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Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information is preliminary at time of publication and subject to change.

Recently Published Bulletin Reports

Reventador (Ecuador) Continued ash emissions and incandescent blocks avalanches; new dome and lava flow emerge in August 2020

Popocatepetl (Mexico) Daily low-intensity emissions with ash and persistent tremor during August 2020-January 2021

Pacaya (Guatemala) Explosions continue, and effusive activity increases during August-November 2020

Stromboli (Italy) Explosions, incandescent ejecta, lava flows, and pyroclastic flows during September-December 2020

Saunders (United Kingdom) Elevated crater temperatures and gas emission through May 2020; research expedition

Santa Maria (Guatemala) Frequent explosions and avalanches August 2020-January 2021; lava extrusion in September 2020

Tengger Caldera (Indonesia) Ash plumes during 26-28 December 2020 with ashfall to the NE

Lewotolok (Indonesia) New eruption in late November 2020 consisting of ash plumes, crater incandescence, and ashfall

Soufriere St. Vincent (Saint Vincent and the Grenadines) New lava dome on the SW edge of the main crater in December 2020

Erta Ale (Ethiopia) Brief increase in strong thermal activity during late November-early December 2020

Bagana (Papua New Guinea) Ongoing thermal anomalies possibly indicating lava flows during May-December 2020

Kadovar (Papua New Guinea) Occasional ash and gas-and-steam plumes along with summit thermal anomalies



Reventador (Ecuador) — February 2021 Citation iconCite this Report

Reventador

Ecuador

0.077°S, 77.656°W; summit elev. 3562 m

All times are local (unless otherwise noted)


Continued ash emissions and incandescent blocks avalanches; new dome and lava flow emerge in August 2020

The andesitic Volcán El Reventador lies almost 100 km E of the main axis of active volcanoes in Ecuador and has historical eruptions with numerous lava flows and explosive events going back to the 16th century. An eruption in November 2002 generated a 17-km-high eruption cloud, pyroclastic flows that traveled 8 km, and multiple lava flows. Eruptive activity has been continuous since 2008. Daily explosions with ash emissions and ejecta of incandescent blocks rolling hundreds of meters down the flanks have been typical for many years. Similar activity continued during August 2020-January 2021, the period covered in this report, with information provided by Ecuador's Instituto Geofisico (IG-EPN), the Washington Volcano Ash Advisory Center (VAAC), and infrared satellite data.

Near-daily emissions of gas and ash often rose 500-1,000 m above the summit and drifted mostly in a westerly direction throughout August 2020-January 2021. Incandescence at night was produced by explosions of ejecta that sent blocks rolling hundreds of meters down the flanks of the pyroclastic cone inside the summit caldera. IG-EPN reported the presence of a new dome inside the crater in early August. A small lava flow about 400 m long persisted on the NE flank through at least the end of 2020; another flow was observed on the N flank in January. Small pyroclastic flows were reported a few times, and ashfall occurred in the San Rafael region (10 km SSE) at the end of October. After a relatively quiet June 2020, thermal activity increased to moderate levels and remained there throughout the period (figure 132).

Figure (see Caption) Figure 132. Thermal activity at Reventador was consistent at moderate to high levels from late June 2020 through January 2021, according to this MIROVA project graph of log radiative power at the volcano. Courtesy of MIROVA.

Gas and ash emissions rose 500-1,000 m above the summit almost every day during August 2020 (figure 133). Incandescence and explosions at the summit crater, visible at night, were accompanied many nights by incandescent blocks that rolled 500-700 m down various flanks. The Washington VAAC issued 1-4 alerts most days, reporting ash observed in satellite data that rose 700-1,400 m above the summit. Drift directions were generally NW, W, or SW. IG reported a pyroclastic flow on the NE flank on 4 August, and a new 200-m-long lava flow near the summit on the NE flank was seen on 10 August (figure 134). By 19 August the lava flow had reached 350 m long; it remained active for the rest of the month but didn’t increase in length. Based on the analysis of webcam photographs and infrared images, they confirmed the growth of a new dome on 17 August (figure 135). MODVOLC thermal alerts were recorded on 3 and 11 August.

Figure (see Caption) Figure 133. Gas and ash rose 500-1,000 m above the summit of Reventador most days during August 2020, as seen here on 17 August. Courtesy of IG-EPN (INFORME DIARIO DEL ESTADO DEL VOLCÁN REVENTADOR No. 2020-231, LUNES, 17 AGOSTO 2020).
Figure (see Caption) Figure 134. IG-EPN reported a new lava flow on the NE flank of Reventador on 10 August 2020. It was about 400 m long and persisted through the end of 2020. Courtesy of IG-EPN (INFORME DIARIO DEL ESTADO DEL VOLCÁN REVENTADOR No. 2020-224, LUNES, 10 AGOSTO 2020).
Figure (see Caption) Figure 135. Infrared images show volcanic activity at Reventador during August 2020, including a pyroclastic flow on 4 August (top right), a lava flow on 6 August (middle left), and a lava dome on 17 August (middle right and bottom row). Courtesy of IG-EPN (Prepared by Cámar IR, S Vallejo; Informe Especial del Volcán El Reventador No. 2-2020).

Incandescence from summit explosions was visible most nights in September 2020; explosions sent glowing blocks 500-800 m down multiple flanks on many nights. The lava flow on the NE flank remained active, growing slightly from 350 to 400 m in length. Three or four VAAC alerts were issued each day for ash plumes that rose usually 700-1,400 m above the summit and drifted NW. IG webcams captured images of ash emissions rising 600-900 m above the summit on most days; a few exceeded 1,000 m in height. IG reported pyroclastic flows on the N flank on 3 and 4 September, and on the W flank on 6 September. Pyroclastic deposits were observed on the E flank of the cone on 26 September, and the webcams captured a pyroclastic flow in the early morning of 29 September along the WSW flank that reached 600 m from the summit (figure 136). All of the pyroclastic flows remained inside the summit caldera. MODVOLC thermal alerts were recorded on 11, 12, and 20 September.

Figure (see Caption) Figure 136. A pyroclastic flow was visible on the WSW flank of Reventador on 29 September 2020 along with an ash plume that rose hundreds of meters above the summit. Courtesy of IG-EPN (IGAlInstante Informativo VOLCÁN REVENTADOR No. 005, MARTES, 29 SEPTIEMBRE 2020).

The 400- to 450-m-long lava flow that first emerged on the NE flank in early August remained active, as seen in thermal imagery, throughout October 2020 (figure 137). Emissions of gas and ash continued rising daily 500-1,000 m above the summit and drifting in multiple different directions. Multiple VAAC reports were issued on most days; the plumes increased in height and frequency during the second half of the month, reaching 1,400 m above the summit. Incandescent blocks rolled 500-800 m down the flanks on most nights. MODVOLC thermal alerts were issued on five days during the month, on 2, 11, 14, 25, and 27 October; five alerts were issued on 25 October. Occasional pyroclastic flows were recorded on the N flank on 21 October. Fine-grained ashfall was reported in the San Rafael region (on the border between the Napo and Sucumbios provinces, 10 km ESE) on 28 and 30 October (figure 138).

Figure (see Caption) Figure 137. The lava flow on the NE flank of Reventador was about 450 m long and active throughout October 2020. In this 6 October 2020 infrared image incandescent ejecta rose from the summit and the lava flow was visible on the NE flank. Courtesy of IG-EPN (INFORME DIARIO DEL ESTADO DEL VOLCÁN REVENTADOR No. 2020-281, MARTES, 6 OCTUBRE 2020).
Figure (see Caption) Figure 138. IGEPN official S. Vallejo reported ashfall on a vehicle in the San Rafael region on the border between the Napo and Sucumbios provinces, 10 km ESE of Reventador on 28 and 30 October. US penny for scale. Photo by S. Vallejo, courtesy of IG-EPN (IGAlInstante Informativo VOLCÁN REVENTADOR No. 007, VIERNES, 30 OCTUBRE 2020).

Steam, gas, and ash emissions continued throughout November 2020, with many plumes rising 800-1,000 m above the summit and drifting NW (figure 139). Multiple daily VAAC reports indicated plumes visible in satellite imagery 1,000-1,400 m above the summit on most days. The lava flow remained active on the NE flank with thermal imagery indicating a strong heat signal 400-450 m from the summit. The explosions that produced the incandescent blocks were strongest during 5-7 November when the blocks rolled as far as 1,000 m from the summit. Cloudy weather and rain obscured views of activity at the end of the month, and a lahar was measured by seismic instruments on 27 November, but no damage was reported. MODVOLC alerts were issued on 3, 10, 26, and 30 November. Cloudy weather during the first week of December prevented many observations, but clearer skies later in the month indicated ongoing activity that included gas and ash emissions rising about 1,000 m and drifting NW; incandescent blocks rolled 500 m down the flanks following explosions inside the crater. Only a single MODVOLC alert was issued on 25 December. The 450-m-long lava flow on the NE flank remained active.

Figure (see Caption) Figure 139. Many ash plumes at Reventador rose 800-1,000 m above the summit during November 2020. They were visible on some days when the mountain was not; clear days revealed blocks rolling down the NE flank and raising ash clouds as they rolled (bottom left). Courtesy of IG-EPN (INFORME DIARIO DEL ESTADO DEL VOLCÁN REVENTADOR Nos. 2020-312, 2020-315, 2020-323, and 2020-327).

A new pulse of lava was first reported from a vent on the N flank on 10 January 2021 and remained active for the rest of the month. That same day incandescent blocks traveled 700 m down the NE flank. Pyroclastic flows were observed on the night of 14 January on the N flank. Satellite imagery on 16 January showed multiple areas of thermal activity at the summit and on the NNE flank (figure 140). On 21 January the ejecta from the explosions rose a hundred meters or more into the air over the pyroclastic cone in addition to traveling several hundred meters down the NE flank (figure 141). MODVOLC thermal alerts were issued on 4, 13, and 31 January.

Figure (see Caption) Figure 140. Sentinel-2 satellite imagery of Reventador on 16 January 2021 indicated strong thermal anomalies at the summit and on the NE flank, even through the frequently dense cloud cover. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 141. On 21 January 2021 the ejecta from explosions at Reventador could be seen rising a hundred meters or more over the pyroclastic cone in addition to traveling several hundred meters down the NE flank. Courtesy of IG-EPN (INFORME DIARIO DEL VOLCAN REVENTADOR No. 2021-021, Quito, jueves 21 de enero de 2021).

Geologic Background. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC 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://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Popocatepetl (Mexico) — February 2021 Citation iconCite this Report

Popocatepetl

Mexico

19.023°N, 98.622°W; summit elev. 5393 m

All times are local (unless otherwise noted)


Daily low-intensity emissions with ash and persistent tremor during August 2020-January 2021

Volcán Popocatépetl is an active stratovolcano near Mexico City that has had frequent historical eruptions dating back to the 14th century. The current eruption has been ongoing since January 2005 and has more recently consisted of lava dome growth and destruction, frequent explosions, and emissions of ash plumes and incandescent ejecta. Activity through July 2020 was characterized by hundreds of daily low-intensity emissions that included gas-and-steam and small amounts of ash, and multiple daily minor and moderate explosions that sent ash plumes more than 1 km above the crater (BGVN 45:08). This report covers somewhat decreased activity from August 2020 through January 2021 using information from México's Centro Nacional de Prevención de Desastres (CENAPRED), the Washington Volcanic Ash Advisory Center (VAAC), and various satellite data.

Popocatépetl had ongoing water vapor, gas, and ash emissions throughout August 2020-January 2021, but far fewer minor and moderate explosions than during the period of the previous report. Ash emissions generally rose to 5.8-7.1 km altitude and drifted in many different directions. Ashfall was reported in multiple communities during August, October, and numerous times in January 2021. Thermal anomalies were recorded in satellite images inside the summit crater a few times each month. The MIROVA thermal anomaly data indicated persistent, low levels of activity throughout the reporting period (figure 162). CENAPRED reported the number of low-intensity emissions or ‘exhalations’ and the number of minutes of tremor in their daily reports (figure 163). Tremor activity was very high at the beginning of August, and then again during January 2021. The daily number of exhalations was highest during late October and November 2020.

Figure (see Caption) Figure 162. MIROVA thermal anomaly data for Popocatépetl for the year ending on 3 February 2021 showed persistent low levels of activity from August 2020 through January 2021, the period covered in this report. Courtesy of MIROVA.
Figure (see Caption) Figure 163. CENAPRED reported the number of exhalations (low-intensity emissions) and the number of minutes of tremor at Popocatépetl in their daily reports. Tremor activity was very high at the beginning of August, and then again during January 2021 (yellow columns). The daily number of exhalations was highest during late October and November 2020 (blue columns). Data courtesy of CENAPRED daily monitoring reports.

During August 2020 daily water vapor and gas emissions often contained small quantities of ash. In addition, low-intensity emissions or exhalations with larger quantities of ash occurred tens of times per day. The daily number of minutes of tremor was over 1,000 at the beginning of the month but dropped back to lower levels of a few tens or hundreds of minutes later in the month. Slight amounts of ashfall were reported in Amecameca and Ozumba in the State of Mexico on 1 August. On 2 August the 1159 minutes of tremor were sometimes accompanied by incandescent ejecta that fell into and a short distance from the summit crater. The Washington VAAC observed an ash emission drifting NE at 6.1 km altitude on 2 August that later rose to 7.6 km altitude. It fanned out from the summit to the N and E for about 15 km. Similar observations were made virtually every day of the month; ash or gas-and-ash emissions generally rose to 5.8-7.6 km altitude and drifted a few tens of kilometers in different directions before dissipating. Constant gas emissions and incandescence were reported at night during 10-23 August; an ash emission that rose to 600 m above the crater rim and drifted W on 14 August was captured in the webcam (figure 164). The largest SO2 emissions during the period were captured by the TROPOMI instrument on the Sentinel-5P satellite during 2-5 August (figure 165).

Figure (see Caption) Figure 164. An ash emission at Popocatépetl rose to 600 m above the crater rim and drifted W on 14 August 2020. Dense steam emissions also drifted just above the summit. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl hoy 14 de Agosto).
Figure (see Caption) Figure 165. The largest SO2 emissions at Popocatépetl during the period were captured by the TROPOMI instrument on the Sentinel-5P satellite during 2-5 August 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Gas and occasional weak ash emissions accompanied the tens of daily low-intensity emissions during September 2020; thermal activity was very low with weak anomalies inside the summit present in satellite images on 3, 8, and 13 September. Ash emissions were visible from a webcam on 18 September and in satellite imagery on 23 September (figure 166). Weak incandescence above the crater was only reported by CENAPRED during 26 and 27 September. The Washington VAAC reported intermittent ash emissions throughout the month that commonly rose to 6-7 km altitude and drifted over 50 km downwind before dissipating.

Figure (see Caption) Figure 166. Ash emissions were visible from a webcam at Popocatépetl on 18 September (left) and in satellite imagery on 23 September 2020 (right). Right image is from Sentinel-2 with natural color rendering (bands 4, 3, 2). Left image courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl hoy 18 de septiembre). Right image courtesy of Sentinel Hub Playground.

Water-vapor and gas emissions with small quantities of ash similar to those seen in September were also typical activity during October 2020. Tens or a few hundred daily low-intensity emissions often produced ash plumes visible in the webcams (figure 167). Ashfall was reported in Tetela del Volcano (20 km SW), in the state of Morelos, and in Amecameca (20 km NW), Atlautla (17 km W), Ayapango (22 km NW) and Ecatzingo (15 km SW), in the State of Mexico on 7 October; a small amount of ashfall was also reported in Amecameca on 13 October. The Washington VAAC issued multiple daily ash advisories throughout the month; many ash plumes were visible in satellite imagery. Incandescence appeared over the summit crater at night during 10-16 October, and was noted in satellite imagery on 3, 8, 18, 23, and 28 October. Incandescence and ash emissions were both captured in satellite imagery on 8 and 18 October (figure 168). Personnel from the Institute of Geophysics of the National Autonomous University of Mexico (UNAM) and the National Center for Disaster Prevention (CENAPRED) conducted an overflight on 16 October and verified that the inner crater at the summit was covered in tephra and about 360-390 m in diameter and 120-170 m deep (figure 169).

Figure (see Caption) Figure 167. Ash plumes and steam rose hundreds of meters above Popocatépetl on 5 (left) and 10 (right) October 2020. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl hoy 5 de octubre y 10 de octubre de 2020).
Figure (see Caption) Figure 168. Thermal anomalies at the summit of Popocatépetl and ash plumes drifting SW were both present in satellite imagery on 8 (left) and 18 (right) October 2020. Images are using Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 169. Personnel from the Institute of Geophysics of the National Autonomous University of Mexico (UNAM) and the National Center for Disaster Prevention (CENAPRED) conducted an overflight of Popocatépetl on 16 October 2020 and verified that the inner crater at the summit was covered in tephra, about 360-390 m in diameter, and 120-170 m deep. Courtesy of CENAPRED (Sobrevuelo al volcán Popocatépetl, 16 de octubre de 2020).

Activity during November 2020 consisted primarily of weak emissions of steam and gas with occasional small quantities of ash that rose a short distance above the summit crater (figure 170). The Washington VAAC reported ash emissions on 19 days during the month, most rising to 5.8-6.7 km altitude and drifting for a few tens of kilometers before dissipating. CENAPRED reported a few hundred low-intensity emissions daily, but only a few tens of minutes of tremor each day, significantly lower than previous months. Satellite imagery showed weak thermal anomalies inside the summit crater on 2, 7, 12, 22, and 27 November.

Figure (see Caption) Figure 170. Activity during November 2020 at Popocatépetl consisted primarily of weak emissions of steam and gas with occasional small quantities of ash that rose a short distance above the summit crater such as this one on 2 November. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl hoy 02 de noviembre).

Emissions of steam and gas with occasional low quantities of ash continued during December 2020. Six explosions on 5 December produced small ash plumes that rose 500-1,000 m above the crater. The next day two explosions produced plumes that rose less than 1,500 m above the crater and drifted NE. Incandescent ejecta was captured in the webcam on 14 December (figure 171). The Washington VAAC issued multiple aviation alerts nearly every day of the month; ash plumes generally rose to 6-7 km altitude and drifted 30-50 km before dissipating. Activity increased during the second half of the month (figure 172). Visible ejecta was seen in webcams during low-energy emissions on 24 December, accompanied by an ash plume that rose 1,000 m above the crater. The next day an ash emission rose 300 m. Ejecta was noted on the SE flank after an explosion on 27 December, and ash plumes rose to 500-1,400 m above the crater each day through the end of December and into January 2021. Thermal anomalies appeared in satellite data inside the summit crater on 2, 17, 22, and 27 December.

Figure (see Caption) Figure 171. Explosions at Popocatépetl produced dense ash emissions and incandescent ejecta. On 6 December the ash plume rose to 1,500 m above the crater and drifted NE (left). On 14 December 2020 incandescent ejecta rose a few hundred meters above the summit crater (right). Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl, 7 de diciembre y 15 de Diciembre de 2020).
Figure (see Caption) Figure 172. Ash emissions occurred daily at Popocatépetl during December 2020. On 20 December the dense plume rose about one kilometer above the summit (left). On 31 December a thermal inversion was the likely reason that the ash from the summit flowed down the flank towards the webcam (right). Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl, 20 de diciembre y 31 de Diciembre de 2020).

