Contents of Monthly Reports

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

All times are local (= UTC + 7 hours)

01/1990 (BGVN 15:01) Explosive eruption produces heavy tephra falls, pyroclastic flows, and lahars; more than 30 people killed

A strong explosive eruption on 10 February produced a large cloud and heavy tephra falls. Although evacuation began before the onset of the eruption, more than 30 people were reported killed in the densely populated area near the volcano.

Local seismicity increased to ~10x the normal rate between the middle and end of November, then returned to background levels. A second episode of increased seismicity occurred during the second and third weeks of January, accompanied by a rise in crater lake temperature from 32 to 38°C. Enhanced earthquake activity was again detected 7 February, and lake temperature peaked at 39-41°C. Measurements on 8 February indicated that lake pH had decreased to 4.2 from its usual 4.9, and hydrophones in the lake recorded noise at 3x normal levels. However, seismicity and hydrophone noise declined that day and remained relatively quiet until the onset of the eruption. During the night of 9-10 February, transmission from the lake instruments (via the ARGOS satellite) ceased. VSI issued an evacuation warning on 10 February at 1000. Press sources estimated the number of evacuees at 60,000.

The eruption began 10 February at 1141, with the strongest explosive phase at 1250, and activity continued until 1700. Pyroclastic flows traveled [5-6] km down the steep-walled valley on the E flank (from the breach in the summit crater), filling it to a depth of ~10 m. The crater lake was emptied during the eruption. However, most of the damage and casualties were attributed to heavy tephra falls that reached 20-30 cm thickness. In Nglegok (~55 km SW of the volcano) residents reported falls of fist-sized tephra, with some material that was head-sized. About 15 cm of ash accumulated at Blitar, ~25 km SW of the summit. Ashfalls were also reported from Malang, ~35 km E of Kelut. The weight of the tephra caused houses to collapse, trapping their occupants. As of 20 February, the official death toll had risen to 32, with >500 homes and 50 schools destroyed and many others damaged.

Tracking of the plume by satellite was made difficult by heavy weather cloud activity in the area. Imagery from Japan's GMS satellite at 1300 showed a bright cloud 53 km across centered over the volcano. At 1347, a NOAA polar orbiter image revealed that the plume, still roughly circular and centered over the volcano, had grown to ~160 km in diameter. Preliminary temperature analysis suggested that the top of the dense cloud was at ~12 km altitude, although diffuse material could have extended higher. By 1600, GMS data indicated that the plume had drifted slightly WSW and was ~310 km long. Very diffuse-appearing material could be seen extending to the NW coast of Australia, ~1,400 km from Kelut, on a NOAA polar orbiter image the next day at 1347. Dispersed remnants of the plume could be traced on GMS images until 1900.

Small explosions with associated glow and/or lightning were continuing during the night of 11-12 February, accompanied by strong seismic activity. A second strong explosive episode occurred between 1512 and 1827 on 12 February. Incandescent tephra rose 7 km above the crater. Rains triggered a major lahar on 15 February that moved downslope at 40-60 km/hour, inundating parts of subdistricts ~16 km NNW (Kepung) and 17 and 28 km NW (Ploso Klaten and Guran) of the summit, forcing residents to flee to high ground. Further heavy rains during the night of 16-17 February forced 50,000 Kepung subdistrict residents to flee. Minor eruptive activity for ~2 hours that night sent thick ash clouds to ~600 m above the vent. Additional lahars the next day moved downslope at ~45 km/hour, destroying hundreds of hectares of agricultural land.

Information Contacts: VSI; Y. Sawada, JMA; O. Karst, SAB; U.S. Embassy, Jakarta; T. Casadevall, USGS; Jakarta Post; UPI.

Further Reference: Sudradjat, Adjat, 1991, A preliminary account of the 1990 eruption of the Kelut volcano: Geol. Jahrbuch, v. A127, p. 447-462.

