materials, indicating that the others involved remobilized older material. A plume was almost always present at the summit.

Information Contacts: M. Vigny and P. Vetsch, Societe de Volcanologie Geneve (SVG), B.P. 298, CH-1225, Chenebourg, Switzerland; Reuters; Department of Humanitarian Affairs, United Nations, Palais de Nations 1211 Geneva, Switzerland (Email: dhagva@un.org); Henry Gaudru and Patrick Barons, European Volcanological Society (SVE), C.P. 1, 1211 Geneva 17, Switzerland (Email: 101626.3303@compuserve.com); Bureau of Meteorology, Northern Territory Regional Office, P.O. Box 735, Darwin NT 0801, Australia.

12/1997 (BGVN 22:12) Intermediate hazard status posted during September 1997

The following summary from the Merapi Volcano Observatory (MVO) describes the situation in September 1997. The alert status was "Waspada Merapi," the second of four progressive stages of alert, for all of September.

Visual accounts of activity were made from five observation posts surrounding Merapi, usually in the morning. A thin, white plume rising under low pressure was seen consistently. The plume rose 400 m above the summit in the first part of the month but attained heights of up to 1,000 m later in September. Low- and moderate- energy rockfalls containing glowing material occurred on the SW flanks, in the Sat, Krasak, Bebeng, Boyong, and Senowo river valleys, running to a maximum of 2.5 km from the summit. A persistent red glow was observed at the dome. No pyroclastic flows were reported in September.

Seismicity decreased in frequency in early September compared to August (table 8). Shallow earthquakes, such as multi-phase and rockfall types were most common. Data from tiltmeters indicated inflation in most areas in the first week of September. No significant changes were seen later in the month. Photographic evidence suggested no major change in the dome volume.

Table 8. Earthquake activity at Merapi during 11 August-21 September 1997. Courtesy MVO.

    Type       11-17 Aug  18-24 Aug  25-31 Aug  1-7 Sep  15-21 Sep

    Low-freq       4          1          1         -         -
    Multi-phase  132        136        112       102        67
    Rockfall     289        330        295       262       298
    Tectonic      26          3          4         4         2

On 9 January 1998 the Associated Press reported a warning of potentially dangerous eruptive activity at Merapi. The warning followed observation of a significant amount of fresh lava at the summit. Local experts warned nearby residents to prepare for quick evacuation to avoid the effects of nuées ardentes and of the danger of debris slides following heavy rain.

Information Contacts: Mas Atje Purbawinata, Director, Merapi Volcano Observatory, Jalan Cendana 15, Yogyakarta 55166, Indonesia (URL: http://www.vsi.esdm.go.id/).

07/1998 (BGVN 23:07) Increasing activity culminates in mid-July pyroclastic flows

Seismic activity and avalanches increased significantly at Merapi beginning in June, and reached a climax in mid-July. According to Xinhua News Agency reports, pyroclastic flows and ashfall near populated areas caused concern among Volcanological Survey of Indonesia (VSI) scientists and civil authorities; evacuations were considered. VSI ranks alert status as follows, in increasing level of concern: Normal, Waspada, Siap, and Awas.

Increasing eruptive activity during the last week of June prompted officials to increase the alert level to Waspada on 2 July. As activity progressed to more dangerous levels, the alert status increased to Siaga at 0500 on 8 July, eventually reaching Awas at 0438 on 11 July, before returning to Siaga at 1200 on 12 July. A solfatara plume was observed during late June and early July; gases escaped with varying pressure to form a thin (or sometimes thick) white cloud attaining maximum heights of 1,400 m above the summit in the first week of July, and 2,000 m by 11 July. Avalanches extending as long as 1.5 km coursed through the upper portions of the Senowo river, and others were seen in the Lamat, Krasak/Bebeng and Boyong rivers (figure 18). Glowing at the summit resumed in late June. During the reporting interval seismic activity showed a significant increase; specifically, the number of shallow volcanic (B-type), multi-phase (MP), low-frequency (LF), and rockfall events increased sharply (table 9).

Figure 18. Contour map of Merapi's southern segment indicating locations referred to in the text. Courtesy of Merapi Volcano Observatory.

Table 9. The number of daily seismic events of various types at Merapi as recorded from mid-June to mid-July 1998. Data courtesy of VSI's Merapi Volcano Observatory.

    Type      15-21    22-28    29 June-    7-12    17-21
              June     June      6 July     July    July

    B-type      4        3         47        21       19
    LF          -        -          3         1        2
    MP         33       45        925     2,029      605
    Rockfalls   5       15        142       613      860
    Tremor      -        -          -         -        2
    Tectonic    4        3          5         2        1

The amount of measured deformation also increased (although the summit tiltmeter station was rendered inoperative after 8 July). Explosions on 11 July could be heard as far away as 20 km S in the city of Yogyakarta. VSI noted, "lava was seen ejecting from the crater." In addition, and presumably with undue exaggeration, Xinhua news reporters claimed that some areas near the volcano were under 1.5 m of ash that blanketed crops and plantations.

On 19 July, Babadan Observatory located 4 km W of the summit reported three 'guguran' (pyroclastic flows resulting from dome collapse in the crater). These occurred between midnight and 0600, some reaching as far as 2,500 m down the Lamat River. VSI also noted a "thick white solfataric ash plume"; it stood 50 m in height and was observed from Kaliurang beginning at 0545. Pyroclastic flows during the remaining morning ran 5,000 m down the Lamat River valley, and an eruptive column rose up to 4,500 m above the summit. Between 0600 and 1313, seismic stations recorded 347 multiphase (MP) events. Tremor occurred between 1325 and 1503 and was accompanied by five pyroclastic flows that reached 2,000-5,000 m from the summit. At 1330 VSI ordered workers on the W sector of the volcano to leave the area. At 1501 Merapi erupted violently; several pyroclastic flows traveled 5,500 m down Lamat River and an eruptive column rose up to 6,000 m above the summit by 1507. At about 1615 ash showered the W side of the volcano, accumulating up to 2 mm in Muntilan. Ash also fell in Purworejo (42 km W of Yogyakarta) and Temanggung (35 km NW of the crater). Shallow volcanic earthquakes at 1625 were followed by small tremor. As many as 25 pyroclastic flows continued until 1800, some causing ash showers in nearby villages. There were B-type events (16), MP events ( 399 ), pyroclastic flows (119), and some glowing rockfalls throughout the afternoon.

Activity had subsided by 21 June, although fog obscured the summit area. Thick white ash rose to 460 m. Glowing rockfalls sometimes ran 1,250 m down the Lamat River valley.

This hazardous stratovolcano is located 70 km SE of Dieng and immediately N of Yogyakarta, a city of half a million people. In 32 of its 67 historical eruptions, nuées ardentes took place-more than known at any other volcano in the world-and 11 of them have caused fatalities. The volcano is carefully watched by several VSI observatories and heavily monitored instrumentally.

Information Contacts: Mas Atje Purbawinata, Director, Merapi Volcano Observatory, Volcanological Survey of Indonesia, Jalan Cendana 15 Yogyakarta 55166 (Email: mvopgm@yogya.wasantara.net.id, URL: http://www.vsi.esdm.go.id/); Xinhua News Agency, 5 Sharp Street West, Wanchai, Hong Kong.

08/1998 (BGVN 23:08) Details of July eruptions, new monitoring equipment

The relative calm in seismic, gas, and rockfall activity at Merapi ended in late June (BGVN 23:07). Activity since November 1994 had been concentrated on the S of the volcano, but activity in July occurred mainly on the W slopes. Further details of the July eruptions are reported below, followed by an account of new monitoring equipment.

Changes in the measured tilt began in early June on the W flank, forecasting an increase in activity. Tilt increased at the end of June and an extension of 1 m was detected by electronic distance measurement during the first week of July. Also, the tilt measured by station ST3, located at the crater rim near the active dome, showed strong inflation at extraordinarily high rates of up to 200 µrad/hour. This high tilt rate was likely influenced by heat radiated from the new dome; an accurate estimate of tilt with this effect removed remains problematic. After the nuée ardente of 8 July, no further signals from ST3 were recorded and an early August field trip failed to find any remnants of the station.

Increases in accumulated seismic energy indicated an approaching change in the eruption regime. Soon after a small explosion on 30 June a plume emerged from the summit and a glowing avalanche rushed down the W slope. The explosion opened at least one hole on the W slope close to the summit. New lava was squeezed out of the opening "like toothpaste" without friction or pressure; the volcano seemed to be partially open. During the next week, avalanches connected to new dome building were observed from Babadan on the W slope. Based on observation of these avalanches, the nuée ardente on 8 July was expected. The daily number of rockfalls increased strongly from a few, to dozens, and then to more than 100; some rockfalls were glowing.

Seismicity (especially multi-phase events) strongly increased in early July (figure 19) before peaking on 11 July when 37 nuées ardentes occurred between midnight and 0500. The most powerful eruption that day happened at 0445; volcanic material flowed 4 km from the summit. The plume reached a height of ~4 km and ash was distributed 15-20 km away. During 11-19 July, 128 nuées ardentes were seen, including a final strong pyroclastic ash-and-block flow at 1500 on 19 July. Seismic activity, except the number of rock falls, decreased after 19 July. Four episodes of volcanic tremor were recorded in July (usually during vigorous eruptive activity), indicating magma movement. The dome grew briskly without special seismic activity, although much of the new lava collapsed, causing hundreds of daily avalanches. Many local residents watched huge glowing rockfalls at night on the W slope.

Figure 19. A graph of rockfall (avalanche) and multi-phase seismicity recorded at Merapi during 15 June-12 August 1998. Data courtesy of MVO.

Explosion sounds were heard only close to the dome (for example, in Klatakan but not in Babadan). On 30 June a seismologist working on the W slope in Klatakan on an active seismic experiment heard a sharp noise at about 1130 that preceded both a plume and pyroclastic flows.

Some W-side stations were covered with more than 2.5 cm of ash. Pyroclastic-flow deposits filled parts of a valley on the W slope, almost reaching the town of Jerung Jeru, 7 km from the summit. The total amount of material erupted during July was estimated to be 8.8 x 106 m3. The huge amount of ash released during July suggested an explosive process rather than gravity collapse, as happened in November 1994 when far less ash was emitted.

New seismic warning installations. German scientists Joachim Wassermann and Juergen Gossler installed an infrasonic network at Babadan on the W slope. Three clusters, each with four microphones installed in tubes directed at the summit, collect infrasonic noise.

Infrasonic noise was recorded beginning three days before the events of 19 July. The data showed a good correlation between seismicity and infrasonic signals during avalanche and lahar activity. A signal recorded before the main pyroclastic flow could have been a precursory event. A volcanic explosion was recorded before 19 July by a member of the active seismic experiment group during fieldwork at Klatakan. No event was heard in Babadan at that time, but the subsequent avalanche was recorded. A few explosions may have occurred earlier in the month, but no acoustic signals were detected, probably because Babadan is too far from the source.

A broad-band seismic station was installed on Pasar Bubar, on a plateau just below the summit, to complement the three stations on the slopes of Merapi. A program is under development that would select different signals automatically and thus enable a "quasi-online calculation" for the hypocenters and epicenters of volcanic events. Infrasonic data together with seismic data could be sent to the Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPTK") of VSI to improve the early warning system. Combined data from the same site would help in locating volcanic events and could provide information about source mechanics.

Information Contacts: Volcanological Survey of Indonesia (VSI), Bandung, Indonesia (URL: http://www.vsi.esdm.go.id/); Mas Atje Purbowinata, Merapi Volcano Obsevatory, Jalan Cendana 15 Yogyakarta 55166, Indonesia (Email: mvopgm@yogya.wasantara.net.id, URL: http://www.vsi.esdm.go.id/mvohomepage.html); A. Brodscholl, BPPTK, Volcanological Survey of Indonesia, Bandung, Indonesia (Email: arnoldb@idola.net.id); J. Gossler, GeoForschungs Zentrum (GFZ), Potsdam, Germany (Email: gossler@gfz-potsdam.de); J. Wassermann, University of Potsdam, Potsdam, Germany (Email: jowa@geo.uni-potsdam.de).

05/1999 (BGVN 24:05) Frequent lahars, lava avalanches, and pyroclastic flows during March-May

Merapi remained active throughout the reporting period of 9 March through 24 May. Although no deaths were reported, the volcano continually threatened surrounding populated areas with lahars, lava avalanches, and pyroclastic flows. Throughout the period, Merapi exhibited weakly pressured, thick, white, sulfur-tinted ash plumes extending 100-700 m above the summit.

During the week of 9-15 March a vigorous "white ash plume" was observed, weakly pressured, with 550 m maximum height above the summit. Observers additionally identified lava glowing along the SW flank, in the direction of the Blongkeng, Lamat, and Sat drainages (the maximum run-out distance was 0.8 km). On 11 March a small pyroclastic flow was noted traveling SW with 0.8 km of run-out distance. During this week multiphase events dominated seismic activity, presumably resulting from the emission of lava and glowing debris. A small lahar traveled down the Sat drainage on 13 March.

During 16-22 March, ash emissions and lava avalanches continued. Avalanches again traveled SW, with maximum run-out distances of 0.4 km. Glow at the lava dome was weak. Surface shocks (assumed to be from lava avalanches) dominated seismicity. From 23 to 29 March the lava avalanches continued in the direction of the SW-flank rivers with 1.8 km maximum run-out distances. These drainages glowed at night. On 24 March a small pyroclastic flow started at the edge of the lava dome, moved in the direction of the Sat River, and attained a 0.6 km run-out distance; no glow was observed at the dome. Seismicity was dominated by surface events mostly interpreted as lava avalanches.

During the week of 27 April to 3 May, sulfur-tinted ash plumes reached their highest point during the recording period, 700 m above the summit. Lava avalanches continued in the direction of Blongkeng, Sat, and Lamat with 0.9 km run-out distances; again night glow was observed in these drainages. In contrast, the body of the lava dome lacked glowing areas. A small pyroclastic flow from the edge of the 1998 lava moved downslope SW for a distance of 1.3 km. Surface events continued to dominate seismicity. A small lahar buried two trucks and a digging machine at Putih on 1 May; no injuries were reported.

Lava avalanches during 4-17 May continued towards the SW-flank drainages with 1-km maximum distances each week. There was a weak glow on the lava dome during the first week and none the second. There was one small pyroclastic flow each week from the edge of the 1998 lava, which again moved SW out to 1 km distance. From 18 to 24 May lava avalanches had 1.8 km run-out distances. Glow within cracks on the lava dome was weak. Seismicity during May continued to be dominated by multiphase shocks and surface events identified as lava avalanches.

Information Contacts: Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).

11/2000 (BGVN 25:11) Consistent gas plume; lava avalanches and landslide; new lava dome and fractures

During June 1999-July 2000, Merapi consistently emitted a low-density, sulfur-rich, light-colored gas plume that ranged from 150 to 1,500 m above the summit. Frequent lava avalanches toward the nearby Blongkeng, Lamat, Sat, and Senowo River drainages reached maximum distances of 2 km. Lava avalanches glowed at night, although no incandescence could be observed inside the summit's lava dome. Tiltmeters lacked significant deformational changes, although a summit visit on 13 May 2000 revealed that the 1998 lava dome was growing. Lava avalanches and multi-phase earthquakes dominated seismicity. No lahars were observed during the period.

At the end of July 2000 low-intensity glow from the lava dome was observed. Seismicity increased in the first week of August with a few deep (A-type) and shallow (B-type) earthquakes. Emissions remained similar in consistency to those of the previous months, and rose 160 m above the summit. The hazard level was raised from 1 to 2 (on a 1-4 scale). The following week seismicity continued to increase, exemplified by a M 2.8 B-type event. Gas emissions rose up to 385 m above the summit. During the third week of August, volcanic and seismic activity continued to increase with gas emissions rising 460 m and greater numbers of A- and B-type earthquakes. Surficial events still dominated the overall seismicity. Plumes rose up to 700 m in the final week of August.

Activity remained similar to the previous weeks during September-October. Emissions continued to rise from 250 to 650 m high. The volume of emitted material was estimated to be 169 tons/day at the end of September. Seismicity changed little until late October, when volcanic tremor was recorded.

On 31 October a team from the Merapi Volcano Observatory (MVO) performed summit observations. The team noted that lava avalanches from the 1957 dome had filled the upper stream beds of the Senowo and Trising Rivers. The active 1998 lava dome was lifted on its W side and split in half. A newly formed dome between the two older sides had an elongated E-W-trending shape. Concentric and radial fractures were observed on the N and SW portions of the summit crater, and some fractures showed significant dilation. Radial fractures N of the summit crater and on the floor of Puncak Garuda appeared to have been sutured and then redeveloped to form a normal fault with a total offset of 30 cm. A fracture located between the 1957 and 1948 domes opened 20.5 cm during 14 May-1 November 2000.

High rainfall during the second week in November caused a landslide at the source of the Boyong River near Kaliurang, causing one death. At the end of November, Merapi still emitted a gaseous plume from its summit. Seismographs continued to register A- and B-type earthquakes, although multi-phase earthquakes dominated the record. The volcano remained at Hazard Level 2.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: dali@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/).

12/2000 (BGVN 25:12) Dome failure and growth during January 2001; over 30 pyroclastic flows

Eruptive activity increased markedly at Merapi during the period of 26 December 2000-22 January 2001. Instrumental monitoring first recorded a significant increase in seismicity, expressed in both shallow and deep volcanic earthquakes, during 26 December-1 January. Visual observations were hindered during this time because of hazy conditions, and VSI maintained a hazard status of 2 (on a scale of 1-4) for Merapi.

Activity continued to increase during 2-8 January. Atmospheric conditions were clearer, allowing observation of a 1,500-m-high plume above the summit. Lava avalanches flowed ~1 km from the summit down to the Sat River. Seismicity remained high, again with a significant number of shallow and deep volcanic earthquakes, and was dominated by multi-phase and avalanche earthquakes.

During 9-15 January, activity again increased with respect to the previous week. Accordingly, VSI elevated Merapi's hazard status to 3. Observers noted a light-colored, variable-density, low-pressure ash plume that rose 500 m above the summit. Glowing lava avalanches flowed into the headwaters of the Lamat, Sat, and Senowo Rivers, up to 2 km from the summit. On 14 January, 29 pyroclastic flows traveled down the volcano's flanks into the three above-mentioned rivers and reached up to 4 km from their source. During the week, lava avalanches and pyroclastic flows occurred with an average interval of 0.5-1 hours.

Visual observations from several post observatories during 16-22 January revealed ash eruptions, glowing lava flows and avalanches, and pyroclastic flows. Merapi ejected a dense, light-colored ash plume under medium to high pressure. Ash rose 850-1,300 m above the summit, with an estimated emission volume of 95 metric tons/day. Ashfall occurred on the surrounding areas of Babadan, Kaliurang, and Ngepos. Glowing lava avalanches, with more than 150 occurring per day, reached as far as 3.5 km from the summit into the Bebeng, Sat, and Senowo Rivers. Observers suggested more than one source vent for these flows. More than 20 pyroclastic flows occurred daily during the week, sending ash and gas a maximum of 3 km down the Bebeng River, 4.5 km down the Sat River, and an unreported distance down the Senowo River.

The Darwin VAAC issued an ash advisory on 19 January to advise pilots of ash emanating from Merapi. The advisory reported an ash plume up to an altitude of ~3,400 m. Prevailing winds were projected to carry ash to the E or SE; cloud cover prevented any further descriptions.

