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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

San Miguel (El Salvador) Small ash emissions during 22 February 2020

Cleveland (United States) Intermittent thermal anomalies and lava dome subsidence, February 2019-January 2020

Ambrym (Vanuatu) Fissure eruption in December 2018 produces an offshore pumice eruption after lava lakes drain

Copahue (Chile-Argentina) Ash emissions end on 12 November; lake returns to El Agrio Crater in December 2019

Nishinoshima (Japan) Ongoing activity enlarges island with lava flows, ash plumes, and incandescent ejecta, December 2019-February 2020

Krakatau (Indonesia) Tephra and steam explosions in the crater lake; explosions in December 2019 build a tephra cone

Mayotte (France) Seismicity and deformation, with submarine E-flank volcanism starting in July 2018

Fernandina (Ecuador) Fissure eruption produced lava flows during 12-13 January 2020

Masaya (Nicaragua) Lava lake persists with lower temperatures during August 2019-January 2020

Reventador (Ecuador) Nearly daily ash emissions and frequent incandescent block avalanches August 2019-January 2020

Pacaya (Guatemala) Continuous explosions, small cone, and lava flows during August 2019-January 2020

Kikai (Japan) Single explosion with steam and minor ash, 2 November 2019



San Miguel (El Salvador) — March 2020 Citation iconCite this Report

San Miguel

El Salvador

13.434°N, 88.269°W; summit elev. 2130 m

All times are local (unless otherwise noted)


Small ash emissions during 22 February 2020

San Miguel, locally known as Chaparrastique, is a stratovolcano located in El Salvador. Recent activity has consisted of occasional small ash explosions and ash emissions. Infrequent gas-and-steam and ash emissions were observed during this reporting period of June 2018-March 2020. The primary source of information for this report comes from El Salvador's Servicio Nacional de Estudios Territoriales (SNET) and special reports from the Ministero de Medio Ambiente y Recursos Naturales (MARN) in addition to various satellite data.

Based on Sentinel-2 satellite imagery and analyses of infrared MODIS data, volcanism at San Miguel from June 2018 to mid-February was relatively low, consisting of occasional gas-and-steam emissions. During 2019, a weak thermal anomaly in the summit crater was registered in thermal satellite imagery (figure 27). This thermal anomaly persisted during a majority of the year but was not visible after September 2019; faint gas-and-steam emissions could sometimes be seen rising from the summit crater.

Figure (see Caption) Figure 27. Sentinel-2 satellite imagery of a faint but consistent thermal anomaly at San Miguel during 2019. Images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Volcanism was prominent beginning on 13-20 February 2020 when SO2 emissions exceeded 620 tons/day (typical low SO2 values are less than 400 tons/day). During 20-21 February the amplitude of microearthquakes increased and minor emissions of gas-and-steam and SO2 were visible within the crater (figure 28). According to SNET and special reports from MARN, on 22 February at 1055 an ash cloud was visible rising 400 m above the crater rim (figure 29), resulting in minor ashfall in Piedra Azul (5 km SW). That same day RSAM values peaked at 550 units as recorded by the VSM station on the upper N flank, which is above normal values of about 150. Seismicity increased the day after the eruptive activity. Minor gas-and-steam emissions continued to rise 400 m above the crater rim during 23-24 February; the RSAM values fell to 33-97 units. Activity in March was relatively low; some seismicity, including small magnitude earthquakes, occurred during the month in addition to SO2 emissions ranging from 517 to 808 tons/day.

Figure (see Caption) Figure 28. Minor gas-and-steam emissions rising from the crater at San Miguel on 21 February 2020. Courtesy of Ministero de Medio Ambiente y Recursos Naturales (MARN).
Figure (see Caption) Figure 29. Gas-and-steam and ash emissions rising from the crater at San Miguel on 22 February 2020. Courtesy of Ministero de Medio Ambiente y Recursos Naturales (MARN).

Geologic Background. The symmetrical cone of San Miguel volcano, one of the most active in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. The unvegetated summit rises above slopes draped with coffee plantations. A broad, deep crater complex that has been frequently modified by historical eruptions (recorded since the early 16th century) caps the truncated summit, also known locally as Chaparrastique. Radial fissures on the flanks of the basaltic-andesitic volcano have fed a series of historical lava flows, including several erupted during the 17th-19th centuries that reached beyond the base of the volcano on the N, NE, and SE sides. The SE-flank flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. The location of flank vents has migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.

Information Contacts: Servicio Nacional de Estudios Territoriales (SNET), Ministero de Medio Ambiente y Recursos Naturales (MARN), Km. 5½ Carretera a Nueva San Salvador, Avenida las Mercedes, San Salvador, El Salvador (URL: http://www.snet.gob.sv/ver/vulcanologia); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Cleveland (United States) — March 2020 Citation iconCite this Report

Cleveland

United States

52.825°N, 169.944°W; summit elev. 1730 m

All times are local (unless otherwise noted)


Intermittent thermal anomalies and lava dome subsidence, February 2019-January 2020

Cleveland is a stratovolcano located in the western portion of Chuginadak Island, a remote island part of the east central Aleutians. Common volcanism has included small lava flows, explosions, and ash clouds. Intermittent lava dome growth, small ash explosions, and thermal anomalies have characterized more recent activity (BGVN 44:02). For this reporting period during February 2019-January 2020, activity largely consisted of gas-and-steam emissions and intermittent thermal anomalies within the summit crater. The primary source of information comes from the Alaska Volcano Observatory (AVO) and various satellite data.

Low levels of unrest occurred intermittently throughout this reporting period with gas-and-steam emissions and thermal anomalies as the dominant type of activity (figures 30 and 31). An explosion on 9 January 2019 was followed by lava dome growth observed during 12-16 January. Suomi NPP/VIIRS sensor data showed two hotspots on 8 and 14 February 2019, though there was no evidence of lava within the summit crater at that time. According to satellite imagery from AVO, the lava dome was slowly subsiding during February into early March. Elevated surface temperatures were detected on 17 and 24 March in conjunction with degassing; another gas-and-steam plume was observed rising from the summit on 30 March. Thermal anomalies were again seen on 15 and 28 April using Suomi NPP/VIIRS sensor data. Intermittent gas-and-steam emissions continued as the number of detected thermal anomalies slightly increased during the next month, occurring on 1, 7, 15, 18, and 23 May. A gas-and-steam plume was observed on 9 May.

Figure (see Caption) Figure 30. The MIROVA graph of thermal activity (log radiative power) at Cleveland during 4 February 2019 through January 2020 shows increased thermal anomalies between mid-April to late November 2019. Courtesy of MIROVA.
Figure (see Caption) Figure 31. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) confirmed intermittent thermal signatures occurring in the summit crater during March 2019 through October 2019. Some gas-and-steam plumes were observed accompanying the thermal anomaly, as seen on 17 March 2019 and 8 May 2019. Courtesy of Sentinel Hub Playground.

There were 10 thermal anomalies observed in June, and 11 each in July and August. Typical mild degassing was visible when photographed on 9 August (figure 32). On 14 August, seismicity increased, which included a swarm of a dozen local earthquakes. The lava dome emplaced in January was clearly visible in satellite imagery (figure 33). The number of thermal anomalies decreased the next month, occurring on 10, 21, and 25 September. During this month, a gas-and-steam plume was observed in a webcam image on 6, 8, 20, and 25 September. On 3-6, 10, and 21 October elevated surface temperatures were recorded as well as small gas-and-steam plumes on 4, 7, 13, and 20-25 October.

Figure (see Caption) Figure 32. Photograph of Cleveland showing mild degassing from the summit vent taken on 9 August 2019. Photo by Max Kaufman; courtesy of AVO/USGS.
Figure (see Caption) Figure 33. Satellite image of Cleveland showing faint gas-and-steam emissions rising from the summit crater. High-resolution image taken on 17 August 2019 showing the lava dome from January 2019 inside the crater (dark ring). Image created by Hannah Dietterich; courtesy of AVO/USGS and DigitalGlobe.

Four thermal anomalies were detected on 3, 6, and 8-9 November. According to a VONA report from AVO on 8 November, satellite data suggested possible slow lava effusion in the summit crater; however, by the 15th no evidence of eruptive activity had been seen in any data sources. Another thermal anomaly was observed on 14 January 2020. Gas-and-steam emissions observed in webcam images continued intermittently.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows intermittent weak thermal anomalies within 5 km of the crater summit during mid-April through November 2019 with a larger cluster of activity in early June, late July and early October (figure 30). Thermal satellite imagery from Sentinel-2 also detected weak thermal anomalies within the summit crater throughout the reporting period, occasionally accompanied by gas-and-steam plumes (figure 31).

Geologic Background. The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://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 (URL: http://dggs.alaska.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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).


Ambrym (Vanuatu) — March 2020 Citation iconCite this Report

Ambrym

Vanuatu

16.25°S, 168.12°E; summit elev. 1334 m

All times are local (unless otherwise noted)


Fissure eruption in December 2018 produces an offshore pumice eruption after lava lakes drain

Ambrym is an active volcanic island in the Vanuatu archipelago consisting of a 12 km-wide summit caldera. Benbow and Marum are two currently active craters within the caldera that have produced lava lakes, explosions, lava flows, ash, and gas emissions, in addition to fissure eruptions. More recently, a submarine fissure eruption in December 2018 produced lava fountains and lava flows, which resulted in the drainage of the active lava lakes in both the Benbow and Marum craters (BGVN 44:01). This report updates information from January 2019 through March 2020, including the submarine pumice eruption during December 2018 using information from the Vanuatu Meteorology and Geohazards Department (VMGD) and research by Shreve et al. (2019).

Activity on 14 December 2018 consisted of thermal anomalies located in the lava lake that disappeared over a 12-hour time period; a helicopter flight on 16 December confirmed the drainage of the summit lava lakes as well as a partial collapse of the Benbow and Marum craters (figure 49). During 14-15 December, a lava flow (figure 49), accompanied by lava fountaining, was observed originating from the SE flank of Marum, producing SO2 and ash emissions. A Mw 5.6 earthquake on 15 December at 2021 marked the beginning of a dike intrusion into the SE rift zone as well as a sharp increase in seismicity (Shreve et al., 2019). This intrusion extended more than 30 km from within the caldera to beyond the east coast, with a total volume of 419-532 x 106 m3 of magma. More than 2 m of coastal uplift was observed along the SE coast due to the asymmetry of the dike from December, resulting in onshore fractures.

Figure (see Caption) Figure 49. Sentinel-2 thermal satellite images of Ambrym before the December 2018 eruption (left), and during the eruption (right). Before the eruption, the thermal signatures within both summit craters were strong and after the eruption, the thermal signatures were no longer detected. A lava flow was observed during the eruption on 15 December. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

Shreve et al. (2019) state that although the dike almost reached the surface, magma did not erupt from the onshore fractures; only minor gas emissions were detected until 17 December. An abrupt decrease in the seismic moment release on 17 December at 1600 marked the end of the dike propagation (figure 50). InSAR-derived models suggested an offshore eruption (Shreve et al., 2019). This was confirmed on 18-19 December when basaltic pumice, indicating a subaqueous eruption, was collected on the beach near Pamal and Ulei. Though the depth and exact location of the fissure has not been mapped, the nature of the basaltic pumice would suggest it was a relatively shallow offshore eruption, according to Shreve et al. (2019).

Figure (see Caption) Figure 50. Geographical timeline summary of the December 2018 eruptive events at Ambrym. The lava lake level began to drop on 14 December, with fissure-fed lava flows during 14-15 December. After an earthquake on 15 December, a dike was detected, causing coastal uplift as it moved E. As the dike continued to propagate upwards, faulting was observed, though magma did not breach the surface. Eventually a submarine fissure eruption was confirmed offshore on 18-19 December. Image modified from Shreve et al. (2019).

In the weeks following the dike emplacement, there was more than 2 m of subsidence measured at both summit craters identified using ALOS-2 and Sentinel-1 InSAR data. After 22 December, no additional large-scale deformation was observed, though a localized discontinuity (less than 12 cm) measured across the fractures along the SE coast in addition to seismicity suggested a continuation of the distal submarine eruption into late 2019. Additional pumice was observed on 3 February 2019 near Pamal village, suggesting possible ongoing activity. These surveys also noted that no gas-and-steam emissions, lava flows, or volcanic gases were emitted from the recently active cracks and faults on the SE cost of Ambrym.

During February-October 2019, onshore activity at Ambrym declined to low levels of unrest, according to VMGD. The only activity within the summit caldera consisted of gas-and-steam emissions, with no evidence of the previous lava lakes (figure 51). Intermittent seismicity and gas-and-steam emissions continued to be observed at Ambrym and offshore of the SE coast. Mével et al. (2019) installed three Trillium Compact 120s posthole seismometers in the S and E part of Ambrym from 25 May to 5 June 2019. They found that there were multiple seismic events, including a Deep-Long Period event and mixed up/down first motions at two stations near the tip of the dike intrusion and offshore of Pamal at depths of 15-20 km below sea level. Based on a preliminary analysis of these data, Mével et al. (2019) interpreted the observations as indicative of ongoing volcanic seismicity in the region of the offshore dike intrusion and eruption.

Figure (see Caption) Figure 51. Aerial photograph of Ambrym on 12 August 2019 showing gas-and-steam emissions rising from the summit caldera. Courtesy of VMGD.

Seismicity was no longer reported from 10 October 2019 through March 2020. Thermal anomalies were not detected in satellite data except for one in late April and one in early September 2019, according to MODIS thermal infrared data analyzed by the MIROVA system. The most recent report from VMGD was issued on 27 March 2020, which noted low-level unrest consisting of dominantly gas-and-steam emissions.

References:

Shreve T, Grandin R, Boichu M, Garaebiti E, Moussallam Y, Ballu V, Delgado F, Leclerc F, Vallée M, Henriot N, Cevuard S, Tari D, Lebellegard P, Pelletier B, 2019. From prodigious volcanic degassing to caldera subsidence and quiescence at Ambrym (Vanuatu): the influence of regional tectonics. Sci. Rep. 9, 18868. https://doi.org/10.1038/s41598-019-55141-7.

Mével H, Roman D, Brothelande E, Shimizu K, William R, Cevuard S, Garaebiti E, 2019. The CAVA (Carnegie Ambrym Volcano Analysis) Project - a Multidisciplinary Characterization of the Structure and Dynamics of Ambrym Volcano, Vanuatu. American Geophysical Union, Fall 2019 Meeting, Abstract and Poster V43C-0201.

Geologic Background. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides Arc. A thick, almost exclusively pyroclastic sequence, initially dacitic then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major Plinian eruption with dacitic pyroclastic flows about 1,900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); 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); 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/).


Copahue (Chile-Argentina) — March 2020 Citation iconCite this Report

Copahue

Chile-Argentina

37.856°S, 71.183°W; summit elev. 2953 m

All times are local (unless otherwise noted)


Ash emissions end on 12 November; lake returns to El Agrio Crater in December 2019

Most of the large edifice of Copahue lies high in the central Chilean Andes, but the active El Agrio crater lies on the Argentinian side of the border at the W edge of the Pliocene Caviahue caldera. Infrequent mild-to-moderate explosive eruptions have been recorded since the 18th century. The most recent eruptive episode began with phreatic explosions and ash emissions on 2 August 2019 that continued until mid-November 2019. This report summarizes activity from November 2019 through February 2020 and is based on reports issued by Servicio Nacional de Geología y Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur (OVDAS), Buenos Aires Volcanic Ash Advisory Center (VAAC), satellite data, and photographs from nearby residents.

MIROVA data indicated a few weak thermal anomalies during mid-October to mid-November 2019. Multiple continuous ash emissions were reported daily until mid-November when activity declined significantly. By mid-December the lake inside El Agrio crater had reappeared and occasional steam plumes were the only reported surface activity at Copahue through February 2020.

The Buenos Aires VAAC and SERNAGEOMIN both reported continuous ash emissions during 1-9 November 2019 that were visible in the webcam. Satellite imagery recorded the plumes drifting generally E or NE at 3.0-4.3 km altitude (figure 49). Most of the emissions on 10 November were steam (figure 50). The last pulse of ash emissions occurred on 12 November with an ash plume visible moving SE at 3 km altitude in satellite imagery and a strong thermal anomaly (figure 51). The following day emissions were primarily steam and gas. SERNAGEOMIN noted the ash emissions rising around 800 m above El Agrio crater and also reported incandescence visible during most nights through mid-November. During the second half of November the constant degassing was primarily water vapor with occasional nighttime incandescence. Steam plumes rose 450 m above the crater on 27 November.

Figure (see Caption) Figure 49. Continuous ash emissions at Copahue during 1-9 November 2019 were visible in Sentinel-2 satellite imagery on 2 and 7 November 2019 drifting NE. Natural color rendering uses bands 4,3, and 2. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 50. Most of the emissions from Copahue on 10 November 2019 were steam. Left image courtesy of Valentina Sepulveda, taken from Caviahue, Argentina. Right image courtesy of Sentinel Hub Playground, natural color rendering using bands 4, 3, and 2.
Figure (see Caption) Figure 51. A strong thermal anomaly and an ash plume at Copahue were visible in Sentinel-2 satellite imagery on 12 November 2019. Courtesy of Sentinel Hub Playground, Atmospheric penetration rendering bands 12, 11, and 8A.

Nighttime incandescence was last observed in the SERNAGEOMIN webcam on 1 December; SERNAGEOMIN lowered the alert level from Yellow to Green on 15 December 2019. Throughout December degassing consisted mainly of minor steam plumes (figure 52), the highest plume rose to 300 m above the crater on 18 December, and minor SO2 plumes persisted through the 21st (figure 53),. By mid-December the El Agrio crater lake was returning and satellite images clearly showed the increase in size of the lake through February (figure 54). The only surface activity reported during January and February 2020 was occasional white steam plumes rising near El Agrio crater.

Figure (see Caption) Figure 52. Small wisps of steam were the only emissions from Copahue on 3 December 2019. Courtesy of Valentina Sepulveda, taken from Caviahue, Argentina.
Figure (see Caption) Figure 53. Small plumes of SO2 were recorded at Copahue during November and December 2019. Top row: 7, 9, and 30 November. Bottom row: 1, 20, and 21 December. Courtesy of Global Sulfur Dioxide Monitoring Page, NASA.
Figure (see Caption) Figure 54. The lake within El Agrio crater reappeared between 5 and 12 December 2019 and continued to grow in size through the end of January 2020. Top row (left to right): There was no lake inside the crater on 5 December 2019, only a small steam plume rising from the vent. The first water was visible on 12 December and was slightly larger a few days later on 17 December. Bottom row (left to right): the lake was significantly larger on 4 January 2020 filling an embayment close to the steam vent. Fingers of water filled in areas of the crater as the water level rose on 24 and 29 January. Courtesy of Sentinel Hub Playground.

Geologic Background. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); 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); 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/); Valentina Sepulveda, Hotel Caviahue, Caviahue, Argentina (URL: https://twitter.com/valecaviahue, Twitter:@valecaviahue).


Nishinoshima (Japan) — March 2020 Citation iconCite this Report

Nishinoshima

Japan

27.247°N, 140.874°E; summit elev. 25 m

All times are local (unless otherwise noted)


Ongoing activity enlarges island with lava flows, ash plumes, and incandescent ejecta, December 2019-February 2020

After 40 years of dormancy, Japan’s Nishinoshima volcano, located about 1,000 km S of Tokyo in the Ogasawara Arc, erupted above sea level in November 2013. Lava flows were active through November 2015, emerging from a central pyroclastic cone. A new eruption in mid-2017 continued the growth of the island with ash plumes, ejecta, and lava flows. A short eruptive event in July 2018 produced a new lava flow and vent on the side of the pyroclastic cone. The next eruption of ash plumes, incandescent ejecta, and lava flows, covered in this report, began in early December 2019 and was ongoing through February 2020. Information is provided primarily from the Japan Meteorological Agency (JMA) monthly reports.

