Telica

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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 12.602°N
  • 86.845°W

  • 1061 m
    3480 ft

  • 344040
  • Latitude
  • Longitude

  • Summit
    Elevation

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    Number

12 September-18 September 2012

During 10-11 September INETER reported "jet" sounds from Telica, two incandescent fumaroles, and gas-and-steam plumes rising 100-200 m above the crater. On 11 September two small explosions occurred in the crater. During 12-14 and 17 September gas plumes rose 30-150 m and incandescence from the crater was observed. Gas measurements on 14 and 17 September showed normal levels of sulfur dioxide emissions.

Source: Instituto Nicaragüense de Estudios Territoriales (INETER)

Index of Weekly Reports


2012: September
2011: May
2007: January | February

Weekly Reports


12 September-18 September 2012

During 10-11 September INETER reported "jet" sounds from Telica, two incandescent fumaroles, and gas-and-steam plumes rising 100-200 m above the crater. On 11 September two small explosions occurred in the crater. During 12-14 and 17 September gas plumes rose 30-150 m and incandescence from the crater was observed. Gas measurements on 14 and 17 September showed normal levels of sulfur dioxide emissions.

Source: Instituto Nicaragüense de Estudios Territoriales (INETER)


18 May-24 May 2011

INETER reported that during April seismicity at Telica increased, with earthquake magnitudes ranging up to 3.3 and some explosions detected. On 14 May at approximately 2310 a series of explosions were detected by the seismic network and were accompanied by ash and gas emissions. Tephra fall was reported in La Quemada, 4 km N. During the previous few days residents in nearby communities observed reddish colored gas plumes, and those living on the flanks felt earthquakes. On 16 May the seismic network registered three explosions that were accompanied by gas-and-tephra emissions. One plume rose 1.2 km above the crater. Nearby communities to the SE, including Cristo Rey, Las Colinas, and La Quemada, were affected by the emissions.

During 17-18 May another series of small explosions was detected. A gas-and-ash plume rose 600 m above the crater. On 18 May an explosion that lasted 6 minutes produced an ash plume that rose 2.6 km above the crater. Fifteen explosions during 18-19 May were accompanied by gas-and-ash plumes that rose 500-800 m high. Women and children living on the flanks were evacuated. Explosions continued to be detected during 19-20 May with gas-and-ash plumes again rising 500-800 m above the crater. Residents on the N flank in the community of El Ñajo reported that new fumaroles had opened, prompting authorizes to plan for monitoring all wells within a 5-km-radius of Telica. During 20-21 May activity decreased. An observer reported four strong explosions and gas-and-tephra plumes that rose 500-700 m high.

Source: Instituto Nicaragüense de Estudios Territoriales (INETER)


11 May-17 May 2011

Based on reports from INETER, the Washington VAAC stated that emissions of gas-and-ash from Telica were detected on 15 May, and ash fell in areas 4 km N. Seismicity was elevated for a period of time.

Source: Washington Volcanic Ash Advisory Center (VAAC)


14 February-20 February 2007

The Washington VAAC reported that continuous emissions of ash from Telica were visible on a web-camera on 15 February. A resultant plume rose to an altitude of 1.5 km (5,000 ft) a.s.l. Based on satellite imagery, the plume drifted SW and a hotspot was present at the summit.

Source: Washington Volcanic Ash Advisory Center (VAAC)


3 January-9 January 2007

On 9 January, INETER reported that a gas-and-ash plume from an eruption of Telica reached an altitude of 1.5 km (4,900 ft) a.s.l., drifted W, and then reached a greater altitude. The eruption was accompanied by increased seismic activity. The Washington VAAC reported that a possible ash plume was visible on satellite imagery and on a web camera, drifting SW.

Sources: Instituto Nicaragüense de Estudios Territoriales (INETER); Washington Volcanic Ash Advisory Center (VAAC)


Index of Monthly 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.

11/1968 (CSLP 53-68) Possible rumbling and steam emission

02/1969 (CSLP 13-69) Intermittent light ashfall since 11 February

03/1969 (CSLP 13-69) Ashfall noticed in León on 4 March

05/1969 (CSLP 13-69) Ash and lapilli eruption on 14 May

08/1969 (CSLP 13-69) Large dark eruption column on 19 August

08/1970 (CSLP 75-70) Sporadic eruptive emissions strengthen during 18-22 August

09/1970 (CSLP 75-70) Largest ashfall in recent years

12/1971 (CSLP 100-71) Active lava lake seen in the summit crater on 1 December

11/1976 (SEAN 01:14) Large dark clouds emitted 3-4 November

12/1976 (SEAN 01:15) Dark landslide material in typical small fume cloud

11/1977 (SEAN 02:11) Explosions observed in late November

12/1977 (SEAN 02:12) Explosion frequency declines

02/1980 (SEAN 05:02) Minor white plume

07/1980 (SEAN 05:07) Small steam plume emission continues

12/1980 (SEAN 05:12) Moderate vapor plume

01/1981 (SEAN 06:01) Small intermittent vapor plume

03/1981 (SEAN 06:03) Holes in crater wall emit vapor plume; occasional minor ash eruptions

12/1981 (SEAN 06:12) Continuous white vapor plume with occassional ash

01/1982 (SEAN 07:01) Small gas and ash eruptions in late December and early January

02/1982 (SEAN 07:02) Largest eruption since 1976; ashfall to coast

03/1982 (SEAN 07:03) Last confirmed eruption on 2 March

08/1982 (SEAN 07:08) Ash eruptions also eject scoria and large incandescent blocks

04/1983 (SEAN 08:04) Increased seismicity and fumarolic activity in February

11/1985 (SEAN 10:11) Continued normal activity and strong seismicity

01/1988 (SEAN 13:01) Eruption in November 1987 forms a new vent in the crater

02/1989 (SEAN 14:02) Incandescence seen at four vents on the crater floor

06/1989 (SEAN 14:06) Fumaroles emit white plumes

02/1991 (BGVN 16:02) Large vapor clouds; fumaroles to 246°C

04/1992 (BGVN 17:04) No significant plume emission

03/1993 (BGVN 18:03) No observed activity

09/1993 (BGVN 18:09) Moderate fumarolic activity

10/1993 (BGVN 18:10) Collapse crater expands; incandescence observed

03/1994 (BGVN 19:03) Passive fumarole and San Jacinto mud-pot temperatures remain stable; possible decrease in fumarole mass flux

07/1994 (BGVN 19:07) Explosive eruption causes ashfall >12 km SW of the summit

09/1994 (BGVN 19:09) Explosion followed by decreased seismicity

04/1996 (BGVN 21:04) Low-level degassing and sulfur deposits observed in crater

03/1997 (BGVN 22:03) Seismicity increases and fumarolic activity continues

05/1997 (BGVN 22:05) Continued high levels of seismicity

06/1997 (BGVN 22:06) June increase in both earthquakes and the extent of fumaroles

03/1998 (BGVN 23:03) February visit reveals slight increase in fumarolic activity and collapse zone

04/1999 (BGVN 24:06) Phreatic eruptions in May and June cause local ashfall

02/2000 (BGVN 25:02) Lava lake seen in August; sporadic ash explosions August-December

03/2000 (BGVN 25:03) Eruptive activity declines in February, but seismicity remains high

09/2000 (BGVN 25:09) Gas-and-ash emissions in early 2000; fumarole temperature measurements

05/2009 (BGVN 34:05) Intermittent ash explosions and incandescence during 2000-2002

06/2009 (BGVN 34:06) Intermittent incandescence and ash explosions through January 2005

08/2009 (BGVN 34:08) Extensive degassing and sporadic ash explosions during 2006-2008

03/2010 (BGVN 35:03) Incandescent crater floor areas seen in November 2009 and March 2010

11/2011 (BGVN 36:11) Degassing in 2011; seismic crisis leading to explosive eruption in May 2011

02/2013 (BGVN 38:02) Degassing continues in 2012; increased micro-earthquake activity in March 2013


Contents of Monthly Reports

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

All times are local (= UTC - 6 hours)

11/1968 (CSLP 53-68) Possible rumbling and steam emission

Card 0215-0216 (04 November 1968) Possible rumbling and steam emission

The following was received from Richard Dillard via radio on 4 November 1968. "The last couple of nights the farm people claim that [Telica] is beginning to rumble a little bit. The only thing that is coming out of it is a little smoke and steam, no ash or anything."

Information Contact: Richard Dillard, León.

02/1969 (CSLP 13-69) Intermittent light ashfall since 11 February

Card 0409 (17 February 1969) Intermittent light ashfall since 11 February

Telica . . . has exhibited limited and intermittent activity since 11 February, primarily comprising light ashfall in the area immediately adjacent to the volcano.

Information Contact: American Embassy, Managua.

03/1969 (CSLP 13-69) Ashfall noticed in León on 4 March

Card 0459 (10 March 1969) Ashfall noticed in León on 4 March

On 10 February the Telica volcano started its activity with emission of white clouds from the NE side of the crater. On 14 February the clouds . . . were darker and heavier in appearance. On the following days, the activity increased in frequency of emissions, so it did in quantity and altitude reached by the clouds formed by the erupted material. On 19 February Telica decreased in activity, diminishing to such a point that on 27 or 28 February it stopped completely during the day. On 4 March, for the first time, falling ash was perceptible in the city of León.

Information Contact: Gladys León Quant, National University of Nicaragua.

05/1969 (CSLP 13-69) Ash and lapilli eruption on 14 May

Card 0560 (27 May 1969) Ash and lapilli eruption on 14 May

Activity . . . started 14 May in the morning, erupting fine ash and lapilli. [On 15 May there was] a very strong eruption in the morning. [On 17 May there was] decreasing activity. Many tremors during the activity.

Information Contact: Jose Viramonte, Servicio Geologico National, Managua.

08/1969 (CSLP 13-69) Large dark eruption column on 19 August

Card 0732 (25 August 1969) Large dark eruption column on 19 August

The following is to report that Telica has not been completely inactive. From time to time it has been throwing out volcanic material but in small quantities and mainly in the early hours of the day. Nevertheless, these last days, it has increased in its activities and today (19 August), at 0900 it had quite a large red-dark brown column of "smoke" that is perhaps four times larger than any previous day's. The clouds of volcanic material seem to be coming out from the northern side of the mouth. It maintained its activity at the same level all day long. Still in activity at 0900 [on 20 August]. It has notoriously diminished. It seems to be one third of what it was yesterday.

Information Contact: Gladys León Quant, National University of Nicaragua.

08/1970 (CSLP 75-70) Sporadic eruptive emissions strengthen during 18-22 August

Card 1000 (28 August 1970) Sporadic eruptive emissions strengthen during 18-22 August

"Telica began a new eruption on 18 August with sporadic eruptive emissions that were not very large and did not seem more special than usual. On [19 August] the activity was very clear. Columns of ash were emitted from time to time and had a dark, almost black color when coming out of the crater, but took on a brown color a little farther from the volcano. It was clearly observed that the heavier particles erupted fell down quite close to the volcano and the ash particles remained suspended in the atmosphere being dragged by the air towards the Pacific coast. On this day, the frequency of the eruptions were more of less two every five minutes. On 20 August the volcano was more active. The columns were larger, darker, and more frequently erupted. On [21 and 22 August] the activity increased. The emission is constant and from time to time becomes stronger."

Information Contact: Jose Viramonte, Servicio Geologico National, Managua; Gladys León Quant, National University of Nicaragua.

09/1970 (CSLP 75-70) Largest ashfall in recent years

Card 1002 (04 September 1970) Small eruption cloud on 17 August

The following was received from the American Embassy, Managua. "Telica erupted at 0430 on 17 August and continued in activity until 25 August, around 2100. Explosion was slight but of sufficient magnitude to be called eruption. No blocks, bombs, or lapilli were ejected. There was no lava flow. Eruption cloud rose to [450 m]. Eruption cycle was every ten minutes. Emission consisted of sand particles of basaltic minute spheres. Local farmers heard rumblings in early morning hours but generally eruption has been quiet. No seismic activity reported. Effects of ash minimal because ash fall was fine and apparently chemically non-toxic. Daily rains washed ash from foliage. Although no adverse effects of ash reported, Viramonte has sent samples to Dartmouth College for confirmation non-toxic character. Geological Service as a body has been interested in investigation. Ash was blown in northwestern direction toward Corinto. Volcano has now returned to normal fumarolic activity."

Card 1005 (08 September 1970) Large ash clouds during 17-25 August

"One of the largest ash eruptions of Telica in recent years took place from 17 to 25 August. Large ash clouds reaching approximately [450 m] high were erupted at intervals (5 to 10 minutes) by the central crater. The direction of the ash clouds was NW, and reached the cities of Chichigalpa, Posoltega, and Corinto, affecting the cotton plantations of the region. Petrographical and chemical analyses were made and the following results were obtained. Petrographical descriptions: Olivinic Basaltic ash with plagioclase (Ab30 An70), 35%; pyroxene (augite), 20%; olivine, 5%; magnetite and ilmenite, 10%; basaltic glass (Nd:1.56), 30%. Granulometric studies: 100 mesh, 8%; 150 mesh, 12%; 200 mesh, 18%; <200 mesh, 62%. Chemical composition (bulk analyses): SiO2, 55.10%; Al2O3, 17.20%; Fe2O3, 2.40%; FeO, 6.54%; MnO, 0.20%; MgO, 3.5%; CaO, 7.42%; Na2O, 2.62%; K2O, 1.50%; TiO2, 0.75%; P2O5, 0.10%; H2O+, 0.25%; H2O-, 1.55%; Total, 99.13%.

Information Contacts:
Card 1002 (04 September 1970) Pablo Martinez Navas, Gen. Geological Service, Managua; Jose Viramonte, Servicio Geologico National, Managua; American Embassy, Managua.
Card 1005 (08 September 1970) Jose Viramonte, Servicio Geologico National, Managua.

12/1971 (CSLP 100-71) Active lava lake seen in the summit crater on 1 December

Card 1335 (22 December 1971) Active lava lake seen in the summit crater on 1 December

"An active lava lake was observed deep within Telica's summit crater on 1 December 1971 by Dartmouth College geologists. Similar observations from the rim one year ago showed no lava lake. The volcano has had numerous small ash eruptions in 1971; none of these affected more than the immediate area of the cone."

Information Contacts: R. Stoiber and Paul Taylor, Dartmouth College.

11/1976 (SEAN 01:14) Large dark clouds emitted 3-4 November

Telica emitted large dark clouds during the morning of 3 and 4 November.

Information Contacts: R. Gleason and R. Stoiber, Dartmouth College.

12/1976 (SEAN 01:15) Dark landslide material in typical small fume cloud

During the morning of 18 or 19 November, there was a little dark material in the small fume cloud that is usually present over Telica. Alain Creusot suggested that landsliding from the crater walls may have been responsible.

Information Contact: R. Stoiber, Dartmouth College.