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09/1990 (BGVN 15:09) February eruption created new pit crater and emptied crater lake; high-temperature gas emission

The following is from Patrick Allard. "Joint investigations . . . were conducted by volcanologists from VSI, the French CNRS, and Paris Univ on 19 July, 25 August, and 2 September. Many months after the 10-12 February explosive eruption, intense activity was persisting.

"The topography of the crater (figure 1) was deeply modified by the eruption. The former crater lake (~2 x 10⁶ m³), blasted out during the initial eruptive phase, has been replaced by a pit crater ~450 x 500 m wide and 100 m deep. The walls of the pit are very steep and unstable, leading to frequent landslides. A lake of muddy water (85°C), 150 x 160 m, occupies its SE floor. Strong, loud emission of steam and gas (193°C, ~14 bars pressure for a steam-saturated reservoir) continuously occurs from two blowing vents N of the lake, contributing much of the plume that rises a few hundred meters above the crater rim. Gas samples were taken from these vents 19 July.

"Thick tephra layers from the February eruption have accumulated in the remaining parts of the crater, dipping with a gentle slope toward the inner pit. These layers are cut by arcuate fractures, more or less concentric to the pit walls, as well as by smaller radial fissures, which probably result from both compaction and sliding of the recent deposits. Some arcuate fractures are >1 m wide and 20 m deep. During our August visit it was discovered that high-temperature gases (>500°C, and up to 850°C at 1 m depth) escape from many of these, red glow being visible in the daylight at some sites. Gas plumes, varying in color from white to blue, mark the active vents, and the fractures and rims are blanketed with abundant sublimates. While some fractures are extinct, others are very recent, since their opening projected blocks and lapilli above the upper mud layer that formed during the rainy season (February-June). The release of high-temperature gases through these fractures may reflect either late (passive) degassing of cooling pyroclastic deposits from the February eruption or active degassing of a shallow magma body (residual intrusion?). Analysis of both stable and radioactive components in gas and aerosol samples collected at different sites may provide some geochemical insight into this question, as well as into the possibility of further phreatic or even phreato-magmatic events.

"Huge devastation in the Kelut area attests to the power of the February eruption. VSI estimated the total volume of erupted tephra at 120 x 10⁶ m³ and that of lahar deposits at 24 x 10⁶ m³. Given this volume and other parameters such as the maximum eruptive column height (~12 km) and the duration of the magmatic phase (~8 hours as a whole; 15:01), a VEI of 3 (high) to 4 (low) can be attributed to this eruption.*

"Rainfall over the volcano averages 5-7 x 10⁶ m³/year, so the crater lake could re-form during the next year or more, depending on the rate of heat output. The explosive blast of the crater lake and consequent lahar formation were responsible for most casualties from the past Kelut eruptions in 1919 (5,160 casualties), 1951 (7), and 1966 (210), even though this hazard was successfully mitigated by VSI during the 1990 eruption."

*Both VSI's estimate of tephra volume (>100 x 10⁶ m³) and measurements of eruption cloud height meet the criteria of Newhall and Self (1982) for a VEI of 4. Preliminary temperature analysis from satellite images suggested that the top of the dense portion of the plume was at ~12 km altitude (15:01), but lidar data from the RV Akademik Korolev detected layers above 20 km altitude, well into the stratosphere, in the central and western Pacific shortly after the eruption [and the SAGE II instrument detected aerosols to 25 km] (see Atmospheric Effects, GVNB 15:08 and 15:12]).

Reference: Newhall, C.G., and Self, S., 1982, The Volcanic Explosivity Index (VEI): an estimate of explosive magnitude for historical volcanism: JGR (Oceans and Atmospheres), v. 87, no. C2, p. 1231-1238.

Information Contacts: VSI; P. Allard, G. Polian, and J-C. Sabroux, CNRS, France; A. Jambon and B. Marty, Univ Paris, France.