Nishinoshima remained quiet after a short eruptive event in July 2018 until MODVOLC thermal alerts appeared on 5 December 2019. Multiple near-daily alerts continued through February 2020. The intermittent low-level thermal anomalies seen in the MIROVA data beginning in May and June 2019 may reflect areas with increased temperatures and fumarolic activity reported by the Japan Coast Guard during overflights in June and July. The significant increase in thermal anomalies in the MIROVA data on 5 December correlates with the beginning of extrusive and explosive activity (figure 63). Eruptive activity included ash emissions, incandescent ejecta, and numerous lava flows from multiple vents that flowed into the sea down several flanks, significantly enlarging the island.

Figure (see Caption) Figure 63. The MIROVA graph of thermal energy from Nishinoshima from 13 April 2019 through February 2020 shows low-level thermal activity beginning in mid-2019; there were reports of increased temperatures and fumarolic activity during that time. Eruptive activity including ash emissions, incandescent ejecta, and numerous lava flows began on 5 December 2019 and was ongoing through February 2020. Courtesy of MIROVA.

A brief period of activity during 12-21 July 2018 produced explosive activity with blocks and bombs ejected 500 m from a new vent on the E flank of the pyroclastic cone, and a 700-m-long lava flow that stopped about 100 m before reaching the ocean (BGVN 43:09). No further activity was reported during 2018. During overflights on 29 and 31 January, and 7 February 2019, white steam plumes drifted from the E crater margin and inner wall of the pyroclastic cone and discolored waters were present around the island, but no other signs of activity were reported. A survey carried out by the Japan Coast Guard during 7-8 June 2019 reported minor fumarolic activity from the summit crater, and high-temperature areas were noted on the hillsides, measured by infrared thermal imaging equipment. Sulfur dioxide emissions were below the detection limit. In an overflight on 12 July 2019, Coast Guard personnel noted a small white plume rising from the E edge of the summit crater of the pyroclastic cone (figure 64).

Figure (see Caption) Figure 64. The Japan Coast Guard noted a small white plume at the summit of Nishinoshima during an overflight on 12 July 2019, but no other signs of activity. Courtesy of JMA (Volcanic activity monthly report, July 2019).

The white plume was still present during an overflight on 14 August 2019. Greenish yellow areas of water about 500 m wide were distributed around the island, and a plume of green water extended 1.8 km from the NW coast. Similar conditions were observed on 15 October 2019; pale yellow-green discolored water was about 100 m wide and concentrated on the N shore of Nishinoshima. No steam plume from the summit was present during a visit on 19 November 2019, but yellow-white discolored water on the N shore was about 100 m wide and 700 m long. Along the NE and SE coasts, yellow-white water was 100-200 m wide and about 1,000 m long.

A MODVOLC thermal alert appeared at Nishinoshima on 5 December 2019. An eruption was observed by the Japan Coast Guard the following day. A pulsating light gray ash plume rose from the summit crater accompanied by tephra ejected 200 m above the crater rim every few minutes (figure 65). In addition, ash and tephra rose intermittently from a crater on the E flank of the pyroclastic cone, from which lava also flowed down towards the E coast (figure 66). By 1300 on 7 December the lava was flowing into the sea (figure 67).

Figure (see Caption) Figure 65. The eruption observed at Nishinoshima on 6 December 2019 included ash and tephra emissions from the summit vent, and ash, tephra, and a lava flow from the vent on the E flank of the pyroclastic cone. Courtesy of JMA (Volcanic activity monthly report, November 2019).
Figure (see Caption) Figure 66. Thermal infrared imagery revealed incandescent ejecta from the summit crater and lava flowing from the E flank vent at Nishinoshima on 6 December 2019. Courtesy of JMA (Volcanic activity monthly report, November 2019).
Figure (see Caption) Figure 67. By 1300 on 7 December 2019 lava from the E-flank vent at Nishinoshima was flowing into the sea. Courtesy of JMA (Volcanic activity monthly report, November 2019).

Observations by the Japan Coast Guard on 15 December 2019 confirmed that vigorous eruptive activity was ongoing; incandescent ejecta and ash plumes rose 300 m above the summit crater rim (figure 68). A new vent had opened on the N flank of the cone from which lava flowed NW to the sea (figure 69). The lava flow from the E-flank crater also remained active and continued flowing into the sea. The Tokyo VAAC reported an ash emission on 24 December that rose to 1,000 m altitude and drifted S. On 31 December, explosions at the summit continued every few seconds with ash and ejecta rising 300 m high. In addition, lava from the NE flank of the pyroclastic cone flowed NE to the sea (figure 70).

Figure (see Caption) Figure 68. Incandescent ejecta and ash rose 300 m above the summit crater rim at Nishinoshima on 15 December 2019. Courtesy of JMA (Volcanic activity monthly report, December 2019).
Figure (see Caption) Figure 69. Lava from a new vent on the NW flank of Nishinoshima was entering the sea on 15 December 2019, producing vigorous steam plumes. Courtesy of JMA (Volcanic activity monthly report, December 2019).
Figure (see Caption) Figure 70. At Nishinoshima on 31 December 2019 lava flowed down the NE flank of the pyroclastic cone into the sea, and incandescent ejecta rose 300 m above summit. Courtesy of JMA and the Japan Coast Guard (Volcanic activity monthly report, December 2019).

Satellite data from JAXA (Japan Aerospace Exploration Agency) made it possible for JMA to produce maps showing the rapid changes in topography at Nishinoshima resulting from the new lava flows. The new E-flank lava flow was readily seen when comparing imagery from 22 November with 6 December 2019 (figure 71a). An image from 6 December compared with 20 December 2019 shows the flow on the E flank splitting and entering the sea at two locations (figure 71b), the flow on the NW flank traveling briefly N before turning W and forming a large fan into the ocean on the W flank, and a new flow heading NE from the summit area of the pyroclastic cone.

Figure (see Caption) Figure 71. Satellite data from JAXA (Japan Aerospace Exploration Agency) made it possible to produce maps showing the changes in topography at Nishinoshima resulting from the new lava flows (shown in blue). In comparing 22 November with 6 December 2019 (A, left), the new lava flow on the E flank was visible. A new image from 20 December compared with 6 December (B, right) showed the flow on the E flank splitting and entering the sea at two locations, the NW-flank flow building a large fan into the ocean on the W flank, and a new flow heading NE from the summit area of the pyroclastic cone. Courtesy of JMA and the Japan Coast Guard (Volcanic activity monthly report, December 2019).

The Tokyo VAAC reported an ash plume visible in satellite imagery on 15 January 2020 that rose to 1.8 km altitude and drifted SE. The Japan Coast Guard conducted an overflight on 17 January that confirmed the continued eruptions of ash, incandescent ejecta, and lava. Dark gray ash plumes were observed at 1.8 km altitude, with ashfall and tephra concentrated around the pyroclastic cone (figure 72). Plumes of steam were visible where the NE lava flow entered the ocean; the E and NW lava entry areas did not appear active but were still hot. Satellite data from ALOS-2 prepared by JAXA confirmed ongoing activity around the summit vent and on the NE flank, while activity on the W flank had ceased (figure 73). An ash plume was reported by the Tokyo VAAC on 25 January; it rose to 1.5 km altitude and drifted SW for most of the day.

Figure (see Caption) Figure 72. Dense, dark gray ash plumes rose from the summit of Nishinoshima on 17 January 2020. Small plumes of steam from lava-seawater interactions were visible on the NE shore of the island as well (far right). Courtesy of JMA and the Japan Coast Guard (Volcanic activity monthly report, January 2020).
Figure (see Caption) Figure 73. JAXA satellite data from 3 January 2020 (left) showed the growth of a new lava delta on the NE flank of Nishinoshima and minor activity occuring on the W flank compared with the previous image from 20 December 2019. By 17 January 2020 (right), the lava flow activity was concentrated on the NE flank with multiple deltas extending out into the sea. The ‘low correlation areas’ shown in blue represent changes in topography caused by new material from lava flows and ejecta added between the dates shown above the images. Courtesy of JMA (Volcanic activity monthly report, January 2020).

On 3 Feburary 2020 the Tokyo VAAC reported an ash plume visible in satellite imagery that rose to 2.1 km altitude and drifted E. The following day the Japan Coast Guard observed eruptions from the summit crater at five minute intervals that produced grayish white plumes. The plumes rose to 2.7 km altitude (figure 74). Large bombs were scattered around the pyroclastic cone, and the summit crater appeared filled with lava except for the active vent. The lava deltas on the NE flank were only active at the tips of the flows producing a few steam jets where lava entered the sea. The active flows were on the SE flank, and a new 200-m-long lava flow was flowing down the N flank of the pyroclastic cone (figure 75). The lava flowing from the E flank of the pyroclastic cone to the SE into the sea, produced larger jets of steam (figure 76). Yellow-brown discolored water appeared around the island in several places.

Figure (see Caption) Figure 74. Ash emissions at Nishinoshima rose to 2.7 km altitude on 4 February 2020; steam jets from lava entering the ocean were active on the SE flank (far side of the island, right). Courtesy of JMA (Volcanic activity monthly report, February 2020).
Figure (see Caption) Figure 75. The lava deltas on the NE flank of Nishinoshima (bottom center) were much less active on 4 February 2020 than the lava flow and growing delta on the SE flank (left). The newest flow headed N from the summit and was 200 m long (right of center). Courtesy of JMA and the Japan Coast Guard (Volcanic activity monthly report, February 2020).
Figure (see Caption) Figure 76. The most active lava flows at Nishinoshima on 4 February 2020 were on the E flank; significant steam plumes rose in multiple locations along the coast where they entered the sea. Intermittent ash plumes also rose from the summit crater. Courtesy of JMA and Japan Coast Guard (Volcanic activity monthly report, February 2020).

JAXA satellite data confirmed that the flow activity was concentrated on the NE flank and shore during the second half of January 2020, but also recorded the new flow down the SE flank that was observed by the Coast Guard in early February. By mid-February the satellite topographic data indicated the decrease in activity in the NE flank flows, the increased activity on the SE and E flank, and the extension of the flow moving due N to the coast (figure 77). Observations on 17 February 2020 by the Japan Coast Guard revealed eruptions from the summit crater every few seconds, and steam-and-ash plumes rising about 600 m. Vigorous white emissions rose from fractures near the top of the W flank of the pyroclastic cone, but thermal data indicated the area was no hotter than the surrounding area (figure 78). The lava flow on the SE coast still had steam emissions rising from the ocean entry point, but activity was weaker than on 4 February. The newest flow moving due N from the summit produced steam emissions where the flow front entered the ocean.

Figure (see Caption) Figure 77. Constantly changing lava flows at Nishinoshima reshaped the island during late January and February 2020. During the second half of January, flows were active on the NE flank, creating deltas into the sea off the NE coast and also on the SE flank into the sea at the SE coast (left). The ‘low correlation areas’ shown in blue represent changes in topography caused by new material from lava flows and ejecta added between the dates shown above the images. By 14 February (right) activity had slowed on the NE flank and expanded on the SE flank and N flank. Data is from the Land Observing Satellite-2 "Daichi-2" (ALOS-2). Courtesy of JMA and JAXA (Volcanic activity monthly report, February 2020).
Figure (see Caption) Figure 78. Vigorous white emissions rose from fractures near the top of the W flank of the pyroclastic cone at Nishinoshima on 17 February 2020, but thermal data indicated the area was no hotter than the surrounding area. Courtesy of JMA and Japan Coast Guard (Volcanic activity monthly report, February 2020).

Sulfur dioxide plumes from Nishinoshima have been small and infrequent in recent years, but the renewed and increased eruptive activity beginning in December 2019 produced several small SO2 plumes that were recorded in daily satellite data (figure 79).

Figure (see Caption) Figure 79. Small sulfur dioxide plumes from Nishinoshima were captured by the TROPOMI instrument on the Sentinel 5P satellite a few times during December 2019-February 2020 as the eruptive activity increased. The large red streak in the 3 February 2020 image is SO2 from an eruption of Kuchinoerabujima volcano (Ryukyu Islands) on the same day. Courtesy of NASA Goddard Space Flight Center and Simon Carn.

Geologic Background. The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Japan Aerospace Exploration Agency-Earth Observation Research Center (JAXA-EORC), 7-44-1 Jindaiji Higashi-machi, Chofu-shi, Tokyo 182-8522, Japan (URL: http://www.eorc.jaxa.jp/); Japan Coast Guard (JCG) Volcano Database, Hydrographic and Oceanographic Department, 3-1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8932, Japan (URL: http://www.kaiho.mlit.go.jp/info/kouhou/h29/index.html); 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/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); 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, Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA (URL: http://www.volcarno.com/, Twitter: @simoncarn).


Krakatau (Indonesia) — February 2020 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 155 m

All times are local (unless otherwise noted)


Tephra and steam explosions in the crater lake; explosions in December 2019 build a tephra cone

Krakatau volcano in the Sunda Strait between Indonesia’s Java and Sumatra Islands experienced a major caldera collapse around 535 CE; it formed a 7-km-wide caldera ringed by three islands. Remnants of this volcano joined to create the pre-1883 Krakatau Island which collapsed during the major 1883 eruption. Anak Krakatau (Child of Krakatau), constructed beginning in late 1927 within the 1883 caldera (BGVN 44:03, figure 56), was the site of over 40 eruptive episodes until 22 December 2018 when a large explosion and flank collapse destroyed most of the 338-m-high edifice and generated a deadly tsunami (BGVN 44:03). The near-sea level crater lake inside the remnant of Anak Krakatau was the site of numerous small steam and tephra explosions from February (BGVN 44:08) through November 2019. A larger explosion in December 2019 produced the beginnings of a new cone above the surface of crater lake. Activity from August 2019 through January 2020 is covered in this report with information provided by the Indonesian Center for Volcanology and Geological Hazard Mitigation, referred to as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG). Aviation reports are provided by the Darwin Volcanic Ash Advisory Center (VAAC), and photographs are from the PVMBG webcam and visitors to the island.

Explosions were reported on more than ten days each month from August to October 2019. They were recorded based on seismicity, but webcam images also showed black tephra and steam being ejected from the crater lake to heights up to 450 m. Activity decreased significantly after the middle of November, although smaller explosions were witnessed by visitors to the island. After a period of relative quiet, a larger series of explosions at the end of December produced ash plumes that rose up to 3 km above the crater; the crater lake was largely filled with tephra after these explosions. Thermal activity persisted throughout the period of August 2019-January 2020. The wattage of Radiative Power increased from August through mid-October, and then decreased through January 2020 (figure 96).

Figure (see Caption) Figure 96. Thermal activity persisted at Anak Krakatau from 20 March 2019-January 2020. The wattage of Radiative Power increased from August through mid-October, and then decreased through January 2020. Courtesy of MIROVA.

Activity during August-November 2019. The new profile of Anak Krakatau rose to about 155 m elevation as of August 2019, almost 100 m less than prior to the December 2018 explosions and flank collapse (figure 97). Smaller explosions continued during August 2019 and were reported by PVMBG in 12 different VONAs (Volcano Observatory Notice to Aviation) on days 1, 3, 6, 17, 19, 22, 23, 25, and 28. Most of the explosions lasted for less than two minutes, according to the seismic data. PVMBG reported steam plumes of 25-50 m height above the sea-level crater on 20 and 21 August. They reported a visible ash cloud on 22 August; it rose to an altitude of 457 m and drifted NNE according to the VONA. In their daily update, they noted that the eruption plume of 250-400 m on 22 August was white, gray, and black. The Darwin VAAC reported that the ash plume was discernable on HIMAWARI-8 satellite imagery for a short period of time. PVMBG noted ten eruptions on 24 August with white, gray, and black ejecta rising 100-300 m. A webcam installed at month’s end provided evidence of diffuse steam plumes rising 25-150 m above the crater during 28-31 August.

Figure (see Caption) Figure 97. Only one tree survived on the once tree-covered spit off the NE end of Sertung Island after the December 2018 tsunami from Anak Krakatau covered it with ash and debris. The elevation of Anak Krakatau (center) was about 155 m on 8 August 2019, almost 100 m less than before the explosions and flank collapse. Panjang Island is on the left, and 746-m-high Rakata, the remnant of the 1883 volcanic island, is behind Anak Krakatau on the right. Courtesy of Amber Madden-Nadeau.

VONAs were issued for explosions on 1-3, 11, 13, 17, 18, 21, 24-27 and 29 September 2019. The explosion on 2 September produced a steam plume that rose 350 m, and dense black ash and ejecta which rose 200 m from the crater and drifted N. Gray and white tephra and steam rose 450 m on 13 and 17 September; ejecta was black and gray and rose 200 m on 21 September (figure 98). During 24-27 and 29 September tephra rose at least 200 m each day; some days it was mostly white with gray, other days it was primarily gray and black. All of the ejecta plumes drifted N. On days without explosions, the webcam recorded steam plumes rising 50-150 m above the crater.

Figure (see Caption) Figure 98. Explosions of steam and dark ejecta were captured by the webcam on Anak Krakatau on 21 (left) and 26 (right) September 2019. Courtesy of MAGMA Indonesia and PVMBG.

Explosions were reported daily during 12-14, 16-20, 25-27, and 29 October (figure 99). PVMBG reported eight explosions on 19 October and seven explosions the next day. Most explosions produced gray and black tephra that rose 200 m from the crater and drifted N. On many of the days an ash plume also rose 350 m from the crater and drifted N. The seismic events that accompanied the explosions varied in duration from 45 to 1,232 seconds (about 20 minutes). The Darwin VAAC reported the 12 October eruption as visible briefly in satellite imagery before dissipating near the volcano. The first of four explosions on 26 October also appeared in visible satellite imagery moving NNW for a short time. The webcam recorded diffuse steam plumes rising 25-150 m above the crater on most days during the month.

Figure (see Caption) Figure 99. A number of explosions at Anak Krakatau were captured by the webcam and visitors near the island during October 2019, shown here on the 12th, 14th, 17th, and 29th. Black and gray ejecta and steam plumes jetted several hundred meters high from the crater lake during the explosions. Webcam images courtesy of PVMBG and MAGMA Indonesia, with 12 October 2019 (top left) via VolcanoYT. Bottom left photo on 17 October courtesy of Christoph Sator.

Five VONAs were issued for explosions during 5-7 November, and one on 13 November 2019. The three explosions on 5 November produced 200-m-high plumes of steam and gray and black ejecta and ash plumes that rose 200, 450, and 550 m respectively; they all drifted N (figure 100). The Darwin VAAC reported ash drifting N in visible imagery for a brief period also. A 350-m-high ash plume accompanied 200-m-high ejecta on 6 November. Tephra rose 150-300 m from the crater during a 43 second explosion on 7 November. The explosion reported by PVMBG on 13 November produced black tephra and white steam 200 m high that drifted N. For the remainder of the month, when not obscured by fog, steam plumes rose daily 25-150 m from the crater.

Figure (see Caption) Figure 100. PVMBG’s KAWAH webcam captured an explosion with steam and dark ejecta from the crater lake at Anak Krakatau on 5 November 2019. Courtesy of PVMBG and MAGMA Indonesia.

A joint expedition with PVMBG and the Earth Observatory of Singapore (EOS) installed geophysical equipment on Anak Krakatau and Rakata during 12 and 13 November 2019 (figure 101). Visitors to the island during 19-23 and 22-24 November recorded the short-lived landscape and continuing small explosions of steam and black tephra from the crater lake (figures 102 and 103).

Figure (see Caption) Figure 101. A joint expedition to Anak Krakatau with PVMBG and the Earth Observatory of Singapore (EOS) installed geophysical equipment on Anak Krakatau and Rakata (background, left) during 12 and 13 November 2019. Images of the crater lake from the same spot (left) in December and January show the changes at the island (figure 108). Monitoring equipment installed near the shore sits over the many layers of ash and tephra that make up the island (right). Courtesy of Anna Perttu.
Figure (see Caption) Figure 102.The crater lake at Anak Krakatau during a 19-23 November 2019 visit was the site of continued explosions with jets of steam and tephra that rose as high as 30 m. Courtesy of Andrey Nikiforov and Volcano Discovery, used with permission.
Figure (see Caption) Figure 103. The landscape of Anak Krakatau recorded the rapidly evolving sequence of volcanic events during November 2019. Fresh ash covered recent lava near the shoreline on 22 November 2019 (top left). Large blocks of gray tephra (composed of other tephra fragments) were surrounded by reddish brown smaller fragments in the area between the crater and the ocean on 23 November 2019 (top right). Explosions of steam and black tephra rose tens of meters from the crater lake on 23 November 2019 (bottom). Courtesy of and copyright by Pascal Blondé.

