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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

Yasur (Vanuatu) Strombolian activity continues during June 2019 through February 2020

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

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



Yasur (Vanuatu) — March 2020 Citation iconCite this Report

Yasur

Vanuatu

19.532°S, 169.447°E; summit elev. 361 m

All times are local (unless otherwise noted)


Strombolian activity continues during June 2019 through February 2020

Yasur has remained on Alert Level 2 (on a scale of 0-4) since 18 October 2016, indicating "Major Unrest; Danger Zone remains at 395 m around the eruptive vents." The summit crater contains several active vents that frequently produce Strombolian explosions and gas plumes (figure 60). This bulletin summarizes activity during June 2019 through February 2020 and is based on reports by the Vanuatu Meteorology and Geo-Hazards Department (VMGD), visitor photographs and videos, and satellite data.

Figure (see Caption) Figure 60. The crater of Yasur contains several active vents that produce gas emissions and Strombolian activity. Photo taken during 25-27 October 2019 by Justin Noonan, used with permission.

A VMGD report on 27 June described ongoing Strombolian explosions with major unrest confined to the crater. The 25 July report noted the continuation of Strombolian activity with some strong explosions, and a warning that volcanic bombs may impact outside of the crater area (figure 61).

Figure (see Caption) Figure 61. A volcanic bomb (a fluid chunk of lava greater than 64 mm in diameter) that was ejected from Yasur. The pattern on the surface shows the fluid nature of the lava before it cooled into a solid rock. Photo taken during 25-27 October 2019 by Justin Noonan, used with permission.

No VMGD report was available for August, but Strombolian activity continued with gas emissions and explosions, as documented by visitors (figure 62). The eruption continued through September and October with some strong explosions and multiple active vents visible in thermal satellite imagery (figure 63). Strombolian explosions ejecting fluid lava from rapidly expanding gas bubbles were recorded during October, and likely represented the typical activity during the surrounding months (figure 64). Along with vigorous degassing producing a persistent plume there was occasional ash content (figure 65). At some point during 20-29 October a small landslide occurred along the eastern inner wall of the crater, visible in satellite images and later confirmed to have produced ashfall at the summit (figure 66).

Figure (see Caption) Figure 62. Different views of the Yasur vents on 7-8 August 2019 taken from a video. Strombolian activity and degassing were visible. Courtesy of Arnold Binas, used with permission.
Figure (see Caption) Figure 63. Sentinel-2 thermal satellite images show variations in detected thermal energy emitting from the active Yasur vents on 18 September and 22 December 2019. False color (bands 12, 11, 4) satellite images courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 64. Strombolian explosions at Yasur during 25-27 October 2019. Large gas bubbles rise to the top of the lava column and burst, ejecting volcanic bombs – fluid chunks of lava, out of the vent. Photos by Justin Noonan, used with permission.
Figure (see Caption) Figure 65. Gas and ash emissions rise from the active vents at Yasur between 25-27 October 2019. Photos by Justin Noonan, used with permission.
Figure (see Caption) Figure 66. Planet Scope satellite images of Yasur show a change in the crater morphology between 20 and 29 October 2019. Copyright of Planet Labs.

Continuous explosive activity continued in November-February with some stronger explosions recorded along with accompanying gas emissions. Gas plumes of sulfur dioxide were detected by satellite sensors on some days through this period (figure 67) and ash content was present at times (figure 68). Thermal anomalies continued to be detected by satellite sensors with varying intensity, and with a reduction in intensity in February, as seen in Sentinel-2 imagery and the MIROVA system (figures 69 and 70).

Figure (see Caption) Figure 67. SO2 plumes detected at Yasur by Aura/OMI on 21 December 2019 and 31 January 2020, drifting W to NW, and on 14 and 23 February 2020, drifting W and south, and NWW to NW. Courtesy of Global Sulfur Dioxide Monitoring Page, NASA.
Figure (see Caption) Figure 68. An ash plume erupts from Yasur on 20 February 2020 and drifts NW. Courtesy of Planet Labs.
Figure (see Caption) Figure 69. Sentinel-2 thermal satellite images show variations in detected thermal energy in the active Yasur vents during January and February 2020. False color (bands 12, 11, 4) satellite images courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 70. The MIROVA thermal detection system recorded persistent thermal energy emitted at Yasur with some variation from mid-May 2019 to May 2020. There was a reduction in detected energy after January. Courtesy of MIROVA.