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03/1991 (BGVN 16:03) Continued fumarolic activity; 1991 pyroclastic-flow deposits to 400°C; small rain-induced lahars

The press reported on 26 November that four people had recently been killed by lahars that overflowed a river channel in the Blitar region (~30 km S of the summit).

During March fieldwork, gas was emitted from numerous fissures within and around the small light-green pool in the SE part of the former crater lake (15:09). The small hummocky area in the center of the former lake bed expelled hot gases (temperatures between 200 and 240°C, up from ~190°C in late 1990) under high pressure with a jet aircraft sound and very strong sulfurous odor.

Workers continued to quarry the still-hot (90-400°C) pyroclastic-flow deposits (~25 m thick) that buried the mouth of the Ampera Tunnel, in the SW side of the crater.

The average daily rainfall in March was 46 mm, and lahars were reported in the Ngobo (WNW flank) and Sumberagung (W flank) rivers. The latter river overflowed in the town of the same name (7 km W of the crater), but no victims or significant damages were reported. An average of two tectonic earthquakes (but no volcanic earthquakes) were recorded daily.

Information Contacts: W. Modjo, VSI; AP.

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11/1996 (BGVN 21:11) Crater lake temperature about 4°C above normal

Around September it was noted that the water temperature in this stratovolcano's crater lake increased from 45.6 to 47.0°C. This is several degrees warmer than the typical water temperature of 43.0°C. Thin white plumes escaped from several areas around the lake in association with the temperature increase. Volcanic earthquakes were absent in September.

Although relatively small and infrequently reported on . . . Kelut has produced some of Indonesia's most deadly eruptions. Multiple historical eruptions have had Volcano Explosivity Index values of 3 to 4. A 1586 eruption may have had a VEI of 5; an estimated 10,000 people died in lahars. There have been 10 fatal crater lake eruptions. Drainage tunnels to control the lake level have greatly reduced the destructive impact of recent eruptions. Kelut's 1000 AD eruption is the oldest historically recorded in Indonesia.

Information Contacts: Wimpy S. Tjetjep, Volcanological Survey of Indonesia, Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email: vsimvo@ibm.net).

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12/2000 (BGVN 25:12) Inflation and increase in crater lake's temperature and surface height

Increasing crater lake temperature, water level, and inflation have been observed since 19 January 2001. Water temperature in the crater lake rose to 47.5-49.1°C. On 21 January water level rose 5 cm. Leveling measurement showed 5.5-6 mm of inflation. During 16-22 January, seismographs recorded 20 tectonic earthquake events. These observations prompted the VSI to increase Kelut's hazard status from 1 to 2 (on a scale of 1-4).

Information Contact: 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/).

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02/2001 (BGVN 26:02) Changes in water temperature, surface level, and pH detected in crater lake

Monitoring of Kelut's crater lake indicated a relative increase of water temperature, a rise in surface level, and a decrease in pH into late February 2001. The Volcanological Survey of Indonesia (VSI) released new information revealing that temperatures actually began to rise as of 8 January 2001, rather than on 19 February as disclosed in a previous report (BGVN 25:12). The lake reached a maximum temperature of 51.2°C on 30 January (table 1).

Table 1. Crater lake temperatures during 8 January-26 February 2001 and pH during November 2000-February 2001. The maximum temperature increase was 12.7°C, while the overall increase for the period was 9.3°C. In contrast, pH decreased. Courtesy of VSI.

    Date          Water Temperature    pH

    Nov 2000             --            6.9
    Jan 2001             --            6.3

    08 Jan 2001         38.5           --
    18 Jan 2001         47.5           --
    19 Jan 2001         49.1           --
    29 Jan 2001         50.1           --
    30 Jan 2001         51.2           --
    02 Feb 2001         50.1           --
    07 Feb 2001         51.0           5.0
    13-19 Feb 2001      47.5           5.3
    20-26 Feb 2001      47.8           5.3

A 60-cm increase in lake water level was observed as of 19 January relative to the height at an undisclosed earlier date. Workers measured pH values of the crater lake water and detected a significant overall decrease in pH, or an increase in acidity (table 1). VSI maintained a hazard status of 2 (on a scale of 1-4) since 19 January 2001.