Activity during December 2019-January 2020. Very little activity was recorded for most of December 2019. The webcam captured daily images of diffuse steam plumes rising 25-50 m above the crater which occasionally rose to 150 m. A new explosion on 28 December produced black and gray ejecta 200 m high that drifted N; the explosion was similar to those reported during August-November. A new series of explosions from 30 December 2019 to 1 January 2020 produced ash plumes which rose significantly higher than the previous explosions, reaching 2.4-3.0 km altitude and drifting S, E, and SE according to PVMBG (figure 104). They were initially visible in satellite imagery and reported drifting SW by the Darwin VAAC. By 31 December meteorological clouds prevented observation of the ash plume but a hotspot remained visible for part of that day.

Figure (see Caption) Figure 104.The KAWAH webcam at Anak Krakatau captured this image of incandescent ejecta exploding from the crater lake on 30 December 2019 near the start of a new sequence of large explosions. Courtesy of PVMBG and Alex Bogár.

The explosions on 30 and 31 December 2019 were captured in satellite imagery (figure 105) and appeared to indicate that the crater lake was largely destroyed and filled with tephra from a new growing cone, according to Simon Carn. This was confirmed in both satellite imagery and ground-based photography in early January (figures 106 and 107).

Figure (see Caption) Figure 105. Satellite imagery of the explosions at Anak Krakatau on 30 and 31 December 2019 showed dense steam rising from the crater (left) and a thermal anomaly visible through moderate cloud cover (right). Left image courtesy of Simon Carn, and copyright by Planet Labs, Inc. Right image uses Atmospheric Penetration rendering (bands 12, 11, and 8a) to show the thermal anomaly at the base of the steam plume, courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 106. Sentinel-2 images of Anak Krakatau before (left, 21 December 2019) and after (right, 13 January 2020) explosions on 30 and 31 December 2019 show the filling in of the crater lake with new volcanic material. Natural color rendering based on bands 4,3, and 2. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 107. The crater lake at Anak Krakatau changed significantly between the first week of December 2019 (left) and 8 January 2020 (right) after explosions on 30 and 31 December 2019. Compare with figure 101, taken from the same location in mid-November 2019. Left image courtesy of Piotr Smieszek. Right image courtesy of Peter Rendezvous.

Steam plumes rose 50-200 m above the crater during the first week of January 2020. An explosion on 7 January produced dense gray ash that rose 200 m from the crater and drifted E. Steam plume heights varied during the second week, with some plumes reaching 300 m above the crater. Multiple explosions on 15 January produced dense, gray and black ejecta that rose 150 m. Fog obscured the crater for most of the second half of the month; for a brief period, diffuse steam plumes were observed 25-1,000 m above the crater.

General Reference: Perttu A, Caudron C, Assink J D, Metz D, Tailpied D, Perttu B, Hibert C, Nurfiani D, Pilger C, Muzli M, Fee D, Andersen O L, Taisne B, 2020, Reconstruction of the 2018 tsunamigenic flank collapse and eruptive activity at Anak Krakatau based on eyewitness reports, seismo-acoustic and satellite observations, Earth and Planetary Science Letters, 541:116268. https://doi.org/10.1016/j.epsl.2020.116268.

Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

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/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/); Amber Madden-Nadeau, Oxford University (URL: https://www.earth.ox.ac.uk/people/amber-madden-nadeau/, https://twitter.com/AMaddenNadeau/status/1159458288406151169); Anna Perttu, Earth Observatory of Singapore (URL: https://earthobservatory.sg/people/anna-perttu); Simon Carn, Michigan Tech University (URL: https://www.mtu.edu/geo/department/faculty/carn/; https://twitter.com/simoncarn/status/1211793124089044994); VolcanoYT, Indonesia (URL: https://volcanoyt.com/, https://twitter.com/VolcanoYTz/status/1182882409445904386/photo/1; Christoph Sator (URL: https://twitter.com/ChristophSator/status/1184713192670281728/photo/1); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); Pascal Blondé, France (URL: https://pascal-blonde.info/portefolio-krakatau/, https://twitter.com/rajo_ameh/status/1199219837265960960); Alex Bogár, Budapest (URL: https://twitter.com/AlexEtna/status/1211396913699991557); Piotr (Piter) Smieszek, Yogyakarta, Java, Indonesia (URL: http://www.lombok.pl/, https://twitter.com/piotr_smieszek/status/1204545970962231296); Peter Rendezvous (URL: https://www.facebook.com/peter.rendezvous ); Wulkany swiata, Poland (URL: http://wulkanyswiata.blogspot.com/, https://twitter.com/Wulkany1/status/1214841708862693376).


Mayotte (France) — March 2020 Citation iconCite this Report

Mayotte

France

12.83°S, 45.17°E; summit elev. 660 m

All times are local (unless otherwise noted)


Seismicity and deformation, with submarine E-flank volcanism starting in July 2018

Mayotte is a volcanic island in the Comoros archipelago between the eastern coast of Africa and the northern tip of Madagascar. A chain of basaltic volcanism began 10-20 million years ago and migrating W, making up four principal volcanic islands, according to the Institut de Physique du Globe de Paris (IPGP) and Cesca et al. (2020). Before May 2010, only two seismic events had been felt by the nearby community within recent decades. New activity since May 2018 consists of dominantly seismic events and lava effusion. The primary source of information for this report through February 2020 comes from semi-monthly reports from the Réseau de Surveillance Volcanologique et Sismologique de Mayotte (REVOSIMA), a cooperative program between the Institut de Physique du Globe de Paris (IPGP), the Bureau de Recherches Géologiques et Minières (BRGM), and the Observatoire Volcanologique du Piton de la Fournaise (OVPF-IPGP); Lemoine et al. (2019), the Centre National de la Recherche Scientifique (CNRS), and the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER).

Seismicity was the dominant type of activity recorded in association with a new submarine eruption. On 10 May 2018, the first seismic event occurred at 0814, detected by the YTMZ accelerometer from the French RAP Network, according to BRGM and Lemoine et al. (2019). Seismicity continued to increase during 13-15 May 2018, with the strongest recorded event for the Comoros area occurring on 15 May at 1848 and two more events on 20-21 May (figure 1). At the time, no surface effusion were directly observed; however, Global Navigation Satellite System (GNSS) instruments were deployed to monitor any ground motion (Lemoine et al. 2019).

Figure (see Caption) Figure 1. A graph showing the number of daily seismic events greater than M 3.5 occurring offshore of Mayotte from 10 May 2018 through 15 February 2020. Seismicity significantly decreased in July 2018, but continued intermittently through February 2020, with relatively higher seismicity recorded in late August and mid-September 2018. Courtesy of IPGP and REVOSIMA.

Seismicity decreased dramatically after June 2018, with two spikes in August and September (see figure 1). Much of this seismicity occurred offshore 50 km E of Mayotte Island (figure 2). The École Normale Supérieure, the Observatoire Volcanologique du Piton de la Fournaise (OVPF-IPGP), and the REVOSIMA August 2019 bulletin reported that measurements from the GNSS stations and Teria GPS network data indicated eastward surface deformation and subsidence beginning in July 2018. Based on this ground deformation data Lemoine et al. (2019) determined that the eruptive phase began fifty days after the initial seismic events occurred, on 3 July 2018.

Figure (see Caption) Figure 2. Maps of seismic activity offshore near Mayotte during May 2019. Seismic swarms occurred E of Mayotte Island (top) and continued in multiple phases through October 2019. New lava effusions were observed 50 km E of Petite Terre (bottom). Bottom image has been modified with annotations; courtesy of IPGP, BRGM, IFREMER, CNRS, and University of Paris.

Between 2 and 18 May 2019, an oceanographic campaign (MAYOBS 1) discovered a new submarine eruption site 50 km E from the island of Mayotte (figure 2). The director of IPGP, Marc Chaussidon, stated in an interview with Science Magazine that multibeam sonar waves were used to determine the elevation (800 m) and diameter (5 km) of the new submarine cone (figure 3). In addition, this multibeam sonar image showed fluid plumes within the water column rising from the center and flanks of the structure. According to REVOSIMA, these plumes rose to 1 km above the summit of the cone but did not breach the ocean surface. The seafloor image (figure 3) also indicated that as much as 5 km3 of magma erupted onto the seafloor from this new edifice during May 2019, according to Science Magazine.

Figure (see Caption) Figure 3. Seafloor image of the submarine vent offshore of Mayotte created with multibeam sonar from 2 to 18 May 2019. The red line is the outline of the volcanic cone located at approximately 3.5 km depth. The blue-green color rising from the peak of the red outline represents fluid plumes within the water column. Courtesy of IPGP.

On 17 May 2019, a second oceanographic campaign (MAYOBS 2) discovered new lava flows located 5 km S of the new eruptive site. BRGM reported that in June a new lava flow had been identified on the W flank of the cone measuring 150 m thick with an estimated volume of 0.3 km3 (figure 4). According to REVOSIMA, the presence of multiple new lava flows would suggest multiple effusion points. Over a period of 11 months (July 2018-June 2019) the rate of lava effusion was at least 150-200 m3/s; between 18 May to 17 June 2019, 0.2 km3 of lava was produced, and from 17 June to 30 July 2019, 0.3 km3 of lava was produced. The MAYOBS 4 (19 July 2019-4 August 2019) and SHOM (20-21 August 2019) missions revealed a new lava flow formed between 31 July and 20 August to the NW of the eruptive site with a volume of 0.08 km3 and covering 3.25 km2.

Figure (see Caption) Figure 4. Bathymetric map showing the location of the new lava flow on the W flank of the submarine cone offshore to the E of Mayotte Island. The MAYOBS 2 campaign was launched in June 2019 (left) and MAYOBS 4 was launched in late July 2019 (right). Courtesy of BRGM.

During the MAYOBS 4 campaign in late July 2019, scientists dredged the NE flank of the cone for samples and took photographs of the newly erupted lava (figure 5). Two dives found the presence of pillow lavas. When samples were brought up to the surface, they exploded due to the large amount of gas and rapid decompression.

Figure (see Caption) Figure 5. Photographs taken using the submersible interactive camera system (SCAMPI) of newly formed pillow lavas (top) and a vesicular sample (bottom) dredged near the new submarine eruptive site at Mayotte in late July 2019. Courtesy of BRGM.

During April-May 2019 the rate of ground deformation slowed. Deflation was also observed up to 90 km E of Mayotte in late October 2019 and consistently between August 2019 and February 2020. Seismicity continued intermittently through February 2020 offshore E of Mayotte Island, though the number of detected events started to decrease in July 2018 (see figure 1). Though seismicity and deformation continued, the most recent observation of new lava flows occurred during the MAYOBS 4 and SHOM campaigns on 20 August 2019, as reported in REVOSIMA bulletins.

References: Cesca S, Heimann S, Letort J, Razafindrakoto H N T, Dahm T, Cotton F, 2020. Seismic catalogues of the 2018-2019 volcano-seismic crisis offshore Mayotte, Comoro Islands. Nat. Geosci. 13, 87-93. https://doi.org/10.1038/s41561-019-0505-5.

Lemoine A, Bertil D, Roulle A, Briole P, 2019. The volcano-tectonic crisis of 2018 east of Mayotte, Comoros islands. Preprint submitted to EarthArXiv, 28 February 2019. https://doi.org/10.31223/osf.io/d46xj.

Geologic Background. Mayotte, located in the Mozambique Channel between the northern tip of Madagascar and the eastern coast of Africa, consists two main volcanic islands, Grande Terre and Petite Terre, and roughly twenty islets within a barrier-reef lagoon complex (Zinke et al., 2005; Pelleter et al., 2014). Volcanism began roughly 15-10 million years ago (Pelleter et al., 2014; Nougier et al., 1986), and has included basaltic lava flows, nephelinite, tephrite, phonolitic domes, and pyroclastic deposits (Nehlig et al., 2013). Lavas on the NE were active from about 4.7 to 1.4 million years and on the south from about 7.7 to 2.7 million years. Mafic activity resumed on the north from about 2.9 to 1.2 million years and on the south from about 2 to 1.5 million years. Several pumice layers found in cores on the barrier reef-lagoon complex indicate that volcanism likely occurred less than 7,000 years ago (Zinke et al., 2003). More recent activity that began in May 2018 consisted of seismicity and ground deformation occurring offshore E of Mayotte Island (Lemoine et al., 2019). One year later, in May 2019, a new subaqueous edifice and associated lava flows were observed 50 km E of Petite Terre during an oceanographic campaign.

Information Contacts: Réseau de Surveillance Volcanologique et Sismologique de Mayotte (REVOSIMA), a cooperative program of a) Institut de Physique du Globe de Paris (IPGP), b) Bureau de Recherches Géologiques et Minières (BRGM), c) Observatoire Volcanologique du Piton de la Fournaise (OVPF-IPGP); (URL: http://www.ipgp.fr/fr/reseau-de-surveillance-volcanologique-sismologique-de-mayotte); Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); Bureau de Recherches Géologiques et Minières (BRGM), 3 avenue Claude-Guillemin, BP 36009, 45060 Orléans Cedex 2, France (URL: https://www.brgm.fr/); Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), 1625 route de Sainte-Anne, CS 10070, 29280 Plouzané, France (URL: https://wwz.ifremer.fr/); Centre National de la Recherche Scientifique (CNRS), 3 rue Michel-Ange, 75016 Paris, France (URL: http://www.cnrs.fr/); École Normale Supérieure, 45 rue d'Ulm, F-75230 Paris Cedex 05, France (URL: https://www.ens.psl.eu/); Université de Paris, 85 boulevard Saint-Germain, 75006 Paris, France (URL: https://u-paris.fr/en/498-2/); Roland Pease, Science Magazine (URL: https://science.sciencemag.org/, article at https://www.sciencemag.org/news/2019/05/ship-spies-largest-underwater-eruption-ever) published 21 May 2019.


Fernandina (Ecuador) — March 2020 Citation iconCite this Report

Fernandina

Ecuador

0.37°S, 91.55°W; summit elev. 1476 m

All times are local (unless otherwise noted)


Fissure eruption produced lava flows during 12-13 January 2020

Fernandina is a volcanic island in the Galapagos islands, around 1,000 km W from the coast of mainland Ecuador. It has produced nearly 30 recorded eruptions since 1800, with the most recent events having occurred along radial or circumferential fissures around the summit crater. The most recent previous eruption, starting on 16 June 2018, lasted two days and produced lava flows from a radial fissure on the northern flank. Monitoring and scientific reports come from the Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN).

A report from IG-EPN on 12 January 2020 stated that there had been an increase in seismicity and deformation occurring during the previous weeks. On the day of the report, 11 seismic events had occurred, with the largest magnitude of 4.7 at a depth of 5 km. Shortly before 1810 that day a circumferential fissure formed below the eastern rim of the La Cumbre crater, at about 1.3-1.4 km elevation, and produced lava flows down the flank (figure 39). A rapid-onset seismic swarm reached maximum intensity at 1650 on 12 January (figure 40); a second increase in seismicity indicating the start of the eruption began around 70 minutes later (1800). A hotspot was observed in NOAA / CIMSS data between 1800 and 1810, and a gas plume rising up to 2 km above the fissure dispersed W to NW. The eruption lasted 9 hours, until about 0300 on 13 January.

Figure (see Caption) Figure 39. Lava flows erupting from a circumferential fissure on the eastern flank of Fernandina on 12 January 2020. Photos courtesy of Parque Nacional Galápagos.
Figure (see Caption) Figure 40. Graph showing the Root-Mean-Square (RMS) amplitude of the seismic signals from the FER-1 station at Fernandina on 12-13 January 2020. The graph shows the increase in seismicity leading to the eruption on the 12th (left star), a decrease in the seismicity, and then another increase during the event (right star). Courtesy of S. Hernandez, IG-EPN (Report on 13 January 2020).

A report issued at 1159 local time on 13 January 2020 described a rapid decrease in seismicity, gas emissions, and thermal anomalies, indicating a rapid decline in eruptive activity similar to previous events in 2017 and 2018. An overflight that day confirmed that the eruption had ended, after lava flows had extended around 500 m from the crater and covered an area of 3.8 km2 (figures 41 and 42). Seismicity continued on the 14th, with small volcano-tectonic (VT) earthquakes occurring less than 500 m below the surface. Periodic seismicity was recorded through 13-15 January, though there was an increase in seismicity during 17-22 January with deformation also detected (figure 43). No volcanic activity followed, and no additional gas or thermal anomalies were detected.

Figure (see Caption) Figure 41. The lava flow extents at Fernandina of the previous two eruptions (4-7 September 2017 and 16-21 June 2018) and the 12-13 January 2020 eruption as detected by FIRMS thermal anomalies. Thermal data courtesy of NASA; figure prepared by F. Vásconez, IG-EPN (Report on 13 January 2020).
Figure (see Caption) Figure 42. This fissure vent that formed on the E flank of Fernandina on 12 January 2020 produced several lava flows. A weak gas plume was still rising when this photo was taken the next day, but the eruption had ceased. Courtesy of Parque Nacional Galápagos.
Figure (see Caption) Figure 43. Soil displacement map for Fernandina during 10 and 16 January 2020, with the deformation generated by the 12 January eruption shown. Courtesy of IG-EPN (Report on 23 January 2020).

Geologic Background. Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic "overturned soup bowl" profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 km3 section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake.

Information Contacts: Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Dirección del Parque Nacional Galápagos (DPNG), Isla Santa Cruz, Galápagos, Ecuador (URL: http://www.galapagos.gob.ec/).


Masaya (Nicaragua) — February 2020 Citation iconCite this Report

Masaya

Nicaragua

11.985°N, 86.165°W; summit elev. 594 m

All times are local (unless otherwise noted)


Lava lake persists with lower temperatures during August 2019-January 2020

Masaya is a basaltic caldera located in Nicaragua and contains the Nindirí, San Pedro, San Juan, and Santiago craters. The currently active Santiago crater hosts a lava lake, which has remained active since December 2015 (BGVN 41:08). The primary source of information for this August 2019-January 2020 report comes from the Instituto Nicareguense de Estudios Territoriales (INETER) and satellite -based imagery and thermal data.

On 16 August, 13 September, and 11 November 2019, INETER took SO2 measurements by making a transect using a mobile DOAS spectrometer that sampled for gases downwind of the volcano. Average values during these months were 2,095 tons/day, 1,416 tons/day, and 1,037 tons/day, respectively. August had the highest SO2 measurements while those during September and November were more typical values.

Satellite imagery showed a constant thermal anomaly in the Santiago crater at the lava lake during August 2019 through January 2020 (figure 82). According to a news report, ash was expelled from Masaya on 15 October 2019, resulting in minor ashfall in Colonia 4 de Mayo (6 km NW). On 21 November thermal measurements were taken at the fumaroles and near the lava lake using a FLIR SC620 thermal camera (figure 83). The temperature measured 287°C, which was 53° cooler than the last time thermal temperatures were taken in May 2019.

Figure (see Caption) Figure 82. Sentinel-2 thermal satellite imagery showed the consistent presence of an active lava lake within the Santiago crater at Masaya during August 2019 through January 2020. Images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 83. Thermal measurements taken at Masaya on 21 November 2019 with a FLIR SC620 thermal camera that recorded a temperature of 287°C. Courtesy of INETER (Boletin Sismos y Volcanes de Nicaragua, Noviembre, 2019).

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed intermittent low-power thermal anomalies compared to the higher-power ones before May 2019 (figure 84). The thermal anomalies were detected during August 2019 through January 2020 after a brief hiatus from early may to mid-June.

Figure (see Caption) Figure 84. Thermal anomalies occurred intermittently at Masaya during 21 February 2019 through January 2020. Courtesy of MIROVA.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras caldera and is itself a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The Nindirí and Masaya cones, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6,500 years ago. Historical lava flows cover much of the caldera floor and there is a lake at the far eastern end. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals have caused health hazards and crop damage.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); 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); La Jornada (URL: https://www.lajornadanet.com/, article at https://www.lajornadanet.com/index.php/2019/10/16/volcan-masaya-expulsa-cenizas/#.Xl6f8ahKjct).