Daily ash emissions were reported by the Washington VAAC during January 2021, rising to 5.8-7.0 km altitude and drifting tens or hundreds of kilometers before dissipating (figure 173). Ash plumes rose 500-600 m above the crater on 1 and 2 January; at least one explosion each of those days produced incandescent ejecta in and around the crater. The Washington VAAC reported the ash plume from 1 January as visible in the webcam and satellite imagery over 200 km NE from the summit before dissipating, and one on 6 January visible about 100 km E of the volcano (figure 174). Ashfall was reported each day during 4-6 January in Puebla to the NW. On 8 January ashfall occurred in Atlixco (23 km SE), San Andrés Cholula (35 km E), San Nicolás de los Ranchos (15 km ENE) and Domingo Arenas (22 km NE), all in the state of Puebla. The following day ashfall was reported in San Salvador el Verde (30 km NNE) and San Nicolás de los Ranchos. Multiple explosions with ash plumes rising 500-700 m were reported on 14 and 15 January followed the next day by ashfall in San Nicolás de los Ranchos. Trace amounts of ash were reported in Tetela del Volcán (18 km SW) in the State of Morelos on 22 January. An explosion on 26 January ejected ash 700 m high and sent incandescent fragments a short distance from the crater rim. Ashfall on 28 January was reported in Ixtlacuixtla de Mariano, Nativitas and part of the center of Tlaxcala (50 km NE). The circular inner crater rim at the summit was sharply defined in a satellite image taken on 31 January 2021; a thermal anomaly was also present inside the crater (figure 175).

Figure (see Caption) Figure 173. Ash plumes were reported daily at Popocatépetl during January 2021, including on 19 (left) and 21 (right) January, some rising over a kilometer above summit and drifting for tens of kilometers before dissipating. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl, 20 y 21 de Enero de 2021).
Figure (see Caption) Figure 174. The Washington VAAC reported an ash plume at Popocatépetl from 1 January 2020 as visible over 200 km NE from the summit before dissipating (left), and one on 6 January as visible about 100 km E of the volcano (right). Sentinel-2 satellite images are with Natural color (bands 4, 3, 2) and Atmospheric penetration (bands 12, 11, 8a) rendering. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 175. A thermal anomaly inside the summit crater of Popocatépetl seen in this Sentinel-2 image was surrounded by a distinct gray circle that was the rim of the inner crater on a clear 31 January 2021. Image uses Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Geologic Background. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Information Contacts: Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México D.F. 04360, México (URL: http://www.cenapred.unam.mx/, Daily Report Archive https://www.gob.mx/cenapred/archivo/articulos); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Pacaya (Guatemala) — February 2021 Citation iconCite this Report

Pacaya

Guatemala

14.382°N, 90.601°W; summit elev. 2569 m

All times are local (unless otherwise noted)


Explosions continue, and effusive activity increases during August-November 2020

Extensive lava flows, bomb-laden Strombolian explosions, and ash plumes emerging from Mackenney crater have characterized the persistent activity at Pacaya since 1961. The latest eruptive episode began with intermittent ash plumes and incandescence in June 2015; the growth of a new pyroclastic cone inside the summit crater was confirmed later that year. The pyroclastic cone has continued to grow, producing Strombolian explosions rising above the crater rim and frequent loud explosions. In addition, fissures on the flanks of the summit crater have produced an increasing number of lava flows traveling distances of over one kilometer down multiple flanks during 2019 and 2020 (figure 129). Increasing explosive and effusive activity during August-November 2020 is covered in this report with information provided by Guatemala's Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), multiple sources of satellite data, and numerous photographs from observers on the ground.

Figure (see Caption) Figure 129. Lava flows traveled down the flank of Pacaya during July 2019 while ash emissions and incandescent ejecta marked the summit of Fuego located 30 km NW. The large edifice on the right is Agua, and the one between it and Fuego is Acatenango, which last erupted in the early 20th century. Photo courtesy David Rojas, used with permission.

After a brief pause in effusive activity at the end of July 2020, two lava flows appeared on the NW flank on 12 August. Another flow began on the NE flank ten days later, and multiple flows were active for the remainder of the month, some reaching 650 m long. Multiple lava flows issued from fissures on the N flank and elsewhere throughout September. A flow on the NE flank was reported as 1,200 m long and was visible from Guatemala City on 8 September. A new flow on the S flank was very active later in the month. Flows were persistent on most of the flanks throughout October; a flow appeared from a fissure on the W flank on 20 October and reached 1 km in length by 24 October. Block avalanches spalled off the front of the flows and generated small ash plumes. Multi-branched flows on the W and SW flanks from the W flank fissure remained active throughout November. The slowdown in effusive activity in late July and early August 2020 is apparent in the MIROVA thermal anomaly data, as is the significant increase in activity during September that persisted into November 2020 (figure 130).

Figure (see Caption) Figure 130. Thermal activity at Pacaya decreased in late July and early August 2020 but then increased significantly in early September and remained high through November 2020; numerous lava flows were reported during the periods of increased thermal activity. Thermal data is shown from 3 February through November 2020. Courtesy of MIROVA.

The break in the lava flow activity that began on 25 July 2020 (BGVN 45:08) lasted until 12 August. During that time, steam plumes were reported rising 25-75 m above the summit and drifting generally S or SW as far as 6 km before dissipating. Strombolian explosions rose 25-150 m above the rim of Mackenney crater and ejecta reached 50 m from the rim; noises as loud as a train engine were heard in nearby communities. Incandescence was observed nearly constantly along with persistent seismic tremor activity. On 12 August two lava flows emerged on the NW flank, each reaching about 150 m long. Incandescence from the flows was visible each day through 21 August on the NW flank in the area just above Cerro Chino (figure 131). The active flows were 100-200 m long during this period. A new lava flow appeared on the NE flank and grew to 300 m in length on 22 August.

Figure (see Caption) Figure 131. A thermal anomaly from a lava flow on the NNW flank of Pacaya was present in Sentinel-2 satellite imagery on 17 August 2020 in addition to a thermal anomaly at the center of the pyroclastic cone inside the summit crater. Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Multiple lava flows were active on the NW, N, and NE flanks for the rest of the August. Incandescence on 24 August from the NW-flank flow near Cerro Chino indicated it was 250-300 m long. During 27 and 28 August flows were reported on the N and NNE flanks, 600 and 300 m long, respectively (figure 132). Incandescent pulses were reported from the crater overnight on 28-29 August; the NW flank flow remained active and was 300 m long. MODVOLC reported three thermal alerts on 29 August. The next day, 30 August, incandescence from the 650-m-long N flank flow and 300-m-long NE flank flow continued. Constant crater incandescence accompanied dense gray ash emissions on 31 August; the lava flow on the N flank remained incandescent for 350-400 m, but there was no incandescence or degassing from the NE-flank flow on the last day of the month.

Figure (see Caption) Figure 132. A 600-m-long lava flow was visible on the N flank of Pacaya as seen from Villa Nueva, part of Guatemala City, late on 27 August 2020. Courtesy of Sh!ft.

White and blue steam and gas plumes were present daily throughout September 2020. They drifted in multiple directions as far as 8 km from the summit before dissipating. Strombolian activity was constant, building up the pyroclastic cone inside of Mackenney crater and sending ejecta as far as 50 m from the rim. Ejecta rose 50-150 m on most days; it was reported at 200 m high on 3, 9, and 14 September and was heard loudly and rattled windows nearby on 17 and 27 September. Constant crater incandescence with prolonged degassing of dense gray ash plumes was reported on 5, 10, 15, 17, and 21 September.

Multiple lava flows issued from fissures on the N flank and elsewhere throughout the month. Two lava flows on 1 September on the N flank were 50 and 350 m long. The next day three flows on the same flank were 300, 350, and 650 m long. On 3 September a new flow appeared on the E flank and extended 600 m from its source in addition to two flows on the N flank. For the next several days multiple flows were active on the N and NE flanks, reaching 450 m on the NE flank on 7 September. The next day the flow on the NE flank reached 1,200 m in length and was visible from Guatemala City. Activity continued with multiple flows 150-300 m long through 12 September (figure 133).

Figure (see Caption) Figure 133. Lava flows at Pacaya were active on multiple flanks on 11 September 2020, including one that reached over a kilometer in length on the NE flank. Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

On 13 September 2020 the flows on the N and NE flanks reached 600 and 300 m long, while a third flow reached 150 m down the S flank. The flow on the S flank was the most active during 14-23 September, extending 550 m from its source and producing numerous block avalanches from the flow front (figure 134). During the last week of the month the focus of the flow activity returned to the NE, N, and NW flanks where multiple flows were reported, some up to 550 m long, along with constant Strombolian activity (figures 135). Increased thermal activity resulted in MODVOLC thermal alerts reported on seven days during the second half of the month.

Figure (see Caption) Figure 134. A large lava flow on the S flank of Pacaya during 14-23 September 2020 produced block avalanches from the flow front. It was seen here in Sentinel-2 satellite imagery on 21 September 2020 using atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 135. Strombolian explosions sent ejecta 40-70 m above the crater at Pacaya on 26 September 2020. In addition, a lava flow 200 m long descended the N flank. Courtesy of CONRED.

Gas and steam plumes persisted throughout October 2020. They generally rose a few hundred meters above the summit and usually drifted S or W up to 10 km. Strombolian explosions continued daily, reported at 75-150 m high for most of the month. In a special report on 8 October INSIVUMEH noted increased Strombolian activity that sent bombs and fine ash 200-300 m above the crater, with ash emissions drifting 12 km W. During the last week of the month the ejecta reached 250 m high on several days. Loud noises and shock waves were periodically reported; vibrations were felt in San Francisco de Sales on 23 October and in areas to the S of Guatemala City on 27 October. INSIVUMEH reported ash emissions that drifted 8-10 km S and W from the summit on 23 October. The Washington VAAC reported ash emissions seen in satellite imagery drifting 15 km NE at 3.7 km altitude on 28 October. Weak sulfur dioxide emissions were recorded by the TROPOMI instrument on 6, 20, and 26 October (figure 136).

Figure (see Caption) Figure 136. Weak SO2 emissions from Pacaya were recorded by the TROPOMI instrument on the Sentinel 5P satellite on 6, 20, and 26 October 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Numerous lava flows were active throughout the month of October 2020 on multiple flanks (figure 137). During 1-4 October INSIVUMEH reported one or two flows active on the N and NE flanks that were 100-500 m long (figure 138). On 4 October there was a 200-m-long flow on the S flank, and another flow on the W flank. The S-flank flow grew to 250 m long by 8 October, had block avalanches spalling off the front, and fine ash that was stirred up by the wind. The next day three flows were active; they were 400 m long on the NE flank, 300 m on the N flank, and 200 m on the W flank. The N-flank flow was the most active during 11-15 October, reaching 650 m long. The W-flank flow was very active from 20 October through the end of the month, issuing from a fissure at mid-flank. It reached 1 km in length by 24 October and burned vegetation at the flow front (figures 139). A flow on the NE flank was 350 m long on 26 October (figure 140). MODVOLC issued thermal alerts on 7 days of the month, including seven alerts on 5 October.

Figure (see Caption) Figure 137. Numerous lava flows were active throughout the month of October 2020 on multiple flanks of Pacaya. On 1 October the flows were concentrated on the N flank (left), and on 31 October a long flow was active on the W flank in addition to strong thermal activity at the summit crater (right). Atmospheric penetration rendering (bands 12, 11, and 8a) of Sentinel-2 satellite data. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 138. A lava flow 125 m long on the N flank of Pacaya was active on 1 October 2020. Courtesy of CONRED.
Figure (see Caption) Figure 139. A flow on the W flank of Pacaya was over 1 km long by 24 October 2020 when it was burning vegetation as it traveled downslope. Courtesy of Noti7.
Figure (see Caption) Figure 140. An active flow on the SW flank of Pacaya issuing from a fissure on the W flank was over 1 km long on 26 October 2020 and had multiple branches flowing down the slope. Numerous people were camped on the slope below the flow. Photo by Mariana Lemus.

Although the weather was cloudy for much of November 2020, white steam and blue gas plumes were visible drifting S or W from the summit on many days, some reaching 10 km from the volcano before dissipating. Sporadic Strombolian explosions rose 100-200 m above the pyroclastic cone inside Mackenney crater; the explosions were often accompanied by small ash plumes that rose a few hundred meters and drifted downwind 8-10 km before dissipating. A small SO2 plume was recorded in the TROPOMI satellite data on 8 November, the same day that INSIVUMEH and the Washington VAAC reported an ash emission drifting NE at 3.4 km altitude over the village of Los Llanos and others in the area (figure 141). An increase in activity reported by INSIVUMEH on 15 November consisted of Strombolian explosions sending material up to 300 m above the summit and ejecting bombs up to 100 m outside the crater.

Figure (see Caption) Figure 141. Ash and steam emissions were observed at Pacaya on 8 November 2020. Courtesy of CONRED.

Lava flows were still very active on the SW flank throughout November, emerging from a fissure a few hundred meters down from the summit that initially opened on 20 October. The main flow was 600 m long on 1 November and grew to 1,200 m long by 11 November (figure 142). On 5 November there were four separate branches of the SW-flank flow that were active. Block avalanches were common at the flow front. On 14 November a second flow was observed emerging from a fissure higher up on the SW flank from the earlier flow; they both were active for several days. INSIVUMEH issued a special report indicating increased effusion on 15 November from the SW-flank fissure. Block avalanches were occurring from the front of the 1-km-long flow, which had several branches. The blocks were 1-3 m in diameter and created small plumes of ash when moving as far as 500 m down the slope. An explosion during the night of 14-15 November at the SW-flank fissure created incandescent ejecta and ash emissions for several hours (figure 143). The flow remained active throughout the rest of November; on 26 November two flows were active from the main fissure, 500 and 400 m long (figure 144). On 30 November the main flow on the SW flank had three branches and extended 600 m from the mid-flank fissure.

Figure (see Caption) Figure 142. A fissure on the W flank of Pacaya that opened on 20 October 2020 sent multiple flows down the W and SW flanks during November. The flow extended more than a kilometer on 10 November (left). It had moved in a SW direction by 20 November (center) and had three major branches active on 25 November (right). Atmospheric penetration rendering (bands 12, 11, and 8a) of Sentinel-2 satellite data. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 143. An explosion at the fissure on the W flank of Pacaya during the night of 14-15 November 2020 produced incandescent ejecta almost as bright as that coming from the Strombolian activity inside the summit crater. For several hours dense ash emissions were visible at the fissure vent (inset). Large copyrighted photo courtesy of David Rojas, used with permission; inset courtesy of Prensa Objetiva.
Figure (see Caption) Figure 144. Two flows with multiple branches were active on the W and SW flanks of Pacaya on 26 November 2020. Both copyrighted photos courtesy of David Rojas, used with permission.

Geologic Background. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/ ); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié 21-72, Zona 13, Guatemala City, Guatemala (URL: http://conred.gob.gt/www/index.php) (URL: https://twitter.com/ConredGuatemala/status/1310057080162844673, https://conred.gob.gt/monitoreo-a-flujo-de-lava-en-el-volcan-pacaya/) ; NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC 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://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); David Rojas, Guatemala (URL: https://www.instagram.com/davidrojasgtfoto/, https://twitter.com/DavidRojasGt/); Mariana Lemus, Guatemala (URL: https://www.instagram.com/marianalemusgt/); Noti7 (URL: https://twitter.com/Noti7Guatemala/status/1320169410833883136); Sh!ft (URL: https://twitter.com/kevingt_/status/1299204020662304768); Prensa Objetiva (URL: https://twitter.com/noticiasprensa/status/1328102695832612865).


Stromboli (Italy) — February 2021 Citation iconCite this Report

Stromboli

Italy

38.789°N, 15.213°E; summit elev. 924 m

All times are local (unless otherwise noted)


Explosions, incandescent ejecta, lava flows, and pyroclastic flows during September-December 2020

Stromboli, located in the northeastern Aeolian Islands, is composed of two active summit craters: the Northern (N) crater and the Central-South (CS) crater that are situated at the head of the Sciara del Fuoco, a large scarp that runs from the summit down the NW side of the volcano (figure 187). The current eruption period began in February 1934 and has been recently characterized by Strombolian explosions at both summit craters, ash plumes, and SO2 plumes (BGVN 45:09). This report covers activity consisting of dominantly Strombolian explosions, incandescent ejecta, and ash plumes from September to December 2020, with information primarily from daily and weekly reports by Italy's Istituto Nazionale di Geofisica e Vulcanologia (INGV) and various satellite data.

Figure (see Caption) Figure 187. Photo of the summit craters at Stromboli showing the North and Central-South crater areas with the location of each active vent: N1 and N2 in the N crater and S1, S2, and C in the CS crater. Photo was taken from the Pizzo sopa la Fossa during an expedition on 22 August by INGV-OE personnel. Courtesy of INGV (Rep. No. 37/2020, Stromboli, Bollettino Settimanale, 31/08/2020 - 06/09/2020, data emissione 08/09/2020).

Activity was consistent during this reporting period. Explosion rates typically ranged from 1-14 events per hour and varied in intensity that ejected material 80-250 m above the N crater and 150-250 m above the CS crater (table 10). An ash plume on 16 November rose 1 km above the crater, accompanied by a pyroclastic flow descending the Sciara del Fuoco to the NW as far as 200 m. As a result, some ash and lapilli fell in the town of Stromboli (2 km NE). Strombolian explosions were often accompanied by gas-and-steam emissions, occasional spattering that deposited material on the Sciara del Fuoco, small lava flows, and small pyroclastic flows. According to INGV, the daily SO2 emissions measured 250-300 tons/day.

Table 10. Summary of activity at Stromboli during September-December 2020. Low-intensity activity indicates ejecta rising less than 80 m, medium-intensity is ejecta rising less than 150 m, and high-intensity is ejecta rising over 200 m above the vent. Data courtesy of INGV.

Month Activity
Sep 2020 Strombolian activity and degassing continued. Explosion rates varied from 2-22 per hour in the N crater and 1-10 in the CS crater. Ejected material rose 80-200 m above the N crater and 250 m above the CS crater. The average SO2 emissions measured 250-300 tons/day.
Oct 2020 Strombolian activity and degassing continued, along with occasional spattering. Explosion rates varied from 2-13 per hour in the N crater and 1-4 per hour in the CS crater. Ejected material rose 80-250 m above the N crater and 150-250 m above the CS crater. The average SO2 emissions measured 250-300 tons/day.
Nov 2020 Strombolian activity and degassing continued. Explosion rates varied from 2-10 per hour in the N crater and 1-4 in the CS crater. Ejected material rose 80-250 m above the N crater and 150 m above the CS crater. The average SO2 emissions measured 250-300 tons/day.
Dec 2020 Strombolian activity and degassing continued, along with some spattering in the N crater. Explosion rates varied from 1-13 per hour in the N crater and 1-5 in the CS crater. Ejected material rose 80-150 m above the N crater and 150 m above the CS crater. The average SO2 emissions measured 250-300 tons/day.

During September the frequency of the Strombolian explosions in the N crater typically ranged from 2-14 per hour; in the CS crater there were 1-10 explosions per hour. N1 consisted of three points of emissions that produced low- to high-intensity explosions, launching lapilli and bombs, sometimes mixed with fine ash, 80-200 m above the N crater and were distributed radially (figure 188); N2 typically showed low-intensity explosions (less than 80 m above the crater). Medium- to high-intensity explosions ejected mostly fine material mixed with some coarse tephra 250 m above the CS crater. On 28 September the number of explosive events reached a high of 22 per hour.

Figure (see Caption) Figure 188. Webcam images of Strombolian activity at Stromboli in the N1 crater on 29 September (left) and in the CS crater on 4 October (right) 2020. Images captured by the SCV surveillance cameras. Courtesy of INGV (Rep. No. 41/2020, Stromboli, Bollettino Settimanale, 28/09/2020 - 04/10/2020, data emissione 06/10/2020).

Explosions with occasional spatter continued in October at a rate of 2-13 per hour in the N crater and 1-4 per hour in the CS crater. In the N crater, N1 consisted of 2-4 eruptive vents that produced explosions of variable intensity while N2 contained two vents that primarily produced low-intensity explosions. Lapilli and bombs, sometimes mixed with fine ash, were ejected 80-250 m above the N crater. Fine ash sometimes mixed with coarse-to-medium tephra rose 150-250 m above the CS crater. Spatter was reported from two hornitos that formed in the N1 crater (figure 189). On 11 October sporadic ash emissions and coarse ejecta were observed above the S2 crater, episodic ash emissions rose above the S1 crater, and occasional degassing with modest spattering were visible in the C crater.