Information Contact: 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/).

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06/2003 (BGVN 28:06) Crater lake temperature drops in early 2001; no activity reported

During 6 March-9 April 2001 at Kelut, the temperature of the crater lake decreased from 50 to 48°C. Tectonic earthquakes were recorded during mid-March 2001, with two occurring per week during 12-23 March. Visual and instrumental observations showed no significant changes. Kelut remained at Alert Level 2 (on a scale of 1-4). No further reports were issued through at least May 2003.

Information Contact: 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/).

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03/2008 (BGVN 33:03) Comparatively passive 2007 lava-dome emplacement in a crater lake

The extrusion of a substantial dome into the center of the active crater lake at Kelut (also spelled Kelud) started in early November 2007. The volcano and lake are among the most historically active and dangerous in Indonesia (Thouret and others, 1998). They were studied by members of the Volcanological Survey of Indonesia (VSI), Alain Bernard, and colleagues. During about 15 years prior to the eruption, the crater lake showed considerable hydrothermal influence, with temperatures several degrees above the ambient air temperature of 19°C, but with near-neutral pH. Prior to this eruption, the lake was ~ 34 m deep, ~ 350 m in diameter, and it held ~ 2.1 x 10⁶ m³ of water (Bernard and Mazot, 2004).

Lava was clearly seen emerging from the center of the lake on 4 November 2007. The activity was passive, even at the contact between the dome and lake. Neither water nor substantial ash were thrown forcefully out of the lake and onto the flanks. The dome rose rapidly above the lake, building a steep construct surrounded by a placid but dwindling lake. A well-defined depression crossed the dome's center, dividing its top surface in two. A few undated photos showed a mildly explosive phase. During 29-30 November the still-erupting dome was stable. As of early May 2008, tentative reports suggested that dome extrusion had ceased or paused. A lake still existed at that point.

Setting, historical lahars, and morphology. The volcano resides in a densely populated part of Java (1,800 people/km²) and could threaten over 3 million residents (Bernard, 2000). Bernard (2000) also noted that Kelut's approximately 30 historical eruptions have caused over 15,000 deaths since 1500 AD. Kelut's last eruption occurred in 1990 (BGVN 15:01). One of the most detailed VSI reports on Kelud's pre-eruptive behavior was issued 30 October 2007 (Surono, 2007).

Although lahars were absent during the 2007 eruption, lahars were associated with eruptions in 1919 and 1966; post-1996 lahars came in response to rainfall (figure 2). To control lahars and related problems, decades before engineers had driven a complex series of drainage tunnels through the edifice's walls, draining much of the lake.

Lake chemistry. Active crater lakes such as Kelut's trap some fraction of the heat and fluids escaping the magmatic and hydrothermal system (Delmelle and Bernard, 1999), and their study has led to breakthroughs in eruption prediction. One example of this kind of study (figure 3) presents various heat and mass-balance factors in a model of Kelut's lake (Bernard and Mazot, 2004). Heat is derived from the enthalpy (E) of hydrothermal fluids (Ebrine + steam) and from solar and atmospheric radiation (Erad). Heat is lost by evaporation (Eevap), conduction (Econd), radiation (Erad), and by the overflow (Eover) of hot waters through the drainage tunnel.

Monitoring instrumentation is in place on and around the lake (figure 4). Fieldwork is also performed to measure the flux of CO₂ emitted at the lake surface (figure 5). Numerous CO₂-bearing gas bubbles rising to the surface were seen in July 2006. Bubbles were also widespread on bathymetric soundings (eg. detected at 50 and 200 kHz) in July 2007, and in some cases observers witnessed frequent discontinuous gas releases (puffing) from bottom fumaroles.