Reventador (Ecuador) — February 2020 Citation iconCite this Report

Reventador

Ecuador

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

All times are local (unless otherwise noted)


Nearly daily ash emissions and frequent incandescent block avalanches August 2019-January 2020

Reventador is an andesitic stratovolcano located in the Cordillera Real, Ecuador. Historical eruptions date back to the 16th century, consisting of lava flows and explosive events. The current eruptive activity has been ongoing since 2008 with previous activity including daily explosions with ash emissions, and incandescent block avalanches (BGVN 44:08). This report covers volcanism from August 2019 through January 2020 using information primarily from the Instituto Geofísico (IG-EPN), the Washington Volcano Ash Advisory Center (VAAC), and various infrared satellite data.

During August 2019 to January 2020, IG-EPN reported almost daily explosive eruptions and ash plumes. September had the highest average of explosive eruptions while January 2020 had the lowest (table 11). Ash plumes rose between a maximum of 1.2 to 2.5 km above the crater during this reporting period with the highest plume height recorded in December. The largest amount of SO2 gases produced was during the month of October with 502 tons/day. Frequently at night during this reporting period, crater incandescence was observed and was occasionally accompanied by incandescent block avalanches traveling as far as 900 m downslope from the summit of the volcano.

Table 11. Monthly summary of eruptive events recorded at Reventador from August 2019 through January 2020. Data courtesy of IG-EPN (August to January 2020 daily reports).

Month Average Number of Explosions Max plume height above the crater Max SO2
Aug 2019 26 1.6 km --
Sep 2019 32 1.7 km 428 tons/day
Oct 2019 29 1.3 km 502 tons/day
Nov 2019 25 1.2 km 432 tons/day
Dec 2019 25 2.5 km 331 tons/day
Jan 2020 12 1.7 km --

During the month of August 2019, between 11 and 45 explosions were recorded every day, frequently accompanied by gas-and-steam and ash emissions (figure 119); plumes rose more than 1 km above the crater on nine days. On 20 August the ash plume rose to a maximum 1.6 km above the crater. Summit incandescence was seen at night beginning on 10 August, continuing frequently throughout the rest of the reporting period. Incandescent block avalanches were reported intermittently beginning that same night through 26 January 2020, ejecting material between 300 to 900 m below the summit and moving on all sides of the volcano.

Figure (see Caption) Figure 119. An ash plume rising from the summit of Reventador on 1 August 2019. Courtesy of Radio La Voz del Santuario.

Throughout most of September 2019 gas-and-steam and ash emissions were observed almost daily, with plumes rising more than 1 km above the crater on 15 days, according to IG-EPN. On 30 September, the ash plume rose to a high of 1.7 km above the crater. Each day, between 18 and 72 explosions were reported, with the latter occurring on 19 September. At night, crater incandescence was commonly observed, sometimes accompanied by incandescent material rolling down every flank.

Elevated seismicity was reported during 8-15 October 2019 and almost daily gas-and-steam and ash emissions were present, ranging up to 1.3 km above the summit. Every day during this month, between 13 and 54 explosions were documented and crater incandescence was commonly observed at night. During November 2019, gas-and-steam and ash emissions rose greater than 1 km above the crater except for 10 days; no emissions were reported on 29 November. Daily explosions ranged up to 42, occasionally accompanied by crater incandescence and incandescent ejecta.

Washington VAAC notices were issued almost daily during December 2019, reporting ash plumes between 4.6 and 6 km altitude throughout the month and drifting in multiple directions. Each day produced 5-52 explosions, many of which were accompanied by incandescent blocks rolling down all sides of the volcano up to 900 m below the summit. IG-EPN reported on 11 December that a gas-and-steam and ash emission column rose to a maximum height of 2.5 km above the crater, drifting SW as was observed by satellite images and reported by the Washington VAAC.

Volcanism in January 2020 was relatively low compared to the other months of this reporting period. Explosions continued on a nearly daily basis early in the month, ranging from 20 to 51. During 5-7 January incandescent material ejected from the summit vent moved as block avalanches downslope and multiple gas-and-steam and ash plumes were produced (figures 120, 121, and 122). After 9 January the number of explosions decreased to 0-16 per day. Ash plumes rose between 4.6 and 5.8 km altitude, according to the Washington VAAC.

Figure (see Caption) Figure 120. Night footage of activity on 5 (top) and 6 (bottom) January 2020 at the summit of Reventador, producing a dense, dark gray ash plume and ejecting incandescent material down multiple sides of the volcano. This activity is not uncommon during this reporting period. Courtesy of Martin Rietze, used with permission.
Figure (see Caption) Figure 121. An explosion at Reventador on 7 January 2020, which produced a dense gray ash plume. Courtesy of Martin Rietze, used with permission.
Figure (see Caption) Figure 122. Night footage of the evolution of an eruption on 7 January 2020 at the summit of Reventador, which produced an ash plume and ejected incandescent material down multiple sides of the volcano. Courtesy of Martin Rietze, used with permission.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed frequent and strong thermal anomalies within 5 km of the summit during 21 February 2019 through January 2020 (figure 123). In comparison, the MODVOLC algorithm reported 24 thermal alerts between August 2019 and January 2020 near the summit. Some thermal anomalies can be seen in Sentinel-2 thermal satellite imagery throughout this reporting period, even with the presence of meteorological clouds (figure 124). These thermal anomalies were accompanied by persistent gas-and-steam and ash plumes.

Figure (see Caption) Figure 123. Thermal anomalies at Reventador persisted during 21 February 2019 through January 2020 as recorded by the MIROVA system (Log Radiative Power). Courtesy of MIROVA.
Figure (see Caption) Figure 124. Sentinel-2 thermal satellite images of Reventador from August 2019 to January 2020 showing a thermal hotspot in the central summit crater summit. In the image on 7 January 2020, the thermal anomaly is accompanied by an ash plume. Courtesy of Sentinel Hub Playground.

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/); 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); 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); Radio La Voz del Santuario (URL: https://www.facebook.com/Radio-La-Voz-del-Santuario-126394484061111/, posted at: https://www.facebook.com/permalink.php?story_fbid=2630739100293291&id=126394484061111); Martin Rietze, Taubenstr. 1, D-82223 Eichenau, Germany (URL: https://mrietze.com/, https://www.youtube.com/channel/UC5LzAA_nyNWEUfpcUFOCpJw/videos).


Pacaya (Guatemala) — February 2020 Citation iconCite this Report

Pacaya

Guatemala

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

All times are local (unless otherwise noted)


Continuous explosions, small cone, and lava flows during August 2019-January 2020

Pacaya is a highly active basaltic volcano located in Guatemala with volcanism consisting of frequent lava flows and Strombolian explosions originating in the Mackenney crater. The previous report summarizes volcanism that included multiple lava flows, Strombolian activity, avalanches, and gas-and-steam emissions (BGVN 44:08), all of which continue through this reporting period of August 2019 to January 2020. The primary source of information comes from reports by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH) in Guatemala and various satellite data.

Strombolian explosions occurred consistently throughout this reporting period. During the month of August 2019, explosions ejected material up to 30 m above the Mackenney crater. These explosions deposited material that contributed to the formation of a small cone on the NW flank of the Mackenney crater. White and occasionally blue gas-and-steam plumes rose up to 600 m above the crater drifting S and W. Multiple incandescent lava flows were observed traveling down the N and NW flanks, measuring up to 400 m long. Small to moderate avalanches were generated at the front of the lava flows, including incandescent blocks that measured up to 1 m in diameter. Occasionally incandescence was observed at night from the Mackenney crater.

In September 2019 seismicity was elevated compared to the previous month, registering a maximum of 8,000 RSAM (Realtime Seismic Amplitude Measurement) units. White and occasionally blue gas-and-steam plumes that rose up to 1 km above the crater drifted generally S as far as 3 km from the crater. Strombolian explosions continued, ejecting material up to 100 m above the crater rim. At night and during the early morning, crater incandescence was observed. Incandescent lava flows traveled as much as 600 m down the N and NW flanks toward the Cerro Chino crater (figure 116). On 21 September two lava flows descended the SW flank. Constant avalanches with incandescent blocks measuring 1 m in diameter occurred from the front of many of these lava flows.

Figure (see Caption) Figure 116. Webcam image of Pacaya on 25 September 2019 showing thermal signatures and the point of emission on the NNW flank at night using Landsat 8 (Nocturnal) imagery (left) and a daytime image showing the location of these lava effusions (right) along with gas-and-steam emissions from the active crater. Courtesy of INSIVUMEH.

Weak explosions continued through October 2019, ejecting material up to 75 m above the crater and building a small cone within the crater. White and occasionally blue gas-and-steam plumes rose 400-800 m above the crater, drifting W and NW and extending up to 4 km from the crater during the week of 26 October-1 November. Lava flows measuring up to 250 m long, originating from the Mackenney crater were descending the N and NW flanks (figure 117). Avalanches carrying large blocks 1 m in diameter commonly occurred at the front of these lava flows.

Figure (see Caption) Figure 117. Photo of lava flows traveling down the flanks of Pacaya taken between 28 September 2019 and 4 October. Courtesy of INSIVUMEH (28 September 2019 to 4 October Weekly Report).

Continuing Strombolian explosions in November 2019 ejected material 15-75 m above the crater, which then contributed to the formation of the new cone. White and occasionally blue gas-and-steam plumes rose 100-600 m above the crater drifting in different directions and extending up to 2 km. Multiple lava flows from the Mackenney crater moving down all sides of the volcano continued, measuring 50-700 m long. Avalanches were generated at the front of the lava flows, often moving blocks as large as 1 m in diameter. The number of lava flows decreased during 2-8 November and the following week of 9-15 November no lava flows were observed, according to INSIVUMEH. During the week of 16-22 November, a small collapse occurred in the Mackenney crater and explosive activity increased during 16, 18, and 20 November, reaching RSAM units of 4,500. At night and early morning in late November crater incandescence was visible. On 24 November two lava flows descended the NW flank toward the Cerro Chino crater, measuring 100 m long.

During December 2019, much of the activity remained the same, with Strombolian explosions originating from two emission points in the Mackenney crater ejecting material 75-100 m above the crater; white and occasionally blue gas-and-steam plumes to 100-300 m above the crater drifted up to 1.5 km downwind to the S and SW. Lava flows descended the S and SW flanks reaching 250-600 m long (figure 118). On 29 December seismicity increased, reaching 5,000 RSAM units.

Figure (see Caption) Figure 118. Lava flows moving to the S and SW at Pacaya on 31 December 2019. Courtesy of INSIVUMEH (28 December 2019 to 3 January 2020 Weekly Report).

Consistent Strombolian activity continued into January 2020 ejecting material 25-100 m above the crater. These explosions deposited material inside the Mackenney crater, contributing to the formation of a small cone. White and occasionally blue fumaroles consisting of mostly water vapor were observed drifting in different directions. At night, summit incandescence and lava flows were visible descending the N, NW, and S flanks with the flow on the NW flank traveling toward the Cerro Chino crater.

During August 2019 through January 2020, multiple lava flows and bright thermal anomalies (yellow-orange) within the crater were seen in Sentinel-2 thermal satellite imagery (figures 119 and 120). In addition, constant strong thermal anomalies were detected by the MIROVA (Middle InfraRed Observation of Volcanic Activity) system during 21 February 2019 through January 2020 within 5 km of the summit (figure 121). A slight decrease in energy was seen from May to June and August to September. Energy increased again between November and December. According to the MODVOLC algorithm, 37 thermal alerts were recorded during August 2019 through January 2020.

Figure (see Caption) Figure 119. Sentinel-2 thermal satellite images of Pacaya showing thermal activity (bright yellow-orange) during August 2019 to November. All images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 120. Sentinel-2 thermal satellite images of Pacaya showing thermal activity (bright yellow-orange) during December 2019 through January 2020. All images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 121. The MIROVA thermal activity graph (log radiative power) at Pacaya during 21 February 2019 to January 2020 shows strong, frequent thermal anomalies through January with a slight decrease in energy between May 2019 to June 2019 and August 2019 to September 2019. Courtesy of MIROVA.

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/); 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).


Kikai (Japan) — February 2020 Citation iconCite this Report

Kikai

Japan

30.793°N, 130.305°E; summit elev. 704 m

All times are local (unless otherwise noted)


Single explosion with steam and minor ash, 2 November 2019

The 19-km-wide submerged Kikai caldera at the N end of Japan’s Ryukyu Islands was the source of one of the world's largest Holocene eruptions about 6,300 years ago, producing large pyroclastic flows and abundant ashfall. During the last century, however, only intermittent minor ash emissions have characterized activity at Satsuma Iwo Jima island, the larger subaerial fragment of the Kikai caldera; several events have included limited ashfall in communities on nearby islands. The most recent event was a single day of explosions on 4 June 2013 that produced ash plumes and minor ashfall on the flank. A minor episode of increased seismicity and fumarolic activity was reported in late March 2018, but no ash emissions were reported. A new single-day event on 2 November 2019 is described here with information provided by the Japan Meteorological Agency (JMA).

JMA reduced the Alert Level to 1 on 27 April 2018 after a brief increase in seismicity during March 2018 (BGVN 45:05); no significant changes in volcanic activity were observed for the rest of the year. Steam plumes rose from the summit crater to heights around 1,000 m; the highest plume rose 1,800 m. Occasional nighttime incandescence was recorded by high-sensitivity surveillance cameras. SO2 measurements made during site visits in March, April, and May indicated amounts ranging from 300-1,500 tons per day, similar to values from 2017 (400-1,000 tons per day). Infrared imaging devices indicated thermal anomalies from fumarolic activity persisted on the N and W flanks during the three site visits. A field survey of the SW flank on 25 May 2018 confirmed that the crater edge had dropped several meters into the crater since a similar survey in April 2007. Scientists on a 19 December 2018 overflight had observed fumarolic activity.

There were no changes in activity through October 2019. Weak incandescence at night continued to be periodically recorded with the surveillance cameras (figure 9). A brief eruption on 2 November 2019 at 1735 local time produced a gray-white plume that rose slightly over 1,000 m above the Iodake crater rim (figure 10). As a result, JMA raised the Alert Level from 1 to 2. During an overflight the following day, a steam plume rose a few hundred meters above the summit, but no further activity was observed. No clear traces of volcanic ash or other ejecta were found around the summit (figure 11). Infrared imaging also showed no particular changes from previous measurements. Discolored seawater continued to be observed around the base of the island in several locations.

Figure (see Caption) Figure 9. Incandescence at night on 25 October 2019 was observed at Satsuma Iwo Jima (Kikai) with the Iwanogami webcam. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, October 1st year of Reiwa [2019]).
Figure (see Caption) Figure 10. The Iwanogami webcam captured a brief gray-white ash and steam emission rising above the Iodake crater rim on Satsuma Iwo Jima (Kikai) on 2 November 2019 at 1738 local time. The plume rose slightly over 1,000 m before dissipating. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, October 1st year of Reiwa [2019]).
Figure (see Caption) Figure 11. During an overflight of Satsuma Iwo Jima (Kikai) on 3 November 2019 no traces of ash were seen from the previous day’s explosion; only steam plumes rose a few hundred meters above the summit, and discolored water was present in a few places around the shoreline. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, October 1st year of Reiwa [2019]).

For the remainder of November 2019, steam plumes rose up to 1,300 m above the summit, and nighttime incandescence was occasionally observed in the webcam. Seismic activity remained low and there were no additional changes noted through January 2020.

Geologic Background. Kikai is a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. It was the source of one of the world's largest Holocene eruptions about 6,300 years ago when rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake lava dome and Inamuradake scoria cone, as well as submarine lava domes. Historical eruptions have occurred at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km E of Tokara-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Tokara-Iojima.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html).

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Bulletin of the Global Volcanism Network - Volume 27, Number 06 (June 2002)

Managing Editor: Richard Wunderman

Asamayama (Japan)

Periods of heightened seismicity during September 2000 and June 2002

Chiliques (Chile)

Signs of awakening despite recent dormancy

Colima (Mexico)

Perilous summit visits during 2001 and 2002

Great Sitkin (United States)

Abnormal tremor and earthquake swarms in May 2002

Karymsky (Russia)

Explosions eject ash to 3 km above summit during April and July 2002

Kick 'em Jenny (Grenada)

Bathymetry indicates circular summit crater with dome missing

Klyuchevskoy (Russia)

Increased seismicity prompts KVERT to raise hazard status to Yellow

Merapi (Indonesia)

Pyroclastic flows and lava avalanches occur during February-June 2002

Popocatepetl (Mexico)

Dome extrusions continue, accompanied by minor explosions

Semeru (Indonesia)

Seismicity increases beginning in March 2002; Alert Level increased to 2

Soufriere Hills (United Kingdom)

During 19-29 February large spines and plumes occurred at tidal maxima

Talang (Indonesia)

Small explosion earthquakes dominate through June 2002

Three Sisters (United States)

Studies suggest magma slowly accumulating at depth

Villarrica (Chile)

General decrease in activity during February-May 2002



Asamayama (Japan) — June 2002 Citation iconCite this Report

Asamayama

Japan

36.406°N, 138.523°E; summit elev. 2568 m

All times are local (unless otherwise noted)


Periods of heightened seismicity during September 2000 and June 2002

Asama has a history of periodic heightened seismicity; the last reported seismicity increase occurred in September 1996 (BGVN 21:11). A previously unreported seismic increase began on 18 September 2000. During 18-24 September the Japan Meteorological Agency (JMA) recorded 138, 431, 310, 243, 96, 33, and 14 earthquakes per day, respectively.

During 22-23 June 2002 another period of heightened seismicity occurred at Asama that was similar to the September 2000 activity (figure 15). The earthquakes began at 0100 on 22 June and at 0900 JMA issued a Volcanic Advisory stating that 210 volcanic tremor events had occurred during 0100-0800. The report also stated that the temperature of the crater floor had increased since May 2002; on 19 June the floor was at 180°C. Prior to the heightened seismicity, on 2 and 4 June plumes rose 700 and 1,000 m above Asama's summit, respectively.

Figure (see Caption) Figure 15. Plot showing volcanic earthquakes registered at Asama during 22-24 June 2002. The number of earthquakes peaked on 22 June around 0300 and gradually decreased, reaching background levels on 24 June. Courtesy of Asama Volcano Observatory, ERI-University of Tokyo.

The Asama Volcano Observatory (ERI, University of Tokyo) reported that the number of B-type earthquakes peaked around 0300 on 22 June, with more than 30 earthquakes recorded per hour at a station located on the middle of Asama's eastern slope. Several A-type earthquakes, with a maximum magnitude of 2.1, occurred during 0300-0700. The B- and A-type earthquakes occurred 1.5 and 3.5 km beneath the volcano, respectively.

The restricted area surrounding Asama's summit was increased from 2 km to a 4-km radius on 22 June. After the 22nd, seismicity gradually decreased and JMA reported that by the afternoon of 24 June neither volcanic tremor nor notable changes in ground deformation had been recorded.

Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.

Information Contacts: Tsuneomi Kagiyama, Earthquake Research Institute, University of Tokyo; Yukio Hayakawa, Gunma University, Japan (URL: http://www.hayakawayukio.jp/).


Chiliques (Chile) — June 2002 Citation iconCite this Report

Chiliques

Chile

23.58°S, 67.7°W; summit elev. 5778 m

All times are local (unless otherwise noted)


Signs of awakening despite recent dormancy

On 12 April 2002, NASA's Jet Propulsion Laboratory reported that new images taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (Aster) on NASA's Terra satellite showed signs of activity at Chiliques. This volcano was previously considered to be dormant; however, on 6 January, a nighttime thermal infrared image from Aster showed a hot spot in the summit crater, as well as several others along the upper flanks, indicating new volcanic activity (figure 1). Examination of an earlier nighttime thermal infrared image from 24 May 2000 showed no such hot spots.

Figure (see Caption) Figure 1. Aster images of Chiliques. The larger view is a daytime image acquired on 19 November 2000, created by displaying ASTER bands 1, 2, and 3. The inset is a nighttime thermal infrared image of Chiliques on 6 January 2002. Both images cover an area of 7.5 x 7.5 km and are centered at 23.6°S latitude, 67.6°W longitude. Courtesy Michael Abrams, NASA's Jet Propulsion Laboratory.