Figure (see Caption) Figure 189. Drone images showing gas-and-steam emissions and Strombolian activity at Stromboli during 8-9 October 2020. The white annotations label the craters and the red show the active hornitos (H). The N2H2 label shows a small explosion (right). Images from the HPHT Lab from INGV-Roma 1. Courtesy of INGV (Rep. No. 42/2020, Stromboli, Bollettino Settimanale, 05/10/2020 - 11/10/2020, data emissione 13/10/2020).

Strombolian explosions persisted into November. The N1 crater consisted of 2-3 vents, producing explosions of variable intensity; the N2 crater also consisted of 2-3 active vents that produced low- to medium-intensity explosions. The frequency of explosions ranged from 2-10 per hour in the N crater and 1-4 per hour in the CS crater. Lapilli and bombs, sometimes mixed with fine ash, rose 80-250 m above the N crater and fine material was ejected 150 m above the CS crater. On 10 November an explosion was detected at 2104 in the S2 crater of the CS area, producing pyroclastic material that was distributed radially along the Sciara del Fuoco, followed by an ash plume (figure 190). Within 30 seconds, another pulse of activity from the C crater in the northern part of the CS area produced intense lava fountaining that ejected coarse incandescent material 300 m above the crater, lasting about two minutes. At 2106 a small explosion was detected in the N2 crater, ending the explosive sequence.

Figure (see Caption) Figure 190. Thermal (rows 1 and 3) and webcam (rows 2 and 4) images showing the evolution of the explosion at Stromboli on the evening of 10 November 2020 accompanied by an ash plume and incandescent ejecta. Images captured by the SCT and SQV surveillance cameras. Courtesy of INGV (Rep. No. 47/2020, Stromboli, Bollettino Settimanale, 09/11/2020 - 15/11/2020, data emissione 17/11/2020).

During an overflight by the 2nd Air Unit of the Coast Guard of Catania on 11 November, scientists identified degassing in the entire summit crater area; a small lava flow was observed in the S1 crater, originating from an intra-crater vent. Additional thermal anomalies were noted at the bottom of the C, N1, and N2 craters. Strong fumaroles were visible originating from a hornito located outside the S1 crater on the Sciara del Fuoco. A second hornito was visible on the slope of the Sciara del Fuoco near the N2 crater. On 16 November a major explosion was detected at 1017 in the N crater area and on the edge of the N2 crater. Thermal and visible images captured the resulting dense, gray ash plume that rose 1 km above the crater and the accompanying pyroclastic flow that descended the Sciara del Fuoco as far as 200 m (figure 191). Some ash and lapilli fell over the town of Stromboli, about 2 km away on the NE coast of the island. A sequence of explosive events at 0133 on 21 November was detected in three different craters: the first two events occurred in the N1 and N2 craters, and the third occurred in the C crater. Coarse material was ejected 300 m above the crater and was distributed radially, affecting the upper part of the Sciara del Fuoco. A small ash plume was also visible.

Figure (see Caption) Figure 191. Thermal (top row) and webcam (bottom row) images showing the evolution of the explosion at Stromboli on the morning of 16 November 2020 accompanied by a significant gray ash plume. Images captured by the SCT and SCV surveillance cameras. Courtesy of INGV (Rep. No. 48/2020, Stromboli, Bollettino Settimanale, 16/11/2020 - 22/11/2020, data emissione 24/11/2020).

During December, similar Strombolian explosions were reported. There were two eruptive vents in the N1 crater and 2-4 in the N2 crater that produced explosions of low intensity and low-to-medium intensity, respectively. The frequency of explosions ranged from 1-13 per hour in the N crater and 1-5 per hour in the CS crater. Fine ash mixed with some coarse material (lapilli and bombs) was ejected 80-150 m above the N crater and mostly fine material rose 150 m above the CS crater. Some spattering activity was reported in the N2 crater, which contributed to the formation of hornitos that produced incandescent material. On 6 December an explosive sequence of events was detected in the CS crater area at 0612. An explosion ejected material 300 m above the crater that were distributed radially, depositing on the upper Sciara del Fuoco. In addition, two small lava flows formed (figure 192). A second explosion was recorded at 0613, characterized by lava fountaining in the CS crater that reached a height of 200 m. Similar activity in the N and CS craters were also captured by webcam images on 21 and 27 December, which showed lava fountaining, accompanied by a small pyroclastic flow (figure 193).

Figure (see Caption) Figure 192. Thermal images of the explosion at Stromboli in the CS crater on 6 December 2020, accompanied by incandescent ejecta and two small lava flows. Some lava fountaining was visible in the bottom center image at 0513:47. Images captured by the SCT surveillance camera. Courtesy of INGV (Rep. No. 50/2020, Stromboli, Bollettino Settimanale, 30/11/2020 - 06/12/2020, data emissione 08/12/2020).
Figure (see Caption) Figure 193. Webcam (top row) and thermal (bottom row) images of Strombolian activity in the N (left column) and CS (right column) crater areas at Stromboli on 21 December (top right) and 27 December (top left and bottom row) 2020. This activity included a small pyroclastic flow and lava fountaining. Images captured by the SCV and SCT surveillance cameras. Courtesy of INGV (Rep. No. 53/2020, Stromboli, Bollettino Settimanale, 21/12/2020 - 27/12/2020, data emissione 29/12/2020).

Intermittent and low-power thermal activity was detected during September through December, according to the MIROVA Log Radiative Power graph using MODIS infrared satellite information (figure 194). Though there were no detected MODVOLC thermal alerts during this reporting period, many thermal hotspots were visible in one or both summit craters on clear weather days using Sentinel-2 thermal satellite imagery, which is due to Strombolian activity (figure 195).

Figure (see Caption) Figure 194. Intermittent, low thermal activity at Stromboli was recorded by the MIROVA graph (Log Radiative Power) during September through December 2020. The frequency of the thermal anomalies had decreased compared to the previous months of May through August; a total of eleven thermal anomalies were detected during this reporting period. Courtesy of MIROVA.
Figure (see Caption) Figure 195. Weak thermal anomalies (bright yellow-orange) at Stromboli were visible in Sentinel-2 thermal satellite imagery from typically both summit craters during September through December 2020. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Geologic Background. Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy, (URL: http://www.ct.ingv.it/en/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Saunders (United Kingdom) — February 2021 Citation iconCite this Report

Saunders

United Kingdom

57.8°S, 26.483°W; summit elev. 843 m

All times are local (unless otherwise noted)


Elevated crater temperatures and gas emission through May 2020; research expedition

The glaciated Saunders Island is located in the remote South Sandwich Volcanic Arc in the South Atlantic between Candlemas (to the north) and Montagu (to the south) islands. The main volcanic features are Mount Michael, lava flows on the northern Blackstone Plain, and the Ashen hills complex near the eastern Nattriss Point (figure 31). The Ashen Hills complex is a group of overlapping craters formed through phreatomagmatic activity, with the largest crater opening towards the NW (figure 32). Gas emissions have been remotely observed from the ice-filled Old crater to the SE, with reports of gas plumes extending back to 1820 (LeMasurier et al., 1990; Patrick and Smellie, 2013; Liu et al., 2021). The current eruption period, centered at the 500-m-diameter Mount Michael summit crater, has been ongoing since at least 12 November 2014, based on remote sensing analysis (Gray et al., 2019). Activity consists of a lava lake, persistent degassing, and intermittent explosions producing ash plumes (Patrick and Smellie 2013; Gray et al. 2019). Visits are infrequent due to the remote location, and cloud and plume cover often prevents satellite observations. This report summarizes activity during June 2019 through May 2020 primarily using satellite data, as well as observations from visiting scientists.

Figure (see Caption) Figure 31. This 24 December 2019 satellite image (PlanetScope 3-Band scene) of Saunders Island shows the locations of the active Mount Michael summit crater and other features on the island. Courtesy of Planet Labs.
Figure (see Caption) Figure 32. Images of the southeastern area of Saunders Island taken in January 2020. The top left image shows Nattriss Point with Ashen Hills in the background. The other photos show the crater and flanks of the Ashen Hills complex with rill and gully features from fluvial erosion. White and black speckled features in the images are penguins. Photos courtesy of Emma Liu and the 2020 Pelagic Australis expedition group.

Activity during June-December 2019. Ashfall deposits on the flanks were sometimes visible on the snow and ice (figure 33). MIROVA thermal anomaly data during June 2019 through June 2020 showed few days where high temperatures were detected by this sensor, but the active summit crater floor is often obscured by cloud cover or condensed gas-and-steam plumes. The TROPOspheric Monitoring Instrument (TROPOMI) detected frequent sulfur dioxide (SO2) plumes of varying concentrations that are dispersed in different directions by wind (figure 34). Small condensed gas-and-steam plumes are often visible in satellite imagery within the crater, and some larger plumes are also imaged (figure 35). All satellite images where the summit crater was not obscured by either cloud cover or gas-and-steam plumes showed elevated temperatures within the summit crater, with three distinct areas visible possibly indicating multiple active vents (figure 36).

Figure (see Caption) Figure 33. This satellite image of Saunders Island acquired on 15 September 2019 shows the snow and ice-covered island and a recent ashfall deposit on the NE flank towards Cordelia Bay, with a green sediment plume in the water. Sentinel-2 image with Natural color (bands 4, 3, 2) rendering. Courtesy of Planet Labs.
Figure (see Caption) Figure 34. These images show data acquired by the TROPOspheric Monitoring Instrument (TROPOMI) that demonstrate detected SO2 (sulfur dioxide) from Mount Michael on Saunders Island on 2, 3, 25, and 29 September 2019. These are examples of gas plumes through the month with wind dispersing the plumes in different directions. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 35. This 10 October 2019 satellite image shows Saunders Island and the surrounding area with light cloud cover, and a condensed gas-and-steam plume from the summit crater drifting towards the E to SE. Sentinel-2 image with Natural color (bands 4, 3, 2) rendering. Courtesy of Planet Labs.
Figure (see Caption) Figure 36. These two Sentinel-2 thermal satellite images of Saunders Island acquired on 2 and 24 December 2019 show three distinct areas of elevated temperature within the Mount Michael summit crater (yellow to red). While the locations of the thermal anomalies look different in these images, the angle of the view into the crater is not specified. Blue is Ice, black is ocean water. Sentinel-2 image with False color (Urban) (bands 12, 11, 4) rendering. Courtesy of Sentinel Hub Playground.

Activity during January-May 2020. During January through May 2020 various remote sensing data showed the same activity as the previous seven months, with abundant cloud cover over the island. The Sentinel-2 satellite imaged a vertical plume on 13 March rising then being dispersed NE (figure 37). Intermittent observations of SO2 plumes continued through TROPOMI data analysis (figure 38). A clear view of the summit area on 29 May showed the ice-free active summit crater producing a weak gas-and-steam plume, and ash deposition on the NE to SE upper flanks (figure 39).

Figure (see Caption) Figure 37. This Sentinel-2 satellite image of the Mount Michael summit area on Saunders Island with a gas-and-steam plume rising from the summit crater above the cloud cover, and dispersing NE. The plume and clouds are casting dark shadows below them. Sentinel-2 image with False color (Urban) (bands 12, 11, 4) rendering. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 38. Examples of SO2 gas plumes originating from Saunders detected by the TROPOMI instrument on 14 and 18 March 2020. The plumes are dispersing N to NNE. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 39. This 29 May 2020 Planet Scope satellite image shows the summit area of Mount Michael above cloud cover with the active summit crater and the old crater to the SE. There is a weak gas plume rising from the crater and ashfall on the upper E flank. Courtesy of Planet Labs.

Research expedition in January 2020. The team of the 2020 Pelagic Australis expedition visited the island on 5-8 January 2020, with shore landings on the last three days, to quantify gas emissions from the island. The following information is from the published expedition results (Liu et al., 2021), with photos supplied by volcanologist Emma Liu.

Across the South Sandwich islands they used a combination of a ground-based and drone-mounted gas detectors (Multi-GAS), a UV imaging camera, sample collection, and NDIR spectrometer analyses to quantify gas output. They confirmed that the summit crater is a persistent source of gas emissions with 145 ± 59 tons per day of SO2 and a CO2 flux of 179 ± 76 tons per day. On the 5th they observed a vertical plume and on the 7th they observed the plume drifting down the E flank before rising (figure 40). They noted that the surface was steaming and was warm to the touch, suggesting widespread geothermal activity. The non-glaciated surfaces of the island contain tephra deposits, with units exposed by erosion and preserved within snow and ice (figure 41). Explosions have emplaced tephra layers across the island as well as ballistic blocks and bombs on the E flank (figure 42; Liu et al., 2021).

Figure (see Caption) Figure 40. These images show the gas emissions from Mount Michael on Saunders Island in January 2020. The top right image is a vertical gas plume rising from the summit crater on the evening of the 5th. The two photos on the right are looking towards the E on the 7th. The bottom left image is a low-lying condensed gas plume on the 8th travelling down the E flank before rising. Courtesy of Emma Liu, and Liu et al. (2021).
Figure (see Caption) Figure 41. Tephra layers are preserved within the stratigraphy of snow and ice on Saunders Island. Scale shown by penguins (top) and volcanologist Kieran Wood (right). Photos courtesy of Emma Liu.
Figure (see Caption) Figure 42. Dense volcanic blocks up to a meter in size are widespread on Saunders Island. The block in the foreground has a height of approximately 35 cm; the Chinstrap penguin in the foreground is around 50 cm tall. Courtesy of Emma Liu and Liu et al. (2021).

References: Liu E J, Wood K, Aiuppa A, Giudice G, Bitetto M, Fischer T P, McCormick Kilbride B T, Plank T, Hart T, 2021. Volcanic activity and gas emissions along the South Sandwich Arc. Bull Volcanol 83. https://doi.org/10.1007/s00445-020-01415-2

LeMasurier W E, Thomson J W, Baker P E, Kyle P R, Rowley P D, Smellie J L, Verwoerd W J, 1990. Volcanoes of the Antarctic Plate and Southern Ocean. American Geophysical Union, Washington, D.C.

Lachlan-Cope T, Smellie J L, Ladkin R, 2001. Discovery of a recurrent lava lake on Saunders Island (South Sandwich Islands) using AVHRR imagery. J. Volcanol. Geotherm. Res. 112: 105-116.

Gray D M, Burton-Johnson A, Fretwell P T, 2019. Evidence for a lava lake on Mt. Michael volcano, Saunders Island (South Sandwich Islands) from Landsat, Sentinel-2 and ASTER satellite imagery. J. Volcanol. Geotherm. Res. 379:60-71. https://doi.org/10.1016/j.volgeores.2019.05.002

Derrien A, Richter N, Meschede M, Walter T, 2019. Optical DSLR camera- and UAV footage of the remote Mount Michael Volcano, Saunders Island (South Sandwich Islands), acquired in May 2019. GFZ Data Services. http://doi.org/10.5880/GFZ.2.1.2019.003

Patrick M R, Smellie J L, 2013. Synthesis A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000–10. Antarct Sci 25:475–500. https://doi.org/10.1017/S0954102013000436

Geologic Background. Saunders Island is a volcanic structure consisting of a large central edifice intersected by two seamount chains, as shown by bathymetric mapping (Leat et al., 2013). The young constructional Mount Michael stratovolcano dominates the glacier-covered island, while two submarine plateaus, Harpers Bank and Saunders Bank, extend north. The symmetrical Michael has a 500-m-wide summit crater and a remnant of a somma rim to the SE. Tephra layers visible in ice cliffs surrounding the island are evidence of recent eruptions. Ash clouds were reported from the summit crater in 1819, and an effusive eruption was inferred to have occurred from a N-flank fissure around the end of the 19th century and beginning of the 20th century. A low ice-free lava platform, Blackstone Plain, is located on the north coast, surrounding a group of former sea stacks. A cluster of parasitic cones on the SE flank, the Ashen Hills, appear to have been modified since 1820 (LeMasurier and Thomson, 1990). Analysis of satellite imagery available since 1989 (Gray et al., 2019; MODVOLC) suggests frequent eruptive activity (when weatehr conditions allow), volcanic clouds, steam plumes, and thermal anomalies indicative of a persistent, or at least frequently active, lava lake in the summit crater. Due to this observational bias, there has been a presumption when defining eruptive periods that activity has been ongoing unless there is no evidence for at least 10 months.

Information Contacts: Emma Liu, University College London, Kathleen Lonsdale Building, 5 Gower Place, London, WC1E 6BS, United Kingdom; Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Planet Labs, Inc. (URL: https://www.planet.com/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Santa Maria (Guatemala) — February 2021 Citation iconCite this Report

Santa Maria

Guatemala

14.757°N, 91.552°W; summit elev. 3745 m

All times are local (unless otherwise noted)


Frequent explosions and avalanches August 2020-January 2021; lava extrusion in September 2020

Santa Maria is one of the most active volcanoes in Guatemala. Major features are the Santa Maria edifice with the large crater that formed in the 1902 eruption, and the Santiaguito dome complex about 2.5 km down the SW flank that includes the currently active Caliente dome (figure 113). Activity typically includes ash plumes, gas emissions, lava extrusion, and avalanches. This report summarizes activity during August 2020 through January 2021 and is based on reports by Instituto Nacional de Sismología, Vulcanología, Meteorología e Hidrología (INSIVUMEH), Coordinadora Nacional para la Reducción de Desastres (CONRED), and satellite data.

Figure (see Caption) Figure 113. Main features of the Santa Maria complex are shown in this March 2021 Planet Labs satellite image monthly mosaic. The large scarp is the wall of the crater produced during the 1902 eruption. Within that the El Brujo, El Monje, La Mitad domes, and the currently active Caliente dome, are from W to E. Courtesy of Planet Labs.

Throughout August weak to moderate explosions were reported most days, some days occurring 2-4 times per hour. These produced ash plumes to an altitude of 3.5 km, typically reaching 3.4 km. The plumes were dispersed mostly W and SW, sometimes S, SE, and NW. Degassing was reported throughout the month, with plumes reaching 3.5 km, but most often 3-3.1 km altitude. On the 3rd, ashfall was reported in San Marcos Palajuno (8 km SW), Loma Linda (6 km WSW) and others in that direction, and again on the 29th. It was also reported in Monte Claro (S of the summit) on the 12th and light ashfall occurred on the flanks through the month. Explosions on the 23rd produced weak pyroclastic flows that traveled down the SW flank of the dome. The activity produced frequent avalanches on the S, SW, and SE flanks of the dome, some reaching the base of the dome and some depositing fine ash onto the flanks. The sound of explosions and degassing were reported most days and incandescence was frequently seen at the crater at night.

This activity continued through September, maintaining the same eruptive pattern of weak and moderate explosions, gas emission, lava extrusion, and avalanches. Incandescence continued to be visible at the crater. There was ashfall reported in Monte Claro, Aldea San Marcos Palajunoj and other surrounding communities on the 7th, Monte Claro on the 11th, and across the Palajunoj area on the 28th. On the afternoon of 25 September lahars occurred in the Cabello de Ángel and Nimá I drainages. Lava extrusion was reported on the morning of the 29th along with resulting block-and-ash flows.

Throughout October explosions, gas emission, avalanches, and elevated crater temperatures producing nighttime incandescence (figure 114) continued in the same manner as the previous months. From the 9th the extrusion of lava was observed over the dome, generating block-and-ash flows mainly down the W flank. Ashfall was reported in of Loma Linda and El Rosario Palajunoj and others in the area on the 13th, 7 km SW on the 18th, and in San Marcos Palajunoj and nearby areas on the 23rd. Lava extrusion generated constant avalanches down multiple flanks from the 23rd, with some producing small ash plumes as they descended.

Figure (see Caption) Figure 114. This Shortwave Infrared (SWIR) image of Santa Maria acquired on 19 October by the Landsat 8 satellite shows elevated temperatures at the Caliente dome. The contour intervals are 30 m. Courtesy of USGS and INSIVUMEH.