Geologic Background. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

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); Planet Labs, Inc. (URL: https://www.planet.com/); 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/); Justin Noonan (URL: https://www.justinnoonan.com/, Instagram: https://www.instagram.com/justinnoonan_/); Doro Adventures (Twitter: https://twitter.com/DoroAdventures, URL: http://doroadventures.com/).


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/).


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).


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).

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Bulletin of the Global Volcanism Network - Volume 31, Number 03 (March 2006)

Managing Editor: Richard Wunderman

Chikurachki (Russia)

Following 2-year repose, several ash plumes in March-April 2005

Colima (Mexico)

Continued ash emission, including some high level ash plumes, since June 2005

Erta Ale (Ethiopia)

Molten lava lake observations as late as 3 January 2006

Galeras (Colombia)

Heightened seismicity through April 2006; increased lava dome volume noted

Lengai, Ol Doinyo (Tanzania)

Unusual activity at summit crater during late March and early April 2006

Lokon-Empung (Indonesia)

Steaming and seismically active during January-October 2005

Mayon (Philippines)

Eruptions resume in February 2006 after a 2-year hiatus

Miyakejima (Japan)

Ash emissions in February 2006; declining SO2 flux

Montagu Island (United Kingdom)

January 2006 visit documenting steam and new lava flows

Poas (Costa Rica)

Small phreatic eruption on 24 March 2006, the first since 1994

Raoul Island (New Zealand)

Eruption on 17 March 2006 preceded by 5 days of earthquakes; 1 fatality

Tinakula (Solomon Islands)

Eruption; increased thermal anomalies during February-April 2006

Ubinas (Peru)

Ash eruption beginning 25 March 2006; heightened seismicity since November 2004

Veniaminof (United States)

Modest ash emissions during September 2005-22 April 2006



Chikurachki (Russia) — March 2006 Citation iconCite this Report

Chikurachki

Russia

50.324°N, 155.461°E; summit elev. 1781 m

All times are local (unless otherwise noted)


Following 2-year repose, several ash plumes in March-April 2005

Chikurachki last erupted during April to June 2003 (BGVN 28:07) and subsequently was apparently dormant for nearly two years. On 1 March 2005, observers in Severo-Kurilsk (~ 70 km NE of Chikurachki) saw a gas-and-steam plume rise ~ 400 m above the volcano. On 12 March 2005, MODIS satellite imagery showed an ash plume extending NNW from the volcano and led KVERT to raise the concern color code from Green to Yellow. On 23 March, satellite imagery showed a weak ash plume extending ~ 70 km E. The height of the plume was unknown, and on 25 March the hazard status was raised again from Yellow to Orange. Chikurachki is not monitored with seismic instruments but KVERT has access to satellite data and occasional visual observations of the volcano. Ash from Chikurachki fell on the southern part of Paramushir Island on 29 March. Ash deposits were visible on satellite imagery on 25 and 29 March; on the 29th they extended 19 km SE. Chikurachki remained at concern color code Orange.

During April 2005, weak fumarolic activity occurred at Chikurachki. Ash deposits covered the WNW slope of the volcano. On 7 April, an ash-and-gas plume rose to ~ 500 m above Chikurachki's crater and extended ~ 10 km S. The concern color code remained Orange through 15 April 2005 and was reduced to Yellow when satellite imagery during the week of 20-26 April did not show any thermal anomalies or ash plumes. Since that time there has been no further indication of activity.

In 2005 Gurenkoa and others published a study of glass inclusions and groundmass glasses from Chikurachki explosions in an effort to better understand the relatively rare, highly explosive eruptions of basaltic composition. Such eruptions may be important in terms of atmospheric impact because of the generally much higher solubilities of S in basaltic melts compared with silicic melts. Concentrations of H2O, major, trace and volatile (S, Cl) elements by EPMA and SIMS from glass inclusions and groundmass glasses of the 1986, 1853, and prehistoric explosive eruptions of basaltic magmas were studied.