General Reference. de Silva, S.L., and Francis, P.W., 1991, Volcanoes of the Central Andes: Berlin: Springer-Verlag, 216 p.

Geologic Background. Volcán Chiliques is a structurally simple stratovolcano located immediately south of Laguna Lejía. The summit contains a 500-m-wide crater. Several youthful lava flows, some of which are considered to be of possible Holocene age (de Silva, 2007 pers. comm.), descend its flanks. The largest of these extends 5 km NW. Older lava flows reach up to 10 km from the summit on the N flank. This volcano had previously been considered to be dormant; however, in 2002 a NASA nighttime thermal infrared satellite image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) showed low-level hot spots in the summit crater and upper flanks.

Information Contacts: Michael Abrams, Jet Propulsion Laboratory, California Institute of Technology, National Aeronautics and Space Administration, Pasadena, CA 91109 (URL: http://www.jpl.nasa.gov/).


Colima (Mexico) — June 2002 Citation iconCite this Report

Colima

Mexico

19.514°N, 103.62°W; summit elev. 3850 m

All times are local (unless otherwise noted)


Perilous summit visits during 2001 and 2002

The following report documents several climbs to the summit of Volcán de Colima, carried out in order to accurately measure the size of the growing lava dome, measure fumarole temperatures, and sample gases when possible. Strict safety precautions were followed and climbs were only undertaken during periods of low seismicity. Time is local (calibrated to RESCO seismographic clock). Coordinates and most calculations were obtained by GPS navigator (accuracies of 3-6 m indicated by the instrument) and GARMIN software.

Between 19 August 2001 and 29 June 2002, Nick Varley, Juan Carlos Gavilanes-Ruiz, Mitchell Ventura-Fishgold, Philippa Swannell, and Ruri Ursúa-Calvario performed four ascents to the growing dome, obtaining fresh lava samples, as well as ballistic-projectile samples ejected by the pre-extrusion explosion that occurred on 22 February 2001 (table 12). The lava sample of 18 February 2002 was obtained by Carlos Navarro-Ochoa (a block from a rockfall at the active lava front).

Table 12. The authors took fresh lava samples at Colima at these specified dates and locations. Latitude and longitude are given in degrees, minutes, and decimal minutes. Courtesy Universidad de Colima and Instituto de Geofísica.

Date Sample Sampling site Coordinates
22 Feb 2001 1 El Playon, 1.72 km to the NE of the crater (ballistic projectile). 19°31.607'N, 103°36.645'W
19 Aug 2001 2 Growing dome (1 meter from a glowing fumarole at 808°C). 19°30.773'N, 103°37.013'W
26 Nov 2001 3 Growing dome (andesitic spine). 19°30.747'N, 103°36.983'W
18 Feb 2002 A W face, ~1.2 km below the lava flow's active front. [location unknown?]
22 Feb 2002 4 Growing dome (see figure 57). 19°30.788'N, 103°37.021'W
29 Jun 2002 5 Growing dome SE part. 19°30.755'N, 103°36.904'W

During each ascent GPS and geometric measurements were taken in order to calculate the volume of the dome and the current rate of extrusion. Figures 53 and 54 show the preliminary calculations of these variations. The samples collected during the ascents were analyzed by Juan Carlos Mora-Chaparro.

Figure (see Caption) Figure 53. Increase in volume of lava dome and flows measured at Colima during May 2001-April 2002. Courtesy Universidad de Colima and Instituto de Geofísica.
Figure (see Caption) Figure 54. Variation in effusion rates seen at Colima from May 2001 to April 2002. Courtesy Universidad de Colima and Instituto de Geofísica.

Ascent to the crater, 19 August 2001. On this occasion Varley and Gavilanes descended into the crater and circumnavigated the dome discovered on 26 May 2001. The volume of the dome had increased by ~77% since then, and a new lobe had appeared. The GPS tracks recorded around the dome revealed a maximum distance of 103 m in its N-S axis, and a maximum of 122 m in the E-W axis. A zone of incandescent fumaroles (with temperatures up to 877°C) was found on the NE slope of the dome and on the adjacent crater floor (figure 55). This high-temperature zone was located in the same position as the high-temperature group of fumaroles that existed above the previous dome and was monitored between 1995 and 1998. This suggests that the location of the main conduit has not changed since then. During the nearly 4-hour-long stay (0950-1400) on the crater rim and inside the crater, only two small rockfalls were heard.

Figure (see Caption) Figure 55. Incandescent fumarole on the E flank of the growing dome inside the major crater on 19 August 2001. A lava sample was obtained 1 m to the left. Photo taken by J.C. Gavilanes-Ruiz. Courtesy Universidad de Colima and Instituto de Geofísica.

Samples of high-temperature fumarolic gases were taken during this ascent. Unlike previous samples from Colima, they were relatively uncontaminated by atmospheric air. The results of the analyses are shown in table 13. The temperature ranges recorded in the N crater-floor field and in the N and NE crater-rim field are shown in table 14.

Table 13. Volume of gases of high-temperature fumarolic gas collected on 19 August 2001 at Colima. R/Ra represents the isotopic ratio of helium normalized to the atmospheric ratio. (Gas volumes are in mol%). Courtesy Universidad de Colima and Instituto de Geofísica.

H2O H2 CO2 CO Stot HCl HF N2 CH4 He R/Ra He/Ne
95.22 0.75 0.99 0.006 2.04 0.42 0.010 0.39 0 0.0001 6.2 48

Table 14. Temperature ranges of fumarole fields at Colima during 19 August 2001-26 November 2002. Courtesy Universidad de Colima and Instituto de Geofísica.

Date Fumarole field Temperature range
19 Aug 2001 N and NE rim 122-330°C
26 Nov 2001 N and NE rim 100-295°C
22 Feb 2002 N and NE rim 128-221°C
29 Jun 2002 N and NE rim 162-272°C
19 Aug 2001 NE crater-floor 590-877°C
26 Nov 2002 South side of the dome 80-140°C

Ascent to the crater and to the base of the active dome, 26 Nov 2001. During this excursion Varley and Ventura descended into the crater and measured temperatures of the new fumarole field on the S border of the growing dome (figure 56). Meanwhile, Gavilanes and Ursúa measured the fields located on the N and NE borders of the main crater and performed GPS measurements. Gas condensates were sampled from the NE fumarole field. Rock samples were taken from the andesitic spine (figure 57) first observed almost one month previously by personnel of Proteccion Civil of the State of Jalisco. The spine was located in the same area where the maximum temperatures were found on 19 August 2001. The mean frequency of rockfalls from the active dome caused by the lava effusion was once every 5 minutes, with larger events occurring approximately once every 30 minutes. Ranges of fumarole temperatures measured on the S side of the dome and in the NE field are shown in table 14.

Figure (see Caption) Figure 56. Composite photos giving a wide-angle view of the growing dome and collapsing spine from the E border of the main crater on 26 November 2001. The circle (left) locates Nick Varley and Mitch Ventura who were measuring fumarole temperatures in the S sector of the main crater. GPS data indicated that by this day the dome measured 98 m along its N-S axis. Photo taken by J.C. Gavilanes-Ruiz. Courtesy Universidad de Colima and Instituto de Geofísica.
Figure (see Caption) Figure 57. Photo taken on 26 November 2001 showing Ruri Ursúa standing on the E inner border of the main crater of Colima. The highest part of the growing dome can be seen in the background, the andesitic spine in the center of the photo (~ 10 m high in the visible part). Photo taken by J.C. Gavilanes-Ruiz. Courtesy Universidad de Colima and Instituto de Geofísica.

Ascent to the dome, 22 Feb 2002. During this ascent several light ashfall-producing, small explosive events were observed (figure 58). One event expelled several bombs (up to 20 cm in diameter) to a height of ~20 m above the dome. The explosions appeared to originate from the central to W side of the dome. Small rockfalls were occurring approximately once every 15 to 20 minutes on the E side of the dome. Due to the potential of rockfalls, a temperature was only obtained from the fumarole field to the N. There had been an increase in the size of this field, which was located outside of the crater, high on the N flank. The temperature range is shown in table 14.

Figure (see Caption) Figure 58. The ~10 m-high E border of the growing dome at Colima on 22 February 2002. The area covered by the outermost blocks is the remaining ~ 20 m-wide part of the 1987 crater. Photo taken by Nick Varley. Courtesy Universidad de Colima and Instituto de Geofísica.

Ascent to the lava flow's front, 7 June 2002. On this ascent Varley and Gavilanes, climbing the S flank of the volcano, reached a point (19°30.218N, 103°37.392W) located at the same elevation (3,090 m) and approximately 75 m to the E of the front of the active lava flow emplaced on the upper part of the Cordobán Central ravine. The maximum length of the Cordobán Central 2002 lava flow was estimated to be 1,290 m on 7 June 2002. During this 6-hour-long ascent, the average frequency of rockfalls originating from both the lava flow front and the active dome was on the order of one rockfall every 10 minutes. No pyroclastic flows were observed.

Ascent to El Volcancito. On 11 June 2001 Juan Carlos Gavilanes and Alejandro Elizalde ascended to the dome formed in 1869-1872 called El Volcancito in order to repair the meteorological station (19°30.996 N, 103°36.511 W). El Volcancito is located on Colima's E summit (1,010 m horizontal distance, and N62°E of the center of the active dome of Volcán de Colima at 19°30.746 N, 103°37.020 W). Only one rockfall was observed on the E face while the team was 1,750 m from the dome, during the period from 1200-1545. In comparison to the 22 February 2001 observations performed from the same distance, no substantial changes in the size of the dome were apparent from El Volcancito (figure 59).

Figure (see Caption) Figure 59. Alejandro Elizalde repairing the meteorological station located on El Volcancito dome. Volcancito sits ~1 km NE of Volcán de Colima's active summit dome, which can be seen capping the summit in the background. Photo taken by J.C. Gavilanes-Ruiz. Courtesy Universidad de Colima and Instituto de Geofísica.

Ascent to the dome, 29 June 2002. Varley and Gavilanes remained on the N (figure 60), NE, and E borders of the active dome during 1147-1540. On the NE and N borders they measured angular heights and distances between the crater's lip and the upper part of the new dome borders. Only a small volume of lava blocks was observed to have fallen outside of the crater rim on the N border, extending only 4 m. No rockfalls were observed. The team tried to reach the center of the dome, but the complicated array of big scoriaceous and fragile new lava blocks, with abundant 3-to 7-m-deep void spaces between them (figure 61), impeded movement. They measured temperatures at the N fumarole field (table 14) and obtained a condensate gas sample. They also saw and/or heard several short-lived and high-pressure emissions of volcanic gas (table 15).

Figure (see Caption) Figure 60. Photo on 29 June 2002 showing Nick Varley walking adjacent to the crater's N rim. The dark blocks of lava (on the right) represent loose debris that has fallen from the active dome. Photo taken by J.C. Gavilanes-Ruiz. Courtesy Universidad de Colima and Instituto de Geofísica.
Figure (see Caption) Figure 61. Photo on 29 June 2002 showing J.C. Gavilanes-Ruiz (enclosed by the circle) walking on the NE border of the active dome. Photo taken by Nick Varley. Courtesy Universidad de Colima and Instituto de Geofísica.

Table 15. High-pressure emissions of volcanic gas at Colima on 29 June 2002. Courtesy Universidad de Colima and Instituto de Geofísica.

Date Time Observations
29 June 2002 1252 Observed and heard at 40 m (white/bluish gas discharges ~30 m high)
29 June 2002 1420 Observed and heard at 50 m (white/bluish gas discharges ~30 m high)
29 June 2002 1520 Heard at 250 m
29 June 2002 1603 Heard at 250 m
29 June 2002 1857 Heard at 1,800 m

Petrographical and chemical analyses were conducted on recent rock samples from Volcán de Colima at the Instituto de Geofísica, UNAM. The results were compared with similar analyses reported by Mora et al. (2002) from the 1998, 1999, and 2001 samples (table 16).

Table 16. Chemical composition of Colima lava. Numbers in parentheses correspond to the sample numbers in table 12. Fe2O3t = Fe total (except 1913). References: 1Mora et al. (2002), 2Luhr and Carmichael (1982). New data courtesy Universidad de Colima and Instituto de Geofísica.

Sample/wt. % 1818 1818 18182 19132 19981 19981 19991 19991 20001 2001 (1) 2001 (2) 2001 (3) 2002 (A) 2002 (4) 2002 (5)
SiO2 58.71 57.70 58.52 57.57 60.44 61.00 60.59 59.83 60.77 59.53 59.81 59.60 60.67 59.10 59.70
TiO2 0.66 0.79 0.83 0.79 0.62 0.55 0.64 0.63 0.61 0.63 0.64 0.64 0.61 0.64 0.64
Al2O3 17.88 17.71 17.53 17.42 18.10 18.06 18.29 18.83 18.08 16.84 17.14 16.90 17.23 17.01 17.32
Fe2O3t 6.25 6.78 6.89 2.64 5.28 4.91 5.09 5.99 5.85 6.14 6.08 6.31 5.83 6.20 6.07
FeO -- -- -- 3.74 -- -- -- -- -- -- -- -- -- -- --
MnO 0.11 0.12 0.12 0.12 0.10 0.09 0.08 0.11 0.11 0.11 0.11 0.11 0.11 0.11 0.11
MgO 3.82 4.26 3.77 4.14 3.22 3.42 3.07 3.70 2.54 4.13 3.96 4.60 2.91 4.35 3.99
CaO 6.54 6.96 7.11 7.02 6.04 5.88 6.56 6.33 6.16 6.18 6.23 6.22 5.76 6.26 6.13
Na2O 4.50 4.49 4.46 4.40 4.69 4.56 4.53 4.68 4.47 4.53 4.56 4.43 4.72 4.51 4.59
K2O 1.22 1.32 1.23 1.16 1.35 1.37 1.12 1.31 1.28 1.30 1.27 1.29 1.36 1.29 1.38
P2O5 0.19 0.24 0.20 0.19 0.13 0.12 0.18 0.20 0.13 0.20 0.20 0.19 0.23 0.19 0.19
LOI 0.19 -0.03 -- 0.49 0.34 0.36 0.12 0.16 0.41 -0.25 -0.24 -0.12 -0.04 0.04 0.02
Total 100.07 100.34 101.66 99.68 100.31 100.32 100.27 100.77 100.91 99.34 99.76 100.17 99.39 99.70 100.14

Chemical analyses indicated that the new rocks registered a slight decrease in SiO2 and Al2O3 contents, and a slight increase in MgO with respect to the 1998 samples. Trace elements registered a decrease of Ba, and increases of Cu, Cr, and Ni (table 16).

Chemical analyses of rocks from 1818 to 2002 eruptions (Luhr, J.F. and Carmichael, I.S.E., 1982; Mora et al. 2002), show maximum variations of ~4 wt.% SiO2 (57 to 61 wt.%), and ~1.6 wt.% MgO (3.0 to 4.6 wt.%). The most mafic compositions were recorded in the products of the largest explosive eruptions (1818 and 1913). Notable disequilibrium textures observed in phenocrysts, as well as the shift to less evolved compositions in the new dome (2002 samples) with respect to the 1998 eruptive products may indicate an input of magma from a deeper chamber or an injection of new magma into the more shallow magma chamber. Therefore, we think that these detailed petrographic and chemical studies of the more recent eruptive products may provide valuable information for the monitoring of this volcano.

References. Luhr, J.F., and Carmichael, I.S.E., 1982, The Colima Volcanic Complex, Mexico: Part III, Ash and scoria-fall deposits from the upper slopes of Volcán Colima: Contrib. Mineral. Petrol., v. 80, p. 262-275.

Mora, J.C., Macías, J.L., Saucedo, R., Orlando A., Manetti, P., and Vaselli, O., 2002, Petrology of the 1998-2000 products of Volcán de Colima, Mexico: Accepted in the Special Issue of the Journal of Volcanology and Geothermal Research "Volcán de Colima, México, and its Activity in 1997-2000" (in press).

Geologic Background. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Information Contacts: N. Varley, J. C. Gavilanes-Ruiz, Facultad de Ciencias and Centro Universitario de Investigaciones en Ciencias del Ambiente, Universidad de Colima; J.C. Mora, J.L. Macias, R. Castro, R. Arias, Instituto de Geofísica, UNAM.


Great Sitkin (United States) — June 2002 Citation iconCite this Report

Great Sitkin

United States

52.076°N, 176.13°W; summit elev. 1740 m

All times are local (unless otherwise noted)


Abnormal tremor and earthquake swarms in May 2002

On 27 and 28 May the Alaska Volcano Observatory (AVO) detected anomalous seismicity at Great Sitkin, a volcano located 1,895 km SW of Anchorage, Alaska. On 27 May two periods of seismic tremor lasted for 20 and 55 minutes and on 28 May earthquake swarms began at 0306 and 1228. The earthquake swarms each began with a relatively large event (ML 2.2 and ML 4.3) followed by tens to hundreds of smaller aftershocks, most located 5-6 km SE of the crater at depths of 0-5 km. Both the tremor and earthquake swarms represent significant changes from background seismicity at Great Sitkin. However, aftershocks declined significantly overnight, and seismicity returned to background levels with a lack of recorded tremor since 27 May. Satellite imagery showed no signs of surface volcanic activity, and no reports of anomalous activity were received by AVO.

Geologic Background. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Information Contacts: Tom Murray and John Eichelberger, Alaska Volcano Observatory (AVO) (URL: http://www.avo.alaska.edu/).


Karymsky (Russia) — June 2002 Citation iconCite this Report

Karymsky

Russia

54.049°N, 159.443°E; summit elev. 1513 m

All times are local (unless otherwise noted)


Explosions eject ash to 3 km above summit during April and July 2002

Seismicity at Karymsky was above background during late March through at least mid-July 2002. Local shallow events occurred at the same rate previously reported in BGVN 27:03 (~10 events per hour). The rate increased briefly during mid-May to ~10-15 events per hour. The character of the seismicity indicated that weak gas-and-ash explosions and avalanches possibly occurred. Thermal anomalies and occasional plumes were visible on satellite imagery throughout the report period (table 2).

Table 2. Thermal anomalies and plumes visible on AVHRR satellite imagery at Karymsky during 30 March-9 July 2002. No airborne ash was detected in any image. Courtesy KVERT.

Date Time (local) Size (pixels) Max. band-3 temperature Background temperature Visible plume
30 Mar 2002 -- -- 13°C -15 to -20°C --
31 Mar 2002 -- -- -- -- Faint thermal anomaly visible through cloud cover.
09 Apr 2002 -- 4 29°C 0°C --
12 Apr-19 Apr 2002 -- 2-5 -- -- --
17 Apr 2002 1807 2 29°C -3°C Faint aerosol/steam plume trended SE.
20 Apr 2002 -- 3 23°C -5 to -20°C --
22 Apr 2002 -- 5 30°C 3°C --
26 Apr-03 May 2002 -- 1-6 42°C 0- ~10°C Possible faint aerosol/steam plume trended SE, visible at 1704 on 28 April.
03 May 2002 -- 3-4 13.4°C -8°C --
04 May 2002 -- 3-4 40°C -1°C Small aerosol/steam plume visible trended S at 1800.
09 May 2002 1740 2 37.5°C 4°C Faint ash-and-gas plume visible extended 20 km to the SE.
10 May-17 May 2002 -- 2-4 ~50°C 2-7°C --
10 May 2002 0727 -- -- -- Ash-and-steam plume visible trended 50 km to the S.
13 May 2002 1744 -- -- -- Faint steam/aerosol plume extended ~60 km to the SE.
20 May 2002 -- 1 16°C -2°C Faint plume extended 30 km to the SE at 0647.
22 May 2002 -- 2 ~49°C 7°C --
24 May 2002 0651 3 16.4°C -2°C --
01 Jun 2002 -- 1 11°C 0°C --
02 Jun 2002 -- 3 49°C 6°C --
09 Jun 2002 0708 2-4 43.5°C -1.5°C --
15 Jun 2002 -- 3 ~49°C 17°C Karymsky lake visible on image at temperature of 33.6°C, six pixels square, warmest to the W.
20 Jun 2002 -- 3 38°C 17°C --
23, 25, 27 Jun 2002 -- 1-3 10 - ~49°C 1 - 18°C Steam/gas plume extended 35 km to the W on 25 June.
29 Jun-30 Jun 2002 -- 1-4 15 - ~49°C -4 - 25°C --
01 Jul-02 Jul 2002 -- -- -- -- Small steam plume extended ~50 km to the NE on 1 July.
06, 08-09 Jul 2002 -- 1-3 ~25 - 31°C 5 - 11.5°C --

According to a pilot's report, at 1115 on 15 April an explosion ejected ash to a height of 3.0 km above the volcano. MODIS imagery on 17 April revealed at least five traces of ashfall extending to ~25 km in various directions.