The CO₂ flux from the lake's surface was measured by IR spectrophotometry using a Dräger Polytron instrument. Bernard's team modified a technique initially developed for monitoring the flux of gases in soil (Chiodini and others, 1996), applying this method by means of the floating accumulation chamber at multiple sites.

According to the VSI report, carbon dioxide (CO₂) concentrations measured during 30 July to 2 August 2007 ranged from below 500 g/m²/d to hotspots of 12,000 g/m²/d, especially in the E portion of the lake. The overall flux of CO₂ from the lake reached more than 500 tons/day on 11 September 2007, about ten times greater than measurements made in 2005 and 2006 (figure 6).

Data on lake chemistry (table 2) was compiled by Surono (2007) and Bernard (2000). The water chemistry of the active crater lake showed both stable and variable parameters. Comparatively stable ones included pH and during various time periods (including 2007), some chemical species. Among the largest perturbations were a sudden, almost two-fold rise in SO₂ during September-October 2007; and a rapid increase in lake water temperature during November 2007. Soluble Cl stood over 1,000 ppm during 1993 and dropped sharply reaching a low of 67 ppm on 20 August 2007. It climbed after that, reaching 354 ppm in the last (11 November) measurement, a value taken about a week after the dome broke the lake surface.

Table 2. A compilation for Kelut's lake water showing temperature, pH, and chemical concentration data from VSI for 2007 (Surono, 2007) and Alain Bernard (2000) during 1993 to 2005. Some of the data presented here were rounded and the number of significant figures reduced. The 23 October 2007 Cl value was variously reported. Some of the original data were presumably collected at different locations and depths; and some of the original data included additional parameters such as total dissolved solids (see cited publications).

    Date            Temp (°C)    pH

    18 Dec 1993       42.8       5.9
    01 Aug 1994       42.1       6.3
    24 Sep 2002       33.2       6.5
    04 Sep 2003       30.7       6.5
    27 Apr 2005       32.2       6.6
    20 Aug 2007       31.5       6.9
    16 Sep 2007       33.2       6.4
    25 Sep 2007       33.4       5.9
    29 Sep 2007       36.1       5.9
    23 Oct 2007       38.4       5.8
    28 Oct 2007       39.2       5.6
    02 Nov 2007       ~50         --
    3-4 Nov 2007    Eruptions began on 3 Nov; the dome emerged above lake surface on 4 Nov.
    06 Nov 2007       77.5       6.7
    11 Nov 2007       77.8       6.2

    Date              Na      K     Ca    Mg    HCO3       Cl          SO4      B

    18 Dec 1993      700     92    105    55     238    1,297          631     11
    01 Aug 1994    1,024    102    130    67     207    1,289          692     14
    24 Sep 2002      342     39    135    80     435      289          670      4
    04 Sep 2003      271     30    147    78     472      202          679    2.5
    27 Apr 2005      198     23    121    71     330      139          571      2
    20 Aug 2007      104     14    166    48     221     66.5          538    0.8
    16 Sep 2007      106     16    184    52     294      120        1,083    1.1
    25 Sep 2007      109     17    178    51     279      133        1,121    1.3
    29 Sep 2007      109     17    179    45     279      137        1,121    1.5
    23 Oct 2007      257     22    186    56     297    210 (173)    1,119    1.3
    28 Oct 2007      117     20    190    48     303      179        1,151    1.4
    02 Nov 2007       --     --     --    --      --       --           --     --
    3-4 Nov 2007    Eruptions began on 3 Nov; the dome emerged above lake surface on 4 Nov.
    06 Nov 2007      124     21    200    48     170    294            542    1.7
    11 Nov 2007      130     21    223    45    26.3    354            615    2.1

Monitoring, hazards status, and dome extrusion. Visual monitoring was carried out by means of a closed-circuit video monitor installed on Mount Lirang, as well as from photographs taken in or near the crater. During 15-28 September, gas emissions from the crater lake increased and spread over a zone within a radius of ~ 5 m.