Throughout November gas emissions and explosions continued to produce gas-and-steam and ash plumes that rose up to 3.4 km altitude. Lava extrusion also continued down the W flank, producing incandescence and frequent avalanches down the SE, S, SW, and W flanks, as well as less frequent block-and-ash flows (figure 115). An increase in thermal energy detected towards the end of the month resulted from this extrusion (figure 116). Ashfall occurred around the volcano from explosions and avalanches. Ashfall was reported SE within the villages of Las Marías, Calaguache and others nearby on the 12th and 22nd, and SSW over the village of San Marcos Palajunoj, Loma Linda and Fincas in the Palajunoj area on the 27th. Degassing and explosions were intermittently heard in nearby communities with reports of sounds similar to an airplane turbine. An explosion on the 16th produced an ash plume up to 3.6 km altitude and pyroclastic flows down the flanks (figure 117).

Figure (see Caption) Figure 115. This nighttime Landsat 8 Shortwave Infrared (SWIR) satellite image of Santa Maria with the contours of the Caliente dome overlain was acquired on 20 November 2020. There are elevated temperatures within the summit crater and lava is flowing down a channel on the western flank. The contour intervals are 20 m. Courtesy of USGS and INSIVUMEH.
Figure (see Caption) Figure 116. This MIROVA log radiative power plot shows the thermal energy released at Santa Maria between April 2020 to February 2021. There was a decrease in energy emitted from May to November, followed by an increase in the frequency and the energy released on some days. The black vertical lines like the two in January-February are more than 5 km from the summit and are likely not a result of volcanic activity. Courtesy of MIROVA.
Figure (see Caption) Figure 117. An explosion from the Caliente dome of Santa Maria is seen here at 0715 on 16 November 2020. The photo shows the ash plume that rose to 3.6 km altitude and pyroclastic flows descending the flanks. The seismogram shows the explosion in the center of the bottom line (the times on the left are given in UTC). Courtesy of INSIVUMEH.

Gas emissions and weak to moderate explosions continued throughout December, producing plumes reaching 3.4 km altitude along with ongoing lava extrusion producing avalanches (figures 118 and 119). Ash from explosions and avalanches was intermittently emplaced onto the flanks, and ashfall was reported in the villages of San Marcos and Loma Linda Palajunoj on the 7th, and in Loma Linda and Finca Montebello on the 11th. Activity increased from 0430 on 11 December 2020 with the generation of moderate to powerful avalanches as well as block-and-ash flows from lava extrusion and accumulation, with 13 events recorded between that time and when a report was released at 0900. The intensity continued with block-and-ash flows and pyroclastic flows moving down the W and SW flanks that generated ash plumes which extended 20 km downwind.

Figure (see Caption) Figure 118. Plumes rise from the Caliente dome at Santa Maria on 9 (top left) and 15 (top right) December 2020. A faint plume rises from the summit of the Caliente dome and another plume rises from a possible avalanche down the SW flank (bottom). Courtesy of INSIVUMEH (Fotografías Recientes de Volcanes).
Figure (see Caption) Figure 119. A gas-and-steam plume rises from the degassing Caliente dome at Santa Maria on 30 December 2020. Around this time weak and moderate explosions produced ash plumes up to 3-3.4 km altitude, resulting in ashfall on the flanks. Courtesy of CONRED.

The high level of background activity associated with lava extrusion continued through January. Satellite images show the lava flow advancing down the W-flank channel (figure 120), reaching approximately 250 m by the 11th. Avalanches also continued, producing ash that was emplaced nearby (figure 121). On the 22nd the collapse of dome material produced a pyroclastic flow to the E and SE. Explosions ejected ash to 3.4 km altitude, with ashfall that was reported in the Aldeas de San Marcos and Loma Linda Palajunoj on the 1st, Aldeas de San Marcos and Loma Linda Palajunoj on the 11th, Aldeas de San Marcos y Loma Linda Palajunoj, Fca. El Patrocinio during the 20-21st. Ashfall was again reported on the 31st to the west on farms, in Aldeas de San Marcos, and in Loma Linda Palajunoj. Sounds generated by explosions were sometimes heard around 10 km away.

Figure (see Caption) Figure 120. PlanetScope satellite images of Santa Maria acquired on 20 December 2020 and 10 and 11 January 2021 show the development of a lava flow down a channel on the W flank (white arrows). In the latest image the flow is approximately 250 m long. Courtesy of Planet Labs.
Figure (see Caption) Figure 121. Thermal infrared satellite images of Santa Maria acquired on 12 and 22 January 2021 show higher temperatures on the Caliente dome. Top: Elevated thermal areas are detected at the summit and hot material is emplaced down the W-flank channel. Bottom: Elevated temperatures at the summit of the lava dome, with a possible avalanche on the E flank. Sentinel-2 thermal satellite images with false color (urban) (bands 12, 11, 4) rendering. Courtesy of Sentinel Hub Playground.

Geologic Background. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié 21-72, Zona 13, Guatemala City, Guatemala (URL: http://conred.gob.gt/www/index.php); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Planet Labs, Inc. (URL: https://www.planet.com/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Tengger Caldera (Indonesia) — February 2021 Citation iconCite this Report

Tengger Caldera

Indonesia

7.942°S, 112.95°E; summit elev. 2329 m

All times are local (unless otherwise noted)


Ash plumes during 26-28 December 2020 with ashfall to the NE

Activity at Bromo, the youngest and only active cone within the 16-km-wide Tengger caldera in East Java, is characterized by occasional explosions with ash plumes followed by periods of relative quiet with only gas-and-steam emissions (BGVN 44:05). There have been more than 30 eruptive periods since 1900. During the first seven months of 2019, ash explosions occurred on 18 February 2019 and became especially numerous in March and April, with more explosive activity in July 2019 (BGVN 44:05, 44:08). The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) and by the Darwin Volcanic Ash Advisory Centre (VAAC).

Following the ash explosion on 28 July 2019, satellite observations frequently showed a white gas-and-steam plume in the Bromo crater (figure 19). No additional eruptive activity was reported until 26-27 December 2020 when PVMBG reported white-and-gray plumes rose 50-700 m above the summit of Bromo’s cone. The next day, at 0550 on 28 December, an observer spotted a gas-and-ash emission rising at least 500 m above the summit. The Darwin VAAC was unable to confirm if there was ash in the plume based on satellite data, but ashfall was reported in the Ngadirejo area, about 5 km NE. The Alert Level remained at 2 (on a scale of 1-4), and visitors were warned to stay outside a 1-km radius of the crater.

Figure (see Caption) Figure 19. Satellite image of the Tengger Caldera on 12 September 2020, with a typical white plume visible in the Bromo crater. Sentinel-2 image with natural color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

Geologic Background. The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Lewotolok (Indonesia) — February 2021 Citation iconCite this Report

Lewotolok

Indonesia

8.274°S, 123.508°E; summit elev. 1431 m

All times are local (unless otherwise noted)


New eruption in late November 2020 consisting of ash plumes, crater incandescence, and ashfall

Lewotolok (also known as Lewotolo) is located on the eastern end of a peninsula connected to Lembata (formerly Lomblen) that extends north into the Flores Sea. Eruptions date back to 1660, characterized by explosive activity in the summit crater. Typical activity has consisted of seismicity and thermal anomalies near the summit crater (BGVN 36:12 and 41:09). A new eruption that began in late November 2020 was characterized by increased seismicity, dense, gray ash plumes, nighttime crater incandescence, and ashfall. This report covers activity through January 2021 using information primarily from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation), MAGMA Indonesia, and satellite data.

Summary of activity during February 2012-October 2020. Activity from February 2012 to November 2020 was relatively low and consisted primarily of a persistent thermal anomaly in the summit crater since at least March 2016 and occasional white gas-and-steam emissions. During January 2012 intermittent white gas-and-steam plumes rose 15-500 m above the crater, accompanied by crater incandescence; no thermal anomalies were reported during 16-24 January. On 6 January there were 500 people in the Lembata district evacuated due to reports of ash plumes that were observed by local residents, the smell of sulfur, and the sound of rumbling (BGVN 36:12).

Thermal activity dates back to 13 October 2014 using MODIS data in MODVOLC satellite data (BGVN 41:09; figure 3). According to the MODVOLC algorithm, a total of seven thermal alerts were detected on 13 October 2014 (1), 27 September 2015 (1), 2, 3, and 4 (2) October 2015, and 5 November 2017 (1). The number of thermal alerts in both MODVOLC and Sentinel-2 satellite data had increased slightly in 2020 compared to 2018 and 2019, though cloud cover often prevented visual confirmation for the latter (figure 3). Sentinel-2 thermal satellite imagery captured occasional thermal anomalies in the summit crater during 2016-2019 (figure 4). White gas-and-steam plumes were intermittently reported from September 2017 through 2 March 2018 that rose as high as 500 m above the crater and drifted dominantly E and W, according to PVMBG.

Figure (see Caption) Figure 3. Graph comparing the number of thermal anomalies using MODVOLC alerts and Sentinel-2 satellite data for Lewotolok during January 2014-January 2021 for MODVOLC and 20 March 2016-January 2021 for Sentinel-2 thermal satellite data. Data courtesy of HIGP - MODVOLC Thermal Alerts System and Sentinel Hub Playground.

Brief seismicity, which included shallow and deep volcanic earthquakes was detected during October 2017. On 9 October 2017 PVMBG issued a VONA (Volcano Observatory Notice for Aviation) reporting that white gas-and-steam emissions rose 500 m above the crater. On 10 October BNPB (Badan Nacional Penanggulangan Bencana) reported that five earthquakes 10-30 km below Lewotolok and ranging in magnitude of 3.9-4.9 as recorded by Badan Meteorologi, Klimatologi, dan Geofisika (BMKG). These seismic events were felt by local populations and resulted in an evacuation of 723 people. The only activity reported between January 2018 and October 2020 was white gas-and-steam plumes that rose 5-100 m above the crater drifting primarily E and W and an occasional thermal anomaly in the summit crater (figure 4).

Figure (see Caption) Figure 4. Sentinel-2 thermal satellite imagery shows a thermal anomaly in the summit crater of Lewotolok during 20 March 2016 (top left), 8 July 2017 (top right), 13 July 2018 (bottom left), and 12 August 2019 (bottom right). Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

New eruption starting in November 2020. On 26 November 2020 a continuous tremor began at 1943, followed by a series of volcanic earthquakes at 1947 and deep volcanic earthquakes at 1951, 1952, 1953, and 2255; white gas-and-steam emissions rose 20 m above the crater. Deep volcanic earthquakes were again recorded at 0242, 0537, 0556 on 27 November. At 0557 an explosion produced a gray ash plume that rose 500 m above the crater and drifted W; by 0630 the plume turned white, according to PVMBG (figure 5). Seismicity decreased slightly after the explosion, but tremor continued. During 27-28 November dense white gas-and-steam plumes rose as high as 500 m above the crater and nighttime crater incandescence was observed.

Figure (see Caption) Figure 5. Webcam image of a dense gray ash plume rising 500 m above the crater of Lewotolok on 27 November 2020. Courtesy of MAGMA Indonesia.

During the morning of 29 November seismicity increased again and consisted of six deep volcanic earthquakes, continuous tremor occurred around 0930. A second explosion was recorded at 0945 that produced an ash plume 4 km above the crater, accompanied by incandescent material that was ejected above the crater (figure 6). The ash plume consisted of two levels: the lower-level drifted W and NW and the upper-level drifted E and SE. The large, gray ash plume was captured in a satellite image as it spread generally E and W (figure 7). Ashfall and a sulfur odor was reported in several surrounding villages; videos from social media showed tephra falling onto the roofs of residential areas. BPBD evacuated residents in 28 villages in two sub-districts; by 29 November at 1300 about 900 people had been evacuated. At 1900 Strombolian activity was observed and during the night, crater incandescence was visible.

Figure (see Caption) Figure 6. Photos of the eruption at Lewotolok on 29 November 2020 that produced a dense, gray ash plume 4 km above the crater. Courtesy of Devy Kamil Syahbana, PVMBG (left) and MAGMA Indonesia (right).
Figure (see Caption) Figure 7. Satellite image showing a strong gray ash plume above Lewotolok on 29 November 2020, expanding roughly E and W. Courtesy of Sentinel Hub Playground and the European Space Agency, Copernicus.

The eruption continued from 29 November into 1 December, where the white-and-gray ash plumes rose 700-2,000 m above the crater and drifted SE and W, accompanied by incandescent material that was ejected above the crater and the smell of sulfur, according to PVMBG (figure 8). A large sulfur dioxide plume was reported drifting SE and extending over the N half of Australia by 30 November (figure 9). By 1300 that day, 4,628 people had been evacuated. Incandescent lava flows near the summit were visible and incandescent material traveled down the flanks during 30 November and 1 December.

Figure (see Caption) Figure 8. Webcam image of the continuous eruption at Lewotolok showing a dense gray ash plume rising above the cloud-covered summit on 30 November 2020. Courtesy of MAGMA Indonesia.
Figure (see Caption) Figure 9. SO2 plume from Lewotolok captured by the Sentinel-5P/TROPOMI instrument on 30 November 2020 drifting SE and along the N part of Australia. Courtesy of Simon Carn and the NASA Global Sulfur Dioxide Monitoring Page.

White-and-gray plumes continued frequently through January 2021, rising 100-1,500 m above the crater, drifting in multiple directions, accompanied by nighttime crater incandescence and occasional incandescent ejecta (figure 10). During 1-8 December gray plumes rose 100-1,000 m above the crater and drifted E, W, and SW accompanied by nightly crater incandescence and incandescent material ejected as high as 20 m above the crater. By 5 December at 2200 about 9,028 residents had been evacuated to 11 evacuation centers, according to BNPB. Black, gray, and brown ash plumes were visible daily during 9-15 December, rising 1 km above the crater, accompanied by nightly Strombolian explosions that ejected material above the crater. More Strombolian explosions on most nights over 16-29 December ejected material 100-300 m above the crater; in addition, the sounds of rumbling and banging could be heard. The material was deposited as far as 1 km from the crater E and SE during 24-25 and 27-31 December and 4-7 January 2021. Strombolian activity continued into January, accompanied by frequent gray-and-white ash plumes, rumbling and banging sounds, and incandescent ejecta up to 600 above the crater that extended as far as 500 m E, SE, and W. Crater incandescence was visible up to 600 m above the crater.

Figure (see Caption) Figure 10. Webcam images showing continuing dense gray ash plumes from Lewotolok on 1 December 2020 (top) and 8 January 2021 (bottom). Courtesy of MAGMA Indonesia.

A consistent level of thermal activity was recorded in the Sentinel-2 MODIS Thermal Volcanic Activity from February 2019 through October 2020; in early December 2020 a slight increase in thermal anomalies were detected (figure 11). This data reflects the start of the new eruption in late November 2020. According to the MODVOLC thermal algorithm, five thermal hotspots were detected between January 2020 and January 2021 on 3 September (1), 29 November (2), 24 December (1), and 5 January 2021 (1). Some of this thermal activity was also observed in Sentinel-2 thermal satellite imagery in the summit crater (figure 12).

Figure (see Caption) Figure 11. Sentinel-2 MODIS Thermal Volcanic Activity data (bands 12, 11, 8A) shows consistent thermal activity (red dots) at Lewotolok during February 2020 through December 2020. Stronger thermal anomalies in early December is likely due to the new eruption that began in late November 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 12. Sentinel-2 thermal satellite imagery showing a thermal anomaly in the summit crater of Lewotolok on 25 October (top left), 9 November (top right), and 3 January 2021 (bottom right). On 14 December (bottom left) a Natural Color image showed a gray ash emission above the clouds and drifted E. On 3 January 2021 (bottom right) two thermal anomalies were visible in the summit crater accompanied by gas-and-steam emissions drifting NE. Sentinel-2 satellite images with “Natural Color” rendering (bands 4, 3, 2) on 14 December 2020, all other images use “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Geologic Background. The Lewotolok (or Lewotolo) stratovolcano occupies the eastern end of an elongated peninsula extending north into the Flores Sea, connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is symmetrical when viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano's high point. Many lava flows have reached the coastline. Eruptions recorded since 1660 have consisted of explosive activity from the summit crater.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC 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://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); European Space Agency (ESA), Copernicus (URL: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Simon Carn, Dept of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931, USA (URL: https://so2.gsfc.nasa.gov/).


Soufriere St. Vincent (Saint Vincent and the Grenadines) — March 2021 Citation iconCite this Report

Soufriere St. Vincent

Saint Vincent and the Grenadines

13.33°N, 61.18°W; summit elev. 1220 m

All times are local (unless otherwise noted)


New lava dome on the SW edge of the main crater in December 2020

Soufrière St. Vincent is the northernmost stratovolcano on St. Vincent Island in the southern part of the Lesser Antilles. The NE rim of the 1.6-km-wide summit crater is cut by a crater (500 m wide and 60 m depth) that formed in 1812. Recorded eruptions date back to 1718, with notable eruptions occurring in 1812, 1902, and 1979. The eruption of 1979 was characterized by ashfall, pyroclastic flows, and lahars, in addition to a series of Vulcanian explosions during 13-26 April 1979 that destroyed the lava dome in the summit crater, which had formed during a 1971 effusive eruption (SEAN 04:04). As a result, more than 20,000 people were evacuated. Beginning around 3 May 1979 another lava dome began to form in the main crater (SEAN 04:05; Shepherd et al., 1979) that continued to grow until the end of October 1979, expanding to 850 m in diameter and 120 m high (SEAN 04:11; Cole et al., 2019).

No further eruptive activity took place until December 2020, when a new lava dome began to grow SW of the pre-existing 1979 lava dome, accompanied by increased seismicity, crater incandescence, and gas-and-steam emissions. This report reviews information through February 2021 using bulletins from the University of the West Indies Seismic Research Centre (UWI-SRC), the National Emergency Management Organisation (NEMO), and various satellite data. Soufrière St. Vincent is monitored by the SRC assisted by the Soufrière Monitoring Unit (SMU) from the Ministry of Agriculture in Kingstown. As of 2004, the monitoring network had consisted of five seismic stations, eight GPS stations, and several dry tilt sites. Seismic data are transmitted from field sites to the Belmont Observatory (9 km SSW), which is operated by the SMU (figure 4). On 1 January 2021 a new seismic station was installed at Georgetown, on 10 January one was installed in Owia, followed on 15 January by another on the upper S flank, station SSVA at the summit on 18 January, and in Fancy on 21 January. In February 2021 the USGS-USAID (US Geological Survey-US Agency for International Development), through the Volcano Disaster Assistance Program (VDAP), donated equipment to build four more seismic stations.

Figure (see Caption) Figure 4. Location map of the Belmont Observatory (yellow star) located in Rosehall, St. Vincent, 9 km SSW from the Soufrière St. Vincent summit crater (red triangle). Base map satellite imagery courtesy of Google Earth.

A spike in seismicity was recorded during June-July 2019 (figure 5), though no cause was reported. The number of events sharply declined after July but continued intermittently through November 2020. Seismicity began to increase in early November through 23 December 2020, which included 126 earthquakes described as volcano-tectonic events and rockfall signals that were captured on one reliable seismic station (SVB) located 9 km from the volcano. The maximum daily count was 11 events on 16 November. After 23 December a total of eight events were detected before seismicity briefly subsided.

Figure (see Caption) Figure 5. Daily count of volcanic earthquakes recorded at Soufrière St. Vincent during 1 January 2019 through February 2021. Increased seismicity was detected during June-July 2019 and mid-October 2020 through February 2021. An installation of station SVV on 6 January 2021 at Wallibou is annotated on this graph. Data courtesy of UWI-SRC.

Activity during December 2020. Staff members of the Soufrière Monitoring Unit (SMU) made visual observations of the crater on 16 December and reported minor changes in fumarolic activity and a small lake on the E side of the crater floor. On 27 December UWI-SRC and NEMO reported that an effusive eruption had begun, which was characterized by a new lava dome in the main crater on the SW perimeter of the 1979 dome (figures 6 and 7). A thermal hotspot in the crater was also detected that day using satellite data by NASA FIRMS. As a result, the Volcanic Alert Level (VAL) was raised to Orange (the second highest level on a four-color scale) on 29 December (figure 8). The Volcano Ready Communities Project, a collaboration between NEMO SVG and UWI Seismic Research Centre, distributed their volcano hazard map for the surrounding communities, in preparation for a potential evacuation (figure 9).