A new lava dome, termed "2001," grew on top of the 1998 dome that had collapsed around 16 January. Growth appeared continuous with the glowing dome visible at night. Researchers speculated that the failure of the 1998 dome and the instability of the new dome accounted for the high frequency and volume of pyroclastic flows.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: dali@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).

01/2001 (BGVN 26:01) Failure of 1998 lava dome on 10 February causes major eruption

Renewed unrest began on the night of 27 January with continuous pyroclastic flows and hot lava avalanches, which lasted up to two hours. Since mid-January a Level 3 hazard status has remained in effect for the volcano. The Volcanological Society of Indonesia (VSI) reported that on 28 January 2001 Merapi's "2001" lava dome (BGVN 25:12) partially collapsed resulting in pyroclastic flows and hot lava avalanches with recurrence intervals of ~2-5 minutes. Pyroclastic material flowed down to the Sat, Bebeng, and Senowo Rivers, to the SW, SW, and W of Merapi, respectively. Their maximum runout distance occurred in the Sat River drainage, where flows reached ~4.5 km from the source. A plume, thick with sulfurous ash, rose 2 km above the summit. The eruption generated ashfalls within a radius of 15-20 km; ash fell on the Dukun, Srumbung, Salam, Ngluwar, and Muntilan Districts surrounding Merapi.

VSI geophysicist Ratdomopurbo reported that the unstable lava dome was actively growing taller and larger; continued magma chamber injection had caused the pyroclastic flows and lava avalanches at the surface. Magma migration was indicated by increased deep volcanic (A-type) and shallow volcanic (B-type) earthquakes since August 2000. On 31 January pyroclastic flows occurred continuously, reaching up to ~3.5 km from the summit and flowing mainly into the Sat River, but also into the Senowo and Bebeng Rivers. At Babadan Observatory, located 4 km from the summit, a seismograph recorded earthquakes related to pyroclastic flows that exceeded the instrument's scale for up to 60 seconds during the interval of 1601-1822. Ashfall continued within 15 km of Merapi. A recent photograph showed a new active vent on Merapi's summit. VSI scientists engaged in Merapi research remained uncertain whether the vent in the photo had only emitted gases or had also emitted lava and tephra.

Pyroclastic flows and lava avalanches continued through 5 February (figures 20 and 21). Approximately 25 pyroclastic flows occurred daily and moved down the flanks to the Sat, Bebeng, and Senowo Rivers with a maximum runout distance of 4.5 km. Lava avalanches flowed down to the Lamat River, W of the volcano, in addition to the three above-mentioned rivers; lava avalanches reached a distance of 3.5 km from Merapi's summit, falling 1 km short of flows from the previous week. Ashfalls continued, and heavy rain on 3 February caused a minor lahar that initiated at 0430. Summarizing observations, Syamsul Rizal Wittiri stated that Merapi's lava dome continued to grow larger with the addition of ~45,000 cubic meters of material per day; lava dome volume as of 6 February was 1 million cubic meters. On 9 February at 2100 a continuous pyroclastic flow occurred for ~1 hour.

Figure 20. A west-flank pyroclastic flow travels down Merapi. Photo taken during the week of 30 January-5 February. Courtesy of VSI.
Figure 21. Night view of Merapi shows incandescent lava avalanches down several flanks. Photo taken during the week of 30 January-5 February. Courtesy of VSI.

A major eruptive episode occurred on 10 February (figure 22). At 0200 purported magma migration toward the surface was associated with a medium-sized, 30-minute-long pyroclastic flow. At 0330 failure of the 1998 lava dome sent an ash cloud billowing 5 km above the summit and generated sizable pyroclastic flows that extended up to 7 km from Merapi in the direction of the Sat River and 4.5 km in the direction of the Lamat River. At 0530 Merapi's alert was raised from 3 to 4, the highest level, for the first time since July 1998 (BGVN 23:07). The ash plume from the eruption spread 60 km toward the E over the communities of Klaten, Solo, Sukoharjo, and Boyolali. Ashfall produced an ash layer with a maximum thickness of 1 cm at a 5 km radius from the volcano. Stations recorded high seismicity accompanying the eruption. Instrumentation detected decreasing magnetic intensity near the summit, indicating high heat and magma near the surface.

Figure 22. A pyroclastic flow on 10 February 2001 sweeping down Merapi's W flanks. Only a small ash cloud rises sub-vertically from the summit. In the left foreground lies the Babadan Observatory Post; it sits on the mid-flanks ~ 7 km W of the summit. Courtesy of VSI.

Syamsul Rizal Wittiri predicted that Merapi's activity will continue and potentially increase because the 2001 lava dome, which attained a volume of 1.4 million cubic meters, is unstable due to the collapse of the 1998 dome. Merapi's alert level remained at 4 as of 14 February.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: dali@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).

07/2001 (BGVN 26:07) Volcanism continues at decreased intensity; Alert reduced from 4 to 2

After the large 10 February eruption (see BGVN 26:01), volcanic activity, including lava avalanches and pyroclastic flows, continued but decreased in intensity. Pyroclastic flows entered the Sat, Lamat, Senowo, and Bebeng rivers to a maximum runout distance of 2-3 km. High fumarole temperatures around the summit indicated that magma remained near the surface. The W and S sides of "lava dome 2001" grew and covered "lava dome 1997" to the S. Several fumaroles appeared to mark a fracture in the area of the 10 February eruption. Fractures formed in a similar manner prior to the November 1994 eruption.

The hazard status was at its highest level, 4 (on a scale of 1-4), through the week of 21-27 February 2001. The Alert Level was reduced to 3 the following week, and then to 2 during 7-13 March, where it remained through August.

Over the interval 14 February to 28 August, ash emissions rose up to ~150 m above the summit, and fumaroles emitted gas that rose up to ~950 m above the summit. Superficial earthquakes dominated the seismicity, though over time they continued to decrease in number and amplitude. Observations on 10 and 17 March revealed that high-pressure fumaroles appeared on most of the dome's surface. An observer reported that on 13 April a small amount of ash fell around the Babadan Post Observatory ~7 km W of the volcano. Activity at Merapi increased during 23-29 April, with reports of several medium-sized pyroclastic flows. Table 10 provides a more detailed description of weekly activity at Mt. Merapi from 14 February through 28 August.

Table 10. Summary of activity at Merapi from 14 February through 28 August 2001. Courtesy of VSI.

    Interval         Description of Activity

    14 Feb-20 Feb    Lava and pyroclastic flows continued but decreased in
                       intensity, pyroclastic flows entered the Sat, Lamat,
                       Senowo, and Bebung rivers. Maximum runut 2-3 km. Flows
                       traveled 1.5-2.5 km to the WSW for 1-2 hours. High
                       temperatures around Merapi indicated that magma was
                       near the surface; the W and S sides of "lava dome bgvn_2001"
                       grew and covered "lava dome 1997" to the S; several
                       fumaroles appeared to mark a fracture along where the
                       10 February eruption occurred.
    21 Feb-27 Feb    Volcanic activity decreased. Daily ash emissions rose to
                       ~150 m above the summit.
    07 Mar-13 Mar    Volcanic activity decreased, 100 avalanches per day.
                       Maximum runout of 2.3-2.5 km SW. On 6 March a
                       pyroclastic flow deposited material up to 1.5 km down
                       the Sat river.
    14 Mar-20 Mar    Volcanic activity continued, hot avalanches continued to
                       enter the Sat, Senowo, Bebeng, and Lamat rivers.
                       Maximum runout of 2.5 km in the Sat river, pyroclastic
                       flows up to 2.75 km down the Sat, Senowo, and Bebeng
                       rivers. Superficial earthquakes dominated the
                       seismicity but decreased. On 19 March high-pressure
                       fumaroles appeared on most of the dome's surface.
    21 Mar-27 Mar    Volcanic activity continued. hot avalanches continued to
                       enter the Sat, Senowo, Bebeng, and Lamat rivers.
                       Maximum runout of 3 km in the Sat river. Pyroclastic
                       flows traveled up to 1 km down the Sat, Senowo, and
                       Bebeng rivers. Superficial earthquakes dominated the
                       seismicity but decreased. On 17 March a summit visit
                       revealed that high-pressure fumaroles remained on most
                       of the dome's surface.
    11 Apr-17 Apr    Volcanic activity continued. Lava avalanches continued to
                       enter upstream areas of the Sat, Senowo, Lamat, and
                       Bebeng rivers. Maximum runout of 2.5 km in the Sat
                       river; an observer reported that 10 pyroclastic flows
                       traveled down the Sat, Senowo, and Bebeng rivers,
                       reaching as far as 2.3 km in the Sat river. Fumaroles
                       emitted steam and gas up to 950 m above the volcano's
                       summit; number and amplitude of earthquakes was high
                       but decreasing, seismic activity was dominated by
                       avalanche earthquakes.
    18 Apr-24 Apr    Lava avalanches continued to fill the upstream areas of
                       the Sat, Senowo, Lamat, and Bebeng rivers. Maximum
                       runout of 2 km in the Sat river; 11 pyroclastic flows
                       entered the Sat and Lamat rivers, reaching as far as 3
                       km. Avalanche earthquakes dominated the seismicity but
                       their amplitude and frequency decreased; on 13 April a
                       small amount of ash fell around the Babadan Post
                       Observatory ~7 km W of the volcano.
    25 Apr-1 May     Lava avalanches continued to flow down the Sat, Senowo,
                       Lamat, and Bebeng rivers. Maximum runout of 2 km.
                       Fumaroles emitted gas that rose up to 500 m above the
                       summit, seismic activity dominated by earthquakes.
    02 May-08 May    Activity increased, with reports of several medium-sized
                       pyroclastic flows. Four pyroclastic flows were observed
                       traveling into the upper reaches of the Sat, Senowo,
                       Lamat, and Bebeng rivers. Maximum runout of 1.8 km in
                       the Sat river; lava avalanches traveled up to 2.5 km
                       down the Sat river. Superficial earthquakes dominated
                       the seismicity.
    11 Jul-17 Jul    Lava avalanches. Maximum runout of 2.5 km SW.
                       Low-pressure emissions from fumaroles rose 700 m above
                       the volcano.
    18 Jul-25 Jul    52 lava avalanches. Maximum runout of 2.8 km SW.
                       Emissions from low-pressure fumaroles rose to 755 m
                       above the summit.
    22 Aug-28 Aug    Lava avalanches. Maximum runout of 2.8 km to the SW.
                       Seismic activity dominated by avalanche earthquakes.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: dali@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/); Darwin VAAC, Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, Northern Territory 0811, Australia; Australian Broadcasting Company; Associated Press; Meteorological and Geophysical Agency of Indonesia (Badan Meteorologi dan Geofisika, BMG), Jalan Angkasa I/2 Kemayoran, Jakarta Pusat 10720, Indonesia (URL: http://www.bmg.go.id/).

10/2001 (BGVN 26:10) Dome collapses and lava avalanches August-November; two unconfirmed deaths

Our last report (BGVN 26:07) covered activity from 14 February through 28 August 2001. The first portion of this report was provided by John Seach, who visited Merapi during 17-20 August 2001. The latter portion came from the Volcanological Survey of Indonesia (VSI); their reports discussed activity during late August through early November 2001.

Unconfirmed reports from volcano guides encountered at Babadan Observatory stated that two tourists were killed by dome collapse phenomena in early August after walking into the S-flank danger zone.

Activity was dominated by regular dome collapse and lava avalanches. On 17 August at 0735 an eruption of Merapi occurred, visible from the city of Yogyakarta. A dark brown plume was observed above the summit followed by a lava avalanche down the S side of the volcano. During the evening of 18 August, glowing avalanches were observed flowing down the SW side of the volcano at regular intervals. Runout distances were ~5 km.

On 19 August, observations were made from a location 220 m below the N-flank summit. Ascent to the summit area above the lava dome was not possible due to the continuing explosions of the dome. During the climb glowing avalanches continued down the SW flank. After dawn a white plume was continuously emitted to 200 m above the lava dome. About every 30 minutes there was an emission of light brown ash, indicating dome collapse. At 0930 burning vegetation was observed on the SW flank at an elevation of 1,400 m, presumably set alight by lava.

That evening, observations were made from Babadan Observatory on the SSW side of the volcano, 4 km from the summit (elevation 1,300 m). Between 2130 and 2330 there were 25 lava dome collapses. Lava was observed to extrude from the dome vertically and then collapse, producing thousands of glowing boulders that rolled 4 km down the flank (figure 23). The larger eruptions were accompanied by rumbling noises and earthquakes.

Figure 23. A night view of the incandescence seen after lava-dome collapse at Merapi on 19 August 2001. Photo taken from the Babadan Observatory on the SSW side of the volcano 4 km from the summit. Courtesy of John Seach.

On the morning of 20 August a dense white plume was visible rising 300 m above the summit. Occasional brown emissions rolled down the SW slope indicating continuing dome collapse.

The Volcanological Survey of Indonesia (VSI) reported that during late August through at least 4 November seismic activity at Merapi was dominated by avalanche earthquakes (table 11). During the week of 27 August-2 September, one low-frequency earthquake was registered. Table 11 also summarizes a white, thin, low-pressure fumarolic plume reported at various heights above the volcano throughout the report period. Lava avalanches were ongoing, traveling mainly in the headwaters upstream of the Lamat river, with a maximum runout distance of 2.75 km (see table 11). On 8 October at 1729 a minor pyroclastic flow traveled ~2 km toward the Sat river; on 24 October, four minor pyroclastic flows again traveled 2 km toward the Sat and Senowo rivers. Despite heavy rain at times, no lahars were reported. Merapi remained at Alert Level 2 (on a scale of 1-4) throughout the 27 August-4 November report period. Fumarolic temperatures at the Gendel and Woro craters varied by ten's of degrees Centigrade during 27 August through 4 November (table 12).

Table 11. A summary describing Merapi's volcanic seismicity, typical plumes, and lava avalanches during 27 August-4 November 2001. Courtesy of VSI.

    Date (2001)      Avalanche     Multiphase    Plume height
                     Earthquakes   Earthquakes   above summit
        Details of lava avalanches

    27 Aug-02 Sep       588            10             50 m
        Flowed down Senowo, Sat, Lamat, and Bebeng rivers with a maximum
        distance of 2.5 km towards the Sat and Lamat.
    03 Sep-09 Sep       652            11            300 m
        Ongoing, observed 36 times, dominantly traveled upstream of Sat and
        Lamat rivers, partly filling Senowo and Bebeng rivers.
    10 Sep-16 Sep       588             2            450 m
        Ongoing, dominantly traveled upstream of Lamat and Senowo rivers,
        reaching as far as 2.5 km away.
    17 Sep-23 Sep       684             1            750 m
        Ongoing, observed 51 times, dominantly upstream of Sat river but
        lesser parts traveled to Lamat, Senowo, and Bebeng rivers (maximum
        distance of 2.5 km).
    24 Sep-30 Sep       756             3            350 m
        Ongoing, traveled down to Sat, Lamat, and Senowo rivers (maximum
        distance of 2.5 km).
    01 Oct-07 Oct       702             8            425 m
        Ongoing, observed 59 times, dominantly to the upstream of Sat river,
        with a lesser part flowing down to Lamat and Senowo rivers (maximum
        distance of 2.5 km).
    08 Oct-14 Oct       692             5            170 m
        Ongoing, observed 53 times, dominantly to the upstream of Sat river,
        partly to Lamat and Senowo rivers (maximum distance of 2 km).
    15 Oct-21 Oct       800             7            575 m
        Ongoing, observed 103 times, dominantly towards the upstream of Sat
        river, and partly to the Lamat and Senowo rivers (maximum distance of
        2.75 km).
    22 Oct-28 Oct       790            --            750 m
        Ongoing, observed 121 times, dominantly towards the upstream of Sat
        river, and partly to the upstream of Lamat and Senowo rivers (maximum
        distance of 2.75 km).
    29 Oct-04 Nov      786             --            480 m
        Ongoing, observed 124 times, dominantly towards the upstream of Sat
        river and partly to the upstream of Lamat and Senowo rivers (maximum
        distance of ~ 2.8 km).

Table 12. Temperatures reported at Gendel and Woro craters of Merapi during 27 August through 28 October. No data collected during 1-14 October. Courtesy of VSI.

    Date (2001)        Gendol crater    Woro crater

    03-09 September      590-595°C       461-465°C
    10-16 September      589-606°C          --
    17-23 September      602-617°C          --
    24-30 September      598-618°C          --
    15-21 October        566-571°C         612°C
    22-28 October        561-575°C          --

Information Contacts: John Seach, PO Box 16, Chatsworth Island, NSW, 2469, Australia (Email: jseach@hotmail.com, URL: http://www.volcanolive.com); Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No.57, Bandung 40122, Indonesia (Email: dali@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/).

02/2002 (BGVN 27:02) Heightened lava dome activity from August 2001 through at least February 2002

During November 2001 through at least February 2002, seismic activity at Merapi was dominated by avalanche earthquakes. Generally white, thin, low-pressure plumes rose as high as 1.3 km above the summit. COSPEC-measured SO2 emission rates ranged from 66 to 225 ton/day (table 13).

Table 13. Seismicity, plume heights, and average SO2 fluxes at Merapi during 29 October 2001 through 24 February 2002. Courtesy VSI.

    Date           Avalanche  Tectonic     Multiphase    Plume height     Average
    (2001-2002)    signals    earthquakes  earthquakes  (above summit)   SO2 flux
                                                                        (tons/day)

    29 Oct-04 Nov    786          1             --            480         78-121
    05 Nov-11 Nov    823         --             --            520           --
    12 Nov-18 Nov    783          1              4            520         67-143
    19 Nov-25 Nov    737          1              3            625         66-98
    26 Nov-02 Dec    865          1              5             60           --
    03 Dec-09 Dec    --          --             --            779           --
    17 Dec-30 Dec   1568          1              1           1100         66-118
    30 Dec-06 Jan    695          4              2            300         65-140
    07 Jan-13 Jan    851          1              7            500           --
    14 Jan-20 Jan    853          4              3            750        120-225
    21 Jan-27 Jan    979          5              7           1300         83-218
    28 Jan-03 Feb    855          3              8            650         92-187
    04 Feb-10 Feb    703          1            120            200           --
    11 Feb-17 Feb    600          4             31            100           --
    18 Feb-24 Feb    607         10             25            400         87-206

Rainfall was heavy at times; during early and late November the maximum weekly rainfall rate was 44 mm/hour, and during 12-18 November the maximum rainfall rate was 78 mm/hour. Despite the heavy rainfall, no lahars were reported. Fumarole temperatures in the Gendol crater during November ranged from 430-570°C.

Incandescent lava avalanches traveled distances of 2.5 to 3 km and flowed toward the headwaters of the Sat and Bebeng rivers and, to a lesser extent, the headwaters of the Lamar and Senowo rivers. During 28 January-3 February 194 of these avalanches occurred.

A pyroclastic flow on 18 December traveled ~1 km toward the headwaters of the Bebeng river. Minor pyroclastic flows were reported throughout the remainder of the report period. During 4-10 February, 7 pyroclastic flows traveled 2.7 km to the Sat river and 2.5 km to the Bebeng river. During 11-17 February, 7 low-frequency earthquakes were recorded and the following week 1 low-frequency event was recorded. Merapi remained at Alert Level 2 throughout the report period.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: dali@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/).

06/2002 (BGVN 27:06) Pyroclastic flows and lava avalanches occur during February-June 2002

From 25 February through 16 June 2002 a generally white, variably dense, low-pressure plume rose 150-820 m above the summit of Merapi. Seismicity was dominated by avalanche earthquakes (table 14). During the week of 25-31 March, one shallow volcanic earthquake was reported. The Volcanological Survey of Indonesia (VSI) reported that Merapi emitted varying amounts of SO2 (table 15).