According to Surono (2007), pre-eruption CO₂ fluxes from the lake were typically 50 metric tons/day. During August 2007 they rose to 333 tons/day; during late August to early September they reached 500 tons/day.

During 2006, the Darwin Volcanic Ash Advisory Center (VAAC) reported a pilot observation. An ash plume on 18 May 2006 allegedly reached an altitude of 5.5 km.

On 17 October 2007 Kelut was the subject of further VAAC reports, first noting the elevation of the hazard status to 4 (the highest level, indicating an eruption imminent). On 23 October there was a brief noting evidence from a satellite of a eruption (to ~ 6 km altitude) but ground observers suggested that it was a meteorological cloud. A VAAC report on 4 November noted "ash not identifiable on satellite imagery." On 8 November an advisory noted the continued absence of identifiable ash.

Seismicity rose suddenly on 10 September 2007 (figure 7). It peaked on 16 October at all four seismic stations on or adjacent the volcano, at 510 events. The next day, the number of earthquakes still stood quite high, 151.

Cross sections showing hypocenters for 10-11 and 26-29 September 2007 depicted them broadly centered below the edifice but distributed around 2.5 km depth; they were initially absent in a zone about 2-3 km below the summit . During mid-October the hypocenters became more closely packed along a narrow vertical band beneath the edifice. They then filled a zone 0.7-1.2 km beneath the summit, with a few other hypocenters centered ~ 2 km below the summit. During 24-29 October, many hypocenters clustered ~ 6 km below the summit, but others strung out on or about a vertical line intersecting near the summit. The shallowest events plotted were then ~ 1 km below the summit. Reports also noted tremor was common during 24 October through 4 November.

VSI issued a series of increases in Kelut's hazard status (a scale of 1-4, figure 7). On 11 September 2007, VSI raised the status from 1 to 2. This corresponded to the CO2 flux mentioned above, a sudden jump in seismicity on 10 September (figure 7), and changes in both lake temperature and color, which shifted from its usual green, becoming yellow in some areas and blue-white in others. On 29 September, the status went from 2 to 3 based on visual observations, increased seismicity, deformation measurements, and further changes of crater lake water chemistry and temperature.

VSI brought the status to 4 on 16 October (figure 7). Factors included the sudden rise in seismicity, and the summit's inflation during 13-16 October. Before the crisis of 16 October the lake water was whitish green; after the crisis, dominantly green. VSI to recommend that villagers within a 10-km radius evacuate. According to a United Nations report, local authorities evacuated ~ 117,000 people within this radius. The UN report cited Indonesian media as stating that an eruption could affect as many as ~ 290,000 people (figure 8).

According to a news article, thousands returned to their homes on 17 October to tend to crops and animals, and to retrieve food. On 8 November the status fell to 3 and residents were allowed to return home. On 29 November the status fell from 3 to 2 following both decreased seismicity and a lack of deformation. At this stage, people were advised to remain at least 1.5 km from the lake.

During 24-31 October, a series of regional earthquakes occurred, dominated by shallow events and tremor. Seismicity intensified during 2-3 November, but then decreased on 4 November.

Dome emerges during 3-4 November 2007. On 3 November, VSI and news media mentioned plumes, and possibly some evidence of erupted solids entering the lake. Also, their buoy ceased functioning. On 4 November, white plumes rose to an altitude of 2.2 km and drifted N.

Plumes on the 4th came from a fresh black lava dome, protruding from the then turbid green lake. Monitoring cameras showed copious steam obscuring the dome. The exposed mass grew quickly. Although steaming continued, relative calm usually prevailed at both the dome and the lake. Although the dome steadily displaced the lake, the water did not undergo violent broad-scale boiling.

According to VSI, the temperature at the surface of the crater lake on 6 November had climbed to over 75°C. The newly exposed dome surface was 150-210°C. Plumes generally inhibited clear views.