During a helicopter flight on 28 April, observers reported an ash explosion to 500 m above the crater. Ash deposits were visible on the W (most intense) and E flanks of the volcano. A new ~100-m-high cone was visible on 28 April inside the active crater.

On 10 May the new cone was visible along with a lava flow 1.3 km down the S-SW slope of the volcano (figure 9). It reached ~300 m wide. The flow was unusual because it had an andesitic composition, rather than the typical basaltic composition that was common in lava flows down the SW flank during 1996-2000. Seismic data on 29 June indicated a possible ash-and-gas explosion to a height of ~4.0 km at 1631. On 9 July at 1032, a helicopter pilot reported a plume to a height of 3.0 km. The Concern Color Code remained at Yellow throughout the report period.

Figure (see Caption) Figure 9. View of Karymsky from a helicopter on 10 May 2002. The billowing plume at the time of this photo concealed the new intracrater cone at the summit; winds carried the plume approximately ENE. The active crater generated a conspicuous lava flow down the S-SW slope that reached ~1.3 km long and ~300 m wide (~ 20% of its length continued beyond the lower right-hand margin of this photo). Caption help courtesy of Victor Ivanov (Institute of Volcanology). Photo by Nikolay I. Seliverstov (Institute of Volcanology); provided courtesy of KVERT.

Geologic Background. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Information Contacts: Olga Chubarova, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tokyo Volcanic Ash Advisory Center (VAAC),Tokyo, Japan (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).


Kick 'em Jenny (Grenada) — June 2002 Citation iconCite this Report

Kick 'em Jenny

Grenada

12.3°N, 61.64°W; summit elev. -185 m

All times are local (unless otherwise noted)


Bathymetry indicates circular summit crater with dome missing

Submarine volcanic eruptions occurred at Kick-'em-Jenny during 4-6 December 2001 (BGVN 26:11). Following the 6 December seismicity, no further volcanic or seismic activity were recorded. On 8 December the Alert Level was reduced from Orange to Yellow.

On 12 March 2002, the NOAA Research Vessel Ronald H. Brown conducted extensive mapping of Kick-'em Jenny using the SeaBeam® sonar mapping system (SeaBeam® is a registered trademark of L-3 Communications SeaBeam Instruments). The resulting bathymetric map (figure 3) shows several interesting features.

Figure (see Caption) Figure 3. Bathymetric sonar map of the Kick-'em-Jenny created on 12 March 2002. Courtesy Seismic Research Unit, University of the West Indies.

The volcano's crater is clearly visible (immediately right of center on the image) on top of a symmetrical cone of about 1 km diameter. The crater is nearly perfectly circular with a diameter of ~330 m and a maximum depth of ~80 m. The crater center is located precisely at 12.3004° N, 61.6378° W. The dome, first noticed in 1978 when it almost filled the crater, has now disappeared except for a few remnants on the crater floor. The sonar image shows a breach of the crater to the NE. A prominent escarpment arcs around the E side of the cone and extends at least a few kilometers to the NE and S of the volcano. A series of ridges, principally in the cone's N to W sectors, trend radial or sub-radial to the cone's crater.

The topographic image furnished a bases for some new studies. Temperature-depth profiles were obtained within the crater and on the flanks, water samples were collected at a range of depths, and rock samples were collected from the summit region.

The Seismic Research Unit of the University of the West Indies reported that complete analysis of the results will take some time but preliminary analysis of the bathymetry confirms that the depth to the summit of the volcano has increased since the last detailed survey in 1989. Depth to the highest point on the crater rim is now ~183 m. The difference between this depth and the depths of ~160 m measured from 1978 to 1989 is probably accounted for by the fact that the dome that filled the crater beginning in 1977 has now completely disappeared.

Geologic Background. Kick 'em Jenny, a historically active submarine volcano 8 km off the N shore of Grenada, rises 1300 m from the sea floor. Recent bathymetric surveys have shown evidence for a major arcuate collapse structure, which was the source of a submarine debris avalanche that traveled more than 15 km W. Bathymetry also revealed another submarine cone to the SE, Kick 'em Jack, and submarine lava domes to its S. These and subaerial tuff rings and lava flows at Ile de Caille and other nearby islands may represent a single large volcanic complex. Numerous historical eruptions, mostly documented by acoustic signals, have occurred since 1939, when an eruption cloud rose 275 m above the sea. Prior to the 1939 eruption, which was witnessed by a large number of people in northern Grenada, there had been no written mention of the volcano. Eruptions have involved both explosive activity and the quiet extrusion of lava flows and lava domes in the summit crater; deep rumbling noises have sometimes been heard onshore. Historical eruptions have modified the morphology of the summit crater.

Information Contacts: John Shepard, Richie Robertson, Jan Lindsay, and Joan Latchman, Seismic Research Unit, University of the West Indies, St. Augustine, Trinidad, W.I. (URL: http://www.uwiseismic.com/).


Klyuchevskoy (Russia) — June 2002 Citation iconCite this Report

Klyuchevskoy

Russia

56.056°N, 160.642°E; summit elev. 4754 m

All times are local (unless otherwise noted)


Increased seismicity prompts KVERT to raise hazard status to Yellow

During mid-September 2001 through at least mid-June 2002 activity at Kliuchevskoi was characterized by brief periods of increased seismicity and minor surface activity. Earthquakes up to M 3 occurred (table 3) along with weak spasmodic tremor with a maximum amplitude up to 1.5 x 10-6 m/s (table 4). Gas-and-steam plumes often accompanied the increased seismicity and were visible reaching up to 2.0 km above the crater (table 5).

Table 3. Seismicity at Kliuchevskoi during mid-September 2001 through mid-June 2002. Courtesy KVERT.

Date Event Magnitude
13 Sep 2001 Two earthquakes M ~2 and ~1.7
01 Oct-02 Oct 2001 Eleven earthquakes five M ~2, six ~1.7
18 Oct 2001 Series of large earthquakes within the edifice --
26 Oct-09 Nov 2001 Series of earthquakes within the edifice and ~30 km depth --
13 Nov 2001 Swarm of shallow earthquakes ~M 3
13 Nov-15 Nov 2001 150+ earthquakes M 1.7
07 Apr 2002 Series of shallow earthquakes began M 2.3
24 May-31 May 2002 Weak earthquakes at a depth of ~30 km --
31 May-07 Jun 2002 ~20 earthquakes/day at a depth of ~30 km M 2.3
11 Jun 2002 ~30 min series of shallow earthquakes M 2.8
07 Jun-14 Jun 2002 22-48 earthquakes/day at a depth of ~30 km --

Table 4. Tremor recorded at Kliuchevskoi during mid-September through mid-June 2002. Courtesy KVERT.

Date Event Magnitude/amplitude (µm/s)
20 Sep 2001 Volcanic tremor 0.15
21 Sep-22 Sep 2001 Volcanic tremor 0.23-0.21
23 Sep 2001 Volcanic tremor 0.28
24 Sep 2001 Volcanic tremor 0.4
25 Sep-26 Sep 2001 Volcanic tremor 0.23-0.27
27 Sep-29 Sep 2001 Weak, continuous volcanic tremor 0.22-0.32
01 Oct 2001 Intermittent weak spasmodic volcanic tremor 0.19
02 Oct-04 Oct 2001 Intermittent weak spasmodic volcanic tremor 0.30
05 Oct 2001 Continuous, spasmodic tremor 0.30
06 Oct 2001 Continuous, spasmodic tremor 0.18
09 Oct 2001 Continuous, spasmodic tremor 0.26
10 Oct 2001 Continuous, spasmodic tremor 0.51
11 Oct 2001 Continuous, spasmodic tremor 0.47
12 Oct 2001 Continuous, spasmodic tremor 0.51
13 Oct 2001 Continuous, spasmodic tremor 0.54
14 Oct 2001 Volcanic tremor 0.13
15 Oct-17 Oct 2001 Volcanic tremor 0.15-0.17
Nov 2001 Episodes of weak volcanic tremor --
Apr-May 2002 Weak volcanic tremor --
30 May 2002 Volcanic tremor 1.5

Table 5. Plumes visible at Kliuchevskoi during 13 September 2001 to 20 June 2002. Plumes were visible from Klyuchi town unless noted otherwise. Heights are above the crater. Courtesy KVERT.

Date Time Plume details
13, 17, 19-20 Sep 2001 -- Gas-and-steam plumes rose 50-100 m.
19 Sep 2001 -- Gas-and-steam plume rose 1.0 km and extended 20 km to the S.
23 Sep 2001 -- Gas-and-steam plume rose 100 m.
24 Sep 2001 1828 Possible gas-and-steam plume observed in satellite image.
01 Oct 2001 0810 Gas-and-steam plume up to 1.0 km extending 30 km to the NW.
01 Oct 2001 1150 Gas-and-steam plume up to 2.0 km extending 15 km to the NW.
01 Oct 2001 1400 Gas-and-steam plume up to 1.5-2.0 km extending 10 km to the W.
01 Oct 2001 1730 Gas-and-steam plume up to 800 m extending 5 km to the S visible from Kozyurevsk.
02 Oct 2001 ~0830 Gas-and-steam plume up to 300 m extending 3 km to the S visible from Kozyurevsk and Klyuchi.
05 Oct 2001 0850 Gas-and-steam plume rose 300 m and extended 3 km to the S visible from Kozyurevsk.
05 Oct 2001 1200 Gas-and-steam plume rose 100 m.
10 Oct 2001 0815 Gas-and-steam plume rose 500 m and extended 5 km to the S.
12, 14, 16, 27-29 Oct 2001 -- Gas-and-steam plumes rose 50-100 m.
30 Oct 2001 -- Gas-and-steam plume rose 700 m and extended 5 km to the SE.
31 Oct 2001 -- Gas-and-steam plume rose 50-100 m and extended 5 km to the SE.
01 Nov 2001 -- Gas-and-steam plume rose 50-100 m.
02 Nov 2001 -- Gas-and-steam plume rose 50-200 m and extended 3 km to the SE.
06 Nov 2001 -- Gas-and-steam plume rose 50-200 m and extended 20 km to the NE.
08 Nov 2001 -- Gas-and-steam plume rose 50-200 m.
09 Nov 2001 -- Gas-and-steam plume rose 600 m.
11-13, 18 Nov 2001 -- Gas-and-steam plume rose 50-100 m.
19 Nov 2001 -- Gas-and-steam plume rose 700 m and extended 10 km to the SE.
21 Nov 2001 -- Gas-and-steam plume rose 500 m and extended to the SW.
09 Apr 2002 2038 Explosion sent a gas-and-steam plume with possible ash to 1.0 km.
06, 09-10 Apr; 24, 27 May 2002 -- Gas-and-steam plume rose 100 m.
31 May; 1-3, 6, 9 15-16, 20 Jun 2002 -- Gas-and-steam plume rose 100-300 m.

On 13 November a swarm of shallow M 3 earthquakes caused the Kamchatkan Volcanic Eruption Response Team (KVERT) to increase the Alert Level from Green to Yellow. According to a pilot's report, at 1315 on 19 November powerful fumarolic activity was observed. Seismicity decreased during the following days and on 23 November KVERT decreased the Color Code to Green. Seismicity remained at or near background levels with only slight increases in activity until 31 May when a series of earthquakes (up to M 2.3) was recorded in the volcano's edifice. As a result, the Color Code was increased to Yellow.

During 31 May-7 June ~20 earthquakes occurred daily at a depth of ~30 km (table 3). Overflight observations on 9 June indicated fresh ash on the volcano's slopes. The deposits were not accompanied by visually or seismically detected explosions. At the end of the report period, seismicity was slightly above background with a small gas-and-steam plume visible from nearby villages.

Geologic Background. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

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 and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Merapi (Indonesia) — June 2002 Citation iconCite this Report

Merapi

Indonesia

7.54°S, 110.446°E; summit elev. 2910 m

All times are local (unless otherwise noted)


Pyroclastic flows and lava avalanches occur during February-June 2002

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

Table 14. Seismicity (low-frequency, avalanche, and multiphase) and crater characteristics at Merapi during 25 February-16 June 2002. Magnetic field strength was measured at Pusang-Lempong and is reported in nanoteslas (nT). "--" indicates that the information was not reported. Courtesy VSI.

Date Low-frequency events Avalanche events Multiphase events Magnetic field strength Gendol crater Woro crater
25 Feb-03 Mar 2002 -- -- -- -- -- 571°C
04 Mar-10 Mar 2002 -- 666 -- -- -- --
11 Mar-17 Mar 2002 5 652 -- -- -- --
18 Mar-24 Mar 2002 1 609 -- -- -- --
25 Mar-31 Mar 2002 60 575 -- -- -- --
01 Apr-07 Apr 2002 135 539 1 -- -- --
15 Apr-21 Apr 2002 46 364 -- 3.09 nT -- --
22 Apr-28 Apr 2002 19 367 1 0.32 nT -- --
29 Apr-05 May 2002 9 383 13 -3.22 nT 737-742°C 421-434°C
06 May-12 May 2002 13 353 -- 4.64 nT 737-746°C 398-431°C
13 May-19 May 2002 2 345 2 8.28 nT 734-748°C 406-430°C
20 May-26 May 2002 -- 308 15 -1.02 nT 734-749°C 421-431°C
27 May-02 Jun 2002 8 310 6 -1.47 nT 620-750°C 354-430°C
03 Jun-09 Jun 2002 9 268 6 -1.65 nT 741-756°C 423-435°C
10 Jun-16 Jun 2002 -- 281 5 1.65 nT 736-755°C 423-434°C

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

Date Average SO2 emission (ton/day) Range (ton/day) Max. avg. (ton/day)
03 Mar-10 Mar 2002 156 96-254 196
11 Mar-17 Mar 2002 131 87-173 138
18 Mar-24 Mar 2002 146 103-206 --
25 Mar-31 Mar 2002 133 74-172 136
01 Apr-07 Apr 2002 107 73-145 108
15 Apr-21 Apr 2002 124 105-167 --
22 Apr-28 Apr 2002 155 97-219 182
29 Apr-05 May 2002 156 109-245 173
06 May-12 May 2002 166 123-210 169
13 May-19 May 2002 90 43-182 145
20 May-26 May 2002 140 64-206 160
27 May-02 Jun 2002 131 62-216 167
03 Jun-09 Jun 2002 141 85-196 167
10 Jun-16 Ju 2002 125 42-218 161

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

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

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

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

Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

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


Popocatepetl (Mexico) — June 2002 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Dome extrusions continue, accompanied by minor explosions

During March through at least late June 2002, volcanic activity at Popocatépetl consisted of small-to-moderate, but at times explosive, eruptions of steam, gas, and generally minor amounts of ash, along with episodes of harmonic tremor. Ash clouds rose up to ~2 km above the summit. Because of the remote location and high elevation of the summit, the dome growth within the crater was often hard to constrain, although seismicity and occasional flights over the summit did shed light on the situation. The following report is compiled from updates from the Centro Nacional de Prevencion de Desastres (CENAPRED) and from reports issued by the Washington Volcanic Ash Advisory Center (VAAC).

March began with activity at low and steady levels with up to 18 small steam-and-gas emissions per day and occasional episodes of harmonic tremor. The amount of ash emitted was generally minor. Occasional M 3 volcano-tectonic (VT) events were recorded. Low fumarolic activity began on 4 March and was frequently visible throughout the report period. Overflight observations on 7 March confirmed the presence of a lava dome in the crater (figure 44). A gas-and-steam plume reached ~2 km above the crater on 9 March. According to CENAPRED, the activity implied the possibility of low-level explosive activity in the coming days or weeks.

Figure (see Caption) Figure 44. Aerial view from the NE on 7 March 2002 of the crater of Popocatépetl. The darkest circle in the center of the crater represents the newest lava-dome growth. Courtesy CENAPRED.

Activity increased during 26-27 March when 42 gas and steam emissions reached 200-500 m above the crater, accompanied by small amounts of ash and low-amplitude harmonic tremor. The Washington VAAC issued a volcanic ash warning based upon seismic observations that indicated a possible ash-bearing eruption, but no ash was visible in satellite images. Activity decreased to levels similar to earlier in the month and continued at those levels through early April.

At 0438 on 8 April, observers recorded a moderate eruption with explosive characteristics accompanied by some visible incandescence. An accompanying ash cloud moved E towards the coastline and diffused within 24 hours. After a M 2.3 VT earthquake was recorded at 0545 on 8 April, activity returned to steady levels.

Activity remained low through mid-April, with the exception of a brief period around 11 April when observers detected a slight increase in low-amplitude tremor and fumarolic activity. An increased number of small-to-moderate exhalations per day (up to 52) accompanied by episodes of low-level harmonic and high-frequency tremor, and weak VT earthquakes characterized increased activity that began in late April and lasted through early May. According to CENAPRED, this activity was most likely related to motion of small amounts of magma towards the surface and growth of the lava dome within the crater.

An air photo taken on 29 April (figure 45) by the Department of Federal Roads showed a small dome ~170 m in diameter. On 1 May CENAPRED reported an ash plume moving W at 1.0 km above the summit. No ash was visible on satellite imagery.

Figure (see Caption) Figure 45. Air photo of the Popocatépetl crater taken by the Department of Federal Roads on 29 April 2002. The darkest circle in the left-center of the photo is the newest lava dome, measuring 170 m across. Subsequent flights indicated that explosive activity on 12 May destroyed part of this dome. Courtesy CENAPRED.

Activity increased slightly during mid-May with 33 small-to-moderate exhalations and 1 hour of low-amplitude tremor on 10 May. At 0609 on 12 May, a small explosive eruption occurred, ejecting incandescent fragments on the N flank up to 500 m from the crater. During the next few days, CENAPRED reported increased numbers of exhalations per day (up to 124 on 14 May) of steam, gas, and sometimes small amounts of ash. It was later determined from overflight observations that this explosive activity destroyed part of the growing dome.

This period of increased activity decreased beginning around 17 May. During the rest of May, activity was again characterized by numerous (up to 66) small-to-moderate gas-and-steam exhalations accompanied by small amounts of ash and periods of harmonic tremor. Fumarolic activity continued at the surface. A pilot reported an ash cloud in the region on 21 May.

Activity declined to steady, low levels through June with the average number of exhalations per day dropping to less than 10, occasional isolated harmonic tremor episodes of ~15 minutes duration, and as many as five VT earthquakes per day (M 2.5).

On 17 June at 1136 an ash plume extended up to 2 km above the summit and drifted to the WSW. Shortly thereafter, CENAPRED recorded high-frequency tremor for almost 8 hours and four VT events (M 2.0-2.2). The resulting ash cloud moved across Mexico to the SW. During the following days the volcano quieted but continued to emit gas, steam, and ash in small quantities with episodes of harmonic tremor lasting less than an hour. On 27 and 29 June ash plumes reaching up to 2 km above the summit were accompanied by periods of harmonic tremor lasting up to 2 hours. The Alert Level remained at Yellow throughout the report period.

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 Prevencion de Desastres (CENAPRED), Delfin Madrigal 665, Col. Pedregal de Santo Domingo, Coyoacán, 04360, México D.F. (URL: https://www.gob.mx/cenapred/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/).