11/1977 (SEAN 02:11) Explosions observed in late November

"During the early morning of 25 November, our group observed a series of ultravulcanian ash eruptions from Telica. An explosion was observed at 0605 from León, 19 km from Telica, producing a light brown ash cloud that rose 0.91 km above the summit. A dispersed cloud of ash from an earlier explosion was noted SW of the volcano. Four more explosions were observed, at 0617, 0622, 0626, and 0644. For the rest of the day, only intermittent observations were possible, but explosions were noted at 0740, 0835, and 1530. Ash fell in a zone extending about 5 km SSW of the volcano. Four kilometers from the source, the ash formed a discontinuous coating << 1 mm thick. Samples were collected for analysis at Dartmouth. A similar explosion, sending ash 1.6 km above the cone, was seen at 0605 on 26 November. At 0920 on 27 November, a dust cloud, presumably produced by another explosion, was seen from the air. The group reports that other Nicaraguan volcanoes show their normal level of fumarolic activity."

Information Contacts: R. Stoiber, R. Birnie, and S. Self, Dartmouth College.

12/1977 (SEAN 02:12) Explosion frequency declines

Increased activity began 11 November, when sizeable explosions began to occur at a rate of about 1/hour, in contrast to about 1/month during the preceding year. Ash from some of the larger explosions reached the Pacific Ocean, about 35 km from the volcano. By early January, explosion frequency had declined to 1-2/day and ashfall was no longer reaching the ocean.

Information Contacts: A. Aburto Q., Instituto de Investigaciones Sísmicas; D. Harlow, USGS.

02/1980 (SEAN 05:02) Minor white plume

A minor white plume was observed in early February.

Information Contacts: R. Stoiber, S. Williams, and M. Bruzga, Dartmouth College.

07/1980 (SEAN 05:07) Small steam plume emission continues

When geologists visited Telica in June, a small steam plume continued to be emitted.

Information Contacts: R. Stoiber and S. Williams, Dartmouth College; M. Carr and J. Walker, Rutgers Univ.; A. Creusot, Instituto Nicaraguense de Energía.

12/1980 (SEAN 05:12) Moderate vapor plume

In late 1980, a moderate-sized but continuous vapor plume rose from the summit crater. SO2 flux was remotely measured and found to be approximately 150 t/d.

Information Contacts: R. Stoiber, S. Williams, H.R. Naslund, L. Malinconico, and M. Conrad, Dartmouth College; A. Aburto Q. and D. Fajardo B., Instituto de Investigaciones Sísmicas.

01/1981 (SEAN 06:01) Small intermittent vapor plume

A small-volume plume of vapor was intermittently released in early 1981. Shallow seismicity was regularly observed in the vicinity.

Information Contacts: R. Stoiber and S. Williams, Dartmouth College; D. de Jerez, IRENA; D. Fajardo B., Instituto de Investigaciones Sísmicas.

03/1981 (SEAN 06:03) Holes in crater wall emit vapor plume; occasional minor ash eruptions

"Two flights were made over the summit crater of Telica, in mid-February and mid-March. Two large holes (each with a diameter of approximately 20-30 m) occurred high on the NW wall of the crater. They are reported (by Alain Creusot, Instituto Nicaraguense de Energía) to coalesce at depth. One or both of them emitted a continuous vapor plume. Occasional minor ash eruptions were reported by local people."

Information Contacts: R. Stoiber, S. Williams, Dartmouth College; D. de Jerez, IRENA; D. Fajardo B., Instituto de Investigaciones Sísmicas.

12/1981 (SEAN 06:12) Continuous white vapor plume with occassional ash

"A small continuous plume of white vapor and occasional ash was observed in late November. The two summit vents on the W wall of the crater had merged into one."

Information Contacts: R. Stoiber, S. Williams, H.R. Naslund, B. Gemmell, and D. Sussman, Dartmouth College; D. Fajardo B., Instituto de Investigaciones Sísmicas.

01/1982 (SEAN 07:01) Small gas and ash eruptions in late December and early January

"A series of small gas and ash eruptions took place in late December and early January. Ash fell only very close to the crater. Seismicity was above normal throughout the period and remained so in late January."

Information Contacts: R. Stoiber and S. Williams, Dartmouth College; D. Fajardo B., Instituto de Investigaciones Sísmicas.

02/1982 (SEAN 07:02) Largest eruption since 1976; ashfall to coast

The quoted material below is from reports prepared by Dartmouth College geologists.

"On 12 February between 1100 and 1200 Telica had its largest eruption since 1976. It began after 1.5 days of relative seismic quiet and lasted about 45 minutes. Blocks and scoria 2-3 m in diameter were thrown over an area extending 200 m from the crater rim. Minor collapse occurred on the crater rim. Fires were ignited in grass up to 1 km from the crater, especially to the E. At 5-6 km downwind, moist sand-sized ash accumulated to 2-3 cm depth. Ash fell to the SW as far away as Corinto (45 km from Telica), on the Pacific coast."

While flying over the Pacific coast of Nicaragua in a commercial aircraft on 12 February at 1200, William I. Rose, Jr. saw a vertical ash column penetrate the top of the cloud deck (at about 1.8-2.4 km altitude) over the Telica area. After about 50 seconds, the eruption column reached its maximum altitude of 3.7-4.3 km. Rose observed a second, smaller eruption column at 1207 before moving out of view of the area at 1215.

"The eruption followed several months of minor gas and ash ejection and notably heightened levels of seismic activity. Eruptive activity had apparently increased in duration and frequency during the week preceding 12 February." Dull red incandescence had been visible in the deepest portion of the vent for weeks and new bright incandescence was noted on 8 February in a fumarole at a much higher elevation, after a day of eruption. A second eruption from 1545-1610 on 12 February also ejected blocks and scoria but was much smaller.

La Prensa reported that between 12 and 14 February at least 50 people (of the roughly 8,000 living nearby) had been evacuated from the S side of the volcano, and the Red Cross established an aid station. Some farm birds were killed and small cotton fields on the flanks of Telica were coated with ash. Wild birds and animals also fled the area. The Red Cross reported strong activity 14 February and ejection of ash and blocks at 0930 on 15 February.

"On 19 February at 1030 a second large eruption sent ash as far to the WSW as Chinandega (35 km away)." William Rose was again flying along the coast of Nicaragua, about 160 km offshore, and observed 2 distinct explosions, the first starting at about 1030, the second between 1100 and 1115. Tephra clouds rose to more than 3.5 km altitude and black ash blew to the NW. "In the following week, 2-3 small eruptions each day sent ash and gas over the immediate area.

"The day geologists visited the crater, 24 February, there were no large eruptions and there had not been since 20 February. An impressive bomb and block field was laid down on the N side of the crater, extending approximately 300 m to the N. Craters 1-1.5 m across were created by low-angle impact of bombs 50 cm in diameter at the 300-m range. At approximately 100 m from the crater rim, the surface was 100% cratered and at 80 m was 100% covered with debris. Maximum thickness was 50 cm at the crater rim. The deposit was strongly inversely graded. Fresh breadcrusted scoria bombs up to 80 cm in diameter were widely scattered throughout the deposit. The active vent had increased in size by about two times. It was elongated N-S and was approximately 75 x 50 m. No incandescence was visible during the day. Slumping of the wall above the vent may have removed about 10 m from the rim of the crater.

"Gas emission between eruptions on 24 February was very small, as it was on 28 January. The gas was bluish in color and smelled like SO2 and HCl, but not H2S. Samples were taken on both days. Volcanic tremor occurred in irregular pulses only. The volcano has been relatively quiet seismically since the eruption of 12 February. In January and early February, there had been several magnitude 2-3 earthquakes each day."

Information Contacts: R. Stoiber, S. Williams, W. Crenshaw, and D. Sussman, Dartmouth College; W. Rose, Jr., Michigan Tech. Univ.; D. Fajardo B., INETER; A. Creusot, Instituto Nicaraguense de Electricidad; La Prensa.

03/1982 (SEAN 07:03) Last confirmed eruption on 2 March

"The eruption sequence that began in mid-December 1981 appears to have drawn to a close. The last confirmed eruption occurred at approximately noon on 2 March, sending ash to Corinto and beyond. Since then the volcano has also been seismically quiet. A crater visit on 19 March revealed continued collapse of the crater walls. The vent was clogged with boulders and a ring of strongly jetting fumaroles was established around its margins."

Further Reference. Williams, S.N., 1985, La Erupción del Volcán Telica, Nicaragua, 1982; Boletín de Vulcanología (Universidad Nacional, Heredia, Costa Rica), no. 15, p. 10-19.

Information Contacts: S. Williams and R. Stoiber, Dartmouth College; I. Menyailov and V. N. Shapar, IVP, Kamchatka; D. Fajardo B., INETER.

08/1982 (SEAN 07:08) Ash eruptions also eject scoria and large incandescent blocks

The diameter of the E part of the crater increased by about 10 m. As of early August no seismicity was being recorded but fumarolic activity was stronger than it had been before the December-March eruption.

Information Contacts: D. Fajardo B., INETER; R. Parnell, Jr., Dartmouth College.

04/1983 (SEAN 08:04) Increased seismicity and fumarolic activity in February

After a tephra eruption ended 1 March 1982, seismicity returned to normal. Through November 1982 about 14 events were recorded per day. On 10 February 1983 a portable seismograph installed on the flank recorded 66 earthquakes. This increase was paralleled by stronger fumarolic activity on the S, SE, and SW part of the volcano.

Information Contact: D. Fajardo B., INETER.

11/1985 (SEAN 10:11) Continued normal activity and strong seismicity

Although normal activity continued, Telica continued to show stronger seismic activity than other Nicaraguan volcanoes. A seismograph registered 24 low-frequency microearthquakes in a 5-hour period on 9 July.

Information Contacts: D. Fajardo B., INETER.

01/1988 (SEAN 13:01) Eruption in November 1987 forms a new vent in the crater

An eruption occurred in November 1987 but was not observed by geologists. Residents of the area near the E side of the crater reported an incandescent column and loud bangs but said that the eruption was less intense than others in recent years. Newspapers printed photographs of a small eruption column.

Geologists found small fresh basaltic bombs 50 m from the E rim of the crater that may have been from the eruption. A vent 30-50 m wide had opened in the NE corner of the crater. The maximum temperature on a rock surface in the new vent was 246°C. Fumarolic activity was markedly stronger than in 1985-86, when only one large fumarole had been present, on the N side of the crater. In January 1988, there were fumaroles on all sides of the crater and on its floor (figure 1). At least one was emitting gas with a loud roar, and the plume was visible from 5 km away.

Figure 1. Sketch map of Telica on 17 January 1988. Temperatures were taken with an infrared radiometer measuring surface brightness temperature in the 8-14 µm range with emissivity set at 1. Temperature measurements of the numbered points were taken from about 500 m away, with a 60-80 m resolution, unless otherwise noted in parentheses. Crater walls are vertical and fumaroles inaccessible. Fumaroles and hot areas are stippled. Measured temperatures: (1) 131°C (60 m2), 60-80°C (1,000 m2); (2 & 3) 50°C (fissures); (4) 60-70°C (1,000 m2); (5) 96°C (25 m2), 60°C (100 m2), 50°C (1,000 m2); (6) 47°C (fissure 10 m long); (7) 245°C (100 m2, including new crater), 100°+C (250 m2), 60-100°C (1,000 m2 – rock slabs); (8) 50-60°C (fissure 30 m long); (9) 45°C (small fumaroles).

The fumarole field [at San Jacinto Hot Springs] had temperatures no higher than 101°C on 17 January.

Information Contacts: B. van Wyk de Vries, H. Rymer, and G. Brown, Open Univ; P. Hradecky and H. Taleno, INETER.

02/1989 (SEAN 14:02) Incandescence seen at four vents on the crater floor

During fieldwork at the summit crater 9-10 March, incandescence from four closely spaced vents on the crater floor was observed at night. Brightness temperatures were obtained with Minolta Cyclops 33 (bandpass 8-14 µm, 1° field of view) and Cyclops 52 (bandpass 0.8-1.1 µm, 0.33° field of view) infrared thermometers. Temperatures are not corrected for emissivity and atmospheric absorption effects. A brightness temperature of 550°C was measured at night (Cyclops 52) but the hot target filled only a fraction of the field of view.

Information Contacts: C.M.M. Oppenheimer and D.A. Rothery, Open Univ; B. van Vyk de Vries, O. Castellon, and L. Urbina, INETER.

06/1989 (SEAN 14:06) Fumaroles emit white plumes

A visit to the volcano on 5 June revealed two small brown crater lakes, 10 m across (figure 2). A number of large collapses had occurred, covering much of the crater floor with blocks. Fumarolic activity was vigorous (particularly from a vent on the SE side) and produced a continuous plume over the crater. No eruptive activity has been reported since December 1987.

Figure 2. Sketch of the active crater of Telica, 5 June 1989. Courtesy of B. van Wyk de Vries and O. Castellón.

Information Contacts: B. van Wyk de Vries and O. Castellón, INETER, Apartado 1761, Managua, Nicaragua.

02/1991 (BGVN 16:02) Large vapor clouds; fumaroles to 246°C

"In February 1990, fumarolic activity had declined from 1989 levels, with no observed incandescence. On 29 May, large clouds were observed from León and El Limón mine (50 km away). Subsequent observations at the crater revealed a strong geyser-like steam vent in the 1984/1987 explosion pits (figures 3 and 4). The steam at the crater edge (200 m above the vent) was warm and highly toxic; respiration was impossible without a gas mask. Local inhabitants reported crop damage from acid rain up to 2 km from the crater.

Figure 3. Sketch map of Telica showing the distribution of craters (numbered in order of increasing age), and the 1984 (A) and 1987 (B) explosion pits. Compiled from from aerial photos. Courtesy of Benjamin van Wyk de Vries.
Figure 4. Sketch map of Telica's W craters, showing fumarole distribution 13 June 1990, drawn from on-site observation and aerial photographs. Courtesy of B. van Wyk de Vries.

"Fumarole temperatures measured with an infrared radiometer on 13 June showed a maximum of 246°C in the SW side of the 1984/1987 explosion pits (figure 5). The steam vent was below 100°C. After heavy rain, the volume of steam increased enormously. The clear relationship between activity and precipitation was confirmed by local inhabitants, who claimed that such activity was common after storms, especially at the start of the wet season."

Figure 5. Sketch of Telica's 1984 / 87 explosion pits showing fumarole distribution and temperatures (in °C), 13 June 1990. All temperatures were measured using a Palmer "Colt" Radiometer with a 1° target field and 8-14 µm band, from 200-400 m distance. Courtesy of B. van Wyk de Vries.

Information Contacts: B. van Wyk de Vries, O. Castellón, A. Murales, and V. Tenorio, INETER.

04/1992 (BGVN 17:04) No significant plume emission

Although no detailed observations were made, no significant plume was emitted during 23-29 April fieldwork. Fumarolic activity that was vigorous in June 1989 (SEAN 14:02 and 14:06) had decreased notably by February 1990 (BGVN 16:02). Fumarole temperatures had also decreased, from around 550°C (9-10 March 1989) to <=246°C on 13 June 1990.