Figure (see Caption) Figure 6. Photo of the first documented observation of the new lava dome at Soufrière St. Vincent on 27 December 2020 taken from the E side of the summit. Courtesy of Melanie Grant, IG, UWI-SRC.
Figure (see Caption) Figure 7. Photo of an early observation of the new lava dome at Soufrière St. Vincent on 29 December 2020 growing WSW of the 1979 lava dome on the SW edge of the summit crater, accompanied by gas-and-steam emissions. The dome was estimated to be 60 m high on 30 December. Courtesy of Kemron Alexander (color corrected), SMU, UWI-SRC.
Figure (see Caption) Figure 8. Volcanic Hazard Alert Level System for Soufriere St. Vincent. Courtesy of UWI-SRC.
Figure (see Caption) Figure 9. Volcanic hazard map for Soufrière St. Vincent, showing different areas that are likely to experience hazardous volcanic events which would require evacuations. The hazard map is divided into four zones: Zone 1 (Red), which is a very high hazard location; Zone 2 (Orange), which is a high hazard location; Zone 3 (Yellow), which is a moderate hazard location; and Zone 4 (Green), which is a low hazard location. This poster was created prior to the current eruption as part of the Volcano Ready Communities Project, a collaboration between NEMO SVG and UWI Seismic Research Centre. Courtesy of UWI-SRC and NEMO.

Activity during January-February 2021. Observations made during a field visit on 5 January, during a helicopter overflight on 6 January, and based on 9 January drone video noted that the new dome was expanding to the W on the WSW edge of the 1979 lava dome and continued to gradually grow through February 2021 (figure 10). Growth of the 2020/21 lava dome produced small, hot rockfalls and gas-and-steam emissions that were visible from the Belmont Observatory. The gas emissions were most notable from a small depression at the top of the dome. Two seismic stations were installed on the flank of the volcano at Wallibou (SVV) and at the summit (SSVA) on 6 and 18 January, respectively.

Figure (see Caption) Figure 10. Map showing the growth of the new 2020/21 lava dome at Soufrière St. Vincent from 27 December 2020 to 12 February 2021. The dome is located on the SW edge of the crater rim and WSW of the 1979 lava dome that is covered in vegetation. Courtesy of UWI-SRC.

Seismic stations recorded 573 events through 0730 on 30 January; this number continued to grow into February (up to 703 events by 0830 on 4 February) (figure 5). Observations on 14 January showed that the dome was growing taller and expanding to the E and W. An overflight on 15 January showed extensive vegetation damage on the E, S, and W inner crater walls; damage previously noted on the upper SW crater rim had expanded downslope (figure 11). Scientists visited on 16 January and recorded temperatures of 590°C at the dome surface (figure 12). During 15-17 January residents to the W of the volcano reported nighttime crater incandescence. Persistent gas-and-steam emissions were observed rising above the dome, as well as from the contact between the 2020/21 and 1979 domes during the rest of the month and through February.

Figure (see Caption) Figure 11. Oblique aerial view of the lava dome at Soufrière St. Vincent between the 1979 dome and the SW crater rim on 15 January 2021, accompanied by gas-and-steam emissions. On this day, the dome was 340 m long, 160 m wide, and 80 m high. Courtesy of Adam Stinton, MVO, UWI-SRC.
Figure (see Caption) Figure 12. Thermal measurements were taken at the base of the freshly extruded lava dome at Soufrière St. Vincent on 16 January 2021. Top: Photo (color corrected) of the base of the new lava dome. Bottom: Thermal FLIR (Forward-Looking InfraRed) image of the base of the new lava dome showing a maximum temperature of 590.8°C. Courtesy of Adam Stinton, MVO, UWI-SRC.

Sulfur dioxide emissions were first detected on 1 February using a Multi-Gas Instrument and a filter pack; the dome had reached an estimated volume of 5.93 million cubic meters. Vegetation on the NW part of the crater (N of the dome) was damaged, likely due to fire. The dome continued to expand laterally to the N and S, according to reports issued on 6 and 8 February. After that it grew about 15 m to the NW and SE, according to 11 and 15 February reports (figure 13). NEMO reported that the growth rate of the lava dome ranged from 1.9 to 2.13 m3/s (figure 14). Active gas-and-steam emissions originated dominantly at contact areas between the pre-existing 1979 dome and the 2020/21 dome, as well as at the top of the new dome.

Figure (see Caption) Figure 13. Photo of the 2020/21 lava dome (dark mass at left) at Soufrière St. Vincent on 12 February 2021 showing continuous gas-and-steam emissions and damaged vegetation on the 1979 lava dome (right). On this day, the dome was 618 m long, 232 m wide, 90 m high, and an estimated volume of 6.83 million cubic meters. Courtesy of Kemron Alexander, SMU, UWI-SRC.
Figure (see Caption) Figure 14. Estimated lava extrusion rates and added volume of material at Soufrière St. Vincent’s 2020/21 lava dome during 27 December 2020 through 3 February 2021. Calculations were based on UAV photography and photogrammetry. Data courtesy of UWI-SRC.

Thermal satellite data. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows the beginning of thermal activity in late December 2020 and continuing at a lower power into early February (figure 15). A single MODVOLC thermal alert was detected on 29 December. This activity marks the beginning of the effusive eruption and the formation of the new lava dome. Sentinel-2 thermal satellite imagery detected a thermal anomaly on the SW side of the main crater during clear weather days in January 2021, which represents the active 2020/21 lava dome (figure 16). Fresh, hot material is also visible surrounding the thermal anomaly, which demonstrates the growth of the lava dome over time.

Figure (see Caption) Figure 15. Thermal activity at Soufrière St. Vincent was detected beginning in late December 2020 and continued through early February 2021, as reflected in the MIROVA data (Log Radiative Power). The power of the thermal anomalies had slightly decreased after December. Courtesy of MIROVA.
Figure (see Caption) Figure 16. Sentinel-2 thermal satellite imagery showing a persistent thermal anomaly (bright yellow-orange) in Soufrière St. Vincent’s growing lava dome on the WSW edge of the main crater during 3 January through 28 January 2021. The dark black color is the freshly cooled material from the effusive activity, which also demonstrates the increasing size of the lava dome. Images using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Field work during mid-January 2021. SRC collected rock samples from the new lava dome and sent them to scientists from the University of East Anglia, University of Plymouth, and University of Oxford on 16 January 2021 as a collaborative project to analyze their composition and compare them with the composition of rocks erupted in 1902, 1971, and 1979. Analyses showed that the new 2020/21 lava dome was basaltic andesite, similar in composition to the earlier domes (figure 17).

Figure (see Caption) Figure 17. Backscattered electron image of a sample from the 2020/21 lava dome showing groundmass texture. Low-contrast dark gray crystals are feldspar microlites in glass (darkest gray). Some of the larger feldspar crystals have Ca-rich cores (paler gray). Clinopyroxenes also make up the groundmass (brighter gray) and some are breaking down to Fe-oxides (small oxides at edges of clinopyroxene bottom center and bottom right). In some areas dark glass is devitrifying (paler gray irregular shapes within dark gray glassy patches). Fe-Ti oxides are also common (bright white crystals). Total image width is about 0.3 mm. Image and description courtesy of Bridie Davies, UEA.

References: Cole P D, Robertson R E A, Fedele L, Scarpati C, 2019. Explosive activity of the last 1000 years at La Soufrière, St Vincent, Lesser Antilles. J. Volcanol. Geotherm. Res., 371:86-100.

Shepherd, J. B., Aspinall, W. P., Rowley, K. C., Pereira, J., Sigurdsson, H., Fiske, R. S., Tomblin, J. F., 1979. The eruption of Soufrière volcano, St Vincent April–June 1979. Nature, 282 (5734), 24–28. doi:10.1038/282024a0.

Geologic Background. Soufrière St. Vincent is the northernmost and youngest volcano on St. Vincent Island. The NE rim of the 1.6-km wide summit crater is cut by a crater formed in 1812. The crater itself lies on the SW margin of a larger 2.2-km-wide caldera, which is breached widely to the SW as a result of slope failure. Frequent explosive eruptions after about 4,300 years ago produced pyroclastic deposits of the Yellow Tephra Formation, which cover much of the island. The first historical eruption took place in 1718; it and the 1812 eruption produced major explosions. Much of the northern end of the island was devastated by a major eruption in 1902 that coincided with the catastrophic Mont Pelée eruption on Martinique. A lava dome was emplaced in the summit crater in 1971 during a strictly effusive eruption, forming an island within a lake that filled the crater. A series of explosive eruptions in 1979 destroyed the 1971 dome and ejected the lake; a new dome was then built.

Information Contacts: University of the West Indies Seismic Research Centre (UWI-SRC), University of the West Indies, St. Augustine, Trinidad & Tobago, West Indies (URL: http://www.uwiseismic.com/); National Emergency Management Organisation (NEMO), Government of Saint Vincent and the Grenadines, Biseé, PO. Box 1517, Castries, Saint Lucia, West Indies (URL: http://nemo.gov.lc/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC 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://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Google Earth (URL: https://www.google.com/earth/); Bridie Davies, University of East Anglia, Norwich Research Park, Norwich, Norfolk, NR4 7TJ, UK (URL: https://people.uea.ac.uk/bridie_davies).


Erta Ale (Ethiopia) — February 2021 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


Brief increase in strong thermal activity during late November-early December 2020

Erta Ale, located in Ethiopia, is a highly active volcano that contains a 0.7 x 1.6 km, elliptical summit caldera with multiple pit craters that frequently host active lava lakes. Another larger 1.8 x 3.1 km wide depression SE of the summit is bounded by curvilinear fault scarps on the SE side. Recent activity has been characterized by lava flow outbreaks (BGVN 45:05) and thermal anomalies detected from pit craters in the summit caldera (BGVN 45:05 and 45:10). This report covers activity from October 2020 through February 2021 and is characterized by a brief period of strong thermal anomalies in late November, which sharply declined in December. Information primarily comes from satellite data.

Activity at Erta Ale had gradually decreased compared to previous months; thermal activity during this reporting period remained primarily in the N summit caldera. MIROVA (Middle Infrared Observation of Volcanic Activity) analysis of MODIS satellite data shows a total of four low-power thermal anomalies from October through most of November. At the end of November, a brief surge of strong thermal activity was detected in the S pit crater of the summit caldera, followed by a sharp decrease the following days (figure 102). Similarly, the MODVOLC system detected a total of eight thermal alerts; two were detected on 29 November and six were detected on 30 November, primarily focused in the summit caldera. Only two thermal anomalies were recorded in the MIROVA graph after this surge of activity; one in mid-December and one in early January. Thermal data from NASA VIIRS detected hotspots on 28-30 November, 1-3 December, and 8 December.

Figure (see Caption) Figure 102. A total of four low-power thermal anomalies were recorded at Erta Ale during October through most of November 2020. Beginning in late November into early December a strong but brief surge of thermal activity was detected according to the MIROVA system (Log Radiative Power). Only two low-power thermal anomalies were recorded after the activity in early December; one in mid-December and one in early January 2021. Courtesy of MIROVA.

According to Sentinel-2 thermal satellite images, a weak thermal anomaly was first visible on 20 October in the summit caldera. Intermittent, weak anomalies were also detected in the summit caldera on 25 and 30 October and 4, 9, 19, and 24 November. On 29 November the thermal activity increased significantly, detected as a strong hotspot in the S pit crater of the summit caldera (figure 103). This brief increase in power was also recorded in the MIROVA graph and by the MODVOLC thermal algorithm. By 4 December the size and power of this thermal activity decreased significantly, though it was still visible in the summit caldera. Thermal activity was no longer observed after 4 December until clear weather days on 2 and 12 February when a faint anomaly was detected.

Figure (see Caption) Figure 103. Sentinel-2 thermal satellite images of Erta Ale during 30 October 2020 to 12 February 2021 showing a single thermal anomaly (bright yellow-orange) in the S pit crater of the summit caldera that varies in strength. Top left: 30 October 2020 shows a faint thermal anomaly in the S pit crater. Top right: 29 November 2020 shows the strongest thermal anomaly in the S pit crater during the reporting period and is also reflected in the MIROVA graph and detected by the MODVOLC system. Bottom left: 4 December 2020 shows that the thermal anomaly from activity in late November remains hot but begins to decrease in strength. Bottom right: 12 February 2021 again shows thermal activity from the S pit but weaker than the previous November and December. Sentinel-2 images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC 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://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).


Bagana (Papua New Guinea) — January 2021 Citation iconCite this Report

Bagana

Papua New Guinea

6.137°S, 155.196°E; summit elev. 1855 m

All times are local (unless otherwise noted)


Ongoing thermal anomalies possibly indicating lava flows during May-December 2020

Bagana is a remote volcano located in central Bougainville Island in Papua New Guinea with eruptions dating back to 1842. The current eruption period began in February 2000, with more recent activity characterized by thermal anomalies along with gas-and-steam and ash plumes (BGVN 44:12 and 45:07). Typical activity consists of episodes of lava flows and intermittent strong passive degassing, especially sulfur dioxide. This report covers activity from May-December 2020 using primarily thermal data and satellite imagery.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed a cluster of intermittent low-power thermal anomalies during June through early August, followed by a period of quiescence during August to mid-October, with the exception of two anomalies detected in early September (figure 44). Thermal activity slightly increased again by mid-October and continued infrequently through December at low levels. This pattern of thermal activity is also reflected in three Sentinel-2 thermal satellite images that showed faint, roughly linear, thermal anomalies, indicative of lava flows trending NE and NW on 21 June, NE on 1 July, and W on 23 November (figure 45). On clear weather days, gas-and-steam emissions could be seen in satellite imagery on 30 August, 4 October, and 23 November, each of which drifted W (figure 45). Gas-and-steam emissions on 13 December drifted E.

Figure (see Caption) Figure 44. Intermittent low-power thermal anomalies were detected at Bagana during late May-December 2020 as recorded by the MIROVA system (Log Radiative Power). Relatively higher power and frequency anomalies were detected during June-early August. Thermal activity declined after early August into mid-October, with the exception of two thermal anomalies in early September. Activity increased again slightly by mid-October and continued through December, but at a lower power and frequency. Courtesy of MIROVA.
Figure (see Caption) Figure 45. Sentinel-2 thermal satellite imagery showing weak thermal anomalies at Bagana during June through December 2020. Top left: Faint, linear thermal anomalies on 21 June 2020 on the NE and NW flanks, which could represent lava effusion, though clouds covered much of the area. Top right: Hot material traveling down the NE flank on 1 July 2020. Middle left and right: Gas-and-steam emissions rising from the summit crater and drifting W on 30 August and 4 October 2020; very faint thermal anomalies can be observed in the crater. Bottom left: Gas-and-steam emissions in the summit crater drifted W on 23 November 2020, and a probable lava flow is visible extending down the NW flank. Bottom right: Gas-and-steam emissions rose above the summit crater on 13 December 2020 and drifted E. Sentinel-2 images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Kadovar (Papua New Guinea) — January 2021 Citation iconCite this Report

Kadovar

Papua New Guinea

3.608°S, 144.588°E; summit elev. 365 m

All times are local (unless otherwise noted)


Occasional ash and gas-and-steam plumes along with summit thermal anomalies

Kadovar is located in the Bismark Sea offshore from the mainland of Papua New Guinea about 25 km NNE from the mouth of the Sepik River. Its first confirmed eruption began in early January 2018, characterized by ash plumes and a lava extrusion that resulted in the evacuation of around 600 residents from the N side of the island (BGVN 43:03). Activity has recently consisted of intermittent ash plumes, gas-and-steam plumes, and thermal anomalies (BGVN 45:07). Similar activity continued during this reporting period of July-December 2020 using information from the Rabaul Volcano Observatory (RVO), the Darwin Volcanic Ash Advisory Center (VAAC), and various satellite data.

RVO issued an information bulletin on 15 July reporting minor eruptive activity during 1-5 July with moderate light-gray ash emissions rising a few hundred meters above the Main Crater. On 5 July activity intensified; explosions recorded at 1652 and 1815 generated a dense dark gray ash plume that rose 1 km above the crater and drifted W. Activity subsided that day, though fluctuating summit crater incandescence was visible at night. Activity increased again during 8-10 July, characterized by explosions detected on 8 July at 2045, on 9 July at 1145 and 1400, and on 10 July at 0950 and 1125, each of which produced a dark gray ash plume that rose 1 km above the crater. According to Darwin VAAC advisories issued on 10, 16, and 30 July ash plumes were observed rising to 1.5-1.8 km altitude and drifting NW.

Gas-and-steam emissions and occasional ash plumes were observed in Sentinel-2 satellite imagery on clear weather days during August through December (figure 56). Ash plumes rose to 1.2 and 1.5 km altitude on 3 and 16 August, respectively, and drifted NW, according to Darwin VAAC advisories. On 26 August an ash plume rose to 2.1 km altitude and drifted WNW before dissipating within 1-2 hours. Similar activity was reported during September-November, according to several Darwin VAAC reports; ash plumes rose to 0.9-2.1 km altitude and drifted mainly NW. VAAC notices were issued on 12 and 22 September, 4, 7-8, and 18 October, and 18 November. A single MODVOLC alert was issued on 27 November.

Figure (see Caption) Figure 56. Sentinel-2 satellite data showing a consistent gas-and-steam plume originating from the summit of Kadovar during August-December 2020 and drifting NW. On 21 September (top right) a gray plume was seen drifting several kilometers from the island to the NW. Images with “Natural color” (bands 4, 3, 2) rendering; courtesy of Sentinel Hub Playground.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows intermittent low-power anomalies during July through December 2020 (figure 57). Some of this thermal activity in the summit crater was observed in Sentinel-2 thermal satellite imagery, accompanied by gas-and-steam emissions that drifted primarily NW (figure 58).

Figure (see Caption) Figure 57. Intermittent low-power thermal anomalies at Kadovar were detected in the MIROVA graph (Log Radiative Power) during July through December 2020. The island location is mislocated in the MIROVA system by about 5.5 km SE due to older mis-registered imagery; the anomalies are all on the island. Courtesy of MIROVA.
Figure (see Caption) Figure 58. Sentinel-2 satellite data showing thermal anomalies at the summit of Kadovar on 23 July (top left), 7 August (top right), 1 September (bottom left), and 21 September (bottom right) 2020, occasionally accompanied by a gas-and-steam plume drifting dominantly NW. Two thermal anomalies were visible on the E rim of the summit crater on 23 July (top left) and 7 August (top right). Images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. It is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. Prior to an eruption that began in 2018, a lava dome formed the high point of the andesitic volcano, filling an arcuate landslide scarp open to the south; submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. A period of heightened thermal phenomena took place in 1976. An eruption began in January 2018 that included lava effusion from vents at the summit and at the E coast.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC 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://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

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Bulletin of the Global Volcanism Network - Volume 26, Number 12 (December 2001)

Managing Editor: Richard Wunderman

Atmospheric Effects (1995-2001) (Unknown)

Multi-year lidar from Hampton, VA, USA shows peaks and current low

Bezymianny (Russia)

Dark mid-December 2001 plume reaches 4 km above dome

Erta Ale (Ethiopia)

Dynamic, molten lava lake in S crater during November 2000-February 2001

Fournaise, Piton de la (France)

Erupting fissures on 5-16 January 2002 in l'Enclos Fouqué caldera

Ijen (Indonesia)

Higher-than-normal seismic activity from October 2001 through at least 6 January 2002

Kerinci (Indonesia)

Minor explosions, ash plumes, and seismicity from May 2001 through early 2002

Kilauea (United States)

Low-to-moderate tremor, surface lava flows and ocean entry through early 2002

Nyamulagira (DR Congo)

MODIS data for February 2001 eruption; no January 2002 eruption

Nyiragongo (DR Congo)

Mid-January 2002 lavas bury ~ 4.5 km2 of Goma's city center

Sheveluch (Russia)

Through January 2002, elevated seismicity, and an unstable, growing lava dome

Tofua (Tonga)

Typical fumarolic emissions continue; geologic mapping of cinder-cone complexes



Atmospheric Effects (1995-2001) (Unknown) — December 2001 Citation iconCite this Report

Atmospheric Effects (1995-2001)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Multi-year lidar from Hampton, VA, USA shows peaks and current low

Despite their infrequent recent reporting in the Bulletin, lidar measurements remain relevant when discussing the atmospheric impact of volcanic eruptions. As discussed below, following the large-scale atmospheric perturbation caused by Pinatubo, smaller atmospheric perturbations have been infrequent, but the eruption of Shishaldin in April 1999 produced aerosol layers that were detected in North America and Europe (Bulletin v. 24, no. 4).