Semeru (Indonesia) — June 2002 Citation iconCite this Report

Semeru

Indonesia

8.108°S, 112.922°E; summit elev. 3657 m

All times are local (unless otherwise noted)


Seismicity increases beginning in March 2002; Alert Level increased to 2

Since mid-July 2001, Semeru was at Alert Level 1 (on a scale of 1-4). On 8 March 2002 two pyroclastic flows traveled 2.5 km downslope to the Besuk Kembar river. The same day, tectonic and volcanic earthquakes increased, prompting the Volcanological Survey of Indonesia (VSI) to raise the Alert Level to 2. Tectonic and volcanic earthquakes continued, along with explosions, avalanches, pyroclastic flows, and tremor (table 7). Plumes, sometimes containing ash, were visible reaching up to 500 m above the summit (table 8).

Table 7. Seismicity registered at Semeru during 3 March-16 June 2002. "--" indicates that information was not reported. Courtesy VSI.

Date Deep volcanic Shallow volcanic Explosion Avalanche Local tectonic Pyroclastic flow Tremor Far tremor
03 Mar-10 Mar 2002 8 1 479 22 2 2 -- --
11 Mar-17 Mar 2002 1 2 444 21 -- -- 3 --
18 Mar-24 Mar 2002 2 -- 514 10 1 -- -- --
25 Mar-31 Mar 2002 9 6 302 171 1 -- 2 --
01 Apr-07 Apr 2002 26 2 415 278 -- -- -- --
08 Apr-14 Apr 2002 9 -- 509 141 3 -- 1 --
15 Apr-21 Apr 2002 16 4 791 194 -- -- -- --
22 Apr-28 Apr 2002 6 0 585 64 3 0 5 14
29 Apr-05 May 2002 0 0 664 52 0 0 3 14
06 May-12 May 2002 5 0 783 62 0 0 0 15
13 May-19 May 2002 1 0 575 146 0 0 0 13
20 May-26 May 2002 -- -- -- -- -- -- -- --
27 May-02 Jun 2002 2 1 556 90 1 -- 2 --
03 Jun-09 Jun 2002 2 -- 556 45 -- -- 1 --
10 Jun-16 Jun 2002 2 -- 637 31 -- -- -- --

Table 8. Plumes observed at Semeru during 8 March-16 June 2002. Courtesy VSI.

Date Plume Type Plume height (above the summit)
08 Mar 2002 White-gray 400 m
12, 14, and 17 Mar 2002 White-gray 300-400 m
19-23 Mar 2002 White-gray ~300-500 m
25-31 Mar 2002 White-gray 300-500 m
15-21 Apr 2002 White-gray, medium pressure 400 m
22 Apr-26 May 2002 White-gray, medium pressure 400 m
10-16 Jun 2002 White-gray ash 200-400 m

On 31 March two tremor earthquakes occurred with amplitudes of ~3-17 mm. During mid-April, a tremor earthquake occurred with an amplitude of 0.2 mm. Lava avalanches continued to travel up to 750 m down to Besuk Kembar. Seismic signals thought to indicate local floods registered 15-21 April. Incandescence was observed up to 25 m above the crater rim during 1820-2025 on 18 April. During that time, seismicity was dominated by low-frequency earthquakes, with amplitudes of 2-3 mm. During 27 May-2 June ash explosions produced white-gray plumes that reached ~200-400 m above the summit, while lava avalanches traveled ~100 m away. Semeru remained at Alert Level 2 through at least 16 June 2002.

Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

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


Soufriere Hills (United Kingdom) — June 2002 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


During 19-29 February large spines and plumes occurred at tidal maxima

Stephen O'Meara and four Volcano Watch International (VWI) team members (Robert Benward, Tippy D'Auria, Scott Ireland, and Larry Mitchell) visually monitored Soufrière Hills for 10 days beginning on 19 February 2002. The observations took place on Jack Boy Hill, a spot at ~180 m elevation 6 km N of the volcano. In addition, for 3 hours on the night of 25 February, the group joined Montserrat Volcano Observatory (MVO) scientists Peter Dunkley and Richard Herd on the runway at Bramble Airport. Except for a storm on 20 February, the weather facilitated exceptionally clear views of the dome during both day and night. The team employed a variety of telescopes and other optical equipment and had an interest in astronomy as well as the volcano (O'Meara, 2002).

Benward brought along a homemade night-vision scope (near-infrared image intensifier) that captured images of the dome, even through local atmospheric conditions where visible light was weakened or scattered. The intensifier was coupled to camera lenses. It could be used visually or attached to a video camera (figure 47). The camera's phosphor viewing screen yielded green-colored images of the hot portions of the dome.

Figure (see Caption) Figure 47. The night-vision scope (image intensifier) put together by Robert Benward and used to obtain images of Soufriere Hills' growing dome. In this configuration the intensifier lies between two other components: a telephoto camera lens (left) and a video camera (right). Courtesy of Steve O'Meara, Robert Benward, and Sky and Telescope magazine.

One purpose of the VWI team's visit to Montserrat was to chronicle changes in the volcano's visible behavior with approach to the time of the full Moon and its perigee (when the Moon is closest to the Earth). The idea was that the tidal influence associated with the full Moon and its perigee might lead to enhanced activity. With approach of the full Moon, there did seem to be a rise in visible indicators, particularly plume height, a strong pulse of extruded spines, and less-substantial increases in the numbers of rockfalls and pyroclastic flows.

As background on tidal forces, the paths of both the Moon around the Earth, and Earth around the Sun are elliptical throughout the lunar cycle (29.53 days) and solar cycle (the year), meaning that the separations and resulting gravitational forces vary with time. The Earth-Moon separations change by ~50,000 km; when they are smallest (perigee) and largest (apogee) the respective tidal forces are higher or lower than usual. In addition, the gravitational attractions of Moon and Sun on the Earth may act along a common line or at changing angles relative to each other. Particularly large tides affect the Earth's crust and oceans when the Sun and the Moon are lined up with the Earth; this occurs at the new and full phases of the Moon. These orientations lead to what are called spring tides (a name not associated with the season of Spring, but which implies a "welling up"). The amount of tidal enhancement is roughly the same whether the Sun and Moon are lined up on opposite sides of the Earth (full Moon) or on the same side of the Earth (new Moon). In contrast, when the Moon is at first quarter or last quarter (meaning that it is located at right angles to the Earth-Sun line), the Sun and Moon produce tidal bulges called neap tides. These are generally weaker than the above-described spring tides.

A two-month record of seismicity and tides at the volcanically active Axial seamount on the Juan de Fuca ridge during 1994 found both bi-weekly and diurnal patterns in earthquakes and volcanic tremor (Tolstoy and others, 2002). The authors concluded that microearthquakes took place at tidal minima.

Montserrat, Moon, and magma. The full Moon occurred at 0518 on 27 February; perigee, ~11 hours later, at 1630. The team's 10-day stay was too short to see more than a partial lunar cycle, but soon after full Moon and perigee, the numbers for the observed visible indicators appeared to drop considerably.

After an initial study of dome activity on 19 February and a storm on 20 February, the group began taking regular visible observations on 21 February. At that time, activity appeared to be on the increase and a high-level of activity was sustained throughout the observation period. According to MVO: "The level of volcanism at Soufrière Hills during 22 February-1 March was higher than it had been in previous weeks." The growing dome was quite active, displaying near continuous rockfall and small pyroclastic flows, most of which traveled E to the Tar River Valley, though some activity was directed to the S and W. During the 10-day observation interval, the dome also rapidly extruded very large spines.

By midnight on 27 February the team had recorded and tabulated 440 observations of notable rockfalls and pyroclastic flows. On the whole during this interval, the number of these events per hour stood well below 10, typically ranging from ~4 to ~8. One low, late on 23 February, only reached 1 event per hour. The average number of these events per hour reached a low of ~5 during 21-23 February rising to ~8 on 27 February. The highest hourly total recorded during the observing period occurred on 27 February with 13 of these events during 0000-0100 and 10 during 1120-1320. These times fall on either side of the full Moon; the second total lies at the midpoint between the full Moon and lunar perigee.

Visible activity decreased sharply on 28 February. The team, which departed on 3 March, made sporadic observations until 1 March. Their observations on and after 28 February suggested dome activity had remained substantially lower than during 21-27 February.

During their interval of observation the team found a direct correlation between the number of large visible events and the size of the dome's emerging and collapsing spines. The mass of each spine also increased during the observation period; the largest spine was observed on 26 February, the day before the full Moon and perigee.

Each of the spines collapsed in less than a day, only to regrow rapidly. The largest (shown on figures 48-53) reached 90 m tall; it enabled the summit to attain 1,080-m elevation, the highest the summit has been during the entire eruption to date (according to the MVO weekly update). It grew rapidly; specifically, it was not present from 1830 to 2100 on the evening of 25 February, but was fully grown by 0600 the following morning. When seen at 0330 on 26 February the new spine appeared as an incandescent obelisk about one-fifth its maximum size. The majority of this massive spine then grew to its record height in 3 hours.

Figure (see Caption) Figure 48. A S-view taken from Jack Boy Hill of Soufrière Hills dome shown with the yet-highest-reaching spine seen to date, which was photographed shortly after sunrise on 26 February 2002. The spine appears as a triangular peak at the summit; it soon began to collapse. Courtesy of Steve and Donna O'Meara, Volcano Watch International.
Figure (see Caption) Figure 49. A S-looking night shot taken from Jack Boy Hill at 0300 on 26 February that depicts Soufriere Hills in a highly incandescent state, with a large and growing spine extruding out of the top of the dome. Disrupted and displaced dome materials, including falling blocks, incandescent rockfalls, and pyroclastic flows, have left a conspicuous apron of hot material on the dome's left (W) side. Surprisingly little ash and steam appear to be present. Courtesy of Steve and Donna O'Meara, Volcano Watch International.
Figure (see Caption) Figure 50. A daytime shot taken from Jack Boy Hill showing part of a comparatively large pyroclastic flow at Soufriere Hills on 24 February 2002. Courtesy of Steve and Donna O'Meara, Volcano Watch International.
Figure (see Caption) Figure 51. The ragged summit of the dome at Soufriere Hills as it lies beneath a small plume at sunset. Taken from Jack Boy Hill looking S on 25 February 2002. Courtesy of Steve and Donna O'Meara, Volcano Watch International.
Figure (see Caption) Figure 52. A night shot of the dome at Soufriere Hills showing the summit dome that was soon to extrude a large spine (not yet visible). This photo was taken from the airport (several kilometers NE of the dome) in conditions of moonlight on 25 February at about 2100. Courtesy of Steve and Donna O'Meara, Volcano Watch International.
Figure (see Caption) Figure 53. Soufriere Hills' glowing dome showing triangular spine in the moonlight with stars in the night sky. Taken from the airport (several kilometers NE of the dome). Courtesy of Steve and Donna O'Meara, Volcano Watch International.

Figure 54 is one of several plots constructed to illustrate the results. It was made by omitting the smaller events, which the team judged from small to medium using a qualitative visual scale that ran from S1 to S3 and continued upwards from M1 to M3 (where event sizes are abbreviated as S for "small" and M for "medium" and termed as S-class or M-class, respectively). Thus, the largest events seen were M3 (i.e., they saw no events in these time periods that they classified as "large"). On their scale, events of size S3 and M1 were judged to be of very similar magnitude. Figure 54 shows the increase in larger event size seen during 21-26 February, culminating in the highest numbers late on 26 February to early on 27 February.

Figure (see Caption) Figure 54. A plot of the number of larger observed rockfall and pyroclastic-flow events seen at Soufrière Hills during 21-27 February 2002. The events counted in this plot excluded the smallest two categories (S1 and S2 classes, see text). High tides were shown (thin vertical lines) for those cases where they occurred during an interval in which observations were conducted; otherwise they are absent. The symbols along the top of the plot indicate processes described in the key. The symbol sizes were increased or reduced for events judged to be of larger or smaller size. For example, the largest spine grew on 26 February (large dark triangle). Courtesy of Steve and Donna O'Meara, Volcano Watch International.

Figure 54 shows six high tides that occurred at times when observations were conducted (on 21, 22, 24, 26 and 27 February). Five of the six of these tides coincided with observation intervals with the day's highest number of the largest events (the M-class events).

Plume height. As shown on figure 55, an increase in plume height took place around the time of first quarter Moon followed by a decrease, then a gradual rise in plume height, until it reached a maximum at the time of perigee on 27 February. Although atmospheric conditions could clearly affect the extent and height of a plume, the team found the pattern of the plotted data compelling. The plot may disclose tidal effects.

Figure (see Caption) Figure 55. Plume heights (in degrees above a reference horizon) at Soufriere Hills plotted against time as observed during 19-28 February 2002. Courtesy of Steve and Donna O'Meara, Volcano Watch International.

References. O'Meara, S., 2002, Firelight nights: Stargazing from the Caribbean's Emerald Isle; A group of American amateur astronomers helps residents of Montserrat and its neighboring island explore the universe: Sky & Telescope, August 2002, p. 79-83.

Tolstoy, M., Vernon, F.L., Orcutt, J.A., and Wyatt, F.K., 2002, Breathing of the seafloor, tidal correlations of seismicity at Axial Volcano: Geological Society of America (GSA), Geology, v. 30, no. 6, p. 503-506.

Geologic Background. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Information Contacts: Steve and Donna O'Meara, Robert Benward, Tippy D'Auria, Scott Ireland, and Larry Mitchell, Volcano Watch International, PO Box 218, Volcano, Hawaii 96785.


Talang (Indonesia) — June 2002 Citation iconCite this Report

Talang

Indonesia

0.979°S, 100.681°E; summit elev. 2575 m

All times are local (unless otherwise noted)


Small explosion earthquakes dominate through June 2002

During 11 March-16 June 2002 at Talang, seismicity was dominated by small explosion earthquakes (table 4). A thin white plume reached 50-100 m above the summit and sometimes drifted E. Hotspring temperatures were 42-64°C. As of 13 May, the Volcanological Survey of Indonesia (VSI) reported that no seismic data were available because of a broken seismograph. During April and early May seismicity had been decreasing. Talang remained at Alert Level 2 (on a scale of 1-4) throughout the report period.

Table 4. Earthquakes at Talang during 11 March-12 May 2002. The seismograph was broken as of 13 May, so no seismicity data was available through at least 16 June. Courtesy VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Small explosion Tectonic
11 Mar-17 Mar 2002 1 17 61 14
18 Mar-24 Mar 2002 2 -- 120 9
25 Mar-31 Mar 2002 2 -- 120 13
01 Apr-07 Apr 2002 2 -- 63 5
08 Apr-14 Apr 2002 1 -- 23 12
15 Apr-21 Apr 2002 3 -- -- 6
22 Apr-28 Apr 2002 6 -- -- 7
29 Apr-05 May 2002 4 -- -- 14
06 May-12 May 2002 3 -- -- 3

Geologic Background. Talang, which forms a twin volcano with the extinct Pasar Arbaa volcano, lies ESE of the major city of Padang and rises NW of Dibawah Lake. Talang has two crater lakes on its flanks; the largest of these is 1 x 2 km wide Danau Talang. The summit exhibits fumarolic activity, but which lacks a crater. Historical eruptions have mostly involved small-to-moderate explosive activity first documented in the 19th century that originated from a series of small craters in a valley on the upper NE flank.

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


Three Sisters (United States) — June 2002 Citation iconCite this Report

Three Sisters

United States

44.133°N, 121.767°W; summit elev. 3159 m

All times are local (unless otherwise noted)


Studies suggest magma slowly accumulating at depth

Uplift (up to ~10 cm) occurred during 1996-2000 over a broad region centered 5 km W of South Sister in the Three Sisters region (BGVN 26:05). At the time scientists did not know exactly when the uplift had occurred, whether it would continue, or its specific cause. Although most of these questions remain, some new data are available.

On 18 March 2002 scientists from the USGS Cascades Volcano Observatory and Central Washington University reported that they, in cooperation with staff from the U.S. Forest Service's (USFS) Willamette and Deschutes National Forests, confirmed that slow uplift of the area was continuing at approximately the same rate as previously reported (i.e., a maximum rate of ~2.5 cm/year).

About a month later NASA's Jet Propulsion Laboratory (JPL) released a simulated natural-color image from the Aster high-resolution imaging instrument on the satellite Terra. Aster uses 14 spectral bands, at wavelengths from visible to thermal-infrared, and it has a spatial resolution of 15-90 m. By draping the Aster data over digital topography from the U.S. Geological Survey's National Elevation Dataset, they created a new perspective view of the Three Sisters and adjacent Cascade volcanoes (figure 2). The image was timely because of concerns about continued uplift in the area. BGVN 26:05 included a radar interferogram showing ground uplift pattern during 1996-2000, movement centered ~ 5 km W of South Sister.

Figure (see Caption) Figure 2. The Three Sisters volcanic area appears in this perspective view from the SW quadrant. The view uses a simulated natural-color image from the satellite-borne Aster imaging system, which has been draped over digital topography taken from the U.S. Geological Survey's National Elevation Dataset. N lies to the upper-right; the distance between the summits of North Sister and South Sister is ~ 7 km. The image was released on 12 April 2002. Courtesy NASA's Jet Propulsion Laboratory.

Analyses of spring water samples collected during late summer 2001 were similar to those from earlier surveys but isotopic studies of carbon and helium in the most recent samples, which were not done previously, suggested a magmatic source. Taken together, the ground deformation, seismic, spring water chemistry, and gas emission results suggest that uplift was caused by slow accumulation of magma at a depth of 6-7 km beneath the surface. If magma intrusion were to continue, it could eventually lead to a volcanic eruption; however, an eruption is unlikely without months to years of precursory activity. In addition to continued or accelerating uplift, precursors to an eruption would include earthquakes, typically swarms of small events generated by fracturing of rock as magma moves upward, and large emissions of volcanic gases, such as carbon dioxide, which is released from the magma.

The Pacific Northwest Seismograph Network (PNSN) has reported three earthquakes in the Three Sisters region since January 2001. On 21 August 2001 a M 1.9 earthquake occurred at a depth of 4.9 km; on 5 November 2001 a M 1 earthquake occurred at a depth of 1 km; and on 18 January 2002 an M 2.4 earthquake occurred at a depth of 3.0 km. The recent earthquakes are consistent with background seismicity at Three Sisters. As of mid-July 2002, the number of earthquakes and gas emissions remained at low-t-obackground levels while steady uplift continued.

General Reference. Scott, W.E., 1987, Holocene rhyodacite eruptions on the flanks of South Sister volcano, Oregon: Geol Soc Amer Spec Pap, v. 212, p. 35-53.

Geologic Background. The north-south-trending Three Sisters volcano group dominates the landscape of the Central Oregon Cascades. All Three Sisters stratovolcanoes ceased activity during the late Pleistocene, but basaltic-to-rhyolitic flank vents erupted during the Holocene, producing both blocky lava flows north of North Sister and rhyolitic lava domes and flows south of South Sister volcano. Glaciers have deeply eroded the Pleistocene andesitic-dacitic North Sister stratovolcano, exposing the volcano's central plug. Construction of the main edifice ceased at about 55,000 yrs ago, but north-flank vents produced blocky lava flows in the McKenzie Pass area as recently as about 1600 years ago. Middle Sister volcano is located only 2 km to the SW and was active largely contemporaneously with South Sister until about 14,000 years ago. South Sister is the highest of the Three Sisters. It was constructed beginning about 50,000 years ago and was capped by a symmetrical summit cinder cone formed about 22,000 years ago. The late Pleistocene or early Holocene Cayuse Crater on the SW flank of Broken Top volcano and other flank vents such as Le Conte Crater on the SW flank of South Sister mark mafic vents that have erupted at considerable distances from South Sister itself, and a chain of dike-fed rhyolitic lava domes and flows at Rock Mesa and Devils Chain south of South Sister erupted about 2000 years ago.

Information Contacts: Cascades Volcano Observatory (CVO), U.S. Geological Survey (USGS), Building 10, Suite 100, 1300 SE Cardinal Court, Vancouver, WA 98683 (URL: https://volcanoes.usgs.gov/observatories/cvo/); Volcano Hazards Team, USGS, 345 Middlefield Road, Menlo Park, CA 94025-3591 USA (URL: http://volcanoes.usgs.gov/); Pacific Northwest Seismograph Network (PNSN), University of Washington Geophysics Program, Box 351650, Seattle, WA 98195-1650 USA (URL: http://www.geophys.washington.edu/SEIS/PNSN/); Jet Propulsion Laboratory, California Institute of Technology, National Aeronautics and Space Administration, Pasadena, CA 91109 (URL: http://www.jpl.nasa.gov/).