Information Contact: S.N. Williams, Arizona State Univ.

03/1993 (BGVN 18:03) No observed activity

There have been no reports of activity in the past year, and none was observed 6-7 January.

Information Contacts: Andrea Borgia, Instituto Nazionale di Geofisica, via di Vigna Murata 605, 00143 Roma, Italy; B. van Wyk de Vries, Open Univ; Peter J. Baxter, Dept of Community Medicine, Fenner's, Gresham Road, Cambridge, England.

09/1993 (BGVN 18:09) Moderate fumarolic activity

On the afternoon of 2 September, the summit area of Telica was visited to gather data on fumarole temperatures and gas compositions. Fumaroles on the flank of a somma wall E of Telica measured 85°C. Fumaroles along angular fractures in the crater appeared strong, but were inaccessible.

Information Contacts: Michael Conway and Andrew Macfarlane, Florida International Univ; Charles Connor, Southwest Research Institute; Oscar Leonel Urbina and Cristian Lugo, INETER.

10/1993 (BGVN 18:10) Collapse crater expands; incandescence observed

In late August a small collapse pit with an estimated diameter of 20 m was observed on the floor in the N zone of the 1982 central crater. An inspection of the vent on 23 October revealed a depth of 50 m and diameter of about 75-80 m. At night, the floor of the crater was partially incandescent. Maximum temperatures were estimated at 700-800°C based on the color of incandescence.

Information Contact: Alain Creusot, Instituto Nicaraguense de Energía.

03/1994 (BGVN 19:03) Passive fumarole and San Jacinto mud-pot temperatures remain stable; possible decrease in fumarole mass flux

Researchers from INETER and FIU visited Telica on 7 March 1994; Mike Conway submitted the following report. In late 1993, INETER deployed a seismic station about 500 m E of the crater, on the crest of an E-W trending ridge. Since the seismic station was deployed, the number of daily seismic events has ranged from 200 to 300. The unusually high seismicity led to concern that Telica was returning to an active phase.

Fumaroles feeding the plume rising from the Telica crater were inaccessible. A small field of passive fumaroles, situated in the E-W trending ridge wall almost immediately below the seismic station, yielded 78-84°C temperatures. These temperatures are similar to the 85°C temperature reported in September for the same fumaroles (BGVN 18:09). Mass flux from the fumaroles, however, appears to have decreased since September 1993. The change in mass flux may be related to seasonal variation in rainfall; the dry season in Nicaragua extends from November through March. Researchers at Telica are currently developing a program to study diffuse gases in soil.

San Jacinto Hot Springs. At the small village of San Jacinto there exist a number of boiling mud pots. San Jacinto is located along Nicaragua Highway 26, about 9 km NE of the town of Telica and 2 km E of Santa Clara volcano. Based on a 9 March 1994 visit by FIU researchers, Mike Conway submitted the following report.

The active mud-pot field measured about 35 x 100 m, elongate N to S. Alteration of basaltic lava flows to the E suggests that the geothermal field was much larger at one time, and probably equidimensional (225 x 225 m).

Individual mud pots ranged in size from 1 m to as much as 3-4 m in diameter. Many of the mud pots were actively spewing mud, and one, located at the SW corner of the field, had, according to local villagers, constructed a mud volcano (to 1-m height) during February-March 1994. For individual mud pots the ratio of mud or muddy water to relatively mud-free water varied. Mud-water temperatures throughout the field, however, were consistent and ranged from 98 to 100°C. These 100°C temperatures were similar to those measured in January 1988 (SEAN 13:01).

Eight soil gas samples, from sites distributed throughout the field, were analyzed for CO2 using a Hewlett Packard chromatograph. Soil gas CO2 ranged from 0.04 to 0.09 vol. %, with a mean value of 0.058 vol. % (standard deviation, 0.0184), well within the normal background range of about 0.04-0.1 vol. % typically found in many non-volcanic areas.

Information Contacts: Cristian Lugo and Martha Navarro, INETER; Michael Conway, Andrew Macfarlane, and Peter LaFemina, Florida International Univ (FIU); John B. Murray, Ben van Wyk de Vries, and Adam Maciejewski, Open Univ.

07/1994 (BGVN 19:07) Explosive eruption causes ashfall >12 km SW of the summit

An eruption on 31 July produced a gas-and-ash column that rose ~800 m above the 1,060-m-high summit. Ashfall was reported SW of the volcano (figure 6). Phreatic activity continued until 12 August with gas emission and minor ash explosions. Seismicity has been recorded continuously since December 1993, when a permanent telemetered seismic station (TELN: short-period, vertical-component) was installed ~500 m E of the active crater rim (figure 7). Also since December 1993, the Instituto Nicaragüense de Estudios Territoriales (INETER) has collaborated with the government, local authorities, civil defense, and the media, to educate the population about the situation at the volcano. Due to the relatively low magnitude of this eruption, it was not necessary to carry out the prepared evacuation plans.

Figure 6. Ashfall from Telica, 31 July-6 August 1994. Courtesy of INETER.
Figure 7. Sketch map of the summit area at Telica, showing locations of crater fumaroles (left) and seismic stations (right). Courtesy of INETER.

A seismic event on 15 June 1994 was recorded by several stations of the Nicaraguan seismic network, up to distances of ~40 km from Telica. This event at a depth of 6 km had a maximum magnitude of 2.1. The 31 July eruption was preceded by a steady increase in seismicity during 15-25 July (figure 8), recorded by station TELN. Seismicity had increased from <25 events/day in February-April to >25 events/day at the end of May. By the end of July there were up to 150 events/day.

Figure 8. Seismicity at Telica, February-August 1994. Courtesy of INETER.

Crater and fumarole observations, March-June 1994. Beginning on 3 June, scientists from Florida International Univ (FIU) and INETER spent 15 days at Telica as part of an ongoing investigation to determine the areal extent and intensity of degassing, and the role of structural controls on degassing from the volcanic complex. A lacustrine deposit was observed in March at the S end of the crater, and a small, muddy brown lake was visible in May-June. All observations were made from the NE rim, where jetting sounds were clearly audible. Sulfur-rich steam from the crater sometimes moved down the slopes of the volcano, filling the NW valley with high concentrations of SO2; sulfur odor could occasionally be smelled on the NE slope. Residents on the flanks of the volcano stated that the activity was not unusual for this time of the year.

Fumarole temperatures near station TELN were in the 81-86°C range, similar to temperatures in September 1993 and March 1994. A low-temperature fumarole was discovered on the lower ESE slope of the ridge occupied by the seismic station. A data-logger recorded fumarole temperatures and barometric pressure for four days. Fumaroles near TELN and in the active crater exhibited increased flux since March. At times the crater fumaroles appeared to be emitting steam and gases in discrete clouds at intervals of several minutes. The most intense fumarole was in the upper NW corner of the crater (A on figure 7). Other fumaroles were observed in the lower NW corner, on the N, E, and SE crater walls, and in avalanche deposits on the S and SE parts of the crater floor. Fumarole A had temperatures of 150-160°C in July 1994 (figure 7). In the NE corner of the crater, fumarole B increased in temperature from 55°C in April to 174°C in July. Another fumarole area on the E side of the crater (C) had a temperature of 498°C in July, a significant increase from 246°C in 1990.

Eruptive activity. A relatively small explosive eruption at about 1645 on 31 July produced a gas-and-ash column that rose ~800 m above the summit. The light-gray ash cloud was driven SW by the wind, depositing about 2 mm of ash in the towns of Chichigalpa (20 km WSW), Quezalguaque (12.5 km SSW), and Posoltega (16 km SW) (figure 6). No seismic events were felt by residents near the volcano, but the sound of the explosion was heard at distances up to 10 km.

Following the 31 July eruption, phreatic activity continued in the next hours and days with varying intensity of gas emanation and ash expulsion. One of the strongest explosions, on 5 August, produced an ash column 1,200 m high. One phase of gas emission reached heights of 200-300 m above the crater rim. Gas also filled a valley W of the volcano with high concentrations of SO2, sometimes causing breathing problems for INETER scientists who traveled through the valley at a distance of ~2 km from the crater. Seismicity at shallow depths (~2 km) beneath the crater was recorded by TELN and four stations installed after the eruption began: telemetric stations TEL 2, 3, & 4, and local digital registration station TEL 5 (figure 7). The numerous weak events during the eruption were only recorded by the local seismic stations.

Chemical analyses of washed ash samples collected on different days indicated an increase of the SO42- and Cl- contents over time. Several very heavy rainfalls occurred during the eruptive period. Analyzed rainwater samples also showed high concentrations of SO42- with respect to Cl- and F2-, and a corresponding low pH level. Similar measurements two weeks before the eruption showed normal low concentrations of SO42- and Cl-.

Early eruption products consisted of very fine-grained, light-colored, blocky ash. INETER volcanologists believe that the ash was non-juvenile, and was ejected during phreatic or phreatomagmatic eruptions. Major explosions generally lasted for ~10-25 minutes. Early eruption columns were mostly white in color, and ranged from several hundred meters to 1,400 m above the vent. On 9 and 10 August, the ash was black, significantly darker than before, with correspondingly darker eruption plumes. The ash remained blocky and non-vesicular. On 10 August, 40-50 high-frequency seismic events were recorded, including one that lasted 4.5 hours. High-frequency events prior to 10 August occurred at a rate of ~70-90/day and were associated with more frequent explosions (10-20/day). The number of daily explosions also decreased to 6 on 10 August, including one major explosion that lasted for 16 minutes. An explosion at 1800 on 11 August generated a plume that rose 350 m, but only 16 high-frequency events were detected that day. On the early morning of 12 August one of the strongest explosions of this eruption occurred; activity then decreased throughout the day. By that evening the explosions had stopped and gas emanation and seismicity reached very low levels.

Seismicity had increased slightly by 16 August, five microseismic events were detected during 24 hours on 17-18 August, and on 20 August tremor lasted for 6.2 hours. However, no seismic events were detected on 21-22 August, and activity remained low as of 26 August.

On 23 August, Oto Matias (INSIVUMEH, Guatemala) arrived with a COSPEC instrument to assist INETER scientists in making SO2-flux measurements. Attempts to carry out COSPEC measurements of the SO2 concentration in the gas plume were made on 24 August, but low levels of gas emission and cloudy skies prevented good results.

Soil sampling. During three field surveys by FIU and INETER scientists in early June, >60 stations were deployed over 50 km2 to determine the concentration of radon (Rn), CO2, Hg, and He in soils. One identified anomaly had intensified between March and May/June 1994. This anomaly, ~750 m long and 250 m wide, surrounded the TELN seismic station. Along this anomaly, Hg values ranged from several tens of ppb to >2,900 ppb, He from 5,399 to 5,415 ppb, CO2 to 2.1 volume %, and Rn to 1,819 pico-Curies/liter.

San Jacinto Hot Springs. The village of San Jacinto, 9 km NE of the town of Telica and 2 km E of Santa Clara volcano, contains a field of boiling mudpots (BGVN 19:03). Soil samples for Hg and CO2 measurements were collected from the hydrothermal field in March and May/June 1994. The March samples contained CO2 concentrations up to 0.09 volume % and Hg from 6,710 to 21,512 ppb. The onset of the rainy season had resulted in an increase in both the size of the field and the steam flux since 9 March. Exploration for a new geothermal power plant was taking place approximately 250 m WNW.

Historical activity. Telica is a composite volcano located 19 km N of León at the NW end of a large volcanic complex. Known historical activity dates from a strong eruption that occurred in 1527-29. Strong activity was also noted in 1685, 1740-43, and at least 7 times in the 20th century. During several eruptions ash has damaged agricultural crops. In February 1982 several strong explosions generated ash columns of 3.5 km height and the ashfall affected nearby towns. The most recent eruption of Telica in November 1987 included Strombolian-type activity.

Eruptions in pre-historical times produced ash deposits of 50 cm thickness or more within a radius of 50 km. A volcanic hazard map (figure 9) suggests that ashfall poses the greatest threat to the local population. Lava flows have occurred, but with low frequency, most recently ~1,000 years ago. The hazard zone for pyroclastic eruptions lies within ~2 km of the crater. Lahars have occurred as a result of very strong eruptions during the rainy season.

Figure 9. Volcanic hazards map of Telica. Hazard zones are shown for ashfall and tephra, lava flows, and column collapse. Courtesy of INETER.

Information Contacts: H. Taleno, L. Urbina, M. Navarro, O. Canales, C. Guzman, C. Buitrago, A. Izaguirre, Christian Lugo M. (Vulcanology), W. Strauch (Seismology), C. Urbina, and A. Acosta (Electronics), INETER, Managua; Peter C. La Femina, Michael Conway, and Andrew MacFarlane, Florida International Univ, USA.

09/1994 (BGVN 19:09) Explosion followed by decreased seismicity

A phreatic explosion on 12 August followed strong tremor two days earlier. Activity that began on 31 July produced a gas-and-ash column that rose ~800 m above the 1,060-m-high summit; detectable amounts of ash fell as far as ~17 km from the summit source vent (BGVN 19:07). Strong tremor again took place on 28 August. From that time until mid-September, weak tremor and few events of high or low frequency were recorded. Geochemical monitoring revealed decreases in SO2, Cl, and F gases. The most significant morphological change in the inner crater was the joining of crater fumaroles A and B (figure 7).

Information Contacts: H. Taleno, L. Urbina, C. Lugo, and O. Canales, INETER.

04/1996 (BGVN 21:04) Low-level degassing and sulfur deposits observed in crater

Telica was visited on 17 March by a joint team from the Open University, the Universite de Montreal, Reading University, and the Instituto Nicaraguense de Estudios Territoriales (INETER). Low-temperature sulfur deposits were noted in many places within the crater. Low-level degassing was observed, particularly on the W side of the crater. Sulfur-rich gases appeared to be concentrated at the bottom, while more H2O-rich gases were being emitted at higher levels in the crater. Gas pressures were generally low, but there was a distinct gas column. SO2 flux measured by COSPEC on 17 March averaged 41 ± 20 t/d, based on nine measurements. Microgravity measurements showed no appreciable changes since the last survey in 1994.

An eruption on 31 July 1994 produced a gas-and-ash column to ~800 m above the summit; detectable ash fell as far as 17 km from the summit (BGVN 19:07). Phreatic explosions continued until 12 August 1994 when seismicity began decreasing (BGVN 19:09).

Information Contacts: Hazel Rymer and Mark Davies, Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom (Email: h.rymer@open.ac.uk); John Stix, Dora Knez, Glyn Williams-Jones, and Alexandre Beaulieu, Departement de Geologie, Universite de Montreal, Montreal, Quebec H3C 3J7, Canada (Email: williamg@ere.umontreal.ca); Nicki Stevens, Department of Geography, University of Reading, Reading RG2 2AB, United Kingdom; Martha Navarro and Pedro Perez, INETER, Apartado Postal 2110, Managua, Nicaragua.