Reports about atmospheric effects of volcanic activity were last provided as follows: Bulletin v. 26, no. 5, "Volcanic aerosol optical thicknesses derived from lunar eclipse observations;" Bulletin v. 24, no. 4, "Tracing recent ash by satellite-borne sensors and ground-based lidar;" Bulletin v. 23, no. 12, "Lidar data from Garmisch-Partenkirchen, Germany;" and Bulletin v. 23, no. 11, "Lidar data from Hampton, Virginia, USA."

NASA lidar measurements at Virginia, USA. Mary Osborn provided measurements from the 48-inch ground-based lidar system at NASA Langley Research Center (table 18) since May 1999. All measurements were taken at a wavelength of 694 nm. Their 48-inch lidar system was out of commission for ~8 months in late 1999 and early 2000, as they used some of its components to conduct the SAGE III Ozone Loss Validation Experiment (SOLVE). That campaign took place during November 1999-March 2000 based out of Kiruna, Sweden.

Table 18. Lidar data from Virginia, USA, for May 1999-December 2001 showing altitudes of aerosol layers. Backscattering ratios are for the ruby wavelength of 0.69 µm. The integrated values show total backscatter, expressed in steradians-1, integrated over 300-m intervals from the tropopause to 30 km. Courtesy of Mary Osborn.

DATE LAYER ALTITUDE (km) (peak) BACKSCATTERING RATIO BACKSCATTERING INTEGRATED
Hampton, Virginia (37.1°N, 76.3°W)
28 May 1999 15-26 (11.0) 1.14 5.28 x 10-5
24 Sep 1999 12-28 (20.3) 1.09 2.93 x 10-5
09 May 2000 16-27 (20.5) 1.08 2.65 x 10-5
08 Sep 2000 14-30 (20.5) 1.08 2.06 x 10-5
12 Oct 2000 15-28 (17.5) 1.08 2.72 x 10-5
20 Oct 2000 14-30 (17.5) 1.12 5.65 x 10-5
30 Oct 2000 12-30 (28.6) 1.12 6.31 x 10-5
27 Feb 2001 12-28 (22.1) 1.12 4.97 x 10-5
01 May 2001 15-27 (19.4) 1.09 2.26 x 10-5
24 May 2001 17-28 (21.8) 1.09 3.28 x 10-5
07 Sep 2001 15-28 (17.0) 1.11 2.88 x 10-5
04 Oct 2001 15-30 (16.9) 1.08 2.38 x 10-5
16 Oct 2001 15-30 (17.5) 1.08 2.36 x 10-5
07 Nov 2001 12-29 (18.5) 1.08 3.56 x 10-5
22 Nov 2001 13-30 (18.8) 1.10 5.01 x 10-5
04 Dec 2001 12-28 (24.8) 1.12 4.85 x 10-5

Figure 13 presents an overview of stratospheric integrated aerosol backscatter since 1974. A slight increase in stratospheric integrated backscatter occurred during late 1998-99, at least partly attributed to the Shishaldin event and several smaller eruptions. After that, the stratospheric integrated backscatter returned to the "background" aerosol loading measured in 1978-1979. Although the current level of stratospheric aerosol loading remains low, another major volcanic eruption could change the situation quite suddenly.

Figure with caption Figure 13. A plot of the 48-inch lidar data versus time showing the stratospheric integrated aerosol backscatter measured since 1974. Important volcanic eruptions that may have led to increased northern mid-latitude aerosol loading are noted on the time axis. Courtesy of Mary Osborn.

Geologic Background. The enormous aerosol cloud from the March-April 1982 eruption of Mexico''s El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin thorugh 1989. Lidar data and other atmospheric observations were again published intermittently between 1995 and 2001; those reports are included here.

Information Contacts: Mary Osborn, NASA Langley Research Center (LaRC), MS 475, Hampton, VA 23681, USA.


Bezymianny (Russia) — December 2001 Citation iconCite this Report

Bezymianny

Russia

55.972°N, 160.595°E; summit elev. 2882 m

All times are local (unless otherwise noted)


Dark mid-December 2001 plume reaches 4 km above dome

During September 2001 through early January 2002, seismicity at Bezymianny remained at or near background levels, although one mid-December outburst was striking. Weak fumarolic activity was observed on 15, 18, and 20 September, on 8, 12, 27, and 29 October, on 1 November, and during 1-2, 6, and 8-10 January. Weak shallow earthquakes were registered under the volcano beginning on 10 November. The earthquakes became stronger beginning on 22 November, but seismicity remained near background levels. Gas-and-steam plumes were observed throughout the report period reaching 50-800 m above the dome and extending up to 60 km from the volcano.

On 16 December, a plume reached 4 km above the dome and extended 60 km NW. The plume appeared dark from 20 km away. Plumes on 8-10 January extended 5-20 km S and NW. On 10 and 12-13 December, gas-and-steam plumes rose to 300 m above the volcano and extended 40 km W, SW, and SE.

Thermal anomalies were observed on satellite imagery several times during December 2001 and early January 2002 (table 1). On 10 December, a four-pixel thermal anomaly was visible, along with a faint, ash-poor plume that extended 87 km SE from the volcano.

Table 1. Thermal anomalies visible on satellite imagery at Bezymianny during December 2001 through 6 January 2002. The anomaly was centered over the dome on 12-13 December 2001. Courtesy KVERT.

Date Local Time Pixels Recovery pixels Maximum band-3 temperature Background temperature
10 Dec 2001 0617 4 -- 10.3°C -29°C
12 Dec 2001 1658 4 2-3 ~49°C -27 to -28°C
13 Dec 2001 0644 4 2-3 ~49°C -27 to -28°C
13 Dec 2001 1635 10 -- 33.8°C -14°C
14 Dec 2001 0622 10 2 48.2°C -22°C
14 Dec 2001 1611 14 -- 49.5°C -13°C
15 Dec 2001 0559 5 1 48.5°C -36°C
21 Dec 2001 0446 1 -- 9.8°C -28.3°C
21 Dec 2001 1834 1 -- -3.44°C -30°C
22 Dec 2001 1810 1 -- -14.03°C -30°C
25 Dec 2001 morning 1 -- -8°C -30°C
31 Dec 2001 0621 1 -- -14°C -26°C
01 Jan 2002 1703 1 -- -7.3°C -24°C
06 Jan 2002 1707 1 -- -6°C -23°C

The Concern Color Code was raised from Green ("volcano is dormant" ) to Yellow ("volcano is restless"). Activity increased during 14-21 December, when many weak shallow earthquakes occurred within the edifice and other local shallow seismic events (possible avalanches) were registered. The Concern Color Code was increased to Orange ("eruption may occur at any time") until around 25 December, when seismicity decreased again. The Concern Color Code was reduced to Green by the end of 2001 and remained there through at least 25 January.

Geologic Background. Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Information Contacts: Olga Chubarova, Kamchatka Volcanic Eruptions Response Team (KVERT) (URL: http://www.kscnet.ru/ivs/kvert/); Tom Miller, Alaska Volcano Observatory (AVO) (URL: https://www.avo.alaska.edu/); Tokyo Volcanic Ash Advisory Center, Tokyo, Japan (URL: https://ds.data.jma.go.jp/svd/vaac/data/).


Erta Ale (Ethiopia) — December 2001 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


Dynamic, molten lava lake in S crater during November 2000-February 2001

The Afar National Regional State has approved a program to grant access to Erta Ale volcano by either land or air transportation. The program, which will precede the formation of a "National Park of Volcanoes," enables visitation by natural science field workers. It also allows for traditional mining and salt transportation by caravans and seeks to protect the traditional life of the region's inhabitants.

Observations during 14 November 2000. Luigi Cantamessa (Géo-Découverte), accompanied by government representatives, visited the N part of the elliptical summit caldera (figure 7) on 14 November 2000. Little had changed since last described in December 1995 (BGVN 20:11/12), but continued collapse of the N crater wall was noted. Dense smoke came from the S rim of the crater, with a very strong smell of sulfur, as in the past. GPS measurements of elevation indicated that the E wall of the N crater was ~600 m high and the N rim, the highest point of the volcano, was ~15 m higher.

Figure (see Caption) Figure 7. Aerial photograph showing the N part of the Erta Ale caldera. In this view looking generally W, the inactive northern crater (with fumarolic emissions) is on the right and the southern crater with an active lava lake is on the left. Courtesy of L. Cantamessa, Géo-Découverte.

The S crater (figure 8), in the central part of the caldera, contained a molten lava lake and had undergone some changes since the 1995 visit. A portion (1-2 m thick) of the NE wall had collapsed. The level of the lava lake, still in the W part of the crater, showed significant variations. The terraces on the E side of the crater appear to have been swamped by lava, after which the lake level apparently receded. The present level appeared to be lower than in 1995. A terrace of 2-3 m width now surrounds the lake at the foot of the crater walls. Intense activity was observed at the lake's surface. There were rapid movements of the surface from S to N. Many lava fountains reached ~10-15 m high.

Figure (see Caption) Figure 8. Aerial photograph looking down into the southern crater of Erta Ale. The crater is about 145 m in diameter, with an active lava lake. Courtesy of L. Cantamessa, Géo-Découverte.

Observations during 29-30 January 2001. An expedition sponsored by Aventure et Volcansmade crater observations for 48 hours during 29-30 January 2001. Because of the extremely dry and hot climate that prevails in this region, smoke or vapor rarely obscured visual observations. The N crater exhibited only fumarolic activity, but due to thick fumes from its southern portion, gas masks were necessary for those who climbed into the crater.

The S crater was determined to be ~170 x 130 m, with the active lava lake (figure 9) on the W side having a diameter of ~121 m. The lava lake was located, based on GPS measurements, at 13° 36' 11" N, 40° 39' 49" E. Cyclic activity, approximately every 4 hours, consisted of the thin, dark crust on the lake surface splitting and causing a "fantastic" bubbling of the liquid lava across the entire ~12,000 m2 of the lake surface. Vigorous degassing created lava fountains 10-20 m high. Several times local collapses were seen which mainly affected the vertical walls in the SE part of the crater. The level of the lava lake remained stable.

Figure (see Caption) Figure 9. Evening photograph showing the active lava lake in the southern crater of Erta Ale during 29-30 January 2001. Molten lava can be seen around the edges and through fractures in the cooled surface of the lake. Courtesy of Guy de Saint-Cyr, Aventure et Volcans.

Observations during 13-18 February 2001. Between 13 and 18 February 2001 two groups from the Société de Volcanologie (SVG), in an expedition organized by Géo-Découverte, reached the volcano by land and by helicopter (3 days later). The principal topographic elements in the N part of the caldera were the subject of GPS and telemetric measurements. The active S crater contained an elliptical lake (80 x 100 m) with a surface level 80 m below the rim and lava fountains rising 5-10 m high.

The relative absence of gas in the active crater allowed excellent observations. Over a period of 14 hours, Yves Bessard and Alain de Chambrier recorded details of the activity occurring at the lava lake, including lake movements and lava fountains. The surface of the lake was renewed approximately every 10 minutes. A continuous video recording over a period of 77 minutes was also taken from the edge of the lava lake at the bottom of the crater.

Systematic measurements of fumarole temperatures were made, primarily on the edge of the N crater and the external N edge of the caldera; values ranged from 60°C to more than 260°C at the strongly active N-crater fumaroles.

The last previous thermal measurements at Erta Ale were carried out in the 1970s by a team led by Haroun Tazieff; the most recent temperatures reported in the literature were obtained from infra-red satellite data (work mainly carried out by Oppenheimer, Francis, and Rothery). The thermal measurements collected by Marc Caillet, Steven Haefeli, and Pierre-Yves Burgi during 13-15 February 2001 are summarized below; more details on this fieldwork will be published in a journal paper.

The SVG team used a pyrometer, which works by remotely measuring the infrared radiations emitted by the lava, for the temperature measurements. Temperature calculations need an emissivity factor, the determination of which required an approach to the lava lake. For the temperature measurement of the crust, the only accessible part of the lake, the following protocol was followed. Using a steel wire, a steel sheet of 18 x 18 cm (8 mm thickness) containing a hole in which the thermocouple was inserted was deposited on the crust of the lake. Because of the distance separating the terrace from the lake (estimated at 15 m), this required the coordination of three people (Marc Caillet, Steven Haefeli, and Pierre-Yves Burgi). Caillet, standing where the ambient temperature reached 300°C, was equipped with a reflective cloth and used a large 8-m steel pole to move the thermocouple away from the wall.

Once the steel sheet was in contact with the lake's crust, temperature measurements were carried out every 30 seconds for 10 minutes, then each minute during the next 20 minutes, until the temperature stabilized. The temperature recorded at this time was 350°C. A pyrometric measurement in the same area of the thermocouple indicated a temperature of 342°C (with an emissivity index set to 0.9 on the pyrometer). By combining the temperatures obtained with the thermocouple and the pyrometer, and knowing the wavelength used by the pyrometer, an emissivity factor of 0.74 was determined. By collecting a sample of basalt, it was possible to confirm this value by the use of a furnace.

Acquisition of temperatures at various lake locations was carried out by pyrometry. Continuous pyrometric measurements were taken over periods of several tens of minutes (with a measurement each second) and were collected on a portable computer. The crust, many faults, and lava fountains were the three types of areas considered. These measurements were made from the edge of the pit and from the lower terrace. The measurements made near the lake were of primary importance because both the absorption of radiation by magmatic gases between the source and the observer and the enlarging of the pyrometer field of view with distance are two factors which tend to distort measurements. A difference of about 25°C was observed between the maxima measured from the edge and the bottom of the pit. In addition, the temperature measurements were taken at night in order to avoid any pollution due to the solar radiation (which can distort values up to 90%). The highest recorded temperature, 1,217°C, was found in a lava fountain. The temperature of the crust of the lake was very variable, 290°C near the cliffs to 520°C in the center of the lake, with an average of 474°C.

Geologic Background. Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Information Contacts: Luigi Cantamessa, Geó-Découverte, 12-14 rue de Cendrier, CH-1201 Geneva, Switzerland (URL: http://geo-decouverte.ch/); Annie Buard, Christophe Toussaint, Jean Claude Boissonnet, Philippe Roy, and Guy de Saint-Cyr, Aventure et Volcans, 73 cours de la Liberté, 69003 Lyon, France; P. Vetsch, Marc Caillet, Steven Haefeli, and Pierre-Yves Burgi, Société de Volcanologie (SVG), PO Box 6423, CH-1211 Geneva 6, Switzerland (URL: http://www.volcan.ch/).


Piton de la Fournaise (France) — December 2001 Citation iconCite this Report

Piton de la Fournaise

France

21.244°S, 55.708°E; summit elev. 2632 m

All times are local (unless otherwise noted)


Erupting fissures on 5-16 January 2002 in l'Enclos Fouqué caldera

An eruption began on 5 January 2002 and continued until 16 January. The eruption, which sent lava to the sea, followed several months of increased seismicity. The most recent previous eruption occurred during 11 June-7 July 2001 (BGVN 26:07).

Seismicity during October 2001-January 2002. During 3-9 October the Observatoire Volcanologique du Piton de la Fournaise (OVPDLF) reported that, beginning in early September, seismicity increased to ~10 events per day. Seismic activity further increased during early October, with up to 40 daily earthquakes. In the first half of October an average of 16 earthquakes per day occurred; in the second half the daily average increased to 26 events. On 5 November seismometers registered 129 earthquakes, an anomalously large number. Their hypocenters plotted at 0.62 km under the N edge of Bory Crater. In November, ~30-50 earthquakes occurred per day.

During late September through mid-October, the volcano was at Alert Level 1, and significant tilt variations were detected S of Dolomieu Crater. These events occurred simultaneously with the widening of fissures at two extensometer stations on the N and S flanks, suggesting slight summit inflation. The extensometer variations were ~3-4 times smaller than those during previous eruptions. Seismicity disappeared until the end of December, but increased again during 26-30 December when the daily earthquake counts were 17, 49, 62, and 70.

On 26 January 2002 a total of 17 earthquakes occurred, including two M 1.8 events. The earthquakes were mostly located 0.5-1.5 km below sea level, and their epicenters were beneath the N edge of Bory to Dolomieu craters. Extensometers at Magne and Chateau Fort continued to reveal slow opening of cracks, reaching 0.27 mm on 27 January.

On that same day 49 earthquakes were recorded, including events of M 2.2, 2.0, and 1.8. On 28 December during 0400-1000 a total of 48 earthquakes registered. The extensometers at Magnes and Château Fort continued to show a slow opening of the cracks. The tiltmeters, which had remained stable since the beginning of December, showed a resumption of inflation. On 29 January seismometers recorded 62 earthquakes, including an M 2.3 event. On 30 January a total of 70 earthquakes included M 2.2 and 2.0 events. Opening of the cracks at Magnes and Chateau Fort continued to progress and reached 0.28 mm.

New eruption during 5-16 January 2002. An eruption began at 2300 on 5 January and ended at 1615 on 16 January. On 5 January fire fountaining occurred and lava flowed from four cracks that opened in the NE part of l'Enclos Fouqué caldera and continued towards the foot of the Nez Coupé de Sainte Rose, a feature located on the E side of the active field of lava flows (see map showing the location of previous fissures there in BGVN 23:09). By 6 January only two cracks remained active and lava flows reached ~1,100 m elevation on the projecting ledge of the Plaine des Osmondes.

On 6 January at 2100 the eruption was visible from Piton Sainte Rose and from the National Road RN2. During 7-9 January, the eruption continued but tremor progressively decreased. On 9 January the tremor was half that of the previous day and almost no fire-fountaining was visible. Other seismicity persisted, although on 7 January only four low-magnitude earthquakes were detected. By 8 January the reading on the Château Fort extensometer had decreased only slightly since the eruption began. Readings at the Magnes extensometer continued to increase slightly.

A field excursion around this time found no further incandescent lava visibly flowing at distance from the vent areas. Observers noted that the initial flow did not extend beyond the Plaine des Osmondes. On the other hand, the interior of the eruption cone was still hot, strong degassing was audible, and small, nearly continuous projections of molten material took place, although the emitted volume was negligible.

Tremor decreased during 7-11 January. As few as 8 small shallow earthquakes were recorded per day. On 12 January tremor started to increase almost continually in comparison to the previous day, and numerous earthquakes were recorded ~4 km beneath the Plaine des Osmondes, near the N caldera wall.

During the evening of 12 January, a new fissure opened at the base of the rampart in the lower part of the Plaine des Osmondes. Lava flowed from a lava tunnel down into the Grand Brûlé close to the northern rampart. On 14 January lava flowed across the highway on its way to the ocean, entering it at 1540. By 15 January tremor was stable and 160 earthquakes were recorded over a 24-hour period on the N side of the volcano. At 0600 a swarm of low-frequency earthquakes was recorded in the NE rift zone.

After 12 days of lava emission and associated tremor, the eruption ended on 16 January, marked by a sudden, large decrease in lava emission at 1610 and the termination of tremor at 1910. After the eruption ended a large number of long-period earthquakes were recorded below the summit and the Plaine des Osmondes, indicating the continued presence of magma beneath the NE rift zone. The total lava volume emitted was estimated to be 10-15 x 106 m3.