Table 14. Seismicity and crater characteristics at Merapi during 25 February-16 June 2002. "--" indicates that the information was not reported. Courtesy VSI.

    Date(2002)                         Seismic Signals
                    Low-frequency    Avalanche    Multiphase    Tectonic

    25 Feb-03 Mar        --              --           --           --
    04 Mar-10 Mar        --             666           --            4
    11 Mar-17 Mar         5             652           --            3
    18 Mar-24 Mar         1             609           --            2
    25 Mar-31 Mar        60             575           --           --
    01 Apr-07 Apr       135             539            1            8
    15 Apr-21 Apr        46             364           --            5
    22 Apr-28 Apr        19             367            1            5
    29 Apr-05 May         9             383           13            4
    06 May-12 May        13             353           --            7
    13 May-19 May         2             345            2            6
    20 May-26 May        --             308           15           11
    27 May-02 Jun         8             310            6            2
    03 Jun-09 Jun         9             268            6            4
    10 Jun-16 Jun        --             281            5            9

    Date(2002)      Magnetic field strength (B)    Gendol        Woro
                       at Pusung-Lempong           crater       crater
                        (nanotesla, nT)

    25 Feb-03 Mar             --                     --          571°C
    04 Mar-10 Mar             --                     --           --
    11 Mar-17 Mar             --                     --           --
    18 Mar-24 Mar             --                     --           --
    25 Mar-31 Mar             --                     --           --
    01 Apr-07 Apr             --                     --           --
    15 Apr-21 Apr           3.09 nT                  --           --
    22 Apr-28 Apr           0.32 nT                  --           --
    29 Apr-05 May          -3.22 nT               737-742°C    421-434°C
    06 May-12 May           4.64 nT               737-746°C    398-431°C
    13 May-19 May           8.28 nT               734-748°C    406-430°C
    20 May-26 May          -1.02 nT               734-749°C    421-431°C
    27 May-02 Jun          -1.47 nT               620-750°C    354-430°C
    03 Jun-09 Jun          -1.65 nT               741-756°C    423-435°C
    10 Jun-16 Jun           1.65 nT               736-755°C    423-434°C

Table 15. COSPEC-measured SO2 gas emission at Merapi during 3 March-16 June 2002. "NR" indicates that the information was not reported. Courtesy VSI.

    Date(2002)       Average SO2 emission      Range     Max. avg.
                          (ton/day)          (ton/day)   (ton/day)

    03 Mar-10 Mar            156               96-254       196
    11 Mar-17 Mar            131               87-173       138
    18 Mar-24 Mar            146              103-206        NR
    25 Mar-31 Mar            133               74-172       136
    01 Apr-07 Apr            107               73-145       108
    15 Apr-21 Apr            124              105-167        NR
    22 Apr-28 Apr            155               97-219       182
    29 Apr-05 May            156              109-245       173
    06 May-12 May            166              123-210       169
    13 May-19 May             90               43-182       145
    20 May-26 May            140               64-206       160
    27 May-02 Jun            131               62-216       167
    03 Jun-09 Jun            141               85-196       167
    10 Jun-16 Jun            125               42-218       161

In total, 69-108 lava avalanches per week were observed during mid-February through late March. The avalanches generally traveled 2.5-2.75 km towards the upstream ends of the Senowo, Sat, and Lamat rivers, and partly to the Bebeng river. During 25 February-3 March, a total of four minor pyroclastic flows traveled to the upstream part of the Bebeng river to a maximum distance of 1.0 km (3 on 25 February and 1 on 3 March). Field observations of the summit on 28 February revealed very thin solfatara sublimation at Gendol and Woro craters. Temperatures at the craters were 354-755°C (table 14). No further pyroclastic flows occurred until 29 and 30 March, when 7 and 2 flows, respectively, traveled 1.8 km down to the upstream ends of the Sat and Senowo rivers. Low-frequency (LF) earthquakes, which had been recorded during the previous few weeks, increased (table 14), and high-intensity rain fell but did not trigger lahars.

Table 15 shows Merapi's SO2 fluxes. The molar concentrations of volcanic gases from Gendol crater on 28 February were as follows: 0.21% H2, 0.02% (O2 + Ar), 0.54% N2, 3.87% CO2, 0.01% CO, 1.00% H2S, 5.49% HCl, 88.86% H2O. One pyroclastic flow was reported during 25-31 March.

During early April, two minor pyroclastic flows traveled 1.3 km toward the Sat river. Activity at Merapi increased significantly; LF earthquakes reached 135 events within the week. The most intense rain was ~65 mm/hour near the Babadan post observatory on 4 April, but it did not trigger lahars. On 14 April, two minor pyroclastic flows reached 1.8 km maximum distance. Seismicity began to decrease but was still higher than normal. Deformation data from Reflector 4 at the Babadan post observatory indicated 7 mm of deflation, and the lava dome morphology did not change.

No further pyroclastic flows were reported through at least mid-June. Seismicity and general activity at Merapi was reportedly decreasing. Merapi remained at Alert Level 2 throughout the report period.

Information Contacts: Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: isya@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/).

09/2002 (BGVN 27:09) Frequent lava avalanches; plumes up to 550 m above summit

During 17 July-1 September, seismicity at Merapi was dominated by avalanche earthquakes. SO2 emissions varied, and generally white, thin, low-pressure plumes rose up to 550 m above the summit. Glowing avalanches traveled 2.6 km, moving towards headwaters of the Sat, Lamat, Senowo, and Bebeng rivers (table 16). On 2 July two pyroclastic flows traveled 0.5 km toward the upstream of the Sat river. One low-frequency earthquake occurred during late August. The temperature of Gendol crater was 734-755°C, and the Woro crater was 418-435°C. Merapi remained at Alert Level 2.

Table 16. Seismicity, SO2 emissions, plume and lava-avalanche observations at Merapi during 17 June-1 September 2002. Courtesy VSI.

    Date(2002)       Avalanche  Multiphase  Tectonic        SO2*          MI
      Plumes (heights are above the summit) and lava avalanches

    17 Jun-  23 Jun    247          6           7     107, 56-197, 174   +0.76
      White, thin, low-pressure plume rose 400 m; 65 glowing lava avalanches
      traveled 2.5 km to the Sat, Lamat and Senowo rivers

    24 Jun-  30 Jun    318          3          16      87, 56-172, 134    --
      White, thin, low-pressure plume rose 500 m; 68 glowing lava avalanches
      traveled 2.5 km to the Sat, Lamat and Senowo rivers

    01 Jul-  07 Jul    226          4           6     113, 73-167, 134   +0.59
                                                         on 6 July
      White, thin, low-pressure plume rose 550 m; 60 glowing lava avalanches
      traveled 2.6 km to the Sat, Lamat, Senowo, and Bebeng rivers

    08 Jul-  14 Jul    180         --          12      85, 65-118, 86    +2.56
                                                         on 11 July
      White, thin, low-pressure plume rose 550 m; glowing lava avalanches
      traveled 2.6 km to the Sat, Lamat, Senowo, and Bebeng rivers

    15 Jul-  21 Jul    201          2           4     117, 76-143, 122   -1.15
                                                         on 16 July
      White, thick low-pressure plume rose 390 m; glowing lava avalanches
      traveled 2.5 km to the Sat, Lamat, Senowo, and Bebeng rivers

    22 Jul-  28 Jul    220         --          10      80, 46-167, 135   -1.69
                                                         on 28 July
      White, thick low-pressure plume rose 350 m; 92 glowing lava avalanches
      traveled 2.5 km to the Sat, Lamat, Senowo, and Bebeng rivers

    29 Jul-  04 Aug    237          3           7     145, 62-210, 162   +1.68
                                                         on 4 August
      White, thin medium-pressure plume rose 394 m; 42 glowing lava avalanches
      traveled 2.6 km to the Sat, Lamat, Senowo, and Bebeng rivers

    05 Aug-  11 Aug    184          1           4     106, 56-123, 155   -1.89
                                                         on 5 August
      White, thick, low-pressure plume rose 525 m; 53 glowing lava avalanches
      traveled 2.5 km to the Sat, Lamat, Senowo, and Bebeng rivers

    12 Aug-  18 Aug    191         --           6      87, 61-115, 93    +0.13
                                                         on 14 August
      White, thin, low-pressure plume rose 300 m; 40 glowing lava avalanches
      traveled 2.5 km to the Sat, Lamat, and Senowo rivers

    19 Aug-  25 Aug    187         15          11     129, 92-154, 137   +0.13
                                                         on 24 August
      White, thin, low-pressure plume rose 350 m; 16 glowing lava avalanches
      traveled 2.5 km to the Sat, Lamat, and Senowo rivers

    26 Aug-  01 Sep    311          4           3     127, 85-190, 157   -0.22
                                                         on 26 August
      White, thin, low-pressure plume rose 400 m; glowing lava avalanches
      traveled 2.5 km to the Sat, Lamat, and Senowo rivers

Information Contacts: Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: isya@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/).

03/2003 (BGVN 28:03) Infrared satellite data show continuous activity through mid-January 2002

During late July-1 September 2002, the Volcanological Survey of Indonesia (VSI) reported frequent lava avalanches and plumes up to 550 m above the summit of Merapi (BGVN 27:09). No further reports were issued by VSI through at least March 2003.

MODIS thermal alerts during 2001 and 2002 indicated continuous activity through mid-January 2002 (figures 24 and 25). This period was characterized by dome collapse and hot avalanches (BGVN 26:01, 26:07, 26:10, and 27:02). Pyroclastic flows occurred too frequently to correlate them with the MODIS alerts, for which data are collected only about once per day (weather permitting). There were no alerts detected during the rest of 2002 except for late March-late May, which corresponded to a temporary renewal of pyroclastic flows before a quieter second half of the year (BGVN 27:06 and 27:09).

Figure 24. MODIS-detected alerts on Merapi during 2001-2002. Thermal alerts collated by Diego Coppola and David Rothery; data courtesy of the Hawaii Institute of Geophysics and Planetology's MODIS Thermal Alert Team.
Figure 25. Center coordinates of alert-pixels on Merapi, relative to the published summit location. Grid squares are 1 km. Thermal alerts collated by Diego Coppola and David Rothery; data courtesy of the Hawaii Institute of Geophysics and Planetology's MODIS Thermal Alert Team.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: dali@vsi.esdm. go.id, URL: http://www.vsi.esdm.go.id/); Diego Coppola and David A. Rothery, Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA, UK (Email: d.coppola@open.ac.uk, d.a.rothery@open.ac.uk). Thermal alerts courtesy of the HIGP MODIS Thermal Alerts Team (URL: http://modis.higp.hawaii.edu/).

05/2006 (BGVN 31:05) Mid-2006 brings multiple pyroclastic flows that kill two, and travel up to 7 km

Seismic activity at Merapi began to increase on 19 March 2006, leading the Center of Volcanology and Geological Hazard Mitigation (CVGHM) to raise the Alert Level from 1 to 2 (on a scale of 1-4). Ten thousand residents were warned to prepare for possible evacuation.

On 10 April, authorities banned mountain climbing due to reports of increased tremor. Unverified preliminary reports indicated "lava" reportedly flowing near Pasar Bubar village, ~ 350 m from the volcano's crater. At 1500 on 12 April, CVGHM raised the Alert Level from 2 to 3. No one was permitted within 8 km of the summit.

During 21-25 April, seismicity remained elevated; several seismic signals associated with rockfalls were recorded. The SO2 flux measured from Merapi was 175 metric tons on 22 April. On 22 and 23 April, fumarolic emissions rose 400 m above the summit. On 25 April, two rockslides from lava-flow fronts were heard from nearby observatories. According to news reports, about 600 of the approximately 14,000 people living near the volcano had been evacuated by 24 April.

According to news reports, on 27 April nearly 2,000 villagers were evacuated from Sidorejo and Tegalmulyo villages. That day, small amounts of ash fell in Gemer village about 5 km from the summit.

On 28 April, CVGHM reported volcanic material traveling ~ 1.5 km SW to the Lamat River. Seismicity that day was dominated by multi-phase earthquakes; but signals from landslides, rockfalls, and low-frequency events were also recorded.

On 6 May, gas plumes rose to 800 m above the summit and eighteen incandescent avalanches of volcanic material were observed. On 7 May, 26 incandescent avalanches that extended ~ 100 m were seen during the morning. On 6 and 7 May, the lava dome continued to grow and seismicity was dominated by multi-phase earthquakes. Shallow volcanic earthquakes and signals from landslides and rockfalls were also recorded. On 8 May, the Darwin VAAC reported that CVGHM warned of a plume rising to ~ 3.7 km, but no ash was visible on satellite imagery.

According to the Darwin VAAC, gas plumes that rose ~ 600 m above the summit were visible on satellite imagery on 11 May. Avalanches of incandescent material extended 200 m SE towards the Gendol River, and 1.5 km SW towards the Krasak River. Several small incandescent avalanches of volcanic material were visible from observatory posts. The new lava dome at the volcano's summit had grown to fill the gap between the 1997 and 2001 lava flows on the W side of the summit, and had reached a height about the same as the 1997 lava flows. Seismicity was dominated by multi-phase earthquakes and signals associated with avalanches.

At 0940 on 13 May, the Alert Level was raised from 3 to 4, the highest level, and ~ 4,500 people living near the volcano were evacuated.

On 15 May pyroclastic flows traveled as far as 4 km to the W. By 16 May, more than 22,000 people had been evacuated, according to figures posted at the district disaster center; about 16,870 people were evacuated from three districts in Central Java Province, and more than 5,600 others were evacuated from the Slemen district. On 17 May, pyroclastic flows traveled as far as 3 km. Local volcanologists reported that the lava dome continued to grow, but at a slower rate than during previous days.

Pyroclastic flows to the SW and SE reached 4 km on 19 May and 3 km on 20 May. On 22 May, the lava dome volume was estimated at ~ 2.3 million cubic meters. The Darwin VAAC reported that low-level emissions continued during 18-19 and 23 May. CVGHM recommended that residents who lived in valleys on the NNW flanks near Sat, Lamat, Senowo, Trising, and Apu Rivers and on the SE flank near Woro River be allowed to return to their homes. Residents remained evacuated from villages within a 7 km radius from the volcano's summit and within 300 m of the banks of the Krasak/Bebeng, Bedog, and Boyong Rivers to the SW, and the Gendol River to the SE.

According to news reports, an eruption produced a cloud of hot gas and ash on 17 May. Witnesses said the size of the plume was smaller than ash-and-gas plumes seen on 15 May. On 18 May, a representative for Merapi from the Center for Volcanological Research and Technology Development (part of CVGHM), reported new ashfall.

On 24-25 May, lava flows were observed moving SW towards the Krasak River and SE towards the Gendol River. News reports indicated that on 27 May a M 6.3 earthquake that killed about 5,400 people resulted in a three-fold increase in activity at Merapi. A M 5.9 earthquake coincided with pyroclastic flows of unknown origin that extended 3.8 km SW. During 28-30 May, multiple pyroclastic flows reached 3 km SE and 4 km SW. Gas plumes reached 500 m above the summit on 25 May, 1,200 m on 26 May, 100 m on 29 May, and 900 m on 30 May.

From 31 May to 6 June, SO2-bearing plumes were observed daily; on 1 June they reached 1.3 km above the summit. According to the Darwin VAAC, low-level emissions were visible on satellite imagery on 1 and 6 June. Multiple pyroclastic flows reached ~ 4 km SE toward the Gendol River and 3.5 km SW toward the Krasak and Boyong Rivers. CVGHM reported on 31 May that lava avalanches moved W for the first time during the recent eruption.

According to a volcanologist in Yogyakarta, lava-flow distances and dome volume had both approximately doubled since the 27 May M 6.2 earthquake. On 6 June, people living near the base of the volcano began to move into temporary shelters. Activities remain restricted within a 7 km radius from the volcano's summit and within 300 m of the banks of Krasak/Bebeng, Bedog, and Boyong Rivers to the SW, and Gendol River to the SE.

On 8 June, the lava-dome growth rate at Merapi was an estimated 100,000 cubic meters per day and the estimated volume was then ~ 4 million cubic meters. An estimated volume loss of 400,000 cubic meters on 4 June had been due to a partial collapse of the S part of the Geger Buaya crater wall, which was constructed from 1910 lava flows.

On 8 June, a pyroclastic flow, lasting 12 minutes, reached a distance of ~ 5 km SE toward the Gendol River, the predominant travel direction since the M 6.2 earthquake on 27 May. According to a news report, this event prompted approximately 15,500 people to evacuate from the Sleman district to the S and the Magelang district to the W. On 13 June, the Alert Level was lowered from 4 to 3 but renewed pyroclastic-flow activity the next day prompted a return to Alert Level 4.

Gas plumes were observed almost daily during 7-13 June and reached ~ 1.2 km above the summit on 10 June. The Darwin VAAC reported small ash plumes visible on satellite imagery; minor ashfall was reported to the S at an observatory outpost, and in Yogyakarta, about 32 km away.

Gas plumes emitted on 14 and 15 June reached 900 m above the summit. On 14 June a dome collapse lasting ~ 3.5 hours produced pyroclastic flows that reached 7 km SE. Two volunteers on a search-and-rescue team assisting with evacuation efforts were trapped in an underground refuge in Kaliadem village and died, the first fatalities of the current eruption. Stone (2006) wrote that the volunteers had ". . . sought refuge in a bunker, one of several on the mountain built for that contingency. The blast door was slightly ajar when rescuers dug down to the bunker the next day. The men had burned to death."

On 15 June, pyroclastic flows reached a distance of 4.5 km SE along the Gendol River. Pyroclastic flows continued during 16-19 June as a new dome grew. The Alert Level remained at 4.

During 21-25 June, seismic signals at Merapi indicated almost daily occurrences of rockfalls and pyroclastic flows. Due to inclement weather, pyroclastic flows were only observed on 24 June and reached a distance of 4 km SE along the Gendol River and 2.5 km SW along the Krasak River. Gas plumes were observed during 22-25 June and reached 1.5 km above the summit on 24 June.

Reference. Stone, Richard, 2006, Volcanology?Scientists steal a daring look at Merapi's explosive potential; Science, American Association for the Advancement of Science (AAAS), v. 312, pp. 1724-6.

Information Contacts: Centre of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Associated Press (URL: http://news.yahoo.com/s/ap/indonesia_volcano), Reuters (URL: http://news.yahoo.com/s/nm/20060418/wl_nm/indonesia_volcano_dc_2).

06/2006 (BGVN 31:06) Fewer pyroclastic flows during July; ASTER thermal data

During mid-March through July 2006, scientists at Merapi noted variations in seismicity, the number and size of explosions, and the abundance of pyroclastic flows and incandescent rockfalls. This led to changes in Alert Levels and, during April and May, thousands of evacuations. The source of in-situ information for this report was Merapi Volcano Observatory and the Center of Volcanology and Geological Hazard Mitigation (CVGHM; formerly VSI, the Volcanological Survey of Indonesia, and still informally referred to in that way). Satellite images collected by the Advanced Spaceborne Thermal Infrared and Reflection Radiometer (ASTER) complemented the ground observations.

Although events of 28 April to 22 June 2006 were previously discussed in more detail (BGVN 31:05), they are presented here in the context of ASTER and summaries of CVGHM field reports. CVGHM observations from 28 June to 25 July revealed an interval of limited significant rockfalls, sparse pyroclastic flows (only one was reported, to 3 km runout distance), and modest gas plumes.