03/1997 (BGVN 22:03) Seismicity increases and fumarolic activity continues

On 27 February, during a visit to the summit crater, scientists noted continuing minor fumarolic activity with maximum temperatures of 300-350°C and an active collapse zone on the E crater rim (figure 10). At this time a portable seismic station recorded microearthquakes at 30-40 minute intervals. Night observations of the crater confirmed the absence of any incandescence.

Figure 10. Sketch of the active crater at Telica indicating areas of fumarolic activity. Temperature is degrees C. Courtesy of Alain Creusot.

During March 1997, seismicity was high with about 150 seismic signals/day recorded. Seismicity levels increased from December 1996, when there were less than 100 signals/day. Most March events had frequencies of 1.5-4.6 Hz and durations of 9-40 seconds. Visits to the summit crater showed the presence of fresh ashfall, numerous small landslides inside the crater, and moderate fumarolic activity in the walls and floor of the crater. Scientists also measured Telica's gas emissions, thermal infrared signals, and microgravity. Small amounts of gas were emitted from fumaroles on the E and W crater walls; however, COSPEC measurements failed to detect any SO2, although local farmers smelled sulfur in the afternoon when the wind shifted to the W. Thus, the amount of released gas appeared to be less than in March 1996.

Fumaroles located along a NE-SW trending fracture near the seismic station outside the active crater had maximum temperatures of 85°C. Soil gas measurements made along the fracture on 11 March 1997 showed maximum CO2 concentrations of 3.2%. This fracture first appeared in September 1996.

Infrared camera measurements on 20 March 1997 detected a zone of high temperatures near the base of the W crater wall. This zone had temperatures up to 190°C. Since this was a remote measurement, it should be considered as a minimum estimate. The crater fumaroles were at a lower temperature than those at the base of the W crater wall. Minimum temperatures measured with the infrared camera were 58°C for fumaroles on the W side, 47°C for fumaroles on the N wall, and 107°C for fumaroles on the E wall.

On 20 March, gravity measurements with a Lacoste and Roberg meter near the crater measured a repetitive signal with a periodicity of about 18 seconds. Also, on 23 March, a large gas emission from the crater was visible at the seismic station.

An eruption on 31 July 1994 produced a gas-and-ash column to ~ 800 m above the summit; detectable ash fell as far as 17 km from the summit (BGVN 19:07). Phreatic explosions continued until 12 August 1994 when seismicity began decreasing (BGVN 19:09).

Information Contacts: Hazel Rymer and Mark Davies, Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom (Email: h.rymer@open.ac.uk); John Stix, Dora Knez, Glyn Williams-Jones, and Alexandre Beaulieu, Departement de Geologie, Universite de Montreal, Montreal, Quebec H3C 3J7, Canada (Email: williamg@ere.umontreal.ca); Nicki Stevens, Department of Geography, University of Reading, Reading RG2 2AB, United Kingdom; Martha Navarro and Pedro Perez, INETER, Apartado Postal 2110, Managua, Nicaragua; Alain Creusot, Instituto Nicaraguense de Energía, Managua, Nicaragua

05/1997 (BGVN 22:05) Continued high levels of seismicity

Seismicity as of mid-May remained at a high level, similar to recent months. There have been ~160 daily volcano-seismic events detected, with little variation. During March there were ~150 seismic signals/day recorded; in December 1996 there were <100 signals/day (BGVN 22:03).

An eruption on 31 July 1994 produced a gas-and-ash column and detectable ash fell as far as 17 km from the summit (BGVN 19:07). Phreatic explosions continued until 12 August 1994 when seismicity began decreasing (BGVN 19:09).

Information Contact: Wilfried Strauch, Department of Geophysics, Instituto Nicaraguense de Estudios Territoriales (INETER), P.O. Box 1761, Managua, Nicaragua (Email: wil@ibw.com.ni).

06/1997 (BGVN 22:06) June increase in both earthquakes and the extent of fumaroles

Seismicity and the extent of fumaroles increased slightly in June. Whereas in April and May the number of volcano-seismic events was near 160/day, during June this rose to ~220/day. Still, crater degassing remained very small. INETER volcanologists observed that NW-flank fissures had grown in number, extent, and apparent depth.

Information Contacts: Wilfried Strauch, Department of Geophysics, and Marta Navarro C., Department of Volcanoes, Instituto Nicaragüense de Estudios Territoriales (INETER), P.O. Box 1761, Managua, Nicaragua (Email: wil@ibw.com.ni).

03/1998 (BGVN 23:03) February visit reveals slight increase in fumarolic activity and collapse zone

Scientists visited Telica's crater on 7 February. They observed a slight increase in fumarolic activity and an active collapse zone on the S crater rim. Light incandescence seen at night had an estimated temperature of 550°C.

Information Contact: Alain Creusot, Instituto Nicaraguense de Energía, Managua, Nicaragua.

06/1999 (BGVN 24:06) Phreatic eruptions in May and June cause local ashfall

At about 0200 on 21 May a phreatic eruption marked by explosions began from the crater. At daybreak the gas plume extended to ~500 m in height. The following day observers on the crater rim noted a new 50-m-diameter vent on the crater floor. At the time of the observations, an intense gas stream was emanating from the new vent, accompanied by a jet engine-like sound. Fumarolic activity within Telica's crater was much stronger as well. Diminishing phreatic eruptions continued until 23 May. No ashfall was reported. INETER geologists who visited Telica on 18 May had not seen any evidence of increased activity; seismic monitoring did not show any precursors.

Wilfried Strauch reported that new phreatic eruptions took place on 5 June 1999, most notably between 1830 and 1900. These explosions were strong enough to register on nearby seismometers and resulted in minor ashfall in Chichigalpa, ~15 km WSW of Telica. Following the explosions, seismic activity rapidly declined. A 7 June article by La Prensa de Nicaragua stated that 6,000 people had to be evacuated in case of eruption. The article claimed that Telica discharged a cloud of ash to the SW that had bathed the bordering communities and part of Chichigalpa and scattered gas and ash caused adjacent inhabitants near the volcano to suffer irritation of eyes, throat, and nose. Observers noted a steaming area in the W sector of the volcano, 500 m from the crater border.

Crater observations March 1997-February 1998. During March 1997 (BGVN 22:03), INETER recorded high seismicity, ~150 events/day. During December 1996 there had been ~100 events/day. Visits to the summit crater revealed fresh ashfall, numerous small landslides inside the crater, and moderate fumarolic activity in the walls and floor of the crater. Fumaroles lying along a fracture trending NE-SW and located near the seismic station outside the active crater had maximum temperatures of 85°C. Infrared camera measurements on 20 March 1997 detected a zone of high temperatures near the base of the W crater wall.

Seismicity and the extent of fumaroles increased slightly in June 1997 (BGVN 22:06). Whereas in April and May the number of volcano-seismic events was near 160/day (BGVN 22:05), during June this rose to ~220/day. Still, crater degassing remained very small. INETER volcanologists observed that NW-flank fissures had grown in number, extent, and apparent depth. During a previously unreported crater visit by Alain Creusot on 29 September 1997, he observed both a small increase in the fumarolic activity and that an active collapse zone on the N crater rim had enlarged by ~15 m. A portable seismic station recorded both an absence of tremor and 10-15 microearthquakes every hour. A February 1998 visit to Telica's crater (BGVN 23:03) also revealed raised temperatures and an active collapse zone.

Information Contacts: Wilfried Strauch, Virginia Tenorio, and Julio Alvarez, Department of Geophysics, Instituto Nicaraguense de Estudios Territoriales (INETER), P.O. Box 1761, Managua, Nicaragua (Email: wil@ibw.com.ni); La Prensa de Nicaragua, Managua, Nicaragua (URL: http://www.laprensa.com.ni); Alain Creusot, Instituto Nicaraguense de Energía, Managua, Nicaragua.

02/2000 (BGVN 25:02) Lava lake seen in August; sporadic ash explosions August-December

As of late November 1999, microseismic activity had been occurring at Telica for more than a year. There were phreatic explosions in May and June 1999 (BGVN 24:06). An eruptive phase began in August 1999, generally producing only sporadic small and local ash falls. Intermittent gas-and-ash emissions continued to be reported through December 1999. One of the more vigorous events took place on 29 December, sending ash to several kilometers altitude and inducing falls detected 45 km away.

A noteworthy event began around 0200 on 10 August. Tremor and earthquakes increased abruptly. Small explosions took place in the crater, expelling gas and volcanic ash. Ash fell ~20 km WSW of Telica in the city of Chichigalpa. An interval of relative calm on 12 August lasted approximately one hour. It ended with the gas explosions and ash outbursts starting again at 1315 and continuing until 1515 with ongoing degassing afterwards. According to the summed seismic amplitudes (RSAM values), the greatest activity was between 2000 on 10 August until the morning of 11 August.

Observers saw a lava lake in the crater on 18 August. On that day, INETER's Wilfried Strauch and Armando Saballos, along with visiting North American specialists, climbed Telica to install GPS equipment. Taking advantage of periods of low degassing, they managed to observe the bottom of the new inner crater that had formed in the last few months (figure 11). To their surprise, they saw a lava lake there. In addition they listened to forceful jetting noises probably generated by the water contact with heated material.

Figure 11.Photograph from the crater rim at Telica showing the new inner crater, 18 August 1999. Courtesy of Wilfried Strauch, INETER.

On 21 August INETER's Virginia Tenorio and Julio Alvarez climbed the volcano and saw that the inner crater had enlarged; and, in addition they again heard jet-engine-like noises. Abundant escaping gases thwarted views into the inner crater so the visitors could not assess whether a lava lake remained. The same day between 0800 and 0900, residents who live on the SE flank of the volcano felt two rumblings from the volcano. Possibly, this caused the inner crater to enlarge even more.

Several days later seismic tremor increased, but the number of microearthquakes fluctuated, first dropping, then increasing again on the 25th. On 29 August seismic tremor began to drop substantially. Then, however, the number of microearthquakes increased. Telica's eruptive activity is typically associated with slightly increased tremor and over 200 to 300 microearthquakes per day.

During September, a month with 2,116 microearthquakes, gas emanations prevailed until the 10th. A seismic swarm at the beginning of October was followed by a series of explosions with tephra expulsions during 3-15 October. On the 5th, INETER staff on the crater's edge witnessed the discharge of both ash and lava (presumably in the form of bombs). The last similar lava-bearing explosion of this type was in 1988 (SEAN 13:01). On the 12th, W-flank residents reported that on the previous day (at about 1400 on the 11th) they had felt an unusually strong explosion shaking their houses. Later, they witnessed the fall of very fine gray ash. Observers also saw that the inner crater had grown wider than when seen in September. By 12 October the seismic amplitude had decreased to background levels. The number of earthquakes registered for October was 888.

During November the earthquake sum was comparatively low, 144, but that did not signify volcanic quiet. On 19 November, INETER's Julio Alvarez and Virginia Tenorio skirted the volcano along the León-Chinandega highway where they saw an ash column. Erminio Rojas, a farmer on Telica's S flank, told them that in the past few weeks the volcano had almost constantly been expelling gray ash. On 17 November he witnessed a very large explosion that caused an ashfall deposit reaching 2.5 cm thickness near his house, damaging his apples and beans. The observers further noticed that on the crater's SW a possible collapse feature had developed. Burned ash-covered plants lay in the area near the edge of the crater. Ash discharges on 17 November occasionally emitted a noise similar to a gunshot.

On 24 November, Civil defense of León reported a black cloud above Telica. An unusual seismic signal on 28 November prompted a visit to Telica by Tenorio and Strauch, along with Rafael Abelia of the Institute of Geomineras Investigations of Madrid, Spain. When they arrived at the volcano, the group found that a zone of disruption had spread over a great part of the N crater wall, and the edge of the crater was covered with a thick layer of fine dust. This indicated to them that there was no explosion and the cloud that the Civil Defense observed was due to the collapse of the N crater wall. COSPEC measurements conducted on 29 November indicated that the volcano was producing between 50 and 500 metric tons/day of SO2 per day.

During December 1999 there were 1,085 volcanic earthquakes, of which, four were located. INETER's seismic network located several earthquakes that took place underneath the volcano on 14 December with magnitudes between 2 and 2.5. During December, tremor stayed low until the 24th, when it was punctuated by sporadic degassing and smaller ash-bearing discharges. On the 25th, tremor began to rise slowly; on the 28th there occurred an abrupt increase in the seismic signal, four-fold larger than seen during previous days. The morning of 29 December seismicity was high. The same day reports were received describing almost continuous ash-bearing explosions, with WSW-directed tephra falls.

Two large explosions at 0900 on 29 December sent ash to heights of more than 1,000 m above the crater. Besides affecting cities adjacent the volcano, ash was later known to have affected the cities of Posoltega (~16 km SW), Chichigalpa (20 km WSW), Quezalguaque (20 km SSW), Chinandega (35 km WSW), and Corinto (~45 km SW). INETER noted that civil-aviation pilots reported that ash rose up to 5 km, although whether this was an altitude or the height over the 1-km-tall volcano remained undisclosed. Tremor initially stayed high on 30 December but dropped on 31 December. Activity continued into January 2000.

Information Contacts: Wilfried Strauch and Virginia Tenorio, Dirección General de Geofísica, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado 1761, Managua, Nicaragua (URL: http://www.ineter.gob.ni/, Email: wil.gf@ineter.gob.ni).

03/2000 (BGVN 25:03) Eruptive activity declines in February, but seismicity remains high

Seismic and eruptive activity consisting of gas-and-ash explosions continued during January. Observations from the León-Chinandega highway during fieldwork on 13 January showed that constant strong ash-and-gas emissions were continuing (figures 12 and 13). A resident on the S flank informed the scientists that strong rumblings had been heard at dawn on the 12th. The observers remained near the summit for several hours and witnessed moderate explosions every five minutes, with occasional periods of more frequent explosions (3/minute). The bottom of the crater could not be seen through the ash, but it appeared that the explosions did not come from the intercrater that formed in May 1999, but from a new vent in the NNW part of the crater. Evidence of collapses were present along all sides of the crater. In January the number of volcanic earthquakes was 3,950, and the RSAM (real-time seismic amplitude measurement) signal oscillated between the 40 and 120 units.

Figure 12. Photograph of the active crater during an ash explosion at Telica, 13 January 2000. View is from the south. Courtesy of INETER.
Figure 13. Photograph of Telica, 13 January 2000. View is from the north. Courtesy of INETER.

Low-intensity eruptive activity with ash-and-gas emanations continued through 17 February, after which the activity began to gradually decline. However, seismicity stayed high with 3,670 earthquakes detected in February. The volcano maintained constant tremor during March, but despite the continued high number of registered earthquakes (2,892) there were no gas or ash expulsions.

Information Contacts: Wilfried Strauch and Virginia Tenorio, Dirección General de Geofísica, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado 1761, Managua, Nicaragua (URL: http://www.ineter.gob.ni/, Email: wil.gf@ineter.gob.ni).