Geologic Background. The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise (OVPDLF), 14 RN3, le 27Km, 97418 La Plaine des Cafres, La Réunion, France.


Ijen (Indonesia) — December 2001 Citation iconCite this Report

Ijen

Indonesia

8.058°S, 114.242°E; summit elev. 2769 m

All times are local (unless otherwise noted)


Higher-than-normal seismic activity from October 2001 through at least 6 January 2002

During 1 October 2001 through at least 6 January 2002, activity at Ijen was higher than normal, though low visibility often restricted visual observation of the summit. Activity included heightened continuous tremor, shallow volcanic (B-type) earthquakes, and one small explosion earthquake (table 2). No deep volcanic (A-type) earthquakes were reported.

Table 2. Summary of seismicity at Ijen during 1 October 2001- 6 January 2002. The left-hand column shows time intervals; the other columns indicate the number of earthquakes or maximum tremor amplitudes seen during the time intervals. Courtesy of the Volcanological Survey of Indonesia (VSI).

Date Shallow volcanic earthquakes (B-type) Small explosion earthquakes Tectonic earthquakes Continuous tremor (max. amp.)
01 Oct-07 Oct 2001 10 -- 1 0.5-6 mm
15 Oct-21 Oct 2001 4 -- 2 0.5-3 mm
22 Oct-28 Oct 2001 5 -- 7 0.5-5 mm
29 Oct-04 Nov 2001 6 -- -- 0.5-6 mm
05 Nov-11 Nov 2001 2 -- 2 0.5-2 mm
12 Nov-18 Nov 2001 1 1 1 0.5-4 mm
19 Nov-25 Nov 2001 4 -- -- 0.5-5 mm
26 Nov-02 Dec 2001 3 -- -- 0.5-6 mm
03 Dec-09 Dec 2001 3 -- -- 0.5-3 mm
17 Dec-30 Dec 2001 5 -- 3 0.5-4 mm
31 Dec-06 Jan 2002 3 -- 1 0.5-4 mm

During 1-7 October a thin, white, low-pressure plume was observed reaching ~50-100 m above the summit. Ijen volcano remained at Alert Level 2 (on a scale of 1-4) through at least 6 January 2002.

Geologic Background. The Ijen volcano complex at the eastern end of Java consists of a group of small stratovolcanoes constructed within the large 20-km-wide Ijen (Kendeng) caldera. The north caldera wall forms a prominent arcuate ridge, but elsewhere the caldera rim is buried by post-caldera volcanoes, including Gunung Merapi, which forms the high point of the complex. Immediately west of the Gunung Merapi stratovolcano is the historically active Kawah Ijen crater, which contains a nearly 1-km-wide, turquoise-colored, acid lake. Picturesque Kawah Ijen is the world's largest highly acidic lake and is the site of a labor-intensive sulfur mining operation in which sulfur-laden baskets are hand-carried from the crater floor. Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of cones forms an E-W zone across the southern side of the caldera. Coffee plantations cover much of the caldera floor, and tourists are drawn to its waterfalls, hot springs, and volcanic scenery.

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


Kerinci (Indonesia) — December 2001 Citation iconCite this Report

Kerinci

Indonesia

1.697°S, 101.264°E; summit elev. 3800 m

All times are local (unless otherwise noted)


Minor explosions, ash plumes, and seismicity from May 2001 through early 2002

During May 2001 through at least early January 2002, seismic activity at Kerinci was dominated by small explosion earthquakes. Plumes were visible above the summit and generally drifted E throughout most of the report period (table 1). Minor explosions occurred and on 9 August an explosion was accompanied by a booming sound heard by people working in rice fields around the volcano. At 0925 the same day a brown, high-pressure plume was observed reaching 700 m above the summit. The plume was visible drifting NNE for ~5 minutes.

Table 1. Seismicity at Kerinci during 7 May 2001 through 6 January 2002. The left-hand column shows time intervals; the adjacent four columns indicate the number of earthquakes or maximum tremor amplitudes seen during the time intervals; the right-hand column adds comments about plume heights. Courtesy VSI.

Date Deep volcanic Shallow volcanic Small explosion Tectonic Plume color and height
07 May-13 May 2001 1 1 436 4 White-thick; 800 m
14 May-20 May 2001 2 3 973 6 --
28 May-03 Jun 2001 -- 7 47 12 Gray; 100-800 m
04 Jun-10 Jun 2001 4 -- 24 7 Gray; 100-300 m
11 Jun-17 Jun 2001 -- 4 continuous 6 Gray; 100-500 m
18 Jun-24 Jun 2001 2 1 continuous 9 Gray; 100-1000 m
25 Jun-01 Jul 2001 1 3 continuous 10 White; 500 m
02 Jul-08 Jul 2001 -- -- 360 10 --
30 Jul-12 Aug 2001 6 6 990 16 Brown; 700 m
13 Aug-26 Aug 2001 1 6 2252 10 White-brown; 500 m
27 Aug-02 Sep 2001 1 2 971 9 Gray; 400 m
03 Sep-09 Sep 2001 1 1 1128 9 Gray; 500 m
10 Sep-16 Sep 2001 5 6 2281 5 Gray; 600 m
17 Sep-23 Sep 2001 3 4 920 6 Gray; 300 m
24 Sep-30 Sep 2001 2 6 1162 6 White-thick; 500 m
01 Oct-07 Oct 2001 2 1 1187 3 White-thick; 400 m
08 Oct-14 Oct 2001 -- 6 219 7 White-thick; 700 m
15 Oct-21 Oct 2001 1 1 continuous 7 White-thick; 700 m
22 Oct-28 Oct 2001 1 11 continuous 4 White-thick; 300 m
29 Oct-04 Nov 2001 4 6 continuous 3 White-thick; 400 m
05 Nov-11 Nov 2001 1 2 310 3 White-thick; 50-300 m
12 Nov-18 Nov 2001 1 3 329 9 White-thick; 50-300 m
19 Nov-25 Nov 2001 3 1 continuous 4 White-thick; 50-500 m
26 Nov-02 Dec 2001 1 -- 664 3 White-thick; 50-300 m
03 Dec-09 Dec 2001 -- -- 736 10 50-400 m
17 Dec-30 Dec 2001 6 4 continuous 9 Gray; 100-800 m
30 Dec-06 Jan 2002 1 -- 341 13 White; 50-100 m

Eruptive activity stopped briefly during mid-August. During 0800-1200 on 9 September, explosive activity produced a brown ash plume that rose 500 m above the summit. Gas pressure was low in early November and seismic activity decreased slightly. The volcano remained at Alert Level 2 (on a scale of 1-4) throughout the report period.

Geologic Background. Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

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


Kilauea (United States) — December 2001 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Low-to-moderate tremor, surface lava flows and ocean entry through early 2002

During September 2001 through at least early 2002, minor seismic events occurred and tremor remained low to moderate at Kilauea's summit and at Pu`u `O`o. Tiltmeters across the volcano showed some deformation, which is normal for Kilauea. A significant tilt event occurred on 9 December, but was not accompanied by unusual seismicity or change in eruptive activity. A survey of vertical and horizontal movement concluded that during 2001 Kilauea's summit continued to subside at a maximum rate of 7cm/year as magma moved from the summit reservoir to the Pu`u `O`o vent; the S flank moved seaward at a maximum rate of 7cm/year. Lava broke out of the tube system and continued to flow down the Paluma Pali slope, resulting in bench growth at the new Kamoamoa ocean entry.

Geophysical activity. Small deflation events occurred at Kilauea's summit on 12, 13, and 28 September, a large decrease followed by tremor on 17 October. By 21 October tremor at Pu`u `O`o became rather continuous; however, short bursts of higher amplitude tremor returned by 24 October. During 1-8 November weak, long-period earthquakes occurred frequently at the summit. On 8 December rapid deflation (~2.4 µrad) took place at Kilauea's summit, followed shortly thereafter by deflation (~1.9 µrad) at Pu`u `O`o cone. On 9 December abrupt inflation (6 µrad) at Kilauea's summit was followed by much weaker inflation at Pu`u `O`o. Strong earthquakes and tremor accompanied the inflation. A shallow M 3.4 earthquake was registered beneath the SE corner of the caldera. The end of summit inflation and beginning of deflation were notably abrupt. By 10 December, seismicity had returned to normal levels at the summit and tremor at Pu`u `O`o remained moderate.

On 1 January during 1200-2300, deflation occurred at Kilauea's summit (~2.3 µrad), followed shortly thereafter by deflation (~2.5 µrad) at Pu`u `O`o cone. On 3 January during 1210-1950, inflation (~1.6 µrad) was again recorded at Kilauea's summit. A small deflation followed on 11 January.

Through mid-January numerous small, long-period earthquakes with bursts of tremor registered at Kilauea's summit and tilt across the volcano showed no significant deformation.

Lava flow. On 6 September a surface lava flow broke out in the E part of the flow field at an elevation of ~ 600 m on the Pulama Pali slope. The lava followed the route of the E tube from the top to the base of the slope, across the coastal flat and into the ocean at the E Kupapa`u ocean entry. On 13 September two surface flows were active along the W tube system of the Pulama Pali slope. During 28-29 September, a lava flow located W of the active flow field began to enter the ocean at a new area S of an old Kamoamoa camping area. The new W flow developed a tube system by 30 September that could reroute lava from East Kupapa'u to the Kamoamoa entry.

Throughout October lava broke out of the Kamoamoa tube system and flowed on the surface along the entire Puluma Pali slope. Flows increased along the main tube and E Kupapa'u. Around 13 November the Kamoamoa flow was confined to the tube system with at least five points of sea entry. Through the end of November, lava was mostly confined to the tube systems with a few surface flows that broke out of the tubes and produced patches of incandescence.

During December, surface flows and breakouts occurred along all tube systems from just below Pu`u `O`o to the coast. On 10 December, major breakouts were in progress just below Pu`u `O`o. On 18 December two parallel flows moved down Pulama Pali, both along the track of the Kamoamoa tube. The flows, which were sluggish and more than half crusted over, broke out from the tube in the upper half of the slope and descended to the lower third before becoming entirely crusted over. On 20 December a 3-m tall hornito formed at an elevation of ~700 m from a break in the roof of the main lava tube (figure 153).

Figure (see Caption) Figure 153. On 20 December at Kilauea a 3-m tall hornito formed at an elevation of ~ 700 m from a break in the roof of the main lava tube. Incandescence was observed at the base of the hornito. Courtesy HVO.

During early January 2002, surface lava flows were visible on Pulama Pali coming from the Kamoamoa lava tube system. A surface flow reached 1.5-2 km down the upper portion of the flow field above the Pulama Pali slope.

Ocean entry. Through most of September lava generally continued to flow down the Pulama Pali slope, across the coastal flat, and into the ocean at the E Kupapa'u ocean entry. The ocean entry tube and the W tube carried lava that broke out on the coastal flat, and the E Kupapa'u bench remained active. Field mapping on 18 September revealed that the relatively larger W flow was within ~ 625 m of the coastline about 1.8 km W of the entry location at East Kupapa`u. Lava flows located W of the active flow field began to enter the ocean at a new area on 28-29 September. By 30 September a new lava bench and an adjacent black sand beach began to form. The new entry, fed by the W flow, was located 500-600 m seaward of the old site of Kamoamoa, 3.7 km from Chain of Craters road.

By 2 October the Kamoamoa bench had widened ten's of meters. The E bench was no longer active and showed signs of rapid erosion under heavy surf. The W bench extended 70 m farther W, reaching a length of about 190 m parallel to the shoreline and extending 60-70 m out from the old sea cliff. The feeding tube, called the Kamoamoa tube, remained small, with supply estimated to be about 15% of the total flux coming from Pu`u `O`o. By mid-October, lava continued to enter the ocean at both E Kupapa'u entries.

On 14 October surf erosion was gradually claiming the eastern part of the bench. Several small-to-moderate littoral explosions were observed at the point where lava entered the sea. By 28 October activity had decreased at the Kamoamoa entry and its bench reached 120 m from the old sea cliff. Surface flow had ended and all lava reached the bench through tubes. On 31 October a new entry point was observed roughly midway between E Kupapa'u and Kamoamoa.

Lava continued to flow into the sea at the Kamoamoa, Kupapa'u, and E Kupapa'u entries through November and December. By 18 November the Kupapa'u entry was inactive, and by 5 December much of the Kupapa'u bench had fallen into the ocean. By 20 December, the Kamoamoa bench was 360 m long, 130 m wide, and was littered with blocks and black sand.

During early January 2002, lava flowed into the ocean at the Kamoamoa entry from multiple locations, mostly at the tip of the bench and especially in the western third or quarter of the bench. The amount of lava entering the ocean at the E Kupapa'u entry was very small.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/).


Nyamulagira (DR Congo) — December 2001 Citation iconCite this Report

Nyamulagira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


MODIS data for February 2001 eruption; no January 2002 eruption

The eruption that began on 6 February 2001 (BGVN 26:03) continued through at least early April. An update from the Goma Volcanological Observatory since our last report stated that the February eruption was preceded by swarm of low-frequency earthquakes that began on 16 December 2000. The eruption started from the summit caldera of Nyamuragira and formed four cones: two on the N flank, one on the S flank, and one inside the caldera. The two main cones were symmetrical and located on the N (Amani) and S (Tumayhini) flanks, along the fissure connecting Nyamuragira and Nyiragongo. Lava flows extended up to 15 km from the two main cones. Ash fell up to 20 km away, damaging farmland and causing health problems.

The Hawaii Institute of Geophysics and Planetology at the School of Ocean and Earth Science Technology (HIGP/SOEST) tracked the eruption using MODIS (Moderate Resolution Imaging Spectroradiometer) global hot-spot data. No hot spots were seen at Nyamuragira until 7 February 2001. Figures 19 and 20 show examples of the hot spot maps for Nyamuragira during 7-12 February.

Figure (see Caption) Figure 19. On 7 February 2001 at Nyamuragira the first-detected hot spot, a ~ 7 x 5 km anomaly, was seen on MODIS satellite imagery on the N flank of the volcano centered 7-10 km due N of the summit. The rectangle indicates the area shown in the following figure. Courtesy HIGP/SOEST.
Figure (see Caption) Figure 20. MODIS satellite imagery over Nyamuragira and vicinity revealed a series of hot-spot anomalies on 8, 11, and 12 February 2001. Compared to the anomaly seen on the previous day, on the 8th, the similarly situated N flank anomaly had increased in size. In addition, a second anomaly (~ 13 x 6 km) was conspicuous just SSE of the summit. On 11and 12 February the two anomalies remained similar to each other and to those on the 8 February image, though the anomalies become less circular than those of the 7 and 8 February images. The 11-12 February images contained a N-flank anomaly that trended NNE for ~ 22 km and the S-flank anomaly trended E for ~ 17 km. Courtesy HIGP/SOEST.

As of 10 March, no lava fountains were observed and all flows had stopped. Only very dense "smoke" was observed coming from the cones. Unlike previous eruptions at Nyamuragira, no significant high-frequency earthquakes were observed; these usually signal the end of the eruption.

After 15 March through at least July 2001, the same seismic patterns that preceded the February eruption were observed. During the end of June, the Goma Volcanological Observatory reported that the magnitude of the low-frequency earthquakes and the amplitude of volcanic tremor had increased significantly. Scientists believed this increased activity could signal a large eruption sometime in the near future. The high seismic activity could also be related to regeneration of the Nyamuragira lava lake or to activity of the Nyiragongo lava lake.

False eruption report, January 2002. Rumors of a new eruption at Nyamuragira circulated soon after a 17 January eruption at Nyiragongo (see this Bulletin). Ash was allegedly ejected from the N flank of Nyamuragira on 22 January, but the reports could not be confirmed because of poor visibility. According to the United Nations Office for the Coordination of Humanitarian Affairs (OCHA), volcanologists determined that ash observed in Goma on 22 January originated from the collapse of Nyiragongo's inner crater and not from a new eruption at Nyamuragira.

Geologic Background. Africa's most active volcano, Nyamulagira (also known as Nyamuragira), is a massive high-potassium basaltic shield about 25 km N of Lake Kivu and 15 km NE of the steep-sided Nyiragongo volcano. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Documented eruptions have occurred within the summit caldera, as well as from the numerous flank fissures and cinder cones. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Recent lava flows extend down the flanks more than 30 km from the summit as far as Lake Kivu; extensive lava flows from this volcano have covered 1,500 km2 of the western branch of the East African Rift.

Information Contacts: Dieudonné Wafula, Observatore Volcanologie de Goma (RDC-E), Goma, Democratic Republic of Congo; Andy Harris, Eric Pilger and Luke Flynn, Hawaii Institute of Geophysics and Planetology at the School of Ocean and Earth Science Technology (HIGP/SOEST), University of Hawaii, 2525 Correa Road, Honolulu, HI 96822; United Nations Office for the Coordination of Humanitarian Affairs (OCHA), United Nations, New York, NY 10017 USA (URL: https://reliefweb.int/).


Nyiragongo (DR Congo) — December 2001 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Mid-January 2002 lavas bury ~ 4.5 km2 of Goma's city center

An eruption began at Nyiragongo on 17 January 2002 with some lava flows and possibly their feeding fissure vents entering the city of Goma (~18 km S of the volcano, population ~400,000) in the Democratic Republic of Congo (DRC) and threatening refugee camps (figure 10). Encroaching lava spurred massive evacuations of the city. A great deal of conflicting information exists concerning the numbers of people killed or displaced, the amount of property destroyed, the specific paths of the lava flows, etc.

Figure (see Caption) Figure 10. Sketch map showing the location of Nyiragongo and other nearby volcanoes. The boundary between the Democratic Republic of Congo (NW) and Rwanda (SE) is shown as a yellow line; roads are red, and the national park boundary is black. National park areas are lighter shades of green (in DR Congo) and blue (in Rwanda). Modified from a base map courtesy of Wheeling Jesuit University/ NASA Classroom of the Future.

The following is taken primarily from reports by the United Nations Office for the Coordination of Humanitarian Affairs (OCHA), the U.S. Agency for International Development - Office of U.S. Foreign Disaster Assistance (USAID/OFDA), and the aid organization Oxfam International.

Numerous dramatic press reports showed multiple lava flows engulfing Goma; city streets became paths for rough-surfaced lava flows, and numerous buildings collapsed, burned, or both. In the end, one of the flows passed completely through Goma to enter Lake Kivu and proceeded to build a lava delta. The lava flows damaged or destroyed agricultural areas around Goma, covered the N part of the runway at the airport, and cut off access to parts of the town. Lava flows destroyed both residential and business districts as well as a cathedral.

Authorities in Goma reported that more than 150,000 people remained there during the peak of the lava flow activity. A report from the UN and USAID/OFDA on 23 January estimated that 147 people were killed because of lava flows and seismically induced building collapses. According to Oxfam International, ~60,000 people lost their homes.

The UN report stated that up to ~250,000 people were displaced as a result of the eruption. These and possibly other displaced people were concentrated in the following places: Goma, DRC (62,500); Sake, DRC (5,000); Rutshuru, DRC (5,000); in camps along the eastern DRC frontier near Gisenyi, Rwanda (6,000-10,000); in Ruhengeri, Rwanda (4,000); in Bukavu, DRC (15,000); in surrounding areas (30,000), in six sites near the NW shore of Lake Kivu (up to 60,000) and in area villages (60,000).

17-21 January 2002 eruption. The start time of the 17 January eruption is uncertain. According to Agence France-Presse, Nyiragongo began to erupt at about 0500. USAID/OFDA reported that the eruption began at about 0930. Most reports stated that three lava flows moved down the E, W, and S flanks. During a 17 January phone conversation with BGVN editors, Richard McDonald, a missionary in the Congo region, noted that his sources had suggested that lava flows traveled to the E, N, and S. Two flows traveled directly S through Goma and divided the city in three. One of these flows continued into Lake Kivu.