Activity during 28 April to 22 June 2006. About eight images from 28 April to 22 June were collected over Merapi by the ASTER satellite and processed by Michael Ramsey. Temperatures over the lava dome and flanks were extracted from daytime and nighttime images; in some cases the contents of plumes were assessed. The temperature and distribution of thermal anomalies were consistently in agreement with ground observations from CVGHM.

ASTER consists of three instrument sub-systems covering fourteen bands over three wavelength regions with various spatial (pixel) resolutions. Three visible and near-infrared (VNIR) bands cover 0.52-0.86 ?m at 15 m spatial resolution. Six short-wavelength infrared (SWIR) bands cover 1.60-2.45 ?m at 30 m resolution. Five thermal infrared (TIR) bands cover 8.125-11.65 ?m at 90 m resolution.

A temperature data point from a pixel is the average temperature for that 30 x 30 m (SWIR) or 90 x 90 m (TIR) pixel area. Temperature data are extracted from the TIR region, unless the pixels are saturated (temperatures greater than 100°C over the 90 m pixel). In those cases, temperatures are extracted from SWIR images. Cross-track pointing of the sensors ? 116 km from nadir allows for repeat times of less than sixteen days. For a target near the equator at a 24° pointing angle, repeat times can average four days. During the Merapi crisis, investigators tasked the satellite to collect more frequent images.

A nighttime TIR image from 28 April showed a weak thermal anomaly over the summit. Approximately 8 pixels were thermally elevated above background, to a maximum temperature of ~ 25.9°C. Further processing of the emissivity spectra from the hottest pixels demonstrated that over 5% of the sub-pixel temperatures may be on the order of 100's of degrees C. SWIR data from the same time showed temperature of no more than ~ 200°C. One small anomaly was visible ~ 650 m SW from the summit. CVGHM reported that volcanic material traveled ~ 1.5 km SW towards the Lamat River on 28 April.

On 12 May, a daytime SWIR image demonstrated increased activity with a larger thermal anomaly than the 28 April image and a pixel average maximum temperature of 213°C. Emissivity spectra collected in the TIR region corroborated the temperature data in the SWIR region. On 11 May, CVGHM reported a sharp increase in eruptive activity and on 13 May, raised the Alert Level from 3 to 4 (the highest level). As noted in BGVN (31:05), about 4,500 people living near the volcano were evacuated.

A significant thermal anomaly was present in the 14 May TIR and SWIR nighttime images. Three pixels in the SWIR region had a maximum average pixel temperature of 442°C. An area of elevated temperature to the SW was interpreted as a pyroclastic flow. On 15 May, CVGHM reported that pyroclastic flows had traveled as far as 4 km W.

A clear nighttime SWIR image acquired on 30 May showed a maximum derived temperature of 447°C and 11 pixels with temperatures greater than 400°C. Two zones of thermally elevated pixels were evident about 600 m SE of the dome and 2 km SW of the summit. Consistent with the imagery, CVGHM reported that during 28-30 May, multiple pyroclastic flows reached a maximum of 3 km SE toward the Gendol River and 4 km SW toward the Krasak and Boyong Rivers.

On 6 June, daytime VNIR, nighttime SWIR, and TIR images were collected. The daytime image shows a large ash-rich plume extending SW over 40 km from the summit (figure 26). Preliminary analysis of the plume by Vince Realmuto (using a decorrelation stretch of the daytime TIR data) indicated a mixture of ash and steam, and low SO2 content. Thermal anomalies over the summit and on the flanks (outlined in white), interpreted as possible pyroclastic flows, extended~ 3 km SE and SW, and ~ 1 km NW. SWIR temperature data showed a maximum average pixel temperature of 420°C and two summit pixels over 400°C. According to CVGHM, on 6 June lava avalanches and two pyroclastic flows reached ~ 2 km SE and lava avalanches traveled 2 km SW.

Figure 26. Composite ASTER image of Merapi acquired on 6 June 2006. A large ash-rich plume drifting over 40 km SW of the summit is evident in this visible near-infrared ASTER image (15 m pixel size) taken during daylight hours. Temperature data from a nighttime thermal infra-red image acquired 12 hours later is superimposed on the image as contour lines. Those on and around the summit represent the minimum extent of elevated temperatures (~ 25°C) from hot material such as pyroclastic flows. Courtesy Michael Ramsey, University of Pittsburgh.

A thermal anomaly, interpreted as cooling pyroclastic flows, that extended ~ 6.4 km S of the summit region was evident on a TIR and SWIR image set acquired on 22 June. The SWIR data showed two pixels greater than 425°C over the summit similar to the 6 June data. Based on interpretation of seismic data, CVGHM reported almost daily occurrences of rockfalls and pyroclastic flows during 21-25 June. Visual observations were mostly inhibited by cloud cover.

Activity during 28 June-25 July 2006. Pyroclastic flows and rockfalls decreased in frequency and intensity during 28 June-4 July. Pyroclastic flows were observed during 28-30 June and reached a maximum distance of 3 km SE along the Gendol River. Gas plumes were observed during 28 June-1 July and reached a maximum height of 1 km above the summit (~ 4 km altitude) on 28 June.

During 5-11 July, gas plumes reached a maximum height of 1.2 km above the summit on 6 July. Due to a decrease in activity, on 10 July the Alert Level was lowered one level to 3 in all areas except the S slope.

Incandescent material reached a maximum distance of 2 km SE along the Gendol River from 12 to 18 July. Gas plumes were also observed daily and reached heights of 1 km above the crater (~ 4 km altitude) On 17 July, CVGHM lowered the Alert Level to 3 for the S slope. During 19-25 July, gas plumes reached maximum heights of 400 m above the summit (~ 3.3 km altitude). Flows of incandescent material were observed daily, advancing at a maximum distance of 1.5 km SE toward the Gendol River. Pyroclastic flows were

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Michael Ramsey and the Image Visualization and Infrared Spectroscopy (IVIS) laboratory, University of Pittsburgh, 200 SRCC Building, Pittsburgh, PA 15260, USA (URL: http://ivis.eps.pitt.edu/, Email: ramsey@ivis.eps.pitt.edu); Vince Realmuto, Jet Propulsion Laboratory, Mail Stop 168-514, 4800 Oak Grove Drive, Pasadena, CA 91109, USA (Email: Vincent.J.Realmuto@jpl.nasa.gov); Advanced Spaceborne Thermal Infrared and Reflection Radiometer satellite (URL: http://asterweb.jpl.nasa.gov/).

02/2007 (BGVN 32:02) March-July 2006 volcanic crisis; May earthquake killed ~5,800

Merapi, one of the most dangerous volcanoes in the world owing to its perched lava dome and location in populous central Java, underwent vigorous dome growth during early to mid-2006, and its increasingly unstable summit dome released numerous pyroclastic flows and incandescent avalanches. Thousands of residents evacuated and the volcano became prominent in international news. The longest pyroclastic flows of mid-2006 took place on 8 and 14 June, with respective run-out distances from the summit area of ~ 5 and 7 km. Merapi's summit lies 32 km N of the large city of Yogyakarta.

This report contains summary notes on activity during 7 March to 1 July 2006. These notes were assembled and reported by scientists from the Merapi Volcano Observatory and the Center of Volcanology and Geological Hazard Mitigation (CVGHM), formerly the Volcanological Survey of Indonesia, and augments material presented previously (BGVN 31:05 and 31:06).

The USGS provided a satellite image with labels showing key drainages and features near the summit (figure 27). The dome's instability leads to pyroclastic flows and various kinds of rockfalls and other mass wasting episodes down the labeled drainages. During the 7 March to 1 July reporting interval, pyroclastic flows followed the headwaters of the Gendol , Krasak, Boyong, and Sat rivers, which trend to the SE, SW, SSW, and W, respectively.

Figure 27. An annotated Ikonos satellite image of Merapi taken 10 May 2006. Image resolution is 2 m; N is to the top, and the scale is such that the entire distance N-S on the image is approximately 1 km. The labeled arrows indicate key rivers into which upslope avalanche shoots drain. Multiple drainage names are separated by a slash, and many western headwaters descend into the Woro river. The "K." stands for Kali, Indonesian for stream. Lava domes and viscous flows ("L") are labeled with the year of extrusion. The Gegerbuaya ridge was formed by 1911 lavas. Garuda, Woro, and Gendol identify headwaters. Letters reference locations used by scientists to facilitate communication. The Kaliurang Observatory lies ~ 4 km to the SE of the summit. The labeled image was a collaborative effort provided here courtesy of John Pallister, USGS. Image copyright 2006, GeoEye.

Tectonic earthquake on 27 May 2006. The tectonics of Java are dominated by the subduction of the Australia plate to the NNE beneath the Sunda plate with a relative velocity of ~ 6 cm/year. The Australia plate dips NNE from the Java trench, attaining depths of 100-200 km beneath the island of Java, and depths of 600 km to the N of the island. The earthquake of 27 May 2006 occurred at shallow depth in the overriding Sunda plate, well above the dipping Australia plate.

The pace of volcanism and the intensity of the regional crisis increased after 27 May 2006. At 0553 that day, a destructive Mw 6.3 earthquake occurred leaving damage across central Java's southern coastal and inland areas (figure 28). The earthquake occurred at 10 km focal depth. The epicenter (at 7.962°S, 110.458°E) was 20 km SSE of Yogyakarta (population, 511,000; 6 million in the larger metro area). Some initial estimates put the earthquake at MR 5.9; this was later revised and even the newer (above-stated) seismic parameters are preliminary.

Figure 28. Epicenter of the 27 May 2006 earthquake in Central Java, including impact on regions around Merapi. The histograms show numbers of people killed (on left bar) and injured (right bar). As mentioned in text, some of the seismic parameters stated were later revised. Modified from a UN OCHA ReliefWeb Map Centre (1 June 2006) map in a 2006 United Nations report (see References).

A US Geological Survey (USGS) summary stated that the earthquake caused 5,749 deaths, 38,568 injuries, and led to as many as 600,000 people displaced in the Bantul-Yogyakarta area. The shaking left more than 127,000 houses destroyed and an additional 451,000 houses damaged in the area, with the total loss estimated at ~3.1 billion US dollars. Modified Mercalli intensities were as follows: at Bantul and Klaten, IX; at Sleman and Yogyakarta, VIII; at Surakarta, V; at Salatiga and Blitar, IV; and at Surabaya, II. The earthquake was felt in much of Java and at Denpasar, Bali. The website of the US Geological Survey's Earthquake Hazards Program features a large number of photos (captioned in English) depicting various aspects of the earthquake.

Events during 7 March-1 July 2006. Tables 17 and 18 summarize some of the details during the reporting interval. Merapi's activity had increased to include volcanic earthquakes and deformation of the summit area a year earlier (in July 2005). Although the number of daily lava avalanches and pyroclastic flows had increased almost a week earlier, a tectonic earthquake, MR 6.3 (Richter scale magnitude), at 0555 (local time, WIB) on 27 May was followed by another significant increase in those events for another week (tables 17 and 18). Pyroclastic flows and lava avalanches between 10 May and 30 June were rare in the W-flank Sat drainage (31 May, 2 June, and 10 June), and did not descend into the Boyong drainage (SSW) after 4 June (table 18). The Krasak river drainage (SW) had material entering it on an almost daily basis after 27 May, except for a brief time during 14-19 June, with maximum run-out distances of 4 km. The Gendol drainage (SE) also experienced daily pyroclastic flows and lava avalanches starting on 28 May. Most of these flows to the SE did not extend more than 5 km, but on 14 June a pyroclastic flow descended 7 km.

Table 17. A compilation of seismic events at Merapi during 7 March to 1 July 2006. In creating this table Bulletin editors merged the category "landslides" with the category "lava avalanches". Similarly, the category "hot cloud reports" was interpreted to be equivalent to "pyroclastic flow" and those were also merged. Those mergers were driven by sudden shifts in terminology found in CVGHM reports. All data courtesy of CVGHM.

    Date (2006)    Plume seen      Lava         Multiphase     Pyroclastic    Tectonic
                   to (meters      avalanche    earthquakes       flow        earthquakes
                   above summit)   signals                       signals

    07-12 Mar          --            --             198            --             --
    13-19 Mar          --            --             239            --             --
    21 Apr             --            13             162            --              1
    22 Apr             --            12              95            --             --
    23 Apr             --             5              60            --              1
    24 Apr             --            21             178            --              1
    25 Apr             200            6              25            --             --
    26-27 Apr        Missing
    28 Apr             --            20             126            --             --
    29 Apr- 5 May    Missing
    06 May             --            82              95            --             --

    07 May             --            59             104            --             --
    08 May           Missing
    10 May             --           133             153            --             --
    11 May             600           88             115            --             --
    12-21 May        Missing
    22 May             --           309              56            25             --
    23 May             700          243              60            31             --
    24-26 May        Missing
    27 May *           100          279              --            54            138
    28 May            1600          237              43           159             95
    29 May             500          332              18            88             57
    30 May             800          337              19            56             40
    31 May             800          276              36           127             24
    01 Jun            1300          315              35           144             13
    02 Jun             650          338              25           163             24
    03 Jun             800          488              79           107             16
    04 Jun             900          397              54           118             25
    05 Jun             400          300               9           157             17
    06 Jun             300          212              10            78             14
    07 Jun             275          256              12            66              8
    08 Jun             300          210              28            67             10
    09 Jun           Missing
    10 Jun             900          337              37            34              4
    11 Jun             800          299              20            20             10
    12 Jun             350          264              31            22              8
    13 Jun            1200          273              88            28              5
    14 Jun             500          371              29            61              2
    15 Jun             900          260             100            27              6
    16-18 Jun        Missing
    19 Jun             600          272              88            21              7
    20 Jun            1250          312             136            38              4
    21 Jun           Obscured       256              65            15              4
    22 Jun            1200          319              39             4              5
    23 Jun **          600           78               5             4              5
    24 Jun            1500          338              48            21              6
    25 Jun             800          321              32            18             17
    26 Jun             800          372              27            17             11
    27 Jun            1000          251              16            23             11
    28 Jun            1000          308              16            19              1
    29 Jun             700          290              11            15             12
    30 Jun             500           74               0             9              3
    01 Jul **          350          250               4            13              4

    * Earthquake, MR 6.3 (Richter scale magnitude) recorded at 0555 (local time, WIB)
    ** Incomplete data only 0000-0600 (local time)

Table 18. Record of run out distances (km) of pyroclastic flows and lava avalanches (the latter, in parentheses) toward river drainages on Merapi from 10 May to 30 June 2006. Courtesy of CVGHM.

    Date         Gendal (km)    Krasak (km)    Boyong (km)    Sat (km)

    10 May       0.2            1.5             --             --
    20 May       3.0            3.0            3.0             --
    22 May        --            3.5             --             --
    27 May        --            3.8 (2.0)          (2.0)       --
    28 May       3.0 (1.0)          (2.5)          (2.5)       --
    29 May       1.0 (1.0)      3.5 (2.0)          (2.0)       --
    30 May       2.0 (1.0)      3.5 (2.00          (2.0)       --
    31 May       2.0 (1.5)      3.5 (2.5)      3.5 (2.5)          (2.5)
    01 Jun       1.5 (1.5)      2.0 (3.0)      2.0 (3.0)       --
    02 Jun       1.0 (1.0)      3.0            3.0                (1.0)
    03 Jun       4.0 (1.0)      2.0 (1.0)      2.0 (2.0)       --
    04 Jun       4.0 (1.0)      1.5 (2.0)      1.5 (2.0)       --
    05 Jun       3.0 (1.0)      1.5 (2.0)       --             --
    06 Jun       2.0 (1.0)          (2.0)       --             --
    07 Jun       3.0 (1.0)      1.5 (2.0)       --             --
    08 Jun       5.0 (1.0)      4.0 (2.0)       --             --
    09 Jun       4.0             --             --             --
    10 Jun       3.5 (1.0)          (2.0)       --                (3.0)
    11 Jun       4.0                (3.0)       --             --
    12 Jun       1.5                (3.0)       --             --
    13 Jun       3.0 (1.0)          (2.0)       --             --
    14 Jun       7.0             --             --             --
    15 Jun       4.5             --             --             --
    16-18 Jun    No data reported
    19 Jun       3.0 (1.0)       --             --             --
    20 Jun       3.5 (1.0)          (2.0)       --             --
    21-22 Jun    Obscured by weather
    23 Jun           (1.0)          (2.0)       --             --
    24 Jun       4.0 (1.0)      2.5 (2.5)       --             --
    25 Jun       3.0 (1.0)          (3.0)       --             --
    26 Jun       4.5 (1.0)      4.0 (3.0)       --             --
    28 Jun       3.0 (1.0)          (2.5)       --             --
    29 Jun       2.0 (1.0)          (2.5)       --             --
    30 Jun       3.0 (1.0)          (2.0)       --             --

Because of the vigor of activity, the Alert Level rose in several steps as follows: 19 March (Green to Yellow), 12 April (Yellow to Orange), and 13 May (Orange to Red). The step to Red (which is the highest alert level, and sometimes also referred to as Level 4) followed clear deformation at the dome during elevated seismicity. On 28 April, a new lava dome emerged. By 20 May, pyroclastic flows several kilometers long were regularly seen passing down several key drainages (table 18). Figure 29 shows a 15 May pyroclastic flow (seen two days after the alert status rose to red).

Figure 29. A photo taken on 15 May 2006 (0555 local time) of a pyroclastic flow traveling down the W flank of Merapi (the Krasak headwaters). Photo taken from the Kaliurang Observatory; courtesy of CVGHM.

Volcano enthusiasts and photographers Martin Rietze and Tom Pfeiffer viewed Merapi on the morning of 27 May, during the destructive earthquake, from a high-elevation parking area ~ 4 km S of the summit. Prior to the earthquake, Rietze took several spectacular photos of incandescent avalanches pouring down avalanche shoots (figure 30 A-B). During the earthquake, he described horizontal swinging motion and dull rumbling sounds lasting perhaps 20 seconds. Dust rose from the volcano. Plants rubbing together also produced a rustling noise. Cries and engine noises in the background came from distant residents responding to the earthquake. At ~1-minute intervals, Merapi emitted about six pyroclastic flows and a substantial ash cloud grew overhead, reaching several kilometers in altitude above them. The photo in figure 30 C depicts the scene on Merapi around that time (which Rietze lists as 0555 on 27 May). His companion, Tom Pfeiffer, also took photos just after the large earthquake (e.g., figure 30 D).

Figure 30. (A and B) Pre-dawn shots of incandescent material traveling down S-flank avalanche shoot(s) at Merapi on 27 May 2006 (prior to the M ~ 6 earthquake). (C) A photo of Merapi's response at 0555 on 27 May during or just after the M ~ 6 earthquake, with several pyroclastic flows clearly visible. (D) A second photo of the scene on Merapi during or just after the earthquake. This photo captured the chaotic scene at the summit and upper slopes, including a complex array of billowing ash clouds seemingly from multiple sources, and suspended dust hanging over many parts of the volcano (particularly distinguishable along the photo's lower central and right-hand areas). Copyrighted photos; those labeled A-C, used with permission of Martin Rietze; the one labeled D, with permission of Tom Pfeiffer.

During early June the activity level of Merapi remained at red and on 4 June, the increase in volume of the new lava dome had caused the southern part of the crater wall called Gegerbuaya (1910 lavas) to collapse. Prior to its collapse, Gegerbuaya had functioned as a barrier to prevent pyroclastic flows moving southward from entering the Gendol River, which they did later in June.

On 8 June, multiple pyroclastic flows reached 4 km from the Krasak and Boyong Rivers and up to 4.5 km down the Gendol River. On 9 June, ash drifted W and NW and accumulated as ashfall ~ 1.5 mm thick. Pyroclastic flows traveled as far as 4 km toward the Gendol River. Figures 31 and 32 show pyroclastic flows on 7 and 10 June.