09/2000 (BGVN 25:09) Gas-and-ash emissions in early 2000; fumarole temperature measurements

Seismic and eruptive activity consisting of gas-and-ash explosions continued during January and through 17 February 2000, after which the activity began to gradually decline (BGVN 25:03). Observers near the summit on 13 January witnessed moderate explosions every five minutes from a new vent in the NNW part of the crater. In January the number of volcanic earthquakes was 3,950, and seismicity stayed high in February with 3,670 events. The volcano maintained constant tremor during March, but despite the continued high number of detected earthquakes (2,892) there were no gas or ash explosions.

Weak gas-and ash emissions occurred in April. Fumarole temperatures in the interior of the main crater and SW of the seismic station were moderate (table 3). In the main crater, fumaroles 1 and 4 (internal crater and on the NW wall, respectively) exhibited temperature increases compared to the last measurement in both February and April. Near the seismic station, between December 1999 and January 2000 the fumarole temperatures changed by less than 3°C, whereas by February temperatures had apparently changed by as much as 14°C compared to January values. However, measurements in February were made using an infrared pistol, a change from the thermocouple used previously.

Table 3. Fumarole temperatures at Telica measured at the Main Crater and SW of the seismic station (500 m E of the crater) during June 1999-April 2000. The measurements in December 1999 and January 2000 near the seismic station were made using a thermocouple; all others were made with an infrared pistol. Courtesy of INETER.

    Fumarole    Jun    Jul    Dec    Jan    Feb    Apr
                1999   1999   1999   2000   2000   2000

    Main Crater
    1          107°C   55°C    --     --    60°C   66°C
    2           58°C     --    --     --    59°C    --
    4          104°C    60°C   --     --    71°C   91°C
    6           69°C    41°C   --     --    67°C   56°C

    SW of the seismic station (500 m E of the crater)
    1            --      --   84°C   85°C   99°C    --
    2            --      --   84°C   84°C   73°C    --
    3            --      --   81°C   84°C   81°C    --
    4            --      --   84°C   83°C   96°C    --
    5            --      --   83°C   84°C   98°C    --

Information Contacts: Wilfried Strauch and Virginia Tenorio, Dirección General de Geofísica, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado 1761, Managua, Nicaragua (URL: http://www.ineter.gob.ni/, Email: wil.gf@ineter.gob.ni).

05/2009 (BGVN 34:05) Intermittent ash explosions and incandescence during 2000-2002

Explosions occurred at Telica during January and through February 2000, after which the activity began to gradually decline (BGVN 25:03 and 25:09). Intermittent ash explosions and crater incandescence were seen through 2002, along with high levels of seismicity related to degassing and constant low tremor. The Geophysics Department of the Nicaraguan Territorial Studies Institute (INETER) monitors activity; visits to the crater described below are by INETER staff unless otherwise noted. Many observations were also made by a local resident who maintains the local seismic station.

Activity during 2000. Tremor remained constant during April-June 2000, with no ash emissions. Visiting geologists reported incandescence in the crater on 5 July 2000. INETER workers who reached the crater on 14 July heard a noise like an airplane turbine coming from the crater and saw glow. They also noted that there had been a widening of the crater due to wall collapses, and an increase in its depth, although the crater floor could not bee seen. On 8 August a crater visit revealed strong fumarolic activity, and sounds resembling gun detonations from the bottom of a new opening.

Residents living near the crater reported on 6 September that ash explosions occurred during the evening and plumes drifted NE. Unfortunately INETER technicians found no traces of ash on 12 September, following rainfall. Small landslides inside the crater were observed. A characteristic strong smell of sulfur was detected in the crater area. Due to the change in wind direction that occurs during September and October, gases and acid rain affected areas to the N, NE, and E. Intense rainfall caused a mudflow down a W-flank drainage.

In the visit on 27 October there was no exhalation of gases, but landslides along the south wall sent material onto the crater floor. Crater visits on 5 and 22 November showed abundant gas output. Jet-like sounds came from fumaroles on the NE wall. Gas emissions were low during December. There were minor landslides in the crater, heard in the last days of November and beginning of December.

Activity during 2001. On the afternoon of 17 January 2001 there were rumbles and a plume of ash and gases 200 m high. On 19 January a visit to the crater found ashfall, to a depth of 1 mm, deposited within a radius of 500 m. The vicinity of the seismic station and SW from the crater had been affected by acid rain. On 22 January visiting scientists observed another small explosion. Activity was low during field visits on 20 and 26 February.

A visit on 3 and 16 March found variable levels of gas emissions. Incandescence was observed within the new crater early on 21 March along with increased output gases. Shortly thereafter a loud explosion was heard, followed by a dark plume about 30 m high and increased glow, but no ashfall. Activity remained low in April.

INETER staff visited the volcano on 6 June and heard a strong jet-like sound, but fumarolic emissions were not abundant. Another visit on the night of 26 June revealed incandescence and landslides inside the crater. Visits to the volcano were made on 13, 16, and 25 July, but no volcanic activity was noted. On 15 July the Civil Defense in Leon informed INETER of sporadic gray ash columns that began the previous day. A local resident reported hearing an explosion at 0315 on 14 July, and saw five emissions of gas-and-ash later that day. This activity lasted until 15 July.

A visit on 15 September revealed little gas emission from the crater, but explosion noises were heard. On 25 October Civil Defense Leon was informed by several farmers that between approximately 0600 and 1000 local time they had observed a column of ash that drifted NW. INETER staff working in the area that day observed strong ash accompanied by expulsion of gas. Rumbling noises and explosions continued until 1430. On 22 November a visitor observed no change in the volcano. Minor ashfall was reported on the morning of 18 December, and the next day explosions were heard coming from the crater.

Activity during 2002. On 17 January 2002 visitors observed strong gas fumes. Observations on 7 March indicated that the crater was wider and deeper than in February. On a 10 July visit there were abundant gas emissions from the crater, a strong smell of sulfur, jet sounds, and noises of breaking rocks. Gas emissions were abundant on 23 August, with columns up to 300 m high, but no landslides, noises, sulfur odor, or incandescence was noted. Rockslides on the N wall of the crater and sulfur odors, along with typical fumarolic activity, were seen during September.

Visitors on 17 October reported abundant gas emissions and strong sulfur odors; noises similar to the movement of waves came from the crater bottom, and some incandescent points were seen. From 7 to 11 October large quantities of gases blew SE, damaging vegetation. Landslides were observed SW of the old crater. Fumarole temperatures were the highest recorded since 1999. Incandescence inside the crater was also observed over several days. Webcam observations in November and December showed intermittent small gas emissions.

Information Contacts: Dirección General de Geofísica, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/geofisica/geofisica.html).

06/2009 (BGVN 34:06) Intermittent incandescence and ash explosions through January 2005

Intermittent ash explosions and crater incandescence were seen during 2000-2002, along with high levels of seismicity related to degassing and constant low tremor (BGVN 34:05). Strong gas emissions were typical in the first half of 2003, with incandescence often noted later in the year. Activity during 2004 included occasional ash explosions as well as incandescence. After small ash explosions in late January 2005 no volcanism was noted for the remainder of the year, with observers primarily noting crater wall collapses and degassing. The Nicaraguan Territorial Studies Institute (INETER) monitors activity; visits to the crater described below are by INETER staff (primarily Pedro Perez) unless otherwise noted, though scientists from other institutions may have also been present. Some observations were also made by a local resident who maintains the local seismic station.

Activity during 2003. In January 2003 gas emissions at Telica fluctuated in their intensity. Dense gas prevented observations of incandescence. During a crater visit on 6 May an observer heard a pressurized sound, smelled sulfur, and saw blue gases. Eucalyptus trees 2 km E of the crater appeared to have been burned by the acidic gases. There was a bluish glow in the crater on 25 June and a strong smell of sulfur. To the W of the volcano several trees dropped the bulk of their leaves due to acid rain. Gas emissions remained almost constant at a moderate level.

On 31 July a high pressure noise was heard and incandescence was observed in the center of the crater. Pressurized gases emerging on 22 August from the vent at the bottom of the crater emitted a loud, jet-like sound. As in July, the vent also showed incandescence and emitted a sulfur odor. Satellite images on 24 September showed a column of gas. On 7 October incandescent was again observed, along with a strong odor of sulfur. There was a collapse of material in the SE sector.

Activity during 2004. On 20 January 2004 a wavelike sound was heard, open fissures emitted little gas, and glow was observed in the crater (figure 14). A small ash explosion on 31 March at about 0856 was reported by the caretaker of the Tel3 seismic station. On 28 April an observer noted that internal collapses had covered almost half of the southern part of the crater floor with debris. As a result incandescence in the crater was difficult to detect.

Figure 14. Photograph of the crater at Telica, showing incandescence on 20 January 2004. Courtesy of P. Perez (INETER).

A seismic swarm N of Telica lasted from 9 to 14 June. The earthquakes had magnitudes up to 2.4 and depths between 1 and 9 km, with some being felt by local residents in the Aguas Calientes area. On 28 June a seismic signal similar to that of an explosion was detected. INETER received no reports of ashfall in surrounding areas. Reports for July-September were not available. Ash explosions occurred from the crater on 5 and 11 November. On 10 December there was significant gas and ash output, with sounds of breaking rocks inside the crater. Unlike the previous months, no incandescence was seen.

Activity during 2005. On 29 January 2005 the volcano produced small ash explosions with abundant gases. The next day when INETER technician Pedro Pérez visited he heard jet-like sounds and smelled strong gas emissions. Low gas emissions persisted during February-April. On 15 May a small earthquake swarm lasted about ten hours. Observers to the crater on 1 May noted small blue gas emissions and sulfur odor, but no incandescence. Collapses were also seen in the W and S portions of the crater.

On 30 June observers saw minor gas emissions and new material in the eruptive fissure from crater wall collapses. Activity was low on 9 August (figure 15), no sounds heard, but the crater walls had some precipitates from the gas emissions. On a 7 September visit additional collapses of the crater walls were observed along with significant gas emission. Small gas emissions were observed by a monitoring webcam for almost the entire month of December.

Figure 15. Photograph showing the Telica crater on 9 August 2005. Rockfall debris from crater wall collapses can be seen on the crater floor. Courtesy of P. Perez (INETER).

Information Contacts: Wilfried Strauch, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/geofisica/geofisica.html).

08/2009 (BGVN 34:08) Extensive degassing and sporadic ash explosions during 2006-2008

Activity at Telica during the second half of 2003 through January 2005 included incandescence and occasional ash explosions, after which only crater wall collapses and degassing occurred for the remainder of 2005 (BGVN 34:06). High seismicity and fumarolic activity continued in 2006, until a brief tremor episode accompanied by ash explosions in early August. Ash explosions during 2007 were reported in January-February, June, and October-November. Most observations in 2008 described degassing, but ash emissions were noted in February and July. The Nicaraguan Territorial Studies Institute (INETER) monitors activity; visits to the crater described below are by INETER staff.

Activity during 2006. Seismicity during January-November 2006 remained high, in the range of about 3,000-6,000 micro-earthquakes/month (100-200/day). Collapses in the southern part of the crater were seen during a visit on 18 April, along with new fumarole locations in that area and one new fumarole on the N side. Similar activity, with strong gas emmissions occurred on 27 April.

An unusual tremor episode that began on 3 August prompted a visit by INETER scientists the next day. The team found that small ash explosions on 4 August were coming from a new vent that had opened in the W part of the crater. Incandescent rocks were also being ejected. Ashfall was reported in the communities of Cristo Rey and Las María, NW of the volcano. In addition, gas emissions were rising from the area of an opening, since covered by landslides, that formed in May 1999. Tremor ended on the 5th, but another ash-and-gas explosion was reported on 6 August. Two more new fumaroles, in the N and W part of the crater floor, were seen on 6 and 28 September.

Seismicity changed character on 25 November, with increased tremor and volcano-tectonic earthquakes. The high but variable seismic activity continued during December, when micro-earthquakes were recorded at a rate of about 400/day. Small seismically-detected explosions took place on 11 and 27 December, although the amount of ash and it's distribution was not known.

Activity during 2007. The high levels of seismicity and swarm episodes that began in November 2006 declined during February 2007. Micro-earthquakes averaged 80-135/day in January-February. A small phreatic explosion was recorded on 9 January, followed on the 10th by explosions of gas and ash. The plume on 9 January reached an initial altitude of 1.5 km (500 m above the summit) and drifted W before rising further. More small explosions occurred on 6, 15, and 17 February. Continuous ash emissions rising to 1.5 km altitude were visible on a webcam during the 15 February activity; satellite imagery showed a plume drifting SW and a thermal hotspot at the summit.

Daily micro-earthquake counts throughout the rest of the year ranged from 64 to 180, until the seismic station ceased operating in December. INETER observers at the crater on 12 June saw abundant gas emissions from multiple areas within the crater, and explosions that may have contained ash. During a visit on 14 August landslides were noted from the NW side of the crater walls, as were 50-cm cracks in the S wall. Large volumes of gray gas emissions were reportedly causing acid rain damage to local vegetation, and affecting area residents. Sporadic gas-and-ash explosions were reported in the last week of October and during November, causing ashfall in Quezalguaque and other locations around the volcano.

Activity during 2008. A fieldwork visit to the crater on 16 January 2008 revealed only gas emissions with jet sounds; a local resident reported similar observations. A farmer near the volcano reported to INETER that there was a heavy outflow of gas and ash on 18 February that affected the W and NW flanks; by the time of a 22 February visit only gas emissions were occurring. Gas emissions accompanied by jetting sounds were the only activity noted during subsequent visits on 10 March and 25 April. Small gas-and-ash explosions took place in early July. However, again only gas output was observed during crater visits on 22 July, 18 August, 9 September, 26 November, and 16 December (figure 16).

Figure 16. Strong gas emissions from Telica, September 2008. Courtesy of INETER.

Seismic data began being reported again in February 2008. Average daily micro-earthquake counts, reported monthly, were 90-150 from February through July. August seismicity was not reported, but there were only 80 events/day in September, and 50 events/day in October. The seismograph was not operational in November or December.

Information Contacts: Wilfried Strauch, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/geofisica/geofisica.html); Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/).

03/2010 (BGVN 35:03) Incandescent crater floor areas seen in November 2009 and March 2010

Telica exhibited extensive degassing and sporadic ash explosions during 2006-2008 (BGVN 34:08). Activity since then had decreased to a relatively low level, but degassing was continuing. This report discusses activity in 2009 and January-February 2010 based on reports from the Instituto Nicaragüense de Estudios Territoriales (INETER) and from fieldwork by Mel Rodgers (University of South Florida) in November 2009 and March 2010.

INETER publishes a monthly bulletin on earthquakes and volcanic activity in Nicaragua. For Telica, most of the monthly data consists of in-field temperature measurements. An observation camera situated 20 km from the crater has not been functional for more than a year. The seismic instrument at Telica was frequently out of order during 2009.