On 8 November, VSI reported a decrease in seismicity, and deformation-monitoring suggested greater stability. An infrared camera (FLIR) captured images of the dome on 9 November as it emerged from the lake. The images revealed considerable radiant heat in the FLIR-sensitive wavelengths (figure 9).

According to a news article by Agence France Presse on 12 November, a volcanologist reported that the lava dome had reached 250 m in diameter and was 120 m above the lake surface.

November photos and videos. On 11 November, a plume rose to an altitude of 3.7 km and ashfall was reported in several areas. News accounts indicated that tremors continued and that Kelut was spewing ash and lava. More photos of the dome, particularly during 10-29 November, would be useful for understanding activity in this period.

An undated video provides views of a short-lived avalanche down from the new dome's upper walls. Based on the size of the dome then, the scene was probably captured in mid- to late November (it was posted on 7 December; Masdjawa, 2007). The avalanche initially contained on the order of 5-20 m³ of loose material, much of it incandescent in daylight. A large portion of this material bounced downslope into the steaming lake. When sufficient fragmental material entered the lake an intense phreatic eruption took place. The clouds rose vertically; they were initially jet black, but within tens of seconds became dominantly white steam, hiding the dome for ~ 1-2 minutes.

Daniel Brazilier visited during 25-26 November and saw mildly to moderately explosive activity; his photos appeared in Societe de Volcanologie Geneve reports (SVG, 2007). Many of his photos were taken during daylight from ~ 1.5 km away; they showed several explosions with billowing white-to-tan clouds. The foreground, the W crater wall, contained small amounts of tephra and some bombs. The billowing clouds appeared to contain minor ash; they vented from the dome upper area or side, and accompanied numerous steaming bombs, which from their arcing trails, seemed destined to land within the crater. Night photos disclosed large areas of incandescence on the W side.

Tom Pfeiffer took a series of remarkable photos on 29-30 November 2007, documenting a surprisingly large and clearly fast-growing dome. He posted over 60 photos on the Volcano Discovery website and elsewhere, and several of them appear here (figures 10, 11, and 12).

Note that Pfeiffer's photos are night-time shots with long exposures and thus the impression of large glowing areas implies more activity than really occurred at any one time. The dome had clearly crowded out the then green or brownish lake, which in the field of view had been reduced to an arcuate sliver. The extent of the lake on the dome's W and SW sides was unclear from his perspective.

Particularly on figures 10 and 11, the dome was rife with abundant glowing zones and numerous red traces due to incandescent dome rocks bouncing downslope. Abundant were glowing avalanche trails, and large rockfall scars. The photos also suggest possible lava seeps and narrow lava flows, although Tom Pfeiffer attributed most of the incandescence to mobile and solidified material, rather than narrow zones occupied by fluid moving lava.

A few of the glowing traces in the photos terminate upon entering the crater lake (figure 12). After their first contact with the water, some of those descending traces also seemingly shattered and bounced, producing one or more secondary arcs (akin to a skipping stone).

Pfeiffer described the scene as "filled with the noises of cracking lava, falling debris, and chilled lava blocks that splashed into the lake." He went on to note the lack of "explosions, or major ash emissions attached to the activity. The lava dome was simply growing quietly and not doing anything else than what is visible on the photos." He was struck by the observation "that the lake was simply there and NOT boiling. A sign how well rock insulates. Also, the upper 10 meters of the dome, its very top, were rather inactive, like the top of a mushroom being lifted up. The most active zones were just underneath that upper crust . . .."

References. Bernard A., and Mazot A., 2004, Geochemical evolution of the young crater lake of Kelud volcano in Indonesia: Proceedings of the Eleventh International Symposium on Water-Rock Interaction, Saratoga Springs, New York, USA, v. 1, p. 87-90.

Bernard, A., 2000, Geochemistry of the crater lake of Kelut volcano, Indonesia: Essay labeled "in preparation" on the http://www.ulb.ac.be/ website.