Figure 31. A pyroclastic flow at Merapi at 08:54:37 on 7 June 2006 shown traveling down Merapi's upslope region in a generally SE direction. Photo credit to BPPTK (The Research and Technology Development Agency for Volcanology, Yogyakarta). Provided courtesy of CVGHM.
Figure 32. A Merapi pyroclastic flow in its early stages as seen at 08:50:53 on 10 June 2006. Photo credit to BPPTK; provided courtesy of CVGHM.

In the period after the hazard level was raised to red, the lava dome grew and by 22 May its volume was ~ 2.3 million cubic meters. The M 6.3 earthquake in S-Central Java on 27 May triggered additional activity at Merapi. The dome's growth rate increased from the previous rate of around 100,000 cubic meters/day, leading to a lava dome volume on 8 June 2006 of ~4.3 million cubic meters. That lava dome stood 116 m above the nominal summit elevation of Merapi's peak (Garuda peak).

Dome collapse created the longest pyroclastic flow of the reporting interval, which took place on 14 June 2006. That pyroclastic flow attained a run-out distance of 7.0 km (table 18, figures 33 and 34, and previously reported in BGVN 31:05).

Figure 33. Deserted houses and dislodged lumber amid ash and volcanic rocks from Merapi (left-background) as seen in the village of Kaliadem (E of Kinahrejo near Bebeng, on the SE flank ~ 5 km from the summit) shortly after the 14 June 2006 pyroclastic flows passed through the settlement. Courtesy of Agence France Presse (photo by Tarko Sudiarno).
Figure 34. Night photo of Merapi (unknown date) showing incandescence on the slopes and, in the foreground, the large pyroclastic flow deposited on 14 June 2006. This photo is taken from nearly the same spot as the photos of 27 May (figure 30, above). Copyrighted photo used with permission of Tom Pfeiffer.

At least in part owing to loss of topographic relief at the Gegerbuaya ridge along the S crater wall (figure 27), the 14 June pyroclastic flow took a different path. It crossed the former barrier and descended the Gendol drainage. As previously noted (BGVN 31:05), the 14 June pyroclastic flow took two lives when the underground bunker where the victims sought refuge was buried by the pyroclastic flow.

The bunker overridden on 14 June resides in Kaliadem village (~ 5 km SE of the summit). News stories showed pictures of the rescue attempt with initial digging commencing using picks and shovels, with the excavation by soldiers wearing dust masks and standing on boards or wooden platforms, presumably to reduce the heat flow from the fresh deposit. The article also noted that the soldiers wore heat-retardant clothes. A report from the Taipei Times of 16 June 2006 and credited to the Associated Press said that "The fierce heat melted the troops' shovels and the tires on a mechanical digger brought in to plow through more than 2 m of volcanic debris covering the bunker, built for protection from volcanic eruption . . .." Later news reports noted that authorities unearthed the bunker, which lay beneath more than 2 m of steaming pyroclastic flow deposit. The two bodies had suffered burns and the facility's door was ajar. A BBC report showed deeper portions of the hole being excavated by a large backhoe. They also noted that upon deeper excavation a probe into the deposit with a hand-held digital thermometer apparently indicated temperatures reached ~ 400°C. Several grim photographs circulated in the press showing the excavated entrance of the bunker and a team in the process of removing the victim's bodies. No report has been found discussing the exact reason for the bunker's failure, although several comments in the press suggested it was not designed to withstand burial by a pyroclastic flow.

Prior to that, on 13 June, the alert status dropped to orange, but it rose back to red again the next day after the pyroclastic flow and increases in multi-phased earthquakes. Activity remained stable but high through June 29 but began to decrease after 30 June. During July the intensity and frequency of pyroclastic flows and rock falls decreased. On 10 July, authorities reduced the alert status to orange on all but the S slopes. By the end of July 2006, pyroclastic flows had ceased.

Merapi's long-term dome growth continued at low to modest levels during the rest of 2006 and early 2007. The Darwin Volcanic Ash Advisory Center noted a plume to 6.1 km altitude drifting NE on 19 March 2007. These later incidents will be discussed in more detail in a forthcoming issue of the Bulletin.

MODVOLC Thermal Alerts. The Hawai'i Institute of Geophysics and Planetology MODIS Thermal Alert System web site lacked any thermal alerts for over a year preceding May 2006. Thermal alerts over Merapi began 14 May 2006 and extended through early September 2006 on nearly a daily basis. The alerts continued intermittently into 2007.

Reference. United Nations, 2006, Indonesia Earthquake 2006 Response Plan: United Nations, OCHA Situation Report No. 5, Issued 31 May 2006, GUDE EQ-2006-000064-IDN, 42 p.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://portal.vsi.esdm.go.id/joomla/); United Nations-Office for the Coordination of Humanitarian Affairs (OCHA), United Nations, New York, NY 10017, USA; National Earthquake Information Center, US Geological Survey, PO Box 25046, Denver Federal Center MS967, Denver, CO 80225, USA (URL: http://earthquake.usgs.gov/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, Northern Territory 0811, Australia (URL: http://www.bom.gov.au/info/vaac/advisories/); John Pallister, Volcano Disaster Assistance Program, USGS Cascades Volcano Observatory, 1300 SE Cardinal Court, Suite 100, Vancouver, WA 98683-9589, USA (URL: http://volcanoes.usgs.gov/); Tom Pfeiffer and Martin Rietze, Volcano Discovery (URL: http://www.decadevolcano.net/; http://www.tboeckel.de/EFSF/); Tarko Sudiarno, Agence France Presse (AFP) (http://www.afp.com/english/home/); Taipei Times (http://www.taipeitimes.com/); Associated Press (http://www.ap.org/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://hotspot.higp.hawaii.edu/).

10/2008 (BGVN 33:10) Lava dome growth with intermittent ash plumes and rock avalanches

Our last report on Merapi (BGVN 32:02) described vigorous dome growth during March-July 2006. The increasingly unstable summit was the scene of numerous pyroclastic flows, avalanches, and volcanic earthquakes. According to the Center of Volcanology and Geological Hazard Mitigation (CVGHM), Merapi's long-term dome growth continued at low to modest levels during the rest of 2006 and early 2007.

Activity in May 2006 included dome growth (figures 35 and 36) and pyroclastic flows (figure 37). According to CVGHM, as a result of decreasing activity, the Alert Level was lowered to 3 (on a scale of 1-4) for all areas on 17 July 2006 and to Level 2 on 3 August 2006. Nearly continuous thermal anomalies were measured by the MODIS/MODVOLC satellite system during the period 14 May-5 September 2006, and small anomalies were noted on 29 November 2006 and 5 January 2007. No thermal anomalies for Merapi have been measured by MODIS since 5 January 2007. The Darwin Volcanic Ash Advisory Center (VAAC) noted a plume to 6.1 km altitude drifting NE on 19 March 2007 (table 19).

Figure 35. Incandescent blocks stream down the growing lava dome on 15 May 2006. Courtesy of Discover Indonesia Online (Associated Press photo).
Figure 36. Newly extruded dome lava on the summit of Merapi seen from the N side on 21 May 2006. Courtesy of Tom Pfeiffer (Volcano Discovery).
Figure 37. Merapi erupting on 23 May 2006 as seen from Cangkringan, near Yogyakarta. The image captured a pyroclastic flow. Courtesy of Discover Indonesia Online.

Table 19. Ash plumes and other events associated with Merapi between 5 July 2006 and 15 November 2008. Distances given under "Other events" represent maximum distances observed. Plume altitudes through 1 August 2006 were calculated from CVGHM information; subsequent plume altitudes were reported by the Darwin VAAC. Courtesy of CVGHM, Darwin VAAC, and various newspaper articles.

    Date                  Plume       Other events
                          altitude

    05 Jul-11 Jul 2006     4 km
    12 Jul-18 Jul 2006     4 km       Lava flows, 2 km SE.
    19 Jul-25 Jul 2006     3.4 km     Daily lava flows, 1.5 km SE.
    26 Jul-01 Aug 2006     3.4 km     Incandescent rock avalanches, 2 km SE.
    02 Aug-04 Aug 2006     6.1 km     Rockfalls, 1 km SE.
    10 Oct 2006            --         Incandescent material, 1 km.
    20 Nov 2006            --         "Hot clouds," 3 km.
    19 Mar 2007            6.1 km
    23 May-29 May 2007     --         Incandescent material and "hot clouds," 1 km SE.
                                      Ashfall 16 km W.
    09 Aug 2007            4.6 km
    19 May 2008           11.6 km

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://portal.vsi.esdm.go.id/joomla/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI (URL: http://hotspot.higp,hawaii.edu); Discover Indonesia Online (URL: http://www.indahnesia.com/); Tom Pfeiffer, Volcano Discovery (URL: http://decadevolcano.net/).

02/2011 (BGVN 36:01) Eruption started 26 October 2010; 386 deaths, more than 300,000 evacuated

This report represents a preliminary discussion of the deadly eruption at Merapi that started on 26 October 2010. That eruption included weeks of instability that generated pyroclastic (block-and-ash) flows, which became particularly vigorous and numerous in early November, with at least one surge reportedly traveling along the Gendol drainage to 15-16 km from the summit dome. Of particular note from a hazards perspective, the path of some of these deposits differed at times from those of the recent past (but we have yet to find maps showing the flow directions and associated dates). An abstract by Lavigne and others (2011) reported the volume of tephra erupted in the 2010 eruption at over 100 x 106 m3, ~10-fold higher than similar deposits after typical eruptions in the past few decades, and among the factors why ongoing lahars are likely to be a hazard.

Our summary covers events into late 2010, with recognition of ongoing seismicity, weaker emissions, and repeated lahars in early 2011. The bulk of this report is based on those from the Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) and their observatory dedicated to Merapi (MVO). According to CVGHM, the 2010 eruption was the biggest since the 1872 eruption. Eruptions in 1930 killed around 1,300 people. The last eruption of Merapi occurred during March 2006-August 2007 (BGVN 31:05, 31:06, 32:02, and 33:10). A table appears near the end of this report summarizing some key events and observations. Fatalities and scale of evacuations are discussed in a separate subsection below. Another subsection notes that at least one commercial airliner sustained serious in-flight engine damage.

Regional background and prior eruptive patterns. Merapi (figures 38, 39, and 40) is located in the central part of Java, and this region and the island as a whole have extremely high population density (roughly double that of Japan or Thailand). Substantial numbers of people live or vacation on the mountain. The most densely settled part of the mountain is the dangerous S side (figure 39).

Figure 38. (Bottom) Two maps showing Merapi's location and (on the larger map) the distribution of block-and-ash flows that took place during 1954-1998. During that interval, these deposits went to the NW, W, and SW. From Hort and others (2006).
Figure 39. A map of the S portion of Merapi showing population data in shaded patterns with key at left. The segments of circles depict distances from the summit. The 2010 eruptions sent pyroclastic flows through Merapi's SE quadrant, thus passing areas of elevated population. Taken from OCHA (8 November 2010).
Figure 40. A set of simple diagrams illustrating Merapi in cross section (looking W; S is to the left) summarizing behavior that occurred during 1986-1994 (such a diagram has yet to be published for the 2010 eruption). The 1989 case shows VT earthquakes in the edifice (circles containing crosses). Taken from Ratdomopurbo and Poupinet (2000).

Figure 38 provides a summary of block-and ash-flow deposits from 1954-1998 (Hort and others, 2006; Schwarzkopf, 2001). The eruptions starting in October 2010 sent pyroclastic flows and possible surges at least 15 km in the volcano's W to S quadrant. Block-and-ash flows are pyroclastic flows formed by dome collapse and containing a substantial amount of broken dome fragments.

The inset map at the lower left shows Merapi with respect to the city of Yogyakarta (30 km SSW). Although the metro area of that city has a population of 1.6 million residents, the Indonesian statistical bureau estimated the 2010 populations of the ~30 km2 city of Yogyakarta at ~396,000 residents, and the broader region at ~3.5 million residents.

Figure 39 shows the summit and S part of Merapi, plotting population data by village at distances up to 20-25 km from the summit. This side of the volcano is by far the most densely populated, and was also crossed by numerous pyroclastic flows both historically and in the 2010 eruptions.

Figure 40 illustrates critical processes in Merapi's mode of eruption in the recent past. A significant portion of the dome is unconfined by the summit crater and the S side is free to descend the volcano's upper slopes endangering residents below. In the recent episode, CVGHM benefitted from daily access to satellite radar imagery that reliably depicted dome morphology despite weather and steam clouds. Vöge and Hort (2008) and Hort and others (2006) discuss monitoring dome instability using Doppler radar.

Monitoring and lead-up to the 26 October 2010 eruption. Since 2007, short swarms of volcanic earthquakes occurred (eg., on 31 October 2009, 6 December 2009, and 10 June 2010). Monitored parameters, including earthquakes, deformation, and gas emmisions increased significantly during September 2010. Steeper increases in seismicity appeared during 15-26 October with the main ramp-up during 20-26 October.

Figure 41 shows several histograms that depict Merapi seismic data and summarize the variations in hazard status. The CVGHM scale, which stretches from 1 (low) to 4 (high), makes a complete ascent and partial descent through the full range of those levels during the date range shown. The heavy vertical line between Alert Levels 3 and 4 took place on 25 October, slightly before the onset of the major eruption on 26 October.

Figure 41. Three histograms describing Merapi seismicity during 1 September 2010 to 6 March 2011. Horizontal scale marked in weeks and extends from 1 September 2010 to 5 March 2011. Words along the top line show hazard status (on an increasing scale starting from 1 [Normal] and extending to 2 [Waspada]), to 3 [Siaga]), and finally to 4 [Awas] and then declining). The top panel contains seismically inferred rockfalls and avalanches (guguran in Indonesian). The middle panel shows multiphase (MP) earthquakes (shallow source, dominant frequency ~1.5 Hz). The bottom panel shows volcanic earthquakes of both A- and B-type (where VTA represents deep volcano-tectonic earthquakes, 2.5-5 km below the summit; VTB represents shallow volcano-tectonic earthquakes, less than ~1.5 km below the summit). Taken from CVGHM report of 7 March, with minor revisions by Bulletin editors.

Figure 42 presents typical waveforms for various types of earthquakes and tremor signals previously recorded at Merapi (Ratdomopurbo and Poupinet, 2000). Both multiphase (MP) and volcanic type-A (VTA) showed strong peaks in seismicity prior to the 26 October eruption's onset. Rockfalls on upper panel (labeled guguran) and type-b events on bottom panel both peaked on or near 26 October.

Figure 42. Typical waveforms, tremor signals, and descriptive seismic terminology in use at Merapi. These include tremor, LF-low frequency (earthquakes nominally from shallow sources, dominant frequency between 3 and 4 Hz), VTA and VTB (volcano-tectonic A and B, where VTA represents deeper volcano-tectonic earthquakes, 2.5-5 km below the summit; and VTB represents shallower volcano-tectonic earthquake, less than ~1.5 km below the summit), and MP-multiphase earthquakes. Records are from Station PUS (~0.5 km E of summit), shown in the upper part of the figure, and from Station DEL (~3 km SE of the summit), in the lower part. From Ratdomopurbo and Poupinet (2000).

The onset of the 26 October explosion occurred ~19 hours after an M 7.7 tectonic earthquake along the trench near the Mentawai islands adjacent to Central Sumatra, 1,200 km NW of Merapi. This earthquake was followed by several aftershocks, including two prior to the eruption (M 6.1 and 6.2) and one after the eruption (M 5.8). One or more of these earthquakes triggered tsunamis that hit the remote Mentawai islands, sweeping entire villages to sea and killing at least 428 people. There, too, thousands of people were displaced. The two near-simultaneous crises taxed authorities, NGOs, and the natural hazards community (figure 43).

Figure 43. A map emphasizing the locations of the M 7.7 tsunamigenic (tsunami-generating) earthquake and the eruption onset at Merapi, events of 25 and 26 October, respectively. (The earthquake time stated is incorrect—according to USGS cataloging, it registered at 1442 UTC on the 25th, which corresponds to 2142 local time that day. The eruption began at 1002 UTC on the 26th). Jakara is Indonesia's capital. Courtesy of Relief Web.

Except for the close timing and regional proximity, the linkage between the M 7.7 earthquake and the eruption remains ambiguous. However, many researchers have noted that tectonic earthquakes can seemingly trigger volcanic responses (eg., Delle Donne and others, 2010; Lowenstern, JB, Smith, RB, and Hill, DP, 2006; Manga and Brodsky, 2006).

In early September 2010, the pattern of increased volcanic seismicity began to appear with MP earthquakes averaging 10/day and VTA and VTB averaging 3/day, with a total daily seismic energy of 603 x 1012 erg.

Gas analyses in August 2010 showed concentrations of HCl of 0.8 % mol and H2O of 80 % mol. Declining levels of H2O (less than 90 %) and increased levels of HCl (>0.5 %) were interpreted to indicate increased activity.

In September, summit inflation increased markedly. Seismicity also increased beginning on 12 September, when an M 2.5 VTA earthquake and pyroclastic flows/avalanches occurred. On 13 September, VTA earthquakes occurred twice, and white plumes rose 800 m above the crater.

During 23-26 October, there were small steam-and-ash emissions. Inflation increased sharply on 24 October to a rate of 420 mm/day. The next day, CVGHM raised the Alert Level to 4, and recommended immediate evacuation for several communities within a 10-km radius. A Reuters photo by Dwi Oblo taken at sunrise on 26 October looking up at the dome and the prominent S-trending avalanche channel revealed comparatively calm conditions, with emissions consisting of a thick white steam plume blowing W from the dome.

Initial October eruptions. The first eruption occurred at 1702 on 26 October 2010, an event characterized by explosions and multiple pyroclastic flows that traveled S ~8 km down the Gendol and Kuning drainages, and to some extent WSW down the Bedog drainage. Most of the pyroclastic flows lasted 2-9 minutes, but the eruptions associated with the final two each lasted 35 minutes. The event killed 35 people including the renowned mystical guardian of Merapi, Mbah Mbahmarijan, at 7 km distance.

Figure 44 shows an exposed ridge affected by pyroclastic flows in a photo taken on 27 October.

Figure 44. An exposed ridge at Merapi as it appeared the day after the 26 October eruption. Pyroclastic flows had reduced forest to stumps, leaving stripped and fallen trees. Courtesy of The Boston Globe website of Merapi photos (Ulet Ifansasti/Getty Images).

According to the Darwin Volcanic Ash Advisory Center (VAAC), an ash plume rose to an altitude of 18 km, followed by extrusion of lava in the summit crater.

By 27 October the lava dome had sustained damage and a new 200-m-diameter crater had formed at the summit. After that, lava extrusions built a small dome in the crater. A space-based estimate made from the ozone monitoring instrument (OMI) indicated the eruption on the 26th vented at least 3,000 metric tons of SO2 gas. According to the Darwin VAAC, ground-based reports indicated that another explosion occurred on 28 October 2010. Cloud cover prevented satellite observations.

Following the eruption and continuing through 4 November, intense tremor took place. It was felt by people up to 20 km from the volcano.

CVGHM reported that two pyroclastic flows occurred on 30 October following an early morning explosion, the third since 26 October. According to a news article, ash fell in Yogyakarta, 30 km SSW, causing low visibility. CVGHM noted four pyroclastic flows on 31 October.

Stronger eruptions in November. According to CVGHM, during 31 October-4 November, a lava dome grew rapidly within Merapi's summit crater. Collapses from the S side of the dome fed minor pyroclastic flows that extended several hundred meters into the upper part of the Gendol valley.