On 20 May 2009, the sulfur dioxide output in the crater ranged from 106-251 tons per day. The maximum temperature of the crater was about 90-112°C in April and May 2009, but rose to 201°C in July, 251°C in August, and 302-317°C during September through November 2009. The maximum temperature of four fumaroles was also measured, which generally ranged from 67-72°C. These temperatures decreased in June 2009 and increased in August 2009 (to 76-105°C). The temperature of fumarole 4 decreased to 59°C in October; gas emission at that fumarole ceased altogether in November.

Visits in November 2009 and March 2010. Mel Rodgers detailed observations during fieldwork at the volcano in November 2009 and March 2010 conducted with Diana Roman (University of South Florida), Peter La Femina and Halldor Geirsson (Pennsylvania State University), and Alain Morales (INETER). On 24-25 November 2009, the group observed a set of elongated fractures flanking the crater floor through which incandescence and/or lava were clearly visible. A high concentration of gas and a steady gas-and-vapor plume were also observed in the crater. Multiple vigorous fumaroles were observed on the W side of the crater close to the top of the crater wall, and an intermittent jetting noise that appeared to be coming from the crater floor was audible from their position at the crater rim. A broadband seismometer was installed and, during the 24-hour visit, a high rate of long-period (LP) seismicity was recorded.

On 15 March 2010, the researchers returned and again observed incandescence within the crater. Incandescence was clearly visible through a C-shaped crack or skylight, SE of the 25 November 2009 location (figures 17 and 18). A high concentration of gas and a steady gas-and-vapor plume in the crater continued and vigorous degassing of the fumaroles on the crater floor was observed (figure 19). Intermittent jetting noises and rockfalls were audible coming from the crater, and at 2202 UTC a loud, low popping noise from the crater was heard. Data retrieved from the single station installed in November 2009 showed a high rate of LP seismicity from November 2009-March 2010.

Figure 17. Photograph taken 25 November 2009 of Telica volcano showing the relative locations of the 25 November 2009 incandescent fracture (right) and the later 15 March 2010 incandescent crack/skylight (left). Courtesy of Mel Rodgers.
Figure 18. Photograph taken 15 March 2010 showing incandescence visible in the C-shaped crack/skylight at Telica volcano. Courtesy of Mel Rodgers.
Figure 19. Photograph taken 15 March 2010 showing a view of the entire Telica crater floor. Locations of sightings of incandescence and of vigorous gas jets are indicated. Courtesy of Mel Rodgers.

A successful installation of the TESAND (Telica Seismic and Deformation) network was completed in March 2010. This network, consisting of six broadband seismometers and eight high-rate (1 Hz) continuous global positioning system stations, will be deployed for 3 years to document background LP seismicity and magmatic processes associated with quiescent volcanism.

According to the Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, no satellite thermal alerts were measured over Telica during 2008, 2009, and through 30 April 2010.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (Email: ineter@ibw.com.ni); Mel Rodgers, University of South Florida (Email: mjrodger@mail.usf.edu); 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 (URL: http://hotspot.higp.hawaii.edu/).

11/2011 (BGVN 36:11) Degassing in 2011; seismic crisis leading to explosive eruption in May 2011

Our last report discussed Telica volcano's intermittent gas emissions from 2009 through early 2010 as well as installation of an early warning system (Sistema de Alerta Temprana, SAT) in March 2010 (BGVN 35:03). New information has been released by INETER (the Instituto Nicaragüense de Estudios Territoriales) detailing the escalation of activity that culminated in a major eruption in May 2011. This report also covers the field investigations from April 2010 through October 2011, seismic data from January 2010 through October 2011, SO2 monitoring from 25 May 2011 through 13 September, and regular thermal measurements from the crater and flank fumaroles.

Volcanic activity at Telica during 2010 was characterized by diffuse degassing. Persistent gas emissions from this volcano have caused a legacy of hazards for local communities and have been linked to acute respiratory infections (Bellos and others, 2010; Freundt and others, 2006; Malilay and others, 1996). Field investigations in 2010 conducted by INETER focused on measuring temperatures from the crater as well as fumaroles located near the flanks (figure 20). Heavy rain and inaccessible roads limited visual and thermal monitoring to short field excursions in April, July, and August 2010.

Figure 20. (A) Telica's 700-m-wide double crater (gray to white central area) and E-flank fumaroles (diamond) were sites of thermal monitoring for 3 months in 2010. The seismic station TELN is located 30 m N of the orange diamond. (B) Typical diffuse degassing from the summit photographed on 14 January 2011. Courtesy of INETER.

Using a thermal camera, INETER determined the maximum temperatures within Telica's crater on 28 July and 18 August were 259°C and 251°C respectively. The four fumaroles located near seismic station TELN were measured three times in 2010. With a digital thermocouple, INETER determined that maximum temperatures from the flank fumaroles gradually increased from April to August: 72.3°C, 81°C, and 105°C. Minimum measured temperatures were irregular and ranged from 66.4 to 76°C.

Few earthquakes were sufficiently large to registered and be located during 2010 (table 4), but INETER reported that those recorded were smaller, and there was frequent tremor. The seismic network for this volcano was installed in 1994. The two local seismic stations, TEL3 and TELN, operated with 3-component sensors but during this reporting interval TELN was offline until July 2010. Microseismicity was reported during four months in 2010 (March, September, November, and December). The highest rate occurred in March, exceeding 150 events per day. In September, more than 120 events were recorded per day, and in November and December, the rate was 80 microseisms per day.

Table 4. Located earthquakes at Telica recorded in the interval from January 2010 through October 2011. Only months with earthquakes reported are shown. High values in May-June were during an eruption. Values are based on monthly reports from INETER.

    Month         Number     Magnitudes    Depths
                of Events

    Apr 2010        4         1.7-2.5      0-3 km
    Oct 2010        1           1.4          0 km
    Feb 2011        1           2.9          3 km
    Apr 2011        5         0.2-1.5      0-1 km
    May 2011     ~175         0.3-4.0      0-4 km
    Jun 2011     ~100         0.1-2.8      0-28 km
    Jul 2011      ~20         0.8-1.8      0-1 km
    Aug 2011      ~22         0.3-2.3      0-1 km

INETER reported that field investigators encountered significant gas plumes from Telica's summit in April and July. The W edge of the crater and a small vent on the E interior wall were constant sources. There were notable rockfalls from the crater rim; an observation from 28 July 2010 mentioned the NE and SE walls in particular experience rockfalls of sufficient magnitude to increase the summit crater's size.

January 2011. Investigators from INETER visited Telica this month for instrument maintenance and monitoring activities. Rockfalls from the S crater wall were noted on 11 January by staff. According to Halldor Geirsson, Mel Rodgers (Univ. of South Florida) was in the vicinity during 25-31 January and noted strong degassing and occasional rockfalls. On 14 January thermal data was collected from the central crater and fumaroles on the outer flank. The maximum temperature recorded from the crater was 295ºC. The four fumaroles located on the W flank (figure 20a) had recorded temperatures ranging from 68ºC to 72ºC.

Seismicity during January 2011 was generally high, with ~ 907 earthquakes recorded. Most were long-period (LP) with dominant frequencies of 1-3 Hz. From 19 to 23 January events were absent. Seismic tremor was recorded throughout January at 30-40 RSAM units with scattered intervals of greater than 100 RSAM units.

February 2011. Collaborative fieldwork was conducted on 26 February between INETER and scientists from the Institute of Renewable Energy (Spain). This team measured temperatures and took thermal images of the fumaroles located both within the crater and on the W flank. Maximum temperatures within the crater ranged from 62-75ºC.

Elevated seismicity continued through February with 676 recorded events. These events were similar to those recorded in previous months; LP events had dominant frequencies of 1-3 Hz. Figure 21 presents an example of frequency analysis for one earthquake at Telica. Volcanic-tectonic (VT) events rarely occurred. Tremor was recorded at 30-40 RSAM units.

Figure 21. The seismic trace of a characteristic LP event (a) from Telica processed with spectrum-analysis software to obtain the dominant frequency ranges. This event was recorded on 1 February 2011 and lasted for more than 20 seconds (b, a zoom on the trace). The dominant frequencies (c, frequency vs. amplitude) ranged from 1 to 2 Hz with some signals to ~10 Hz. Courtesy of INETER.

Ashfall in March 2011. On 6 March residents living near Telica felt an earthquake during the night and during the following day they observed small plumes rising from the volcano. INETER scientists visited on 8 March for routine data collection and to investigate reports of fresh ashfall. Light ash was still visible on leaves and rooftops and appeared directed towards the N and SE. Residents also reported strong sulfurous odors during the explosive events. Field investigators found evidence of juvenile material along the SE rim of the crater.

INETER collected thermal data on 8 March from fumaroles located within the crater and near the seismic station (TELN) on the E flank. The maximum temperature measured within the crater was 137ºC. Two fumaroles were identified within the crater on the W side; these sites had recorded temperatures in the range of 47-71ºC. Thermal measurements near TELN ranged from 51-60ºC. This site did not emit steam or other gases.

The INETER field crew noticed that degassing appeared to be more intense during the 8 March field visit compared to their previous 26 February visit. The view to the crater was often obscured from the point of view of seismic station TELN (figure 20b).

In their March report, INETER discussed the relevance of the new temperatures measured during the 8 March field campaign. The issue was the apparent decrease compared to temperatures recorded from Telica in January. INETER staff acknowledged the limits of monthly temperature readings but looked forward to longer-term correlations with seismic data.

Seismicity in March remained high with ~ 572 events recorded. The majority of the earthquakes were LP events with dominant frequencies between 1-3 Hz. Few VT events were recorded. Seismic tremor was between 30-40 RSAM units.

April 2011. New seismic data from an early warning system (Sistema de Alerta Temprana, SAT) was presented for the first time in INETER's April report. The new 6-station network contained five stations with 3-component sensors and one station with a single-component sensor. The network included two short-period stations, TEL3 and TEL4 (note that TEL4 was TELN), that continued to send data.

From late March through the second week of April, small explosions, LP earthquakes, and seismic swarms were detected. There was a three-day lull in early April, but VT earthquakes began occurring with increasing magnitudes and small explosions from the summit occurred at least once per week throughout the month. By 30 April, explosions were registered having 30-minute durations and were followed by periods of degassing and low-altitude ash plumes. For an interval in late April, seismicity was very high, with more than 600 events recorded each day with a range of M 0.1-3.3. A maximum of 380 RSAM units was recorded and seismic tremor ranged between 30-40 RSAM. The VT earthquakes were strong enough to be noticed by residents in local communities.

During field investigations on 11 April, INETER measured temperatures within the crater, recording a of maximum 254ºC. One fumarole within the W wall of the crater had decreased temperature by 10ºC while the other had increased by 1ºC compared to values from March. The four fumaroles near TEL4 had recorded temperatures in the range of 53-69ºC.

Eruptions in May 2011. The escalation of seismic activity and recurrence of ash plumes seen since March prompted INETER to issue an alert to civil defense on 13 May warning that eruptive activity was possible. During the first week of May seismicity increased to 500 microseismic events per day (in general, microseismic events in April occurred at a rate of ~ 220 per day) and VT events suddenly became rare (figure 22).

Figure 22. Telica's seismicity recorded during May 2011: epicenters shown on map and cross section (roughly aligned with map) were located with the new, early warning system (the 6 stations shown as blue triangles). Note that the focal depths are clustered under the volcano at depths mainly below 5 km. Courtesy of INETER.

Large explosions from Telica were registered at midnight on 13 May. After that, INETER reported that residents in three different communities observed pink-colored ash had fallen, and residents had also felt earthquakes. Frequent explosions of abundant gas and falls of coarse-to-fine ash occurred 14-15 May. Seismicity during 14 May was dominated by M 1.0-3.3 events with depths between 1 and 5 km (figure 23). Ash fell over the community of La Quemada, located 4 km N of the volcano. Residents heard loud noises from the volcano.

Figure 23. This minor explosion at Telica was observed on 16 May 2011. Courtesy of Halldor Geirsson (Pennsylvania State University).

On 16 May observers first saw gray ash clouds rising from Telica's summit. Later, this activity visibly escalated and ashfall was observed in continuous plumes (figure 23). The highest plumes reached 1.2 km altitude and ash fell to the SE over communities. By mid-May the number of seismic events had increased to 800 microseismic events per day, most of which were explosions with a few VT events (figure 24). INETER noted that seismic stations recorded up to 140 RSAM units on 16 May.

Figure 24. The number of seismic events registered per day during March-May 2011. This record was dominated by microseismicity and explosions from Telica. Courtesy of INETER.

Fieldworkers from INETER and others, deployed a large tarp, collected ~ 80 kg of tephra during 16-18 May. Preliminary assessments determined the nature of material that landed on the tarp included dominant lithics, fragmented rock and crystalline material of 0.5-1.0 mm diameter, and round fragments of pink-colored tephra (as opposed to the gray, sand-size grains from a small event on 12 May). These observations were also reported in field notes by Halldor Geirsson and in an abstract by Witter and others (2011). During a lull in activity on 16 May 2011, the team visited Telica's summit. Upon approaching the N rim, they heard no sounds coming from the crater, and they measured temperatures on the crater floor of ~ 395ºC. They observed fresh, inward-directed rockfalls from the crater's rim and found the N wall unstable and dangerous, seemingly on the verge of falling. The team also observed a dark area on the SE wall and floor of the crater, which suggested that recent explosions had concentrated tephra on these surfaces.

Washington VAAC 15 and 17 May. The Washington Volcanic Ash Advisory Center (VAAC) reported that the GOES-13 satellite detected at least two plumes on 15 and 17 May 2011. This satellite imagery confirmed gas-rich plumes on both days at ~ 1.8 km altitude, but ash content could not be determined from available images. INETER reported that these events were accompanied by elevated seismicity on 15 May and associated ashfall occurred 4 km N of the summit. After three emissions of gas on 17 May, ash and tephra fell SE of the summit. The last time plumes from Telica appeared in VAAC reports was in early months of 2007 when plumes reached an altitude of ~ 1.5 km for three days in January and February drifting SW.

Explosion with sustained ash plumes. On 18 May INETER posted two online reports ("Volcanic Communications" 5 and 6) indicating the peak of activity starting on that day. After two hours of sustained explosive activity producing ash plumes ~ 600 m high, the largest explosion suddenly occurred at 1350 on the 18th. A column of ash rose to an altitude of 2.6 km and was maintained for six minutes (figure 25). More than 15 explosions were seismically recorded (with a maximum of 350 RSAM units). The episodic explosions produced ash, steam, and, at times, lightning within the plume. Temperatures within the crater were gauged at a maximum 432ºC, and flank fumaroles were measured to be 60-126ºC.

Figure 25. A sustained ash plume issued from Telica during the peak of activity in 21 May 2011. Courtesy of Halldor Geirsson.