MODIS (Moderate Resolution Imaging Spectroradiometer) images from 17 January at 1050 showed a substantial ash plume moving W from Nyiragongo (figure 11).

Figure (see Caption) Figure 11. An annotated MODIS satellite image showing the region surrounding Nyiragongo as captured at 1050 on 17 January 2002. Lava flows are not yet conspicuous at this stage of the eruption. Instead, a W-trending ash plume is visible extending more than 150 km from the volcano. Courtesy NASA.

OCHA stated that at 1100 on 17 January observers flew over the volcano in a helicopter and reported a large lava flow approaching Goma. The lava flow cut the road between Goma and Rutshuru (to the N, figure 10). By 1430, with a small hill slowing its progress, the lava flow had reached 2 km N of the airport and was still progressing southward. The lava flow had reached a width of 2 km, and its velocity was estimated at 2-3 m/minute (0.2 km/hour), a very slow flow rate compared to those reported for the very high velocity 1977 eruption which reached up to 60-100 km/hour (see SEAN 02:03). The smaller of the two lava flows heading toward Goma cut the road leading in from the W (figure 12). OCHA reported that a fourth fissure opened during the afternoon of 17 January. A total of 14 neighboring villages were affected by the lava flows.

Figure (see Caption) Figure 12. Map of Goma showing lavas from the 17-21 January 2002 eruption of Nyiragongo. Lavas from the eruption ultimately trisected Goma and one branch entered Lake Kivu. Courtesy OCHA Humanitarian Information Center (HIC).

News reports made much about fires in Goma. Fuel depots exploded and kerosene storage facilities at the airport burned. On 21 January a petrol station exploded killing ten's of people (~50 according to news reports). A UN worker in Goma reported that the air was full of ash and dust during the eruption. News reports also emphasized the fires' smoke and soot.

On 18 January, OCHA reported that tremors occurred every hour, and some were strong enough to damage buildings in Gisenyi (figure 10). Several tremors were felt as far away as at the S end of Lake Kivu in Bukavu (~125 km SE). As of 24 January, earthquakes and tremors up to M 4.7 continued in the vicinity of Nyiragongo.

Representatives from OCHA reported on 20 January that a new crater had opened on the NW side of Nyiragongo, and the temperature of some parts of Lake Kivu reached up to 40°C.

By 21 January, the rapid advance of new lava flows appeared to be over, but residual molten lava still slowly seeped into Lake Kivu, where it formed a ~100-m-wide delta. Although no new lava flows threatened the city, some scientists feared that lava entering the lake or seismic activity could disturb the lake sufficiently to release significant amounts of carbon dioxide and methane gas lying at the lake bottom. News and other scientific sources suggested a gas release was unlikely.

OCHA reported that a 22 January a flight over the volcano confirmed a lack of new activity, including the crater where only a few fumaroles were present. A system of fractures was visible along the southern slope of the volcano, starting from the eastern flank of Shaheru crater (close to the main Nyiragongo cone) and propagating down close to the outskirts of Goma. The fractures were generally meters wide, and during the eruption lava poured out from different locations and altitudes along the fracture system. The lowest lava emission point in this fracture system, as estimated from the helicopter, was at least ~2 km from Goma.

According to OCHA, volcanologists determined that ash observed in Goma on 23 January originated from the collapse of Nyiragongo's inner crater and not from a Nyamuragira eruption, as was originally (incorrectly) stated in several news reports. During a visit to Nyiragongo's main crater on 28 January, the UN Volcano Surveillance Team found that the crater floor had collapsed more than 600 m. In addition, they reported no ongoing volcanism nor any fumaroles at the bottom of the crater, although they could smell SO2. A few weak steam vents were visible on the inner crater wall and a small gas plume was seen above the crater rim to the NE. On 28 January the volcano was at Alert Level Yellow (second on a four-color scale).

Regional seismicity. On 4 January 2002, an M 4.8 earthquake occurred near Nyiragongo. Local volcanologists had planned to visit Nyiragongo on 19 January to observe its activity, but the volcano erupted before the visit.

According to Bruce W. Presgrave of the USGS National Earthquake Information Center (NEIC), there was an unusual number of tectonic earthquakes in the Goma-Nyiragongo region starting ~9 hours after Nyiragongo's alleged initial lavas at 0500. The sequence included ~100 earthquakes M 3.5 or larger. Tectonic swarms of this size occasionally appear in conjunction with volcanism. For example, seismologists noted intense protracted swarms during Miyake-jima's intrusions and eruptions during the year 2000 (BGVN 25:05, 25:07, and 25:09).

The largest earthquake to date in the sequence was M 5; it struck at 0214 on 20 January at 1.76°S, 29.08°E. The second largest, M 4.8, struck at 2201 on 17 January at 1.74°S, 29.08°E, about 17 hours after the estimated onset of the lava flows according to news reports. Though imprecisely fixed, these estimated epicenter locations are just a few ten's of kilometers WSW of Goma; and the probable uncertainty could place them closer to Goma and Nyiragongo.

In addition to registering at the two closest stations in Mbarara, Uganda (MBAR, 0.602°S, 30.738°E) and Kilima Mbogo, Kenya (KMBO, 1.127°S, 37.252°E), the earthquakes also left clear signatures on instruments at great distances, for example in China and at the South Pole, Antarctica. The earthquakes contained sharp P- and S-wave arrivals. Also, as would be expected of tectonic events at teleseismic distances, the associated signals at even the closest stations MBAR and KMBO lacked tremor. The signals were not the sort that could be expected to arise from surficial processes like sudden mass wasting, fuel explosions, building collapses, etc. First motion or minimal tensor results are not yet available.

Comparatively few news accounts discussed the seismic activity or seismically induced damage, perhaps because residents were concerned with more pressing aspects of Nyiragongo's eruption. However, NEIC has received email messages indicating that numerous earthquakes were felt near Kigali, Rwanda (~100 km E of Nyiragongo, table 2).

Table 2. Summary of earthquakes felt near Kigali, Rwanda (~ 100 km E of Nyiragongo) during 10-22 January 2002. The earthquakes were all recorded instrumentally as well. Courtesy Bruce Presgrave (NEIC) and Fr. Stephen Yavorsky, S.J.

Date Local Time Estimated Location Magnitude Comment
~10 Jan 2002 ~1530-1600 -- 4.0 --
17 Jan 2002 2201 1.75°S, 29.07°E, ~115 km W of Kigali 4.8 15 km depth
18 Jan 2002 1008 -- 4.0 --
18 Jan 2002 2309 -- 4.0 --
19 Jan 2002 ~1606 -- ~4.0 --
19 Jan 2002 ~2233 -- ~4.0 --
19 Jan 2002 ~1912 -- ~4.0 --
20 Jan 2002 0214 1.76°S, 29.08°E 5.0 --
21 Jan 2002 ~0130-0530 -- ~4.0 Numerous tremors felt during 4-hour period
21 Jan 2002 0640 -- ~4.7 --
21 Jan 2002 1553 -- ~4.0 --
21 Jan 2002 1630 -- ~4.0 --
22 Jan 2002 1732 1.72°S, 20.10°W, ~15 km WSW of Gisenyi 4.9 --
22 Jan 2002 1822 -- 4.4-4.7 --

As a result of the seismicity, many buildings collapsed in Goma. At least 25 buildings in Gisenyi were also destroyed. By 28 January seismicity had decreased and earthquakes were not large enough to be felt by the population.

Humanitarian crisis. According to OCHA and various news reports, refugees began to return to Goma just a few days after the eruption, despite the dangers that still existed in the area. USAID/OFDA reported that on the morning of 20 January, more than 15,000 people per hour were returning to Goma from points E of the city, while simultaneously 3,000 people per hour were fleeing the city to locations W. Aid workers reported that the refugees would rather return to Goma and risk another eruption than stay in displacement camps in Rwanda, which they perceived to be a hostile country. On 21 January, continuing seismic activity caused buildings to collapse, resulting in more deaths.

Poor access to people in affected parts of Goma was a problem for relief efforts. Several humanitarian groups, along with news agencies, reported that aid workers, along with returning refugees, crossed freshly crusted lava flows to access certain areas. On 18 January two out of three water pumping stations were not working.

Eye irritation and breathing difficulties were reported as a result of the ash and fumes in Goma. Health care centers were provided with medication, and all health care has been free thus far. A few suspected cases of cholera have been reported, but OCHA reported that relief agencies felt prepared for possible disease outbreaks.

According to Oxfam International, the major problems facing the people of Goma were water supply and sanitation facilities, shelter, food, medical care, and damage to schools. A qualitative helicopter assessment on 23 January indicated that ~30% of Goma was destroyed by the lava flows and that up to 50,000-60,000 people in the E of the town lost their homes. On the other hand, the 27 January map-based assessment illustrated by figure 12 concluded that lava flows had affected 4.5 km2 of the city's 35 km2 populated area. Thus, this analysis suggested that ~13% of Goma had been affected.

Figure 12 shows that the E portion of Goma had been cut off from the rest of the town by lava. During the first four days of the eruption, speedboats transported relief workers between the E and W parts of Goma.

On 23 January, 11 sites (in Goma and Sake) operated by the World Food Program began to distribute food and non-food items to refugees (several of these sites appear on figure 12). Other NGO's had collaborated to purchase food locally to provide food for refugees prior to this distribution, but many people had not received food since the eruption began.

A report from OCHA on 25 January confirmed that two access roads into Goma had been cut through the hardened lava and that a third would soon be completed. They reported that 50% of the water network in Goma was operational and that aid agencies had positioned bladders in areas not served by the network. Agencies planned to have the entire water network operational by 4 February. On 25 January, Oxfam reported that the operational portion of the water network still mainly serviced the western part of Goma, and that in the eastern part an estimated 100,000 people remained in dire need of drinking water. Water from Lake Kivu was determined to be potable for adults if filtered. About 22 water purification points were established for residents withdrawing lakewater.

The Goma airport reopened to small aircraft on 25 January. However, the tower was considered inoperable due to the risk of gas explosion.

As of 25 January, seismic activity continued, and monitoring in Goma suggested that some epicenters were at shallow depth beneath the city. OCHA warned that further eruptions were still possible near Goma and Lower Gisenyi. Several humanitarian efforts continued to help the people in Goma through the ongoing crisis. Further information will be forthcoming in future Bulletin reports, including more technical information from volcanologists on the scene.

Geologic Background. One of Africa's most notable volcanoes, Nyiragongo contained a lava lake in its deep summit crater that was active for half a century before draining catastrophically through its outer flanks in 1977. The steep slopes of a stratovolcano contrast to the low profile of its neighboring shield volcano, Nyamuragira. Benches in the steep-walled, 1.2-km-wide summit crater mark levels of former lava lakes, which have been observed since the late-19th century. Two older stratovolcanoes, Baruta and Shaheru, are partially overlapped by Nyiragongo on the north and south. About 100 parasitic cones are located primarily along radial fissures south of Shaheru, east of the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by voluminous lava flows that extend long distances down the flanks, which is characterized by the eruption of foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities, as did lava flows that inundated portions of the major city of Goma in January 2002.

Information Contacts: United Nations Office for the Coordination of Humanitarian Affairs (OCHA), United Nations, New York, NY 10017 USA (URL: https://reliefweb.int/); Oxfam International, Suite 20, 266 Banbury Road, Oxford, OX2 7DL, United Kingdom (URL: https://www.oxfam.org/); Richard McDonald, c/o Independent Missionaries, Box 42, Cyangugu, Rwanda; U.S. Agency for International Development (USAID)/Office of U.S. Foreign Disaster Assistance (OFDA), Ronald Reagan Building, Washington, DC 20523-1000, USA (URL: https://www.usaid.gov/); Bruce Presgrave, USGS National Earthquake Information Center (NEIC), MS 967, Denver Federal Center, Box 25046, Denver, CO 802225, USA (URL: https://earthquake.usgs.gov/); Fr. Stephen Yavorsky, S.J., Maison Régionale Jésuite, B.P. 6039, Kigali, Rwanda; National Aeronautics and Space Administration (NASA), Washington, DC 20456-0001, USA (URL: https://www.nasa.gov/).


Sheveluch (Russia) — December 2001 Citation iconCite this Report

Sheveluch

Russia

56.653°N, 161.36°E; summit elev. 3283 m

All times are local (unless otherwise noted)


Through January 2002, elevated seismicity, and an unstable, growing lava dome

In mid-July 2001, the level of concern for Shiveluch was raised from Yellow to Orange (BGVN 26:08) and remained at that level until the end of November 2001 when it was returned to Yellow. During a very active period, 30 September through 1 October, the level of concern was set to Red. The level of concern remained at Yellow through early January 2002, rising briefly to Orange in mid-January and returning to Yellow at the end of the report period, 25 January 2002.

During mid-July through at least 25 January 2002, seismicity was above background levels. The lava dome, now with a summit at ~2,500 m, continued to grow. Typical activities throughout the period included explosions, some producing pyroclastic flows, ash and/or gas-and-steam plumes typically rising 1-2 km (3,500-4,500 m altitude) above the dome, and localized ash falls. Plumes drifted in various directions depending upon local wind conditions and extended from several to as much as 80 km from the volcano. As many as 60 or more earthquakes over M 1.7 (including some over M 2.0) occurred weekly, with many other weak, shallow earthquakes occurring within the volcano's edifice. Other local, shallow seismic events (possible collapses, avalanches, weak gas-ash explosions), and episodes of weak, volcanic tremor also were registered. In mid-January the earthquake rate decreased but the energy of individual events increased (maximum magnitude, 2.7).

The AVHRR satellite images of the active dome area showed thermal anomalies almost daily throughout the period. Anomalies ranged from 1 to 10 pixels in size with maximum temperatures from a few degrees C to 49°C on numerous occasions. Background temperatures typically ranged from -14 to -29° C.

Activities from the end of August to late-January 2002 include visual reports on 4 September of a gas-and-steam plume rising 1,200 m above the dome and extending 10 km E, and a pyroclastic flow ~1 km long later that day. On 11 September, several hot avalanches from the summit of the dome were observed. An explosive eruption began at 1323 on 30 September and, at 2010, another explosion sent an ash plume 9,000 m above the dome. A small circular cloud ~25 km in diameter located directly over the volcano was reported later. On 1 October, ash plumes were observed to be as high as 7,500 m above the dome with localized ashfall thicknesses in the millimeter range. This eruption was the beginning of a very active period that extended into the first week of October, e.g., eleven M 2 and nine M 1.7 earthquakes were registered during 1-4 October. On 19 November a 10-pixel thermal anomaly was observed with temperatures ranging from 0 to 49°C. A steam plume observed on 7 January extended ~100 km SE. On 14 January, continuous rock avalanches were reported by observers in Klyuchi town. Gas-and-steam plumes that week rose 1,000-1,500 m above the dome and extended 10 km SE. Seismicity decreased during 19-25 January compared to the previous week. Several gas-and-steam plumes were observed, one extending 75 km to the SE on 21 January. Thermal anomalies continued but no ash was detected in any image.

Geologic Background. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Information Contacts: Olga Chubarova, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tom Miller, Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Tofua (Tonga) — December 2001 Citation iconCite this Report

Tofua

Tonga

19.75°S, 175.07°W; summit elev. 515 m

All times are local (unless otherwise noted)


Typical fumarolic emissions continue; geologic mapping of cinder-cone complexes

On 1 August 2000, Jeff and Raine Williams, aboard the sailing yacht Gryphon, reported that they spent a couple nights at Uanukuhahaki island, approximately 48 km E of the volcanic islands of Kao and Tofua. They noted that "steam can be seen rising from Tofua almost continuously." They also observed that pumice stones were scattered all along the beach at Uanukuhahaki.

Tim Worthington (Christian-Albrechts-Universität zu Kiel) notes that the activity seen on 1 August 2000 is the normal state of Tofua. In September 1999, Worthington mapped a thick compound ash layer (with three distinct units) containing abundant pumice clasts that is widespread on Kotu, Ha'afeva, Matuku, and other islands in the group 30-50 km E of Tofua and Kao. The ash represents the distal part of the pyroclastic flow sequence associated with a pre-historic caldera-forming eruption on Tofua. Other workers, including Shane Cronin (GEOMAR), are looking at these units in more detail with a view to dating the eruption. The "pumice stones" seen on Uanukuhahaki may be blocks of andesitic pumice eroded from this ash sequence.

Geologic mapping and observations, November 2000. Worthington was part of a group that spent 8 days mapping and sampling at Tofua in late November 2000. Tofua is a nearly circular island 9.5 x 7.1 km in diameter. The flanks rise steeply to a well-defined caldera rim reaching 515 m elevation in the NW and SE. The inner caldera walls are precipitous, and the caldera is occupied by a large, cold, fresh-water lake standing at 30 m elevation. The most recent volcanism took place from vents within the N half of the caldera, where there are three cinder-cone complexes.

The westernmost cinder-cone complex is densely forested and rather degraded. The easternmost complex consists of four distinct but intergrown small cinder cones with well-formed craters (two have sub-craters). A series of young rubble-topped basaltic andesite lavas were erupted from these cones and flowed towards (and into) the lake. Different degrees of vegetation on each flow suggest a recurrence interval of about 50 years, and the youngest may have been emplaced during the 1958-60 eruptions. It was mapped by visiting geologists in the early 1970s.

The northernmost cinder cone is the large and vigorously degassing Lofia, with a basal diameter of ~500 m and a summit at 380 m elevation. Lofia has a summit crater 70 m in diameter with vertical inner walls, which was completely filled by dense brownish-blue SO2-rich steam during the visit. Intermittent chugging sounds resembling a train starting to move could be heard from the crater rim. From the yacht, occasional dull orange reflections were observed in clouds above the caldera rim on two nights. However, there was no evidence of recent spatter around the crater rim, nor any indication of significant volcanic activity since the 1958-60 eruptions.

On calm days the plume from Lofia rose above the caldera rim and was visible from nearby islands and to passing ships; more commonly it dispersed in the wind before passing the caldera rim. Numerous breadcrust bombs were plastered onto the NW caldera wall downwind from Lofia, and had welded to form a sparsely vegetated 20-m-thick rootless lava flow on the NW caldera rim. The region of sparse vegetation on the outer NW caldera wall extended from 300 to 515 m elevation, gaving the NW summit of Tofua a "burnt" appearance to passing ships. The spatter testifies to vigorous fire-fountaining at Lofia, whose summit is 130 m below and 700 m S of the caldera rim. The latest episode of this activity may have taken place during the 1958-60 eruptions, but the spatter almost certainly represents the accumulated result of many such episodes.

Geologic Background. The low, forested Tofua Island in the central part of the Tonga Islands group is the emergent summit of a large stratovolcano that was seen in eruption by Captain Cook in 1774. The summit contains a 5-km-wide caldera whose walls drop steeply about 500 m. Three post-caldera cones were constructed at the northern end of a cold fresh-water caldera lake, whose surface lies only 30 m above sea level. The easternmost cone has three craters and produced young basaltic-andesite lava flows, some of which traveled into the caldera lake. The largest and northernmost of the cones, Lofia, has a steep-sided crater that is 70 m wide and 120 m deep and has been the source of historical eruptions, first reported in the 18th century. The fumarolically active crater of Lofia has a flat floor formed by a ponded lava flow.

Information Contacts: Tim J. Worthington, Institut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24118 Kiel, Germany; Jeff and Raine Williams, P.O. Box 729, Funkstown, MD 21734, USA.

Atmospheric Effects

The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. Descriptions of the initial dispersal of major eruption clouds remain with the individual eruption reports, but observations of long-term stratospheric aerosol loading will be found in this section.

Atmospheric Effects (1980-1989)  Atmospheric Effects (1995-2001)

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements  Obituaries

Misc Reports

Reports are sometimes published that are not related to a Holocene volcano. These might include observations of a Pleistocene volcano, earthquake swarms, or floating pumice. Reports are also sometimes published in which the source of the activity is unknown or the report is determined to be false. All of these types of additional reports are listed below by subject.

Additional Reports  False Reports