On 1 November, an explosion began mid-morning with a low-frequency earthquake, and avalanches occurred. About seven pyroclastic flows occurred during the next few hours (figure 45), traveling SSE a maximum runout distance of 4 km, and in another (possibly later) case that day, 9 km. The Darwin VAAC reported that the explosion produced an ash plume that rose to an altitude of 6.1 km. News reports noted flight diversions and cancellations in and out of the airports serving Solo (40 km E) and Yogyakarta.

Figure 45. On 1 November 2010, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite captured this thermal signature of Merapi's lava dome and hot pyroclastic flows. The thermal information is overlaid on a three-dimensional map of the volcano to show the approximate location of the pyroclastic flow. The three-dimensional data is from a global topographic model created using ASTER stereo observations. Courtesy of NASA Earth Observatory website (credit to Robert Simmon and Jesse Allen and NASA/GSFC/METI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team). Original caption by Holli Riebeek.

On 2 November, an ash plume was seen in satellite imagery drifting 75 km N at an altitude of 6.1 km. On the same day, CVGHM reported 26 pyroclastic flows. On 3 November, observers stationed at multiple posts reported ash plumes from pyroclastic flows. One pyroclastic flow traveled 10 km, prompting CVGHM to extend the hazard zone from a radius of 10 km to 15 km, and they recommended evacuations from several more communities. Another pyroclastic flow traveled 9 km SE later that day. Figure 46 shows a 2 November view of Merapi.

Figure 46. Incandescent material spilled from Merapi's dome glows orange-red in colored versions of this long-exposure photograph taken on 2 November 2010 from ~25 km SSE of the summit (Klaten district). Condensate droplets in the thin (lenticular) clouds over the summit also reflect considerable light. Courtesy of The Boston Globe (Boston.com website); photo credit to Sonny Timbelaka (AFP/Getty Images).

CVGHM reported that, during 3-8 November, the eruption from Merapi continued at a vigorous pace, characterized by incandescent avalanches from the lava dome, pyroclastic flows, ash plumes, and occasional explosions.

Visual observations were often difficult due to inclement weather and eruption plumes. To overcome these challenges, people working on the crisis gained regular access to satellite radar data of high resolution (RADARSAT2). That data was made available 25 October through an agreement called the International Charter Space and Major Disasters.

According to the NASA Earth Observatory website, the strongest explosion during the 2010 eruption took place on 4-5 November, lasting more than 24 hours, when plumes rose to ~18 km altitude and drifted 110 km W. They claimed that some surges of pyroclastic material reached an 18 km runout distance (direction and damage unstated and several kilometers longer than some other observations). They also said that, according to local geologists, this explosion was the most violent one at Merapi since the 1870's. They noted that, by some estimates, the 4-5 November eruption was five times more intense than the one on 26 October.

A CVGHM report on the 4-5 November eruption stated that 38 pyroclastic flows had occurred before it ended. Although dense fog hampered visual observations, a CVGHM observer from Kaliurang post (~7 km S of the summit) saw 19 of those 38 flows travel ~4 km S. Another traveled 9 km SE. Ashfall was noted in some nearby areas. Satellite data indicated this explosion released much more SO2 than previous recent Merapi eruptions, ~300,000 metric tons.

Residents in towns up to 240 km away reported that 'heavy gray ash' blanketed trees, cars, and roads. On 5 November, rumbling sounds were heard in areas 30 km away, and pyroclastic flows continued to descend the flanks. Ash fell in Yogyakarta and "sand"-sized tephra fell within 15 km. CVGHM recommended evacuations from several more towns within a 20-km radius. Observations shortly after the 5 November eruption showed that the large lava dome of the previous week had been destroyed, and the summit crater had enlarged to a diameter of 300-400 m. However, by 6 November, another lava dome had grown, amassing, according to RADARSAT images 11 hours apart, at a rate of ~35 m3 per second.

Activity remained very intense on 6 November. Pyroclastic flows continued to descend the flanks; one flow traveled 4 km down the Senowo drainage to the W. Incandescent flashes from the lava dome were reported from observations posts, and incandescent material was ejected above the crater. Incandescent avalanches traveled 2 km down multiple drainages to the SSE, S, and SSW. The Darwin VAAC reported that ash plumes seen in satellite imagery rose to an altitude of 16.8 km on 5 and 6 November.

During this period, ashfall was heavy on Merapi's flanks, and was observed in multiple surrounding areas, including the villages of Selo (~5 km NNE) and Magelang (26 km WNW). In Muntilan village (18 km WSW), tephra and ash accumulated up to 4 cm. At the volcano, a new dome formed during 6-7 November 2010; it stood ~240 m in a NW-SE orientation, 140 m wide, and 40-50 m high.

On 7 November, the number of pyroclastic flows increased from the previous day. An explosion was heard, and ash plumes rose 6 km and drifted W. Lightning was seen from Yogyakarta. Pyroclastic flows traveled 5 km, and lava avalanches moved 600 m S and SW. The next day, ash plumes rose to altitudes of 6-7 km and were accompanied by rumbling sounds. According to the Darwin VAAC, satellite imagery during 7-8 November showed ash plumes at an altitude of 7.6 km drifting 165-220 km W and SW.

Figure 47 shows Merapi's erupted SO2 in the atmosphere during 4-8 November 2010. On 9 November, an SO2 cloud was seen over the Indian Ocean at altitudes of 12-15 km.

Figure 47. SO2 concentration-pathlength (in Dobson units, with 100 DU as darkest colors) during 4-8 November 2010, as observed by the OMI on NASA's Aura spacecraft. OMI data provided courtesy of Simon Carn (Michigan Technical University). Courtesy of Natural Hazards NASA Earth Observatory website (image by Jesse Allen, and original caption by Michon Scott).

The European Space Agency (ESA) has created updates on SO2 gas retrieval from their Envisat, Eumetsat's MetOp, and NASA's Aura satellites. For the interval 4-13 November 2010, the peak atmospheric loading of SO2 appeared on 8 November at 227 kT SO2. The estimates can be seen presented as animations that depict complex rotating dispersal patterns. As seen in figure 47, significant portions of the gas blew over Western Australia. In Norwegian Institute for Air Research models shown in the article, many of the Merapi plumes centered around 15 km altitude, with tops and bottoms ~5 km above and below that height.

ESA (2010) quoted Andrew Tupper as saying, "The updates from ESA have been very useful to Darwin VAAC [Volcanic Ash Advisory Center] when received in real time, and we expect that in the post-event analysis we'll be able to show lots more potential value." The SO2 maps can help the aviation community avoid dangerous emissions from volcanoes.

ESA (2010) noted that they send SO2 email alerts in near-real time. The alerts link to a web page with a map showing the location of the sulphur dioxide peak.

Reduced eruptive vigor; lahars. Eruptions and seismicity generally dropped during mid-November 2010 into March 2011, but lahars became a problem. On 9 November, CVGHM noted a reduction in the intensity of activity; a single pyroclastic flow occurred in a 6-hour period. Rumbling sounds were accompanied by an ash plume that rose to an altitude of 4.5 km, and ashfall was reported in Selo (~5 km NNE). Lava-dome incandescence was again observed, and lava avalanches moved 800 m SSE.

During 10-11 November, seismicity continued to decrease. Lahar deposits were seen in multiple drainages, at a maximum distance of 16.5 km from the summit. On 10 November, plumes generally rose 0.8-1.5 km above the crater. Heavy ashfall was reported in areas to the WSW and WNW. A 3.5-km-long pyroclastic flow and a 200-m-long avalanche both traveled S in the Gendol drainage. Incandescence from the crater was observed through a closed-circuit television system at the Merapi museum (in the village of Kaliurang, ~7 km S of the summit). On 11 November, roaring was followed by light ashfall at the Ketep Merapi observation post, ~9 km NW of the summit. Plumes, brownish-black at times, rose 800 m above the crater and drifted W and NW, and one plume rose 1.5 km. Avalanches again proceeded S in the Gendol drainage.

According to the Darwin VAAC, during 12-21 November, ash plumes rose as high as 7.6 km and drifted in multiple directions. The SO2 concentration at high altitudes decreased. About 300,000 residents also began to return home after the "danger zone" was reduced in some areas due to decreased activity.

Between 10 November and 1 December, lahar deposits were seen in multiple drainages and in all rivers flowing from Merapi. CVGHM noted that several bridges had been damaged. On 29 November, a narrow tongue of lava was observed, and light-colored flow deposits extended S down several narrow channels (Gendol and Kuning drainages) at least 5 km from the summit.

According to CVGHM, seismicity declined further during 1-3 December, in number of volcanic earthquakes and their associated energy. Deformation measurements were either stable or did not show significant changes. Although fog often prevented visual observations, gas plumes were seen rising 500 m above the crater and drifting W. SO2 plumes were no longer detected in satellite imagery. On 4 December, the Alert Level was lowered to 3.

On 9 January, as seismicity continued to decrease, CVGHM lowered the Alert Level to 2. Plumes continued to rise above the crater and, on 12 January, avalanches descended the Krasak drainage, traveling 1.5 km SW. Lahars and high water during 15-23 January damaged infrastructure and caused temporary road closures. On 22 January, plumes rose 175 m above the crater and drifted E.

According to a news account (vivanews.com), Merapi spewed thick white plumes as of the first week of February 2011. CVGHM reported that gas plumes rose from Merapi during 28 February-6 March. The highest plume, on 5 March, rose 100 m and drifted E. The number of MP earthquakes was slightly lower compared to the previous week.

Analysis of the lahar problem emerged as this issue went to press. According to Lavigne and others (2011) the volume of pyroclastic debris from the 2010 eruptive episode was in excess of 100 x 106 m3, ~10-fold higher than similar deposits after more conventional eruptions. These deposits and subsequent lahars filled most of the protective Sabo-dam structures. The eruption coincided with the onset of the rainy season, an interval that usually brings 4 m of rain but due to La Niña conditions, is predicted to bring more rain than usual. The 50-year absence of lahars in Kuning and Woro drainages altered the perception of risk in residents there. Thousands of sand miners work in the riverbed of all lahar-prone channels.

Fatalities and scale of evacuations. As previously noted, on 26 October, pyroclastic flows killed ~35 people who 7 km from the summit. They had refused to evacuate the village of Kinahejo (Kinahrejo).

According to the U.S. Agency for International Development (USAID) (quoting the Government of Indonesia's National Disaster Management Agency-Badan Nasional Penanggulangan Bencana or BNPB), the 2010 eruptions killed 386 people, injured 131 people, and displaced initially more than 300,000 residents (USAID, 2011). According to Relief Web, the 11,000 displaced remained unable to return to their homes at least as late as January 2011.

Lahars followed the eruptive processes and caused at least one additional death and one injury. An 11 January IRIN News article stated that " . . . more than 300,000 people have been able to return home, another 11,000 remain displaced, living with family or in camps, according to the government's National Disaster Management Agency."

According to the UN's Integrated Regional Information Networks (IRIN News), a source of humanitarian news and analysis, rainfall triggered lahars on Merapi's flanks on 3 and 9 January 2011. This caused damage to houses, farms, and infrastructure in multiple villages in the Magelang district, 26 km WNW of Merapi. One death and an injury were reported. The flooded area reportedly affected an estimated 3,000 residents but the number evacuated was unstated. The flooding on 9 January was more intense and, according to IRIN News, the Red Cross evacuated dozens of people trapped in their homes.

Referring to the larger 2010 eruption and evacuees, the same 11 January IRIN article stated that " . . . more than 300,000 people have been able to return home, another 11,000 remain displaced, living with family or in camps, according to the government's National Disaster Management Agency." This article also quoted the same agency with regard to the 386 reported deaths and the 131 injuries from the 2010 eruption.

Airlines affected. According the Jakarta Post, a total of 13 international carriers stopped their flights to Jakarta on 6 November, citing concerns about volcanic ash in the air that could cause damage to their aircraft and engines, and thus jeopardize safety. They included Malaysia Airlines, Air Asia, Singapore Airlines, Emirate, Ethihad, Turkish Air, Japan Airlines, Lufthansa, and KLM.

Andrew Tupper at the Australian Bureau of Meteorology notified us that Indonesian media reported that a plane encountered a volcanic cloud N of Java ascribed to Merapi on 28 October 2010. The suspected ash-plume encounter occurred at altitudes in the range 9.1-11.6 km. An engine stall message alerted the crew, who also noted a strong burning odor that disappeared as the plane descended from 9.1 to 6.1 km altitude.

According to another news account (Kompas.com), possibly reporting the same incident, on 28 October, a Garuda Indonesia airplane with 383 passengers from Solo, Central Java, landed safely at Hang Nadim Airport, Batam, a scheduled refueling stop. Enroute, volcanic ash from Merapi had been sucked into the left engine of the Airbus 330 aircraft, disrupting the engine. Richard Wijaya, Operational Duty Manager of Garuda Indonesia in Batam, explained that the pilot had notified ground staff of the disruption before landing, and as soon as they landed in Batam, the engine was checked. The crew cancelled the next leg of the scheduled flight to Jeddah, Saudi Arabia.

On 2 November, an unspecified number of international airlines had to cancel flights to airports at Solo and Yogyakarta, as plumes blackened the sky. Poor visibility and heavy ash on the runway caused the cancellations. According to an ABC news report, Yogyakarta airport reopened on 20 November after being closed for ~2 weeks.

Data table. Table 20 summarizes currently available CVGHM reports on Merapi's behavior during September to 1 December 2010. In the first row, it presents some background values commonly seen at Merapi during non-eruption conditions. Seismic terminology in the table is equivalent to that seen in figure 42 (Ratdomopurbo and Poupinet, 2000). Note the rise in seismic energy on 19 September, various changes in Alert Level, and major events in bolded type. Comparative calm prevailed after early November, but lahars became a problem (see text). The table is intended to give readers an overview of the eruption rather than capture all the details.

Table 20. Preliminary summary of pyroclastic flows as well as some collateral observations, and hazard status changes relating to Merapi during early September through 22 November 2010. Pyroclastic flows (locally termed AP for awan panas, hot clouds) here are tallied both from seismic detection and visual observations). The table omits seismic data shown in figure 41. The "ber" (beruntun) refers to episodes of densely spaced signals indistinguishable from each other. Those signals were common beginning 4 November and complicated assessments of tremor (not shown). Courtesy of CVGHM and A. Ratdomopurbo (personal communication).

Date, 2010Pyroclastic flows detected
by seismic data
[and visual observations
(with direction of travel)]
Related comments
Background
(pre-eruption)
- Seismic energy less than 342 x 1012 erg (normal, non-eruptive conditions)
Early Sept - Seismic energy, 603 x 1012 ergs
19 Sep - Seismic energy, ~6,000 x 1012 erg
20 Sep - Alert Level raised to 2
21 Oct - Alert Level raised to 3
25 Oct - Regional M 7.7 earthquake; Alert Level raised to 4
26 Oct 8 [Multiple (WSW, SE)] Initial eruption at 1702 LT
30 Oct 2 Second explosive eruption; ashfall in city of Yogyakarta
31 Oct 4 Eruption
01 Nov 7 during several hr  
02 Nov 26 Eruption; 9 and 10 km runout distances
03 Nov 38 [At least 19 (S)] Eruption
04 Nov ber [Multiple] Eruption (over 24 hours)
05 Nov ber [Multiple] 4-5 Nov. eruption was largest 2010 eruption (ash plume to 16.8 km asl); runout distances of ~18 km(?); widespread ash fall; dome destruction
06 Nov 5 [Multiple] Eruption—rapid dome extrusion
07 Nov ber [Multiple] Eruption
08 Nov 7 Eruption
09 Nov 2 [1 in 6 hr period] Weaker eruption
10 Nov 1 [At least 1 (S)] Weaker eruption
11 Nov 1 [At least 1 (S)] Weaker eruption
14 Nov 2 [0 (none)] Weaker eruption
15 Nov [1] Weaker eruption
16 Nov [1] Weaker eruption
22 Nov [5] Eruption

 

References. Delle Donne, D., Harris, AJL, Ripepe, M, and Wright, R., 2010, Earthquake-induced thermal anomalies at active volcanoes, Geology, Sept. 2010; v. 38; pp. 771-774 [DOI: 10.1130/G30984.1].

European Space Agency (ESA), 2010, Satellites tracking Mt Merapi volcanic ash clouds, ESA News (online; 15 November 2010) (URL: http://www.esa.int/esaCP/SEMY0Y46JGG_index_0.html).

Hort, M, Vöge, FM., Seyfried, R, and Ratdomopurbo, A, 2006, In situ observation of dome instabilities at Merapi volcano, Indonesia: A new tool for volcanic hazard mitigation, Journal of Volcanology and Geothermal Research, v. 154, no. 3-4, p. 301-312.

Lavigne,F, de Bélizal, E, Cholik, N, Aisyah, N, Picquout, A, and Wulan Mei, ET, 2011, Lahar hazards and risks following the 2010 eruption of Merapi volcano, Indonesia, Geophysical Research Abstracts, v. 13, EGU2011-4400, 2011, EGU General Assembly 2011.

Lowenstern, JB, Smith, RB, and Hill, DP, 2006, Monitoring super-volcanoes: geophysical and geochemical signals at Yellowstone and other large caldera systems, Phil. Trans. R. Soc. A, 15 August 2006, v. 364, no. 1845, p. 2055-2072.

Manga, M. and Brodsky, E, 2006, Seismic triggering of eruptions in the far field: volcanoes and geysers, Annual Review of Earth and Planetary Sciences, v. 34, p. 263-291 [DOI: 10.1146/annurev.earth.34.031405.125125].

Ratdomopurbo, A, and Poupinet, G, 2000, An overview of the seismicity of Merapi volcano (Java, Indonesia), 1983-1994, Journal of Volcanology and Geothermal Research, v. 100, no. 1-4, p.193-214 (DOI: 10.1016/S0377-0273(00)00137-2).

Schwarzkopf, L, 2001, The 1995 and 1998 block and ash flow deposits at Merapi volcano, Central Java, Indonesia: implications for emplacement mechanisms and hazard mitigation. Ph.D. Thesis, University at Kiel, Kiel, Germany.

USAID (U.S. Agency for International Development), 2011 (February 4), Indonesia - Tsunami and Volcano, Fact Sheet 2, Fiscal Year 2011.

Vöge, FM, and Hort, M, 2008, Automatic classification of dome instabilities based on Doppler radar measurements at Merapi volcano, Indonesia: Part I. Geophysical Journal International, v. 172, no. 3, p. 1188-1206 (DOI: 10.1111/j.1365-246X.2007.03605.x).

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://portal.vsi.esdm.go.id/joomla/); Merapi Volcano Observatory (MVO); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/); U.S. Agency for International Development (USAID) (URL: http://www.usaid.gov); Antonius Ratdomopurbo, Nanyang Technological University, Earth Observatory of Singapore, Nanyang Avenue, Singapore (URL: http://www.earthobservatory.sg/); Andrew Tupper, Australian Bureau of Meteorology (URL: http://www.bom.gov.au/); European Geosciences Union (URL: http://www.egu.eu/); Badan Nasional Penanggulangan Bencana (BNPB - Indonesian National Disaster Management Agency) (URL: http://dibi.bnpb.go.id/); Relief Web (URL: http://www.reliefweb.int/); Kompas News, Jakarta, Indonesia (URL: http://www.Kompas.com); The Jakarta Post (URL: http://www.thejakartapost.com/); Reuters (URL: http://www.reuters.com/); Vivanews.com (URL: http://vivanews.com/); ABC News (Australia) (URL: http://www.abc.net.au/); The Boston Globe (URL: http://www.boston.com/bigpicture/2010/11/mount_merapis_eruptions.html); IRIN News (URL: http://www.IRINnews.org/).