In a 19 May statement to news agencies, the municipal committee for disaster prevention and mitigation (COMUPRED) reported the evacuation of 390 families from nine villages near the volcano. The villages included Agua Fría (150 m from the edifice) and Los Patos, the most distant of the villages at 8 km from the edifice.

On 19 May, public meetings were held that included INETER, civil defense, and national disaster response (SINAPRED) representatives. A widely discussed issue was how the heavy ashfall and volcanic gases were affecting water quality. Officials favored monitoring local wells within 5 km of Telica's edifice. By 20 May, Telica's explosions became infrequent: three were registered that day. Only ash and resulting plumes rose to 500-800m altitude. Microseismicity remained high (850 events) and 60 earthquakes (M 0.8-2.2) were located at depths of 0.7-2.2 km (table 4).

On 20 May, explosions were also infrequent but four large events from the crater emitted plumes with heights of 500-700 m. In addition, at 1500 on the 20th, one large, continuous explosion occurred that lasted 36 minutes. Observers described a plume containing gas, steam, tephra, and small rocks. The largest ballistics did not reach farther than the crater rim and lightning was observed in the plume. INETER noted that wind conditions allowed the plume to reach 2 km altitude. Nine hundred microseismic events were recorded on 21 May and 57 earthquakes (M 0.5-2.0) were located with average depth of 1 km.

Well monitoring on 21 May revealed slight changes in local water quality. Sites located NE and within 5 km of the summit showed elevated quantities of sulfates, chlorides, alkalinity and PH.

New SO2 monitoring efforts. On 22 May, Universidad Tecnológica de Chalmers (Switzerland) and SNET (El Salvador) installed two portable Mini-DOAS stations (Differential Optical Absorption Spectrometer) at Los Angeles and Mendoza to measure SO2 levels.. These stations were installed downwind from Telica, SW of the edifice (figure 26). While the fixed stations collected data, traverses were made across the plume with mobile Mini-DOAS.

Figure 26. Location map of SO2 monitoring stations, Los Angeles and Mendoza, located SW of Telica Volcano (green stars). The 22 May 2011, Mini-DOAS traverse is highlighted in red. Courtesy of INETER.

The first Mini-DOAS results from fixed stations were obtained on 24 May. Data from the Los Angeles and Mendoza monitoring stations showed that flow of SO2 oscillated between 50 and 150 tons/day. Data collected from traverses below the plume on 23-27 May were processed by the Universidad Tecnológica de Chalmers (Switzerland). The traverse results compared well with the fixed stations: reported values ranged from 40 to 130 tons/day. Peak SO2 values from the fixed stations appeared as follows: Mendoza station, 420 tons/day on (28 May); Los Angeles station, 194 tons/day (30 May).

May 2011 eruption declines. INETER reported that ash explosions became infrequent during 23-30 May. That said, a cluster of eight explosions occurred sequentially on 24 May and created plumes reaching 600 m above the crater. Microseismicity remained high throughout the rest of the month. During 23-24 May, the largest number of earthquakes were located. Approximately 100 earthquakes (M 0.7-2.5) occurred with hypocenters at depths of 1-15 km.

According to the information supplied by the Directiorate of Meteorology of INETER, on 24 May ash expelled from Telica drifted SE at 8-15 km/hour at altitudes of 1.5 km. In their 24 May report, INETER warned that eruptive conditions could continue during the remainder of the month. They recommended the authorities of the Institute Nicargüense of Aeronaútica Civil (INAC) to caution air traffic about persistent and dispersed volcanic ash.

SO2 monitoring in June. On 3 June INETER conducted field investigations and measured SO2 with Mini-DOAS and Mobile DOAS. There were eight successful on-land traverses below the plume, each covering 18 km. Mobile DOAS data indicated a decrease in SO2: the maximum value recorded was 39 tons/day. SO2 flux from the two fixed stations, Mendoza and Los Angeles, also showed reduced levels during the early part of the month but an increase appeared from both sites in 13-15 June. INETER suggested that the low SO2 flux in early June may have been influenced by local wind patterns. Observers in the area noticed that the summit plume was very dispersed during this time. Wind velocities reported by NOAA were as low as 1.2 m/s on 3 June.

During a field visit by INETER on 14 June, the investigators managed to count 17 explosions that expelled ash and gas. The explosions occurred within short intervals of time, from two to three minutes and the longest interim was 10 minutes. The field team visited fumaroles S of the TEL4 seismic station and recorded temperatures from three fumaroles with values ranging from 64-76ºC.

Field data collected on 30 June included a maximum temperature of 590ºC from the crater (figure 27). The team observed incandescence within the crater and from a new vent near the NE wall. There were jetting and collapse sounds emitting from the crater.

Figure 27. Telica's crater temperatures measured January-October 2011. Note multiple measurements taken during the peak of activity in May and two measurements in September. The value measured in February was obtained with an infrared camera (Institute of Renewable Energy). Courtesy of INETER.

During June the number of earthquakes diminished but seismicity remained high. Approximately 500 earthquakes were registered per day. Approximately 100 earthquakes (up to M 2.8) were located (half the number located in May) at a maximum depth of 28 km (table 4). The majority of the events were volcanic-tectonic (VT) and doublet earthquakes (paired events). The dominant frequencies of the earthquakes shifted in June to 4.0-8.0 Hz.

Routine monitoring in July. During fieldwork on 12 July, INETER measured SO2 flux with Mobile DOAS. Five traverses, each one 8.5 km in distance, were recorded. The average value of SO2 was higher than the previous month, 484 tons/day. In their monthly report, INETER discussed the strong impact of inferred wind speed on their new gas measurements. During the month wind patterns were variable with speeds average ~ 5.8 m/s. They commented that the plume was noticeably less dispersed when they conducted the gas measurements.

On 22 July routine fieldwork was conducted at Telica. Residents of La Joya had heard loud jetting noises and at night saw incandescence at the summit. During the day, the team also heard jetting but did not see any explosive activity or feel earthquakes. Crater temperatures averaged 265ºC (five measurements), very low compared to the previous month (figure 27). Temperatures taken from fumaroles S of the seismic station ranged from 68-72ºC (three fumaroles).

Incandescence during August to October 2011. Halldor Geirsson noted that incandescence was seen in August 2011 (by Mel Rodgers and INETER staff). Further anomalous activity was not reported that month. A night visit took place on 9 September. The INETER team observed incandescence from the crater and measured temperatures with a thermal camera recording a maximum 458ºC. No jetting sounds were heard.

On 13 September INETER measured SO2 with Mobile DOAS. There were seven traverses along an 8.5-km stretch of road to cross below Telica's gas plume. SO2 flux was significantly lower than the previous month with an average of 81 tons/day.

On 13 October, SO2 traverses were attempted, but no gas was detected. Wind patterns had been disrupted by a low-pressure system that caused major flooding along Nicaragua's W coast.

During INETER's 27 October field visit, the team observed incandescence during the day and fragments of molten spatter were released during moderate gas explosions (figure 28). They also observed minor gas emissions and loud jetting persisted from the crater. INETER took five measurements of crater temperature, which averaged 280ºC. Temperatures from three fumaroles S of seismic station TEL4 were 66-72ºC. Vegetation was noticeably affected by volcanic gases; numerous dead plants were photographed during the 27 October visit.

Figure 28. Two photos both showing the same scene, centered on active vents within Telica's summit crater on 27 October 2011. Original photo (left); black and white copy (right). Gas explosions and spatter escaped from these vents during the field visit. Courtesy of INETER.

References. Bellos, A., Mulholland, K., O'Brien, K.L., Qazi, S.A., Gayer, M., Checchi, F., 2010, The burden of acute respiratory infections in crisis-affected populations: a systematic review: Conflict and Health, v. 4, no. 3.

Freundt, A., Kutterolf, S., Schmincke, H.-U., Hansteen, T., Wehrmann, H., Peréz, W., Strauch, W., Navarro, M., 2006, Volcanic hazards in Nicaragua: Past, present, and future, in Rose, W.I., Bluth, G.J.S., Carr, M.J., Ewert, J.W., Patino, L.C., and Vallance, J.W., eds., Volcanic hazards in Central America: Geological Society of America Special Paper 412, p. 141-165.

Malilay, J., Real, M.G., Vanegas, A.R., Noji, E., and Sinks, T., 1996, Public Health Surveillance after a Volcanic Eruption: Lessons from Cerro Negro, Nicaragua, 1992: Bulletin of Pan American Health Organization, v. 30, no. 3.

Witter, M.R., Geirsson, H., La Femina, P.C., Roman, D.C., Rodgers, M., Muñoz, A., Morales, A., Tenorio, V., Chavarria, D., Feineman, M.D., Furman, T., and Longley, A., 2011, May 2011 eruption of Telica Volcano, Nicaragua: Multidisciplinary observations, Abstract V53E-2670, Fall Meeting, AGU, San Francisco, California.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/geofisica/); Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/); Halldor Geirsson, The Pennsylvania State University, Department of Geosciences, 536 Deike Building, University Park, PA 16802, USA; La Prensa: (URL: http://www.laprensa.com.ni/2011/05/19/departamentos/60948); Mel Rodgers, University of South Florida, Department of Geology, 4202 East Fowler Ave., SCA528, Tampa, FL 33620, USA.

02/2013 (BGVN 38:02) Degassing continues in 2012; increased micro-earthquake activity in March 2013

Degassing that followed the May 2011 explosive eruption of Telica (figure 29; see also BGVN 36:11) continued through 2012 and into 2013. The following information summarizes observations by the Nicaraguan Institute of Territorial Studies (INETER) for 2012 and through March 2013.

Figure 29. A location map of Telica, Nicaragua, in Central America. Telica (red triangle) is located ~105 km NW of the capitol, Managua. It last erupted in May 2011 (BGVN 36:11), but no major damage was reported. Gases emitted by Telica normally affect communities in the nearby provinces of Leon and Chinandega. Small black triangles in the figure depict other known Holocene volcanoes in the region. Courtesy of USGS.

INETER issues a monthly bulletin, Boletín mensual Sismos y Volcanes de Nicaragua (Newsletter, Earthquakes and Volcanoes in Nicaragua), reporting on monitoring of Nicaraguan volcanoes including San Cristóbal, Telica, Cerro Negro, Momotombo, Masaya, and Concepcion (figure 30). In the Boletín, INETER presents monitoring data for Telica crater and adjacent fumarol temperatures, seismic activity, and sulfur dioxide (SO2) fluxes. In addition, visual observations are made during periodic field trips. Generally, the time difference between the arrival of P (primary) and S (secondary) waves from local earthquakes ranges from 0.5 to 2 sec, suggesting a source depth of 4 to 10 km.

Figure 30. An oblique view of a schematic map of Nicaragua with high vertical exaggeration highlights the locations of Nicaraguan volcanoes. Courtesy of INETER.

As an example of normal ongoing activity at Telica, INETER reported that during 10-11 September 2012, ‘jet’ sounds were heard from the volcano, and two incandescent fumaroles were observed, along with gas-and-steam plumes rising 100-200 m above the crater. On 11 September two small explosions occurred in the crater. During 12-14 and 17 September gas plumes rose 30-150 m and incandescence from the crater was observed. Gas measurements on 14 and 17 September showed normal levels of SO2 flux.

2012 Sulfur dioxide flux. Average daily SO2 flux measurements made using the Mini-DOAS (differential optical absorption spectroscopy) mobile technique in 2012 were 303 metric tons per day in April, 627 metric tons per day in June, 377 metric tons per day in August, and 130 metric tons per day in October.

2012 Seismic Events. INETER has developed some novel ways for grouping seismic events at Telica. The types of seismic events monitored at Telica and activity during 2012 are shown in tables 5 and 6, respectively.

Table 5. Types of seismic activity monitored at Telica volcano, with characteristics as recorded and interpreted during 2012. Courtesy of Virginia Tenorio, INETER.

Activity type        Frequency       Duration     Possible explanation
nomenclature         range/peak                   for events during 2012
(abbreviations)         (Hz)

Long period (LP)     1.0-4.5/4.0     20-40 sec    Magma movement at 6-10 km depth

Tremor               5.0-7.0         short        Degassing and magma movement

Volcano-tectonic     10.0-20.0+/     1+ min       Rupture of rock at 6-10 km depth
 (VT; VTA + VTB)         12

Double earthquake    4.0-7.0/        40-60 sec    Brittle fracture followed by
 (SDO)               4.0 and 7.0                  magma displacement

Gas eplosion (EG)    4.0-10.0        1-2 min      Release of gas in volcanic conduit

Swarms of seismic    5.0-7.0         1-3 min      Breaking rocks combined with LP-type
 events (TS)                                      events (avg. of 10 events per swarm)

Degasification       5.0-10.0        1 min        -
 signal (SD)

Table 6. Total volcano-seismic events and numbers of various types of events (see table 5 for descriptions) that were reported at Telica during 2012; percentages indicate the contribution of each type of event to the total recorded number of events during that month. Courtesy of INETER.

Activity type     18-31 March     April        May            June           July

Total events      1,986           3,222        3,544          5,754          4,112
LP                535 (27%)       953 (30%)    1,077 (30%)    827 (14%)      332 (8 %)
Tremor            0 (0%)          72 (2%)      78 (2%)        0 (0%)         125 (3%)
VT (VTA+VTB)      168 (8%)        299 (9%)     315 (9%)       2,418 (42%)    997 (24%)
SDO               658 (33%)       638 (20%)    635 (18%)      -              -
EG                625 (32%)       609 (19%)    686 (19%)      -              -
TS                -               -            -              2,519 (44%)    2,658 (65%)
SD                -               651 (20%)    753 (21%)      -              -

2012 Temperature measurements. Figure 31 shows INETER staff members measuring crater and fumarole vent temperatures at Telica; temperatures are measured approximately once per month (figure 32). Temperatures measured during 2012 at the 4 fumaroles (figure 33), vents located E and outside of Telica crater, ranged between 52° and 79°C.

Figure 31. INETER staff measuring temparatures at the Telica crater using a thermal imaging camera (left) and one of the fumarole vents using an IR thermometer (right). Courtesy of INETER.
Figure 32. (a) Maximum monthly temperatures for Telica crater during January 2011-February 2012, and (b) average monthly temperatures during 2012. Courtesy of INETER.
Figure 33. A W looking Google Earth view of Telica showing the approximate location of the fumarole vents E of Telica crater (lower arrow) and the location of temperature measurements in the crater (upper arrow). Courtesy of INETER.

2013 activity. The Costa Rica News reported on 24 March 2013 that Virginia Tenorio of INETER announced that Telica was experiencing increased micro-earthquakes. According to the INETER report, dozens of micro-earthquakes had occurred per day since 17 March. The increase continued to at least 24 March; 20 earthquakes occurred on 22 March, but only one reached as high as M 2.1. Tenorio was reported to state that, although earthquakes were located within the volcano’s structure, an imminent eruption was not indicated. She further stated that while some changes may occur in the magmatic system and in the expulsion of gases, conditions were stable. Local observers reported elevated vapor and gas emissions associated with the spike in seismicity and incandescence in a fissure at the bottom of the active crater. Since 21 March 2013, the member institutions of the National System for Prevention, Mitigation and Attention to Disasters (SINAPRED), have been ordered to monitor Telica’s activity and keep it under close observation.