Bourdier, J. L., Pratomo, I., Thouret, J.C., Boudon, G. and Vincent, P.M., 1997. Observations, stratigraphy and eruptive processes of the 1990 eruption of Kelut volcano, Indonesia: J. Volcanol. Geotherm. Res., v. 79, p. 181-203.

Delmelle, P., and Bernard, A., 1999, Volcanic lakes, in Encyclopedia of volcanoes, H. Sigurdsson (ed.): Academic Press, p. 877-895.

Masdjawa, 2007, Kelud-Kubah Lava: Kelud_03.mpg (23.2 Mb), 2 min 20 sec; http://masdjawa.multiply.com/video/item/4

Rodolfo, K. S., 1999, The hazard from lahars and Jökulhaups, in Encyclopedia of volcanoes, H. Sigurdsson (ed.): Academic Press, p. 973-995.

Surono, 2007, Pusat Vulkanologi Dan Mitigasi Bencana Geologi, Pos Pengamatan Gunungapi Kelut (Hasil evaluasi tingkat kegiatan G. Kelut): Departemen Energi Dan Sumber Daya Mineral, Republik Indonesia, Badan Geologi, Nomor, 112/GK/X/2007, 30 Oktober 2007.

Thouret, J. C., Abdurachman, K. E., and Bourdier, J. L., 1998, Origin, characteristics, and behavior of lahars following the 1990 eruption of Kelud volcano, eastern Java (Indonesia): Bull. Volcanol., v. 59, p. 460-480.

Information Contacts: Volcanological Survey of Indonesia, Center of Volcanology and Geological Hazard Mitigation, Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://portal.vsi.esdm.go.id/joomla/); Alain Bernard, Free University of Brussels, CP 160/02, 50, avenue F, Roosevelt, 1050 Brussels, Belgium (URL: http://www.ulb.ac.be/sciences/dste/volcano/garde/page%20de%20garde.html); Relief Web, United Nations Office for the Coordination of Humanitarian Affairs, Resident Coordinator's Office, Jakarta, Indonesia (URL: http://www.reliefweb.int; http://ochaonline.un.org/).; Darwin Volcanic Ash Advisory Center, Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, Northern Territory 0811, Australia (Email: darwin.vaac@bom.gov.au; URL: http://www.bom.gov.au/info/ vaac/); Tom Pfeiffer, Volcano Discovery (Email: tpfeiffer@decadevolcano.net; URL: http://www.decadevolcano.net/; http://www .VolcanoDiscovery.com/); Daniel Brazilier, 71, rue du Vieux Rû, F-77210 Avon, France.

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07/2008 (BGVN 33:07) Lava dome reached 35 million cubic meters; eruptions ceased in mid-May

According to Alain Bernard, the lava dome that extruded in late 2007 (BGVN 33:03) continued to increase in size until it covered much of the crater lake and it rose to overwhelm the drainage inlets. Bernard noted that dome growth had seemingly ceased by April 2008. Around that time (but at unstated date), VSI made initial estimates of the dome's dimensions as 200 m high, 400 m wide, with a volume of 35 x 10⁶ m³.

The lake was almost gone by the middle of May 2008. The temperature of flow of waters at the end of the drainage tunnel (~ 960 m away from the dome) has been reported to be higher than in the crater lake, 66.7°C. Both phreatic and magmatic degassing was very minor. A very small amount of ash was emitted, and there were no lahars

On 12 May 2008, the eruption status was downgraded to Green, a level indicating that either no significant eruption is expected or that fewer than 100,000 people within 100 km of the volcano would be affected by activity.

Information Contacts: Alain Bernard, Free University of Brussels, CP 160/02, 50, avenue F, Roosevelt, 1050 Brussels, Belgium (URL: http://www.ulb.ac.be/sciences/dste/volcano/garde/page%20de%20garde.html); Volcanological Survey of Indonesia, Center of Volcanology and Geological Hazard Mitigation, Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://portal.vsi.esdm.go.id/joomla/).

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