05/2011 (BGVN 36:05) Recovery; intermittent activity; damaging lahars

A VEI 4 (Volcanic Explosivity Index) eruption began at Merapi volcano on 26 October 2010. Within the last 100 years, this volcano had not produced such large-magnitude explosions (Surono and others, in review; Andreastuti and others, 2011). The eruption and secondary events affected areas in all directions around the volcano; pyroclastic flows reached 4 km to the N, 11.5 km to the W, 7 km to the E, and ~15 km to the S, and explosive bombs reached 4 km from the summit in all directions (Jousset, 2010). These events included explosive central vent eruptions that caused significant changes in the summit morphology (figure 48) and according to Act Forum Indonesia, triggered evacuations of communities within a 20 km radius of the summit. In BGVN 36:1/2 we reported on preliminary damage assessments that included significant fatalities and damaged infrastructure.

Figure 48. A photo comparison of Merapi's morphological changes on 23 March 2010 and 16 March 2011. Viewed from the S flank, these photos focus on the summit dome. Non-juvenile material was excavated during two episodes of explosive activity. During 26-29 October ~1.4 x 106 m3 was excavated from the crater and from 4-5 November ~10 x 106 m3 was removed (Surono and others, in review). Photo courtesy of the Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPK") from their report covering 14-20 March 2011.

The explosive events of 2010 represent a break in Merapi's iconic style of activity (Surono and others, in review). "Merapian" is a term often assigned to volcanic events characterized by hot pyroclastic block flows generated during the collapse of growing viscous lava domes (Schmincke, 2004). Standard eruptive activity at Merapi includes "continuous degassing and extrusion of andesitic lava domes whose collapses generate block avalanches and gravitational pyroclastic flows" (Allard and others, 2011).

At least 17 VEI = 2 events have occurred since the catastrophic 15 April 1872 eruption (Siebert and others, 2010). While explosive activity is characteristic of past behavior, assessments of data from 2010 confirm that the 26 October eruptive sequence did not begin with lava extrusion (typical of past eruptions). Instead, intense explosions initiated activity that lasted for ~5 weeks (Surono and others, in review).

During the Merapi special session at the EGU General Assembly held in April 2011, Andreastuti and others (2011) concluded that "the rate of magma extrusion [during the peak of Merapi's 2010 activity] was as much as 17-to 21-times higher [than] the 2006 eruption and the distance of pyroclastic flows in the same drainage (Gendol River) reached 15 km in 2010 and only 7 km in 2006."

This assessment and others (e.g. Alder and others, 2011) linked the highly explosive eruptions of October-November 2010 to elevated and variable gas emissions.

On 4 December 2010, after 40 days of maintaining the highest alert, the Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) downgraded the hazard Alert Level from 4 to 3 ("Awas," Red Alert to "Siaga," Watch). The Alert Level was reduced again on 19 January 2011 from 3 to 2 (to "Waspada," Advisory). The Alert Level remained at Level 2 into June 2011.

In this report we review the recovery efforts, Merapi's intermittent activity, and the long-term lahar crisis from March to June 2011. We also include a review of intervals of gas geochemistry data recorded prior to the 26 October 2010 disaster that recently became available.

Recovery efforts. Since October 2010, of the ~300,000 people evacuated, 11,000 were still displaced as of January 2011 (Jakarta Post and IRIN). Authorities had set up nine camps within the city of Yogyakarta and ~70 camps were located farther away within Central Java. On 2 May 2011 the head of Badan Nasional Penanggulangan Bencana (BNPB), Indonesia's National Disaster Management Agency, reported: "With almost all the displaced having moved to temporary shelters, our focus now is how to rebuild communities affected by the disaster" (IRIN, 2011).

In May 2011 the Indonesian government sought international aid (including the International Red Cross and United Nations) and international non-governmental organizations were working in Indonesia for relief efforts. The Jakarta Post reported on 12 May 2011 that Australia had agreed to help Indonesia establish a Disaster Relief Center for disaster management training; the location will be in Sentul, West Java and will serve members of the Association of Southeast Asian Nations (ten countries currently belong to ASEAN). BNPB had called upon the World Bank to begin a Risk Transfer scheme, allowing the local government to focus aid specifically on reconstruction programs.

According to reports from the Jakarta Globe in April 2011, the recent disaster and long history of volcanism at Merapi prompted the Indonesian government to implement an extensive recovery plan for the Yogyakarta province. They prioritized the development of spatial planning maps, expansion of the Merapi National Park, large-scale reforestation (approximately 1,300 hectares), and allocation of 1.35 trillion Rupiah ($155 million) to improve housing, infrastructure, social efforts, and economic stimulation plans. New mapping in the province will reassign land-use and designate relocation sites for former residents. In general, residential areas lying within 10 km of the summit will remain off limits (Sayudi and others, 2010). The Jakarta Post noted these maps also highlight where reforestation will occur. Impacts were substantial to Merapi National Park which lost up to 2,800 hectares out of 6,410 hectares of forest due to the recent eruptions. The Volcano Technical Research Center (BPPTK) reassessed zones in the Sleman region, the area hardest hit by volcanic activity, and will release a map indicating hazard zones. "[These maps] will show which areas are safe, unsafe and suitable for habitation," stated Sleman administration spokeswoman Endah Sri Widiastuti (Jakarta Post).

A controversial location within the 10 km exclusion zone is the village of Kinahrejo, the former home of spiritual leader Mbah Maridjan, called the guardian of Merapi. Working with a team of 17 respected community members, he preserved traditional ceremonies and local culture for Merapi residents. Pyroclastic flows covered the village on 26 October 2010, taking the life of the guardian and other inhabitants who did not evacuate.

The new guardian is Mbah Maridjian's son, Asihono (his new name: Mas Lurah Suraksosihono). During Merapi's disastrous eruptions of October and November, Asihono cooperated with the local government and agencies including the Volcanology and Geological Disaster Mitigation Agency (PVMBG) and BPPTK. On 4 April 2011 Sultan Hamengku Buwono X elected Asihono from a group of eight candidates. In an interview with Jakarta Globe on 5 April 2011, the new guardian explained: "I'm not just going to take a cultural approach based on the dreams or guidance from the spirits, but I will also coordinate with the authorities to protect human life and the environment on Mount Merapi and anticipate the fall of victims to future eruptions."

New dome growth. Seismicity was variable and intermittent explosions were observed at Merapi at least every month through June 2011 since the main eruptive events of October and November 2010. This activity kept local residents vigilant and caused some alarm when incandescence suddenly appeared on Merapi's summit on 25 March and 13 April (figure 49). On these two occasions, a bright glow on the crater's E side was recorded on closed circuit television (CCTV).

Figure 49. Bright incandescence visible on the E side of Merapi's crater was observed at 1940 on 25 March 2011. Courtesy of Volcano Technical Research Center (BPPTK Activity Report 21-27 March 2011).

The point of incandescence was a location of concentrated degassing. In the aftermath of the eruption in 2010, fumaroles became well established and BPPTK intends to resume gas monitoring. They reported that a new dome was growing in the crater: "The final phase is usually marked by eruption of lava dome growth. However, we won't lower the [alert] status as long as the condition of Merapi is still volatile," reported Subandriyo of BPPTK on 11 April 2011 (Kompas News). Since 19 January 2011, the Alert Level was at 2, Advisory.

Gas monitoring. From ultraviolet correlation spectrometer (COSPEC) measurements, BPPTK reported continuous SO2 emissions for both 1992 through early 2009 (BPPTK, 2011b) and January 2005-January 2010 (figure 50). Other data resulted from sampling with Giggenbach bottles; a method of condensate retrieval requiring evacuated alkaline-solution-filled bottles (Williams-Jones and Rymer, 2000). Gas species such as CO2, SO2, H2S, and HCL were analyzed during June 2003-June 2010 (figure 51).

Figure 50. Merapi SO2 fluxes measured from January 2005 to roughly April 2009 using COSPEC (sulfur dioxide in metric tons per day). The curve shown displays an undisclosed averaging function on the data. Modified from BPPTK, 2011a.
Figure 51. Gas sampling at Merapi's Woro Crater (a location map is posted in BGVN 32:02) conducted during June 2003-January 2011. Results from Giggenbach bottle collection and lab analysis for gas species are plotted on log scales. Right-hand vertical axis corresponds to upper (blue) data and trendlines. Left-hand vertical axis corresponds to the lower (black) data trendlines and data. Original concentration units were undisclosed (but Bulletin editors hope to clarify these units in later discussions on Merapi). Modified from BPPTK, 2011a.

SO2 ranged from ~75 metric tons/day (t/d) to ~285 t/d and appeared to peak mid-year in 2005 and 2006 (figure 50). A sudden decrease of 50 t/d in January 2007 preceded an increasing trend that ended in mid-2008. These fluxes also had fewer sustained peaks around March 2008 and declined until the available record ends around March 2009.

The SO2 peak of ~200 t/d generally correlated with the 2005 mid-year episode of elevated seismicity that prompted the BPPTK (at that time called the Directorate of Volcanology and Geological Hazard Mitigation, "DVGHM") to raise the Alert Level from Normal to Advisory (from 1 to 2). However, there were no additional reports of plumes or increased dome activity then (BGVN 32:02).

In 2006, the Alert Level was raised to the highest level on 13 May due to intense dome growth and earthquake activity (BGVN 31:05), a time when SO2 reached ~225 t/d.

According to information recorded in Bulletin reports, the abrupt decrease of SO2 in late 2006-early 2007 did not appear to correlate with significant volcanism in that time interval. The gradual increasing-and-decreasing trend in SO2 flux from 2007 until the end of the record was marked by rare ash plumes (e.g. 19 March 2007, 9 Aug 2007, and 19 May 2008), and modest dome growth (BGVN 32:02). Bulletin reports also noted incandescence and ashfall had continued during 23 May-29 May 2007. MODVOLC thermal anomalies became rare after 5 September 2006 (BGVN 33:10).

Intermittent activity during 18 April-1 May 2011. Unrest at Merapi since the 2010 crisis was characterized by intermittent increases in seismicity as observed from 18 to 24 April 2011 (figure 52). Over the course of that week, rockfall signals doubled from the previous observation period and 39 multiphase events were recorded.

Figure 52. Histograms from September 2010 to June 2011 summarize the number of seismic events from four categories is summarized for Merapi. Events shown are rockfalls; MP, multiphase (shallow source, dominant frequency ~1.5 Hz); VA, deep volcano-tectonic earthquakes, 2.5-5 km below the summit; VB, shallow volcano-tectonic earthquakes, less than ~1.5 km below the summit. Tremor episodes were infrequent and thus excluded. Courtesy of BPPTK (Activity Report 6-12 June 2011). (A figure in BGVN 36:1/2 presented representative samples of these various waveforms.)

BPPTK also reported that ground deformation was variable throughout this time period as EDM (Electronic Distance Meter) measurements were recorded across the summit. Measurements made on 18 April 2011 compared with those recorded on 25 April 2011 from the monitoring post of Selo showed the following changes: a difference in distance amounting to +8 mm (R1) and a change in movement amounting to 0.1 mm per day.

Measurements carried out on 18 April 2011 compared to those of 24 April 2011 from Jrakah monitoring post indicated the following changes: a difference in distance amounting to -4 mm (R1) with a change in movement amounting to 0.5 mm per day, and a difference in distance of +6 mm (R2) with a movement of 0.7 mm per day.

Plumes of ash and gas reached an altitude of ~800 m on 24 and 25 April. Communities near Merapi's flanks reported ashfall on 29 April, 30 April, and 1 May 2011. (BPPTK Activity Report 25 April-1 May 2011).

Ongoing hazards. The recent weekly report by BPPTK (20 March to 12 June 2011), described plumes of gas and ash that occurred regularly. As measured from above the summit, the average height of these plumes was ~500 m; a maximum height of 900 m was recorded on 20 April. The tallest plume was accompanied by a ramping up of earthquakes and the regular occurrence of lahars, some hot enough to steam while racing through river drainages (figure 53).

Figure 53. On 21 March 2011 and 14 April 2011 steaming lahars descended Merapi's flanks. This photo was taken on 14 April 2011from a CCTV camera installed in Pencar village, less than 20 km S of Merapi in the Desa Bimomartani region. Note Merapi volcano in upper right-hand area of the photo. Courtesy of BPPTK (Activity Report discussing 11-17 April 2011).

A large amount of volcanic ash fell from Merapi's explosive eruptions in 2010; this has aggravated slope stability and led to increased lahar hazards. In an interview on 11 April 2011 for Kompas News, Subandriyo, the Head of the BPPTK explained that "only about 30 percent" of the material that fell on Merapi's flanks has been remobilized by erosion. "Therefore, the threat of [lahars] will occur two to three years ahead."

As of June 2011, 15 major lahars had occurred since November 2010. The worst occurred on 23 January 2011 along the eroded banks of the Putih river. The major highway between Magelang and Yogyakarta was cut off when a 60 m wide section of blacktop was torn away by torrential mudflows. As a result, hundreds of homes within 12 different villages near the river were inundated forcing 5,000 people to flee. There were three fatalities.

Major infrastructure was also affected; 52 levees were damaged and 14 bridges were destroyed. Intense lahar damage was also reported along the SE rivers: Blongkeng, Batang, Progo, Code, and Gendol.

References. Allard, P., Métrich, N., and Sabroux, J.-C., 2011, Volatile and magma supply to standard eruptive 549 activity at Merapi volcano, Indonesia. EGU General Assembly 2011, Geophysical 550 Research Abstracts 13, EGU 2011-13522 (2011).

Andreastuti, S., Costa, F., Pallister, J.,Sumarti., S., Subandini, S., Heriwaseso, A., Kurniadi, Y. , Petrology and pre-eruptive conditions of the 2010 Merapi magma. EGU General Assembly 2011, Geophysical 550 Research Abstracts 13, EGU2011-5150 (2011).

BPPTK, Volcano Technical Research Center, 2011a, Geochemistry of Merapi. (URL: http://www.merapi.bgl.esdm.go.id/aktivitas_merapi.php?page=aktivitas-merapi&subpage=geokimia)BPPTK, Volcano Technical Research Center, 2011b, Monitoring of Geochemical and Temperature of Merapi. (URL: http://www.merapi.bgl.esdm.go.id/pages.php?page=geokimia-dan-suhu)

Schmincke, H.-U, 2004, Volcanism, Berlin:Springer, 324 pp.

Jousset, P., 12/6/10, Centennial Eruption at Merapi volcano: October/November 2010, MIAVITA, European Commission. (URL: http://miavita.brgm.fr/Documents/MIAVITA-Merapi-eruption.pdf)

Sayudi, D.S., Nurnaning, A., Juliani, DJ., Muzani, M.; 2010, "Peta Kawasan Rawan Bencana Gunungapi Merapi, Jawa Tengah Dan Daerah Istimewa Yogyakarta 2010," (The map of the Rawan Bencana Gunungapi Merapi Region, Central Java: Yogyakarta Special District 2010), Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPTK"). (URL: http://www.merapi.bgl.esdm.go.id/peta/2011/04/KRBGMerapi2010FINALcopyright_78a74b.jpg)

Siebert L., Simkin T., and Kimberly P., 2010, Volcanoes of the World, 3rd edition, University of California Press, Berkeley, 558 p.

Surono, Jousset, P., Pallister, J., Boichu, M., Buongiorno, M.F., Budisantoso, A., Costa, F., Andreastuti, S., Prata, F., Schneider, D., Clarisse, L., Humaida, H., Sumarti, S., Bignami, C., Griswold, J., Carn, S., Oppenheimer, C., (in review), 100-year explosive eruption of Java's Merapi volcano, Journal of Volcanology and Geothermal Research.

Williams-Jones, G. and Rymer, H., 2000, Hazards of Volcanic Gases, in Sigurdsson, H., ed., Encyclopedia of Volcanoes: San Diego, California, Academic Press, p. 997-1004.

Information Contacts: Volcano Technical Research Center (Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian, "BPPTK"), (URL: http://www.merapi.bgl.esdm.go.id/index.php); Badan Nasional Penanggulangan Bencana (BNPB- Indonesian National Disaster Management Agency), (URL: http://dibi.bnpb.go.id); Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://portal.vsi.esdm.go.id/joomla/); IRIN News (URL: http://www.IRINnews.org); Jakarta Globe (URL: http://www.thejakartaglobe.com); The Jakarta Post (URL: http://www.thejakartapost.com); KompasNews, Jakarta, Indonesia (URL: http://www.Kompas.com); Mitigate and Assess risk from Volcanic Impact on Terrain and human Activities project (MIAVITA), (URL: http://miavita.brgm.fr/default.aspx); Act Forum Indonesia (URL: http://www.actalliance.org/); Relief Web (URL: http://www.reliefweb.int).

Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. Merapi is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi volcano beginning during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the volcano's western-to-southern flanks and caused many fatalities during historical time. The volcano is the object of extensive monitoring efforts by the Merapi Volcano Observatory.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
2014 Mar 9 2014 Apr 20 Confirmed   Historical Observations
2013 Nov 18 2013 Nov 18 Confirmed   Historical Observations
2010 Oct 26 2012 Jul 15 Confirmed 4 Historical Observations
[ 2008 May 19 ] [ Unknown ] Uncertain    
2006 Mar 2007 Aug 9 (?) Confirmed 1 Historical Observations
1992 Jan 20 2002 Oct 19 (?) Confirmed 2 Historical Observations NW of 1984 lava dome
1986 Oct 10 1990 Aug (?) Confirmed 2 Historical Observations
1972 Oct 6 1985 Mar Confirmed 2 Historical Observations
[ 1971 Jan ] [ 1971 Jul 26 ] Uncertain 1  
1967 Jan 12 1970 (?) Confirmed 2 Historical Observations Upper Batang breach (2600 m)
1961 Apr 11 1961 Nov 28 Confirmed 3 Historical Observations
1953 Mar 2 1958 Dec Confirmed 2 Historical Observations
1948 Sep 29 1948 Dec Confirmed 2 Historical Observations
1942 May 30 1945 May Confirmed 2 Historical Observations
1939 Dec 13 1940 Sep Confirmed 2 Historical Observations
1933 Oct 1 1935 Apr Confirmed 2 Historical Observations
1932 Nov Unknown Confirmed 1 Historical Observations
1930 Nov 25 1931 Sep Confirmed 3 Historical Observations
1924 Sep 10 1924 Sep 12 ± 1 days Confirmed 1 Historical Observations
[ 1923 Sep ] [ 1923 Nov ] Uncertain    
1922 Feb 18 1922 Aug 8 Confirmed 1 Historical Observations
1920 Jul 25 1921 Feb Confirmed 2 Historical Observations
1918 Jan Unknown Confirmed 1 Historical Observations
1915 Mar 28 1915 May 15 Confirmed 1 Historical Observations
1909 Feb 1 1913 May Confirmed 1 Historical Observations West dome
1908 Unknown Confirmed 1 Historical Observations
1906 Jan 26 ± 5 days 1907 Feb 17 Confirmed 2 Historical Observations Summit and upper east flank (2600 m)
1905 Jan 1905 Jun 1 Confirmed 2 Historical Observations
1902 Dec 1904 Jun 20 ± 5 days Confirmed 2 Historical Observations
1902 Feb 3 1902 Feb 3 Confirmed 1 Historical Observations
1897 Unknown Confirmed 2 Historical Observations
1894 Oct Unknown Confirmed 1 Historical Observations
1894 Jan 27 1894 Feb 2 Confirmed 2 Historical Observations
1893 Oct Unknown Confirmed 1 Historical Observations
1891 Aug 25 1892 Confirmed 2 Historical Observations
1889 Jul Unknown Confirmed 1 Historical Observations
1888 Aug 18 1888 Dec 20 Confirmed 2 Historical Observations
1885 Feb 24 ± 4 days 1887 Confirmed 1 Historical Observations
1883 Jan (?) 1884 Nov Confirmed 1 Historical Observations East dome
1878 1879 Jun 20 Confirmed 2 Historical Observations
1872 Nov 3 1873 Jan (?) Confirmed 2 Historical Observations
1872 Apr 15 1872 Apr 21 Confirmed 4 Historical Observations
1865 Oct 24 1871 Aug (?) Confirmed 2 Historical Observations
1862 May 26 1864 Confirmed 2 Historical Observations
1861 Unknown Confirmed 2 Historical Observations
[ 1854 Sep ] [ Unknown ] Uncertain    
1849 Sep 14 1849 Sep 24 Confirmed 3 Historical Observations
1849 Apr 26 1849 Apr 26 Confirmed 2 Historical Observations
[ 1848 Jan 8 ] [ Unknown ] Uncertain    
1846 Sep 2 1847 Oct Confirmed 3 Historical Observations Summit and upper SE flank (2600 m)
1846 Apr 6 Unknown Confirmed 2 Historical Observations
1840 Jan 4 Unknown Confirmed 1 Historical Observations
1837 Aug 10 1838 Jun Confirmed 2 Historical Observations
1832 Dec 25 1836 Confirmed 2 Historical Observations
1828 Dec 18 1828 Dec 19 Confirmed 2 Historical Observations
1822 Dec 27 1823 Apr 6 Confirmed 3 Historical Observations
1812 1822 Confirmed 1 Historical Observations
1810 Unknown Confirmed 1 Historical Observations
1807 Unknown Confirmed 1 Historical Observations
1797 Unknown Confirmed 1 Historical Observations
1791 (in or before) Unknown Confirmed 2 Historical Observations
1786 Jul 17 Unknown Confirmed 1 Historical Observations
1768 Aug 19 Unknown Confirmed 2 Historical Observations
1755 Unknown Confirmed 2 Historical Observations
1752 Unknown Confirmed 2 Historical Observations
1745 Unknown Confirmed 2 Historical Observations
1678 Aug 19 Unknown Confirmed 3 Historical Observations
1677 Unknown Confirmed 3 Historical Observations
1672 Aug 4 Unknown Confirmed 3 Historical Observations
1663 Dec 31 ± 365 days Unknown Confirmed 3 Historical Observations
1658 Unknown Confirmed 3 Historical Observations
1587 Unknown Confirmed 3 Historical Observations
[ 1586 ] [ Unknown ] Uncertain    
1584 Unknown Confirmed 3 Historical Observations
1560 Unknown Confirmed 3 Historical Observations
1554 Unknown Confirmed 3 Historical Observations
1548 Unknown Confirmed 3 Historical Observations
1480 ± 300 years Unknown Confirmed   Radiocarbon (corrected) Sambisari Ash
1440 ± 100 years Unknown Confirmed   Radiocarbon (corrected)
1380 ± 300 years Unknown Confirmed   Radiocarbon (corrected) Sambisari Ash
1300 ± 75 years Unknown Confirmed   Radiocarbon (corrected)
1230 ± 200 years Unknown Confirmed   Radiocarbon (corrected) Deles Tephra
1190 ± 30 years Unknown Confirmed   Radiocarbon (corrected)
1140 ± 150 years Unknown Confirmed   Radiocarbon (corrected)
1090 ± 100 years Unknown Confirmed   Radiocarbon (corrected)
1010 ± 25 years Unknown Confirmed   Radiocarbon (corrected)
[ 1006 ] [ Unknown ] Discredited    
0940 ± 100 years Unknown Confirmed 3 Radiocarbon (corrected) Selo Tephra
0870 ± 100 years Unknown Confirmed   Radiocarbon (corrected)
0680 ± 200 years Unknown Confirmed   Radiocarbon (corrected)
0630 ± 30 years Unknown Confirmed   Radiocarbon (corrected)
0540 ± 50 years Unknown Confirmed   Radiocarbon (corrected)
0480 ± 75 years Unknown Confirmed   Radiocarbon (corrected)
0410 ± 150 years Unknown Confirmed 3 Radiocarbon (corrected) Plalangan Tephra
0280 ± 150 years Unknown Confirmed   Radiocarbon (corrected)
0190 ± 300 years Unknown Confirmed   Radiocarbon (corrected)
0120 ± 75 years Unknown Confirmed   Radiocarbon (corrected)
0020 ± 300 years Unknown Confirmed 4 Radiocarbon (corrected) Tegalsruni tephra
0340 BCE ± 500 years Unknown Confirmed 3 Radiocarbon (corrected) Ngrangkah Tephra
0700 BCE ± 150 years Unknown Confirmed   Radiocarbon (corrected)
1010 BCE ± 200 years Unknown Confirmed   Radiocarbon (corrected)
1180 BCE ± 75 years Unknown Confirmed 4 Radiocarbon (uncorrected) Bakalan tephra
1410 BCE ± 50 years Unknown Confirmed   Radiocarbon (corrected)
1770 BCE ± 75 years Unknown Confirmed   Radiocarbon (corrected)
1890 BCE ± 55 years Unknown Confirmed   Radiocarbon (corrected)
2910 BCE ± 150 years Unknown Confirmed   Radiocarbon (corrected)
4690 BCE ± 75 years Unknown Confirmed   Radiocarbon (corrected)
7310 BCE ± 300 years Unknown Confirmed   Radiocarbon (corrected)
8780 BCE ± 150 years Unknown Confirmed   Radiocarbon (corrected) Old Merapi

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.


Cones

Feature Name Feature Type Elevation Latitude Longitude
Batuwalang Merapi Stratovolcano 2551 m
Bibi, Gunung Cone

Craters

Feature Name Feature Type Elevation Latitude Longitude
Pasarbubar Crater

Domes

Feature Name Feature Type Elevation Latitude Longitude
Batang Dome

Thermal

Feature Name Feature Type Elevation Latitude Longitude
Gendal, Kawah Thermal
Woro, Kawah Thermal
Merapi (left) and Merbabu (right) volcanoes tower above the lowlands between the cities of Yogjakarta and Surakarta (Solo) in this aerial view from the SE. Both 3145-m-high Merbabu and 2911-m-high Merapi have erupted during historical time, but Merapi is by far the more vigorous of the two. A growing lava dome in the summit crater frequently collapses, producing pyroclastic flows and lahars that sweep down the steep slopes of the volcano, often with catastrophic results.

Photo by Jeff Post, 1991 (Smithsonian Institution).
A gas plume is blown to the west from the summit of Merapi volcano on December 7, 1986, accompanying growth of a new lava dome. Small-to-moderate explosive eruptions began in October 1972, associated with growth of a lava dome in the summit crater. Periodic collapse of the growing lava dome produced pyroclastic flows and lahars that damaged cultivated lands on the SW flank of the volcano.

Photo by Tom Casadevall, 1986 (U.S. Geological Survey).
A blocky lava dome produced during eruptions from 1972 to 1985, lies within the summit crater of Merapi volcano in central Java. A small spine appears on the right in this July 4, 1986 photo, which was taken during a period of inactivity prior to destruction of the dome on October 10, 1986. Merapi's historical eruptions have been characterized by repeated growth and collapse of the summit lava dome, periodically producing pyroclastic flows that have affected populated areas on the volcano's western and southern flanks.

Photo by Tom Casadevall, 1986 (U.S. Geological Survey).
Merapi volcano, one of Indonesia's most active, rises above the city of Yogyakarta in central Java. This May 1987 view from the southern flank with the red-roofed Plawangan observatory on the forested ridge in the foreground shows Merapi's steaming summit lava dome. Unvegetated areas on the left result from periodic rockfall avalanches and pyroclastic flows from the growing lava dome.

Photo by Tom Casadevall, 1986 (U.S. Geological Survey).
An aerial view from the WSW on January 6, 1987 shows a black lava tongue descending from the summit crater of Merapi. During a five-day period beginning October 10, 1986, the dome had been partially destroyed by a series of dome-collapse pyroclastic flows. The period of dome growth and lava effusion seen in this photo then began and continued for several years before stabilizing in mid 1990.

Photo by Tom Casadevall, 1987 (U.S. Geological Survey).
A pyroclastic flow descends the SW flank of Merapi volcano on June 14, 1984. A long period of lava dome growth began on October 2, 1972, and continued intermittently until 1990, occasionally punctuated by partial dome collapse that formed pyroclastic flows that swept down the volcano's flanks.

Photo by Ministry of Public Works, 1984 (courtesy of Volcanological Survey of Indonesia).
Low ashclouds rise from a small pyroclastic flow traveling down the western flank from the breached crater of Merapi volcano in December 1930. A much larger pyroclastic flow that month traveled 12 km from the volcano, totally or partially destroying 42 villages and killing 1369 persons in one of Merapi's deadliest eruptions. Explosions had begun from Merapi on November 22, 1930. Explosive activity was accompanied by growth of a new lava dome and and extrusion of a lava flow. Dome growth and associated pyroclastic flows continued until October 1931.

Photo published in Neumann van Padang, 1933 (courtesy of Volcanological Survey of Indonesia).
Steam rises from still-hot pyroclastic-flow deposits in the Kali Blongkeng valley, 12 km from the summit of Merapi in December 1930. Thirteen villages were totally destroyed and 29 more partially destroyed by these pyroclastic flows, which killed 1369 persons on December 18.

Photo published in Neumann van Padang, 1933 (courtesy of Volcanological Survey of Indonesia).
A dark lava flow at the center of the photo descends from the breached summit crater of Merapi on April 27, 1931, following the devastating eruption of December 18, 1930.

Photo published in Neumann van Padang, 1933 (courtesy of Volcanological Survey of Indonesia).
Steam rises from the growing lava dome of Merapi volcano on January 20, 1954, as viewed from the SE, two days after a major pyroclastic flow that caused 64 fatalities. Lava dome growth had began on March 2, 1953, accompanied by frequent pyroclastic flows. Several additional cycles of lava dome growth and destruction continued until December 1958.

Photo by Suryo, 1954 (Volcanological Survey of Indonesia).
Incandescent rockfalls accompanying slow growth of the summit lava dome descend from beneath a cloudcap covering the summit of Merapi volcano in this 1993 nighttime view. Periodic collapse of Merapi's lava dome has produced pyroclastic flows down the western and southern flanks that have devastated populated areas and agricultural lands.

Photo by Ruska Hadian, 1993 (Volcanological Survey of Indonesia).
Scientists from the Volcanological Survey of Indonesia make theodolite measurements to determine the height and volume of the growing lava dome at the summit of Merapi volcano in central Java. The pinnacle at the left is the former summit spine of Merapi.

Photo by Ruska Hadian, 1993 (Volcanological Survey of Indonesia).
Steam rises from the moat between the growing lava dome in the crater of Gunung Merapi volcano and the steep-walled western crater rim (left), which culminates in Merapi's dramatic summit spire. The dome visible at the right began growing in 1992. Periodic collapse of the growing dome during successive years produced pyroclastic flows that devastated the western and southern flanks.

Photo by Lee Siebert, 1995 (Smithsonian Institution).
Merapi volcano, one of Indonesia's most active volcanoes, looms above the renowned Hindu temple complex of Prambanan, Indonesia's largest, dating back to 900 AD. Many of the temple complexes on the culturally rich Prambanan plain below Merapi have been affected by lahars (mudflows) that traveled tens of km from the volcano.

Photo by Lee Siebert, 1995 (Smithsonian Institution).
Collapse of the growing lava dome on November 22, 1994, produced a pyroclastic flow that swept 7.5 km down the south flank, overrunning several villages and killing 64 persons. Six thousand persons were evacuated as a result of this eruption.

Photo by Panut, 1994 (Volcanological Survey of Indonesia).
This photo, taken the day after devastating pyroclastic flows swept down the south flank of Merapi, shows the light-colored path taken by the pyroclastic flows, which descended diagonally to the left. The darker-brown areas to the right of the pyroclastic-flow deposits are trees that were scorched by pyroclastic-surge clouds. Sixty-four persons were killed by these pyroclastic surges in a village near the location of this photo.

Photo by Yustinus Sulistiyo, 1994 (Volcanological Survey of Indonesia).
Merapi stratovolcano in central Java is capped by an unvegetated, growing lava-dome complex. The modern edifice of Merapi, at the left in this view, is constructed to the SE of the arcuate scarp on the right formed by destruction of the older Batulawang volcano. Merapi is one of Indonesia's most active volcanoes. Periodic collapse of its growing lava dome has produced pyroclastic flows and lahars that have devastated populated areas below the volcano.

Photo by Yustinus Sulistiyo, 1994 (Volcanological Survey of Indonesia).
This slender pinnacle capping Merapi forms what was one of the world's most dramatic volcanic summits. The remnant of a lava spine topping one of Merapi's older lava domes was about 10 m high at the time of this 1989 photo, but had collapsed by 2006. The slope on the left drops off steeply into Merapi's summit crater.

Photo by Tom Pierson, 1989 (U.S. Geological Survey).
This aerial photo was taken from the SE on August 14, 1922, less than a week after the end of an eruption that began on February 18, 1922. It shows the configuration of the summit of Merapi prior to a major eruption in 1930 during which much of the summit lava dome collapsed. Eruptions were reported on February 18, April 4-5, and August 8, 1922, during which frequent rock avalanches accompanied lava dome growth. The thin light-colored streak descending diagonally to the left from the summit is a lava flow that traveled 180 m down the western flank.

Photo published in Taverne, 1926 "Vulkaanstudien op Java," (courtesy of Volcanological Survey of Indonesia).
An ash-rich eruption column rises above the summit of Merapi volcano in 1961 and pyroclastic flows descend the western flank. During 1961, eruptions took place April 13, May 7-8, and November 27-28. Pyroclastic flows during the May 8 eruption destroyed 10 villages and killed 6 persons.

Photo by I.Suryo, 1961 (published in Kusumadinata 1979, Data Dasar Gunungapi Indonesia).
A pyroclastic flow sweeping down the SW flank of Merapi volcano is seen from the Plawangan Observatory on April 12, 1967. Explosive eruptions, pyroclastic flows, and lava dome growth took place during 1967-70. Eruptive activity began on January 12, 1967. Paroxysmal phases took place on October 7-9, 1967 and October 8, 1968, during which partial collapse of the lava dome produced frequent pyroclastic flows. The velocity of the pyroclastic flow seen in this photo was estimated by the Volcanological Survey of Indonesia to be 60 km/hr.

Photo by I. Suryo, 1967 (Volcanological Survey of Indonesia).
A pyroclastic flow travels down the SE flank of Merapi on June 7, 2006. Renewed lava dome growth had begun at Merapi in April 2006. Ashfall took place on April 27. Beginning in May, pryroclastic flows descended the flanks of the volcano, sometimes reaching populated areas.

Photo courtesy of The Research and Technology Development Agency for Volcanology, Yogyakarta (BPPTK), 2006.

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Adreastuti S D, Alloway B V, Smith I E M, 2000. A detailed tephrostratigraphic framework at Merapi volcano, central Java, Indonesia: implications for eruption predictions and hazard assessment. J Volc Geotherm Res, 100: 51-67.

Bourdier J-L, Abdurachman E K, 2001. Decoupling of small-volume pyroclastic flows and related hazards at Merapi volcano, Indonesia. Bull Volc, 63: 309-325.

Camus G, Gourgaud A, Mossand-Berthommier P-C, Vincent P-M, 2000. Merapi (central Java, Indonesia): an outline of the structural and magmatological evolution, with a special emphasis to the major pyroclastic events. J Volc Geotherm Res, 100: 139-163.

Charbonnier S J, Gertisser R, 2008. Field observations and surface characteristics of pristine block-and-ash flow deposits from the 2006 eruption of Merapi volcano, Java, Indonesia. J Volc Geotherm Res, 177: 971-982.

Gertisser R, Keller J, 2003. Temporal variations in magma composition at Merapi volcano (Central Java, Indonesia): magmatic cycles during the past 2000 years of explosive activity. J Volc Geotherm Res, 123: 1-23.

Green J, Short N M, 1971. Volcanic Landforms and Surface Features: a Photographic Atlas and Glossary. New York: Springer-Verlag, 519 p.

Hantke G, 1951. Ubersicht uber die Vulkanische Tatigkeit 1941-1947. Bull Volc, 11: 161-208.

Hartmann M, 1934. The volcanic activity of Merapi volcano (central Java) in its eastern summit area between 1902 and 1908. Ing Ned-Indie, 1: 61-73.

Lavigne F, Thouret J C, Voight B, Suwa H, Sumaryono A, 2000. Lahars at Merapi volcano, central Java: an overview. J Volc Geotherm Res, 100: 423-456.

Neumann van Padang M, 1951. Indonesia. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 1: 1-271.

Newhall C G, Bronto S, Alloway B, Banks N G, Bahar I, del Marmol M A, Hadisantono R D, Holcomb R T, McGeehin J, Miksic J N, Rubin M, Sayudi S D, Sukhyar R, Andreastuti S, Tilling R I, Torley R, Trimble D, Wirakusumah A D, 2000. 10,000 years of explosive eruptions of Merapi volcano, central Java: archaeological and modern implications. J Volc Geotherm Res, 100: 9-50.

Purbo-Hadiwidjoyo M M, Suryo I, 1980. Distribution pattern of the Merapi volcanic debris, south central Java with special reference to the period since 1900. Seminar Volcanic Debris Flow, Yogjakarta, 13-14 March 1980, p 276-291.

Schwarzkopf L M, Schmincke H-U, Cronin S J, 2005. A conceptual model for block-and-ash flow basal avalanche transport and deposition, based on deposit architecture of 1998 and 1994 Merapi flows. J Volc Geotherm Res, 139: 117-134.

Siswowidjoyo S, Suryo I, Yokoyama I, 1995. Magma eruption rates of Merapi volcano, Central Java, Indonesia during one century (1890-1992). Bull Volc, 57: 111-116.

Taverne N J M, 1926. Vulkanstudien op Java. Vulk Meded, 7: 1-132.

Thouret J-C, Lavigne F, Kelfoun K, Bronto S, 2000. Toward a revised hazard assessment at Merapi volcano, central Java. J Volc Geotherm Res, 100: 479-502.

van Bemmelen R W, 1949b. The Geology of Indonesia. The Hague: Government Printing Office, v 1, 732 p.

Voight B, Constantine E K, Siswowidjoyo S, Torley R, 2000. Historical eruptions of Merapi volcano, central Java, Indonesia, 1768-1998. J Volc Geotherm Res, 100: 69-138.

Volcanological Survey of Indonesia, 1986b. Annual report of the Volcanological Survey 1984-1985. Bull Volc Surv Indonesia, no 113.

Wirakusumah A D, Juwarna H, Loebis H, 1989. Geologic map of Merapi volcano, Central Java. Volc Surv Indonesia, 1:50,000 geol map.

Volcano Types

Stratovolcano
Lava dome(s)

Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Rock Types

Major
Andesite / Basaltic Andesite
Trachyandesite / Basaltic trachy-andesite
Minor
Basalt / Picro-Basalt
Trachybasalt / Tephrite Basanite

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
49,205
185,849
4,348,473
24,728,414

Affiliated Databases

Large Eruptions of Merapi Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.