Information Contacts: Virginia Tenorio, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni); Costa Rica News, San Jose, Costa Rica (URL: http://thecostaricanews.com); Sistema Nacional para la Prevención, Mitigación y Atención de Desastres (SINAPRED), Managua, Nicaragua (URL:http://www.sinapred.gob.ni/); MODVOLC, 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/).

Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of 1061-m-high Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately SE of Telica, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
2011 May 14 2011 Jun 17 (?) Confirmed 2 Historical Observations
2008 Jul 5 ± 4 days 2008 Jul 5 ± 4 days Confirmed 1 Historical Observations
2007 Oct 28 ± 3 days 2008 Feb 18 Confirmed 1 Historical Observations
[ 2007 Jun 12 ] [ 2007 Jun 12 ] Uncertain 1  
2006 Dec 11 (?) 2007 Feb 17 Confirmed 1 Historical Observations
2006 Aug 4 2006 Aug 6 Confirmed 1 Historical Observations
2004 Nov 5 2005 Jan 29 Confirmed 1 Historical Observations
2004 Mar 31 2004 Mar 31 Confirmed 1 Historical Observations
2002 Oct 17 Unknown Confirmed 0 Historical Observations
2001 Jan 17 2001 Dec 19 (?) Confirmed 1 Historical Observations
1999 May 21 2000 Sep 6 Confirmed 2 Historical Observations
1994 Jul 31 1994 Aug 12 Confirmed 2 Historical Observations
1987 Nov 1987 Nov Confirmed 1 Historical Observations Vent in NE corner of crater
1981 Nov 25 ± 5 days 1982 Mar 2 Confirmed 2 Historical Observations
1981 Feb (?) Unknown Confirmed 1 Historical Observations
1976 Nov 3 1978 Jan (in or after) Confirmed 1 Historical Observations
1975 May 1976 Mar Confirmed 0 Historical Observations
1969 Feb 11 1971 Dec (in or after) Confirmed 2 Historical Observations
1966 Jun 1966 Jun Confirmed 1 Historical Observations
1965 Jan 16 1965 Jan 28 Confirmed 1 Historical Observations
1962 Jan 1962 Jan Confirmed 1 Historical Observations
1951 Jul 15 ± 45 days 1951 Oct 15 ± 5 days Confirmed 2 Historical Observations
1948 Jun 1949 Nov Confirmed 2 Historical Observations
1948 Jan 1948 Jan Confirmed 2 Historical Observations
1946 Apr 1946 Aug Confirmed 2 Historical Observations
1943 Dec 1944 Apr Confirmed 2 Historical Observations
[ 1941 ] [ Unknown ] Uncertain    
1940 Jun 1940 Oct Confirmed 2 Historical Observations
1939 Nov 1939 Nov Confirmed 2 Historical Observations
1939 Jan 1939 Jun Confirmed 2 Historical Observations
1937 Nov 1938 Aug Confirmed 2 Historical Observations
1934 Jan Unknown Confirmed 2 Historical Observations
1929 Jan 1929 Jan Confirmed 1 Historical Observations
1928 Unknown Confirmed 2 Historical Observations
1927 Aug 1927 Nov Confirmed 2 Historical Observations
[ 1919 Oct 26 ± 5 days ] [ Unknown ] Uncertain 2  
[ 1918 Jan ] [ Unknown ] Uncertain 2  
1907 Nov Unknown Confirmed 2 Historical Observations
[ 1850 ] [ Unknown ] Discredited    
1791 Jan 24 Unknown Confirmed   Historical Observations
1765 Unknown Confirmed 2 Historical Observations
[ 1743 Apr ] [ Unknown ] Uncertain 2  
1685 Aug Unknown Confirmed 2 Historical Observations
1613 Unknown Confirmed 2 Historical Observations
1529 Unknown Confirmed 4 Historical Observations
1527 (?) Unknown Confirmed 3 Historical Observations

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
Aguero, Cerro de Cone 744 m 12° 37' 44" N 86° 50' 46" W
Liston, El Stratovolcano 12° 36' 18" N 86° 49' 19" W
Montoso, Cerro Cone 721 m 12° 36' 50" N 86° 52' 5" W
Portrillo, Los Cone 670 m 12° 37' 0" N 86° 52' 0" W
Santa Clara
    San Jacinto
Stratovolcano 834 m 12° 34' 44" N 86° 48' 43" W


Thermal
Feature Name Feature Type Elevation Latitude Longitude
Najo, El Thermal
San Jacinto, Hervideros de Thermal 180 m 12° 34' 0" N 86° 49' 0" W
Tisate, Hervideros de Thermal 180 m 12° 34' 0" N 86° 49' 0" W
This low-angle aerial view from the west shows the profile of the Telica volcanic complex, which consists of several interlocking cones and vents with a general NW alignment. Telica itself, the high peak at the left, is a steep-sided, 1061-m-high cone with a 700-m-wide double crater. El Liston, immediately SE (right) of Telica, has several nested craters. Santa Clara volcano is the symmetrical cone at the right.

Copyrighted photo by Dick Stoiber, 1972 (Dartmouth College).
A small ash cloud from an eruption in 1977 rises from the crater of Telica volcano as seen from the outskirts of the city of León. Intermittent explosions began in November 1976, and continued at a rate of one sizeable explosion a month until November 1977, when activity increased. On November 11 ashfall reached the Pacific Ocean. The eruption continued into January 1978.

Photo by Jaime Incer, 1977.
Mud pots boil in this 1978 view of the San Jacinto thermal area at El Salvador's Telica volcanic complex. The alignment of fumaroles and mud pots suggests an underlying fault running NNE. Magmatic steam and gases have been emitted from the thermal area for many years at a fairly constant rate.

Photo by Jaime Incer, 1978.
A prominent fumarole on the NE rim of the summit crater of Telica volcano produces a diffuse plume in this 1981 view. The double summit crater is viewed from the SE with the grassy cone of Cerro de Aguero, the northernmost cone of the Telica volcanic complex, at the upper right. The flanks of La Pelona caldera, part of the neighboring San Cristóbal volcanic complex, can be seen at the top of the photo across a low saddle.

Photo by Jaime Incer, 1981.
This aerial view on July 1987 looks almost directly down into the double summit crater of Telica volcano in Nicaragua. An older shallower crater is located on the SW side (top). Steam rises from fumaroles in the NE crater (bottom), the source of recent eruptions. The steep-walled crater is 120 m deep. Ash from frequent historical eruptions keeps the outer slopes of the cone unvegetated.

Photo by William Melson, 1987 (Smithsonian Institution).
An ash column rises in 1977 from the crater of Telica volcano, behind the ridge at the right. This was one of many explosive eruptions that took place between November 1976 and January 1978. The steep-sided symmetrical peak at the left is Santa Clara, one of several overlapping volcanoes of the Telica volcanic complex. Reports of historical eruptions from Santa Clara, located at the south end of the Telica complex, have not been substantiated. This view is from the SE.

Photo by Jaime Incer, 1977.
Cerro Negro volcano provides a vantage point for a NW-looking view down the Marrabios Range volcanic chain. The forested slopes in the foreground are part of Rota volcano. The light-colored conical peak in the center is Volcán Santa Clara, part of the Telica volcanic complex, whose principal peak, Telica itself, just pokes its head above the horizon behind and to the right of Santa Clara. The large conical peak on the center horizon is San Cristóbal, the highest peak of the Marrabios Range. The satellitic peak of El Chonco is on the left horizon.

Photo by Dennis Nielson, 1972 (courtesy of Mike Carr, Rutgers University).
Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the time of the Spanish conquest. The Telica volcano group consists of several interlocking cones and vents with a general NW alignment. Telica itself, seen here in an aerial view from the NE, is a steep-sided cone with a 700-m-wide double crater. The steaming NE crater, the source of recent eruptions, is 120 m deep. The rim of an older crater of the Telica complex forms the ridge at the lower left.

Photo by Robert Citron, 1968 (Smithsonian Institution).
Most recent eruptions of Telica have occurred from the lower NE summit crater. Fumarolic plumes rise from its floor and just below its rim. The double summit crater is about 300 x 700 m wide. Erosional gullies extend into the NE crater from the shallower SW crater. It lies below the summit, which is out of view below the bottom of the photo.

Photo by Robert Citron, 1968 (Smithsonian Institution).
Steam fills the large double crater of Telica volcano in this 1968 aerial view from the NE. The crater is about 300 x 700 m wide; its morphology suggests several generations of crater formation. Most recent eruptions have occurred from the lower NE crater.

Photo by William Melson, 1968 (Smithsonian Institution).
A convecting ash-bearing eruption cloud from Telica volcano punches through a low cloud layer in February 1982. Continuous white vapor columns with occasional ash were observed beginning in late November 1982, and small gas-and-ash eruptions took place in late December and early January. Large eruptions on February 12 and 19 sent clouds to 3.7-4.3 and 3.5 km above sea level, respectively. Eruptive activity ended on March 2.

Photo by Bill Rose, 1982 (Michigan Technological University).
A jointed lava flow underlain and capped by pyroclastic ejecta is exposed in the western crater wall of Telica's NE summit crater, the source of most of the volcano's recent eruptions. The crater is about 300 m wide and several hundred meters deep.

Photo by Bill Rose, 1978 (Michigan Technological University).
Volcán Santa Clara lies across a 400-m-high saddle (left) from Telica volcano. The crater rim of 834-m-high Santa Clara is higher on its far SE side and is breached to the NW. Santa Clara was considered to be active during the 16th century, but these reported eruptions more likely originated from Telica.

Photo by Alain Creusot-Eon, 1977 (courtesy of Jaime Incer).
Telica's impressive summit crater is not visible in this aerial view from the west. Erosional gullies scar the flanks of the unvegetated cone. The broad ridge in the background is El Liston, an older part of the Telica volcanic complex. An E-W-trending line of shallow craters extends from Telica to the broad summit of El Liston.

Photo by Jaime Incer, 1991.
The 700-m-wide double summit crater of Telica volcano is seen here in an aerial view from the north with farmlands of the Nicaraguan depression in the background. The 1061-m-high volcano is the highest and most recently active of the Telica volcanic complex. The Telica volcano group consists of several interlocking cones and vents with a general NW alignment. The bench at the lower right and the ridge at the left are remnants of older craters of the complex.

Photo by Jaime Incer, 1991.
Mud pots and steaming vents of the San Jacinto thermal area lie at an elevation of 140 m at the eastern end of the Telica volcanic complex. Thermal manifestations cover a broad area here and along a N-S-trending fault at Tizate, about 2 km to the NNE. Conical Santa Clara volcano rises to 834 m in the background.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
Telica volcano, seen here from the León-Chinandega highway, is one of a group of interlocking cones and vents along a NW trend. The summit of Telica, which is one of Nicaragua's most active volcanoes, is unvegetated, and deep erosional gulleys have been dissected into the lower flanks of the cone. Frequent historical eruptions have been recorded at Telica since the 16th century.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
Conical Santa Clara volcano lies at the SE end of the Telica volcanic complex. The 834-m-high stratovolcano, seen here from the south, has a small summit crater about 150 m in diameter. Santa Clara was considered to have been active during the 16th century, and early explorers reported the volcano to be smoking, but no specifically dated eruptions have been recorded.

Photo by Paul Kimberly, 1998 (Smithsonian Institution).
The San Jacinto-Tizate geothermal prospect at the eastern end of the Telica volcanic complex has undergone intermittent exploration by a Nicaraguan-Russian consortium. During the 1993-1995 period, seven exploration-production wells were drilled in the San Jacinto-Tizate geothermal area. The wells had total depths between 724 and 2235 m and encountered temperatures from 264 to 289 degrees Centigrade. Subsequent development by Polaris Geothermal resulted in inauguration of the first 10 MW production well in June 2005.

Photo by Paul Kimberly, 1998 (Smithsonian Institution).
Forested Rota volcano rises above steaming ground of the San Jacinto thermal area at the eastern end of the Telica volcanic complex. Highway 26 between Telica and Malpaisillo crosses the low saddle between Rota and the Telica complex and provides easy access to the mud pots and steaming vents of the thermal area. Visitors to San Jacinto are accompanied by groups of vendors who live in settlements near the thermal area.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
A view from Casita volcano to the SE along the Marrabios Range shows the Telica volcanic complex covering much of the center of the photo. A thin steam plume rises from the summit of Telica itself (right-center), while the cone of Cerro de Aguero lies at the left-center, with shadows defining older, more dissected parts of the Telica complex. The forested ridge of La Pelona caldera (part of the San Cristóbal complex) cuts across the lower part of the photo, while Momotombo (left), Las Pilas, and Cerro Asososco (right) lie on the horizon.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
Telica volcano is seen here in a telephoto view looking down the Marrabios Range from near the summit of Casita volcano. A thin steam plume rises from a fumarole in the summit crater. Behind Telica on the left horizon is Las Pilas volcano, and the conical peak at the extreme right is Cerro Asososca, at the south end of the Las Pilas complex.

Photo by Paul Kimberly, 1998 (Smithsonian Institution).
Mudpots and fumaroles mark the San Jacinto - Tizate geothermal area on the NE side of the Telica volcanic complex, the first geothermal power facility in Nicaragua to be fully developed by the private sector. Feasibility studies suggest possible power generation of 173-240 MW. Inauguration and reliability testing of the first 10 MW of power generation began in June 2005.

Photo by Eliecer Duarte, 2002 (OVSICORI-UNA).

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.

Carr M J, 1984. Symmetrical and segmented variation of physical and geochemical characterisitics of the Central American volcanic front. J Volc Geotherm Res, 20: 231-252.

Cecchi E, van Wyk de Vries B, Lavest J-M, 2005. Flank spreading and collapse of weak-cored volcanoes. Bull Volc, 67: 72-91.

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..

Incer J, 1988. Central American volcanic events (1524-1924). Unpublished manuscript, 52 p.

Mooser F, Meyer-Abich H, McBirney A R, 1958. Central America. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 6: 1-146.

Ostapenko S V, Spektor S V, Netesov Y P, 1998. San Jacinto-Tizate geothermal field, Nicaragua: exploration and conceptual model. Geothermics, 27: 361-378.

Ostapenko S V, Spektor S, Netesov Y, Romero F, 1997. Geothermal exploration of El Najo field Nicaragua. Stanford Geotherm Prog Proc, 22: 511-518.

Sapper K, 1925. The Volcanoes of Central America. Halle: Verlag Max Niemeyer, 144 p.

Volcano Types

Stratovolcano(es)

Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Rock Types

Major
Basalt / Picro-Basalt
Andesite / Basaltic Andesite

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
1,079
21,990
327,294
2,982,538

Affiliated Databases

Large Eruptions of Telica 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.