Villarrica (Chile) — June 2002 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


General decrease in activity during February-May 2002

Our last report described activity at Villarrica during January 2001 (BGVN 27:02) through January 2002, when incandescent lava was observed in the crater and ballistics were ejected ~80-150 m. At that time explosions generally occurred every ~1-10 minutes and degassing sounds were occasionally heard.

During February through at least May 2002, sporadic observations showed a general decrease in activity. Degassing noises were sometimes heard; however, no incandescence or ballistics were reported. A crater visit on 9 April revealed that no incandescence or explosive noises occurred. The surface of the lava lake, last seen on 19 January, remained low (~200 m below the crater rim). On 10 April, explosions occurred every ~10-13 minutes.

Geologic Background. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Information Contacts: Proyecto de Observacion Villarrica (POVI), Wiesenstrasse 8, 86438 Kissing, Germany (URL: http://www.povi.cl/).

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

Additional 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 subregion and subject.

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

08/1997 (BGVN 22:08) False Report of Mount Pinokis Eruption

False report of volcanism intended to exclude would-be gold miners

12/1997 (BGVN 22:12) False Report of Somalia Eruption

Press reports of Somalia's first historical eruption were likely in error

11/1999 (BGVN 24:11) False Report of Sea of Marmara Eruption

UFO adherent claims new volcano in Sea of Marmara

05/2003 (BGVN 28:05) Har-Togoo

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

False report of activity; confusion caused by burning dung in a lava tube



False Report of Mount Pinokis Eruption (Philippines) — August 1997

False Report of Mount Pinokis Eruption

Philippines

7.975°N, 123.23°E; summit elev. 1510 m

All times are local (unless otherwise noted)


False report of volcanism intended to exclude would-be gold miners

In discussing the week ending on 12 September, "Earthweek" (Newman, 1997) incorrectly claimed that a volcano named "Mount Pinukis" had erupted. Widely read in the US, the dramatic Earthweek report described terrified farmers and a black mushroom cloud that resembled a nuclear explosion. The mountain's location was given as "200 km E of Zamboanga City," a spot well into the sea. The purported eruption had received mention in a Manila Bulletin newspaper report nine days earlier, on 4 September. Their comparatively understated report said that a local police director had disclosed that residents had seen a dormant volcano showing signs of activity.

In response to these news reports Emmanuel Ramos of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) sent a reply on 17 September. PHIVOLCS staff had initially heard that there were some 12 alleged families who fled the mountain and sought shelter in the lowlands. A PHIVOLCS investigation team later found that the reported "families" were actually individuals seeking respite from some politically motivated harassment. The story seems to have stemmed from a local gold rush and an influential politician who wanted to use volcanism as a ploy to exclude residents. PHIVOLCS concluded that no volcanic activity had occurred. They also added that this finding disappointed local politicians but was much welcomed by the residents.

PHIVOLCS spelled the mountain's name as "Pinokis" and from their report it seems that it might be an inactive volcano. There is no known Holocene volcano with a similar name (Simkin and Siebert, 1994). No similar names (Pinokis, Pinukis, Pinakis, etc.) were found listed in the National Imagery and Mapping Agency GEOnet Names Server (http://geonames.nga.mil/gns/html/index.html), a searchable database of 3.3 million non-US geographic-feature names.

The Manila Bulletin report suggested that Pinokis resides on the Zamboanga Peninsula. The Peninsula lies on Mindanao Island's extreme W side where it bounds the Moro Gulf, an arm of the Celebes Sea. The mountainous Peninsula trends NNE-SSW and contains peaks with summit elevations near 1,300 m. Zamboanga City sits at the extreme end of the Peninsula and operates both a major seaport and an international airport.

[Later investigation found that Mt. Pinokis is located in the Lison Valley on the Zamboanga Peninsula, about 170 km NE of Zamboanga City and 30 km NW of Pagadian City. It is adjacent to the two peaks of the Susong Dalaga (Maiden's Breast) and near Mt. Sugarloaf.]

References. Newman, S., 1997, Earthweek, a diary of the planet (week ending 12 September): syndicated newspaper column (URL: http://www.earthweek.com/).

Manila Bulletin, 4 Sept. 1997, Dante's Peak (URL: http://www.mb.com.ph/).

Simkin, T., and Siebert, L., 1994, Volcanoes of the world, 2nd edition: Geoscience Press in association with the Smithsonian Institution Global Volcanism Program, Tucson AZ, 368 p.

Information Contacts: Emmanuel G. Ramos, Deputy Director, Philippine Institute of Volcanology and Seismology, Department of Science and Technology, PHIVOLCS Building, C. P. Garcia Ave., University of the Philippines, Diliman campus, Quezon City, Philippines.


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


Press reports of Somalia's first historical eruption were likely in error

Xinhua News Agency filed a news report on 27 February under the headline "Volcano erupts in Somalia" but the veracity of the story now appears doubtful. The report disclosed the volcano's location as on the W side of the Gedo region, an area along the Ethiopian border just NE of Kenya. The report had relied on the commissioner of the town of Bohol Garas (a settlement described as 40 km NE of the main Al-Itihad headquarters of Luq town) and some or all of the information was relayed by journalists through VHF radio. The report claimed the disaster "wounded six herdsmen" and "claimed the lives of 290 goats grazing near the mountain when the incident took place." Further descriptions included such statements as "the volcano which erupted two days ago [25 February] has melted down the rocks and sand and spread . . . ."

Giday WoldeGabriel returned from three weeks of geological fieldwork in SW Ethiopia, near the Kenyan border, on 25 August. During his time there he inquired of many people, including geologists, if they had heard of a Somalian eruption in the Gedo area; no one had heard of the event. WoldeGabriel stated that he felt the news report could have described an old mine or bomb exploding. Heavy fighting took place in the Gedo region during the Ethio-Somalian war of 1977. Somalia lacks an embassy in Washington DC; when asked during late August, Ayalaw Yiman, an Ethiopian embassy staff member in Washington DC also lacked any knowledge of a Somalian eruption.

A Somalian eruption would be significant since the closest known Holocene volcanoes occur in the central Ethiopian segment of the East African rift system S of Addis Ababa, ~500 km NW of the Gedo area. These Ethiopian rift volcanoes include volcanic fields, shield volcanoes, cinder cones, and stratovolcanoes.

Information Contacts: Xinhua News Agency, 5 Sharp Street West, Wanchai, Hong Kong; Giday WoldeGabriel, EES-1/MS D462, Geology-Geochemistry Group, Los Alamos National Laboratory, Los Alamos, NM 87545; Ayalaw Yiman, Ethiopian Embassy, 2134 Kalorama Rd. NW, Washington DC 20008.


False Report of Sea of Marmara Eruption (Turkey) — November 1999

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

Following the Ms 7.8 earthquake in Turkey on 17 August (BGVN 24:08) an Email message originating in Turkey was circulated, claiming that volcanic activity was observed coincident with the earthquake and suggesting a new (magmatic) volcano in the Sea of Marmara. For reasons outlined below, and in the absence of further evidence, editors of the Bulletin consider this a false report.

The report stated that fishermen near the village of Cinarcik, at the E end of the Sea of Marmara "saw the sea turned red with fireballs" shortly after the onset of the earthquake. They later found dead fish that appeared "fried." Their nets were "burned" while under water and contained samples of rocks alleged to look "magmatic."

No samples of the fish were preserved. A tectonic scientist in Istanbul speculated that hot water released by the earthquake from the many hot springs along the coast in that area may have killed some fish (although they would be boiled rather than fried).

The phenomenon called earthquake lights could explain the "fireballs" reportedly seen by the fishermen. Such effects have been reasonably established associated with large earthquakes, although their origin remains poorly understood. In addition to deformation-triggered piezoelectric effects, earthquake lights have sometimes been explained as due to the release of methane gas in areas of mass wasting (even under water). Omlin and others (1999), for example, found gas hydrate and methane releases associated with mud volcanoes in coastal submarine environments.

The astronomer and author Thomas Gold (Gold, 1998) has a website (Gold, 2000) where he presents a series of alleged quotes from witnesses of earthquakes. We include three such quotes here (along with Gold's dates, attributions, and other comments):

(A) Lima, 30 March 1828. "Water in the bay 'hissed as if hot iron was immersed in it,' bubbles and dead fish rose to the surface, and the anchor chain of HMS Volage was partially fused while lying in the mud on the bottom." (Attributed to Bagnold, 1829; the anchor chain is reported to be on display in the London Navy Museum.)

(B) Romania, 10 November 1940. ". . . a thick layer like a translucid gas above the surface of the soil . . . irregular gas fires . . . flames in rhythm with the movements of the soil . . . flashes like lightning from the floor to the summit of Mt Tampa . . . flames issuing from rocks, which crumbled, with flashes also issuing from non-wooded mountainsides." (Phrases used in eyewitness accounts collected by Demetrescu and Petrescu, 1941).

(C) Sungpan-Pingwu (China), 16, 22, and 23 August 1976. "From March of 1976, various large anomalies were observed over a broad region. . . . At the Wanchia commune of Chungching County, outbursts of natural gas from rock fissures ignited and were difficult to extinguish even by dumping dirt over the fissures. . . . Chu Chieh Cho, of the Provincial Seismological Bureau, related personally seeing a fireball 75 km from the epicenter on the night of 21 July while in the company of three professional seismologists."

Yalciner and others (1999) made a study of coastal areas along the Sea of Marmara after the Izmet earthquake. They found evidence for one or more tsunamis with maximum runups of 2.0-2.5 m. Preliminary modeling of the earthquake's response failed to reproduce the observed runups; the areas of maximum runup instead appeared to correspond most closely with several local mass-failure events. This observation together with the magnitude of the earthquake, and bottom soundings from marine geophysical teams, suggested mass wasting may have been fairly common on the floor of the Sea of Marmara.

Despite a wide range of poorly understood, dramatic processes associated with earthquakes (Izmet 1999 apparently included), there remains little evidence for volcanism around the time of the earthquake. The nearest Holocene volcano lies ~200 km SW of the report location. Neither Turkish geologists nor scientists from other countries in Turkey to study the 17 August earthquake reported any volcanism. The report said the fisherman found "magmatic" rocks; it is unlikely they would be familiar with this term.

The motivation and credibility of the report's originator, Erol Erkmen, are unknown. Certainly, the difficulty in translating from Turkish to English may have caused some problems in understanding. Erkmen is associated with a website devoted to reporting UFO activity in Turkey. Photographs of a "magmatic rock" sample were sent to the Bulletin, but they only showed dark rocks photographed devoid of a scale on a featureless background. The rocks shown did not appear to be vesicular or glassy. What was most significant to Bulletin editors was the report author's progressive reluctance to provide samples or encourage follow-up investigation with local scientists. Without the collaboration of trained scientists on the scene this report cannot be validated.

References. Omlin, A, Damm, E., Mienert, J., and Lukas, D., 1999, In-situ detection of methane releases adjacent to gas hydrate fields on the Norwegian margin: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Yalciner, A.C., Borrero, J., Kukano, U., Watts, P., Synolakis, C. E., and Imamura, F., 1999, Field survey of 1999 Izmit tsunami and modeling effort of new tsunami generation mechanism: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Gold, T., 1998, The deep hot biosphere: Springer Verlag, 256 p., ISBN: 0387985468.

Gold, T., 2000, Eye-witness accounts of several major earthquakes (URL: http://www.people.cornell.edu/ pages/tg21/eyewit.html).

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

48.831°N, 101.626°E; summit elev. 1675 m

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

In December 2002 information appeared in Mongolian and Russian newspapers and on national TV that a volcano in Central Mongolia, the Har-Togoo volcano, was producing white vapors and constant acoustic noise. Because of the potential hazard posed to two nearby settlements, mainly with regard to potential blocking of rivers, the Director of the Research Center of Astronomy and Geophysics of the Mongolian Academy of Sciences, Dr. Bekhtur, organized a scientific expedition to the volcano on 19-20 March 2003. The scientific team also included M. Ulziibat, seismologist from the same Research Center, M. Ganzorig, the Director of the Institute of Informatics, and A. Ivanov from the Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences.

Geological setting. The Miocene Har-Togoo shield volcano is situated on top of a vast volcanic plateau (figure 1). The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Pliocene and Quaternary volcanic rocks are also abundant in the vicinity of the Holocene volcanoes (Devyatkin and Smelov, 1979; Logatchev and others, 1982). Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Figure (see Caption) Figure 1. Photograph of the Har-Togoo volcano viewed from west, March 2003. Courtesy of Alexei Ivanov.

Observations during March 2003. The name of the volcano in the Mongolian language means "black-pot" and through questioning of the local inhabitants, it was learned that there is a local myth that a dragon lived in the volcano. The local inhabitants also mentioned that marmots, previously abundant in the area, began to migrate westwards five years ago; they are now practically absent from the area.

Acoustic noise and venting of colorless warm gas from a small hole near the summit were noticed in October 2002 by local residents. In December 2002, while snow lay on the ground, the hole was clearly visible to local visitors, and a second hole could be seen a few meters away; it is unclear whether or not white vapors were noticed on this occasion. During the inspection in March 2003 a third hole was seen. The second hole is located within a 3 x 3 m outcrop of cinder and pumice (figure 2) whereas the first and the third holes are located within massive basalts. When close to the holes, constant noise resembled a rapid river heard from afar. The second hole was covered with plastic sheeting fixed at the margins, but the plastic was blown off within 2-3 seconds. Gas from the second hole was sampled in a mechanically pumped glass sampler. Analysis by gas chromatography, performed a week later at the Institute of the Earth's Crust, showed that nitrogen and atmospheric air were the major constituents.

Figure (see Caption) Figure 2. Photograph of the second hole sampled at Har-Togoo, with hammer for scale, March 2003. Courtesy of Alexei Ivanov.

The temperature of the gas at the first, second, and third holes was +1.1, +1.4, and +2.7°C, respectively, while air temperature was -4.6 to -4.7°C (measured on 19 March 2003). Repeated measurements of the temperatures on the next day gave values of +1.1, +0.8, and -6.0°C at the first, second, and third holes, respectively. Air temperature was -9.4°C. To avoid bias due to direct heating from sunlight the measurements were performed under shadow. All measurements were done with Chechtemp2 digital thermometer with precision of ± 0.1°C and accuracy ± 0.3°C.

Inside the mouth of the first hole was 4-10-cm-thick ice with suspended gas bubbles (figure 5). The ice and snow were sampled in plastic bottles, melted, and tested for pH and Eh with digital meters. The pH-meter was calibrated by Horiba Ltd (Kyoto, Japan) standard solutions 4 and 7. Water from melted ice appeared to be slightly acidic (pH 6.52) in comparison to water of melted snow (pH 7.04). Both pH values were within neutral solution values. No prominent difference in Eh (108 and 117 for ice and snow, respectively) was revealed.

Two digital short-period three-component stations were installed on top of Har-Togoo, one 50 m from the degassing holes and one in a remote area on basement rocks, for monitoring during 19-20 March 2003. Every hour 1-3 microseismic events with magnitude <2 were recorded. All seismic events were virtually identical and resembled A-type volcano-tectonic earthquakes (figure 6). Arrival difference between S and P waves were around 0.06-0.3 seconds for the Har-Togoo station and 0.1-1.5 seconds for the remote station. Assuming that the Har-Togoo station was located in the epicentral zone, the events were located at ~1-3 km depth. Seismic episodes similar to volcanic tremors were also recorded (figure 3).

Figure (see Caption) Figure 3. Examples of an A-type volcano-tectonic earthquake and volcanic tremor episodes recorded at the Har-Togoo station on 19 March 2003. Courtesy of Alexei Ivanov.

Conclusions. The abnormal thermal and seismic activities could be the result of either hydrothermal or volcanic processes. This activity could have started in the fall of 2002 when they were directly observed for the first time, or possibly up to five years earlier when marmots started migrating from the area. Further studies are planned to investigate the cause of the fumarolic and seismic activities.

At the end of a second visit in early July, gas venting had stopped, but seismicity was continuing. In August there will be a workshop on Russian-Mongolian cooperation between Institutions of the Russian and Mongolian Academies of Sciences (held in Ulan-Bator, Mongolia), where the work being done on this volcano will be presented.

References. Devyatkin, E.V. and Smelov, S.B., 1979, Position of basalts in sequence of Cenozoic sediments of Mongolia: Izvestiya USSR Academy of Sciences, geological series, no. 1, p. 16-29. (In Russian).

Logatchev, N.A., Devyatkin, E.V., Malaeva, E.M., and others, 1982, Cenozoic deposits of Taryat basin and Chulutu river valley (Central Hangai): Izvestiya USSR Academy of Sciences, geological series, no. 8, p. 76-86. (In Russian).

Geologic Background. The Miocene Har-Togoo shield volcano, also known as Togoo Tologoy, is situated on top of a vast volcanic plateau. The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Information Contacts: Alexei V. Ivanov, Institute of the Earth Crust SB, Russian Academy of Sciences, Irkutsk, Russia; Bekhtur andM. Ulziibat, Research Center of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulan-Bator, Mongolia; M. Ganzorig, Institute of Informatics MAS, Ulan-Bator, Mongolia.


Elgon (Uganda) — December 2005

Elgon

Uganda

1.136°N, 34.559°E; summit elev. 3885 m

All times are local (unless otherwise noted)


False report of activity; confusion caused by burning dung in a lava tube

An eruption at Mount Elgon was mistakenly inferred when fumes escaped from this otherwise quiet volcano. The fumes were eventually traced to dung burning in a lava-tube cave. The cave is home to, or visited by, wildlife ranging from bats to elephants. Mt. Elgon (Ol Doinyo Ilgoon) is a stratovolcano on the SW margin of a 13 x 16 km caldera that straddles the Uganda-Kenya border 140 km NE of the N shore of Lake Victoria. No eruptions are known in the historical record or in the Holocene.

On 7 September 2004 the web site of the Kenyan newspaper The Daily Nation reported that villagers sighted and smelled noxious fumes from a cave on the flank of Mt. Elgon during August 2005. The villagers' concerns were taken quite seriously by both nations, to the extent that evacuation of nearby villages was considered.

The Daily Nation article added that shortly after the villagers' reports, Moses Masibo, Kenya's Western Province geology officer visited the cave, confirmed the villagers observations, and added that the temperature in the cave was 170°C. He recommended that nearby villagers move to safer locations. Masibo and Silas Simiyu of KenGens geothermal department collected ashes from the cave for testing.

Gerald Ernst reported on 19 September 2004 that he spoke with two local geologists involved with the Elgon crisis from the Geology Department of the University of Nairobi (Jiromo campus): Professor Nyambok and Zacharia Kuria (the former is a senior scientist who was unable to go in the field; the latter is a junior scientist who visited the site). According to Ernst their interpretation is that somebody set fire to bat guano in one of the caves. The fire was intense and probably explains the vigorous fuming, high temperatures, and suffocated animals. The event was also accompanied by emissions of gases with an ammonia odor. Ernst noted that this was not surprising considering the high nitrogen content of guano—ammonia is highly toxic and can also explain the animal deaths. The intense fumes initially caused substantial panic in the area.

It was Ernst's understanding that the authorities ordered evacuations while awaiting a report from local scientists, but that people returned before the report reached the authorities. The fire presumably prompted the response of local authorities who then urged the University geologists to analyze the situation. By the time geologists arrived, the fuming had ceased, or nearly so. The residue left by the fire and other observations led them to conclude that nothing remotely related to a volcanic eruption had occurred.

However, the incident emphasized the problem due to lack of a seismic station to monitor tectonic activity related to a local triple junction associated with the rift valley or volcanic seismicity. In response, one seismic station was moved from S Kenya to the area of Mt. Elgon so that local seismicity can be monitored in the future.

Information Contacts: Gerald Ernst, Univ. of Ghent, Krijgslaan 281/S8, B-9000, Belgium; Chris Newhall, USGS, Univ. of Washington, Dept. of Earth & Space Sciences, Box 351310, Seattle, WA 98195-1310, USA; The Daily Nation (URL: http://www.nationmedia.com/dailynation/); Uganda Tourist Board (URL: http://www.visituganda.com/).