Reference. Gurenko, A.A., Belousov, A.B., Trumbull, R.B., and Sobolev, A.V., 2005, Explosive basaltic volcanism of the Chikurachki Volcano (Kurile arc, Russia): Insights on pre-eruptive magmatic conditions and volatile budget revealed from phenocryst-hosted melt inclusions and groundmass glasses: Journal of Volcanology and Geothermal Research, v. 147, p. 203-232. (URL: http://www.sciencedirect.com/)

Geologic Background. Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red color. Frequent basaltic plinian eruptions have occurred during the Holocene. Lava flows from 1781-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The Tatarinov group of six volcanic centers is located immediately to the south of Chikurachki, and the Lomonosov cinder cone group, the source of an early Holocene lava flow that reached the saddle between it and Fuss Peak to the west, lies at the southern end of the N-S-trending Chikurachki-Tatarinov complex. In contrast to the frequently active Chikurachki, the Tatarinov volcanoes are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.

Information Contacts: Olga Girina, Kamchatka Volcanic Eruptions Response Team (KVERT), a cooperative program of the Institute of Volcanic Geology and Geochemistry, Far East Division, Russian Academy of Sciences, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia, the Kamchatka Experimental and Methodical Seismological Department (KEMSD), GS RAS (Russia), and the Alaska Volcano Observatory (USA); Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), the Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and the Alaska Division of Geological and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Colima (Mexico) — March 2006 Citation iconCite this Report

Colima

Mexico

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

All times are local (unless otherwise noted)


Continued ash emission, including some high level ash plumes, since June 2005

Eruptive activity has continued at Colima from July 2005 through February 2006. Explosions that generated ash plumes were common during this period.

The Colima Volcano Observatory reported that ash emission continued at Colima during 29 June 2005 to 5 July 2005 and several plumes rose to 9-10 km altitude. On 30 June, lahars traveled SW down La Lumbre Ravine and SSE down Montegrande Ravine to a maximum length of ~ 10 km. The lahars did not reach populated areas. Due to the presence of new ash on the flanks of the volcano, seasonal heavy rains, and the subsequent threat of lahars forming, Universidad de Colima advised avoiding the ravines of La Lumbre, San Antonio, Monte Grande (in Colima state), and La Arena (in Jalisco state) throughout this interval.

The Washington VAAC reported that the Colima video camera and satellite imagery confirmed an explosive eruption on 5 July at 1821 (figure 80). The Mexico City Meteorological Watch Office (MWO) reported that the resultant ash plume reached an altitude of ~ 9.1 km and drifted NW. Pyroclastic flows accompanying the eruption traveled down the E flank.

Figure (see Caption) Figure 80. A photo of the explosive eruption on Colima on 5 July 2005 taken from the E. Courtesy of CVO.

Several explosions continued during 6-19 July, and small landslides traveled down the volcano's flanks during 8-9 July and 15-18 July. On 21 and 23 July, small ash emissions and lahars occurred. On the 21st during 1750-1830 a lahar traveled SSE down the Monte Grande ravine. Emissions rose to a maximum altitude of 9.1 km on 27 July. During 29 July to 1 August, steam-and-ash emissions occurred at Colima. According to the Washington VAAC, the highest-rising emission reached 6.1 km altitude on 30 July.

On 4 August the Washington VAAC reported that the Mexico City MWO observed a steam plume rising to 7.2 km altitude in imagery seen on the Colima video camera. During15-31 August, small explosions produced low-level ash plumes. The largest events, on 21 and 22 August, produced plumes that drifted W. On 31 August a 45-minute seismic signal associated with a lahar was recorded at the Monte Grande station. The lahar caused no damage.

Throughout the month of September, several small explosions occurred at Colima. On 16 September at 1045 an explosion sent an ash plume to ~ 9.8 km altitude. The local civil defense agency stated in a news report that ash fell on towns NW of the volcano. Prior to the explosion, microseismicity was recorded for several days. Universidad de Colima reported that microseismicity often precedes significant explosions. On 27 September at 0507 an explosion produced a plume to a altitude of ~ 7.6 km altitude. The plume drifted WSW, depositing small amounts of ash in the cities of Colima, Villa de álvarez, and Comala. On 28 September another explosion sent an ash plume to an altitude of ~ 6.1 km altitude and drifted NNW.

Small explosions continued to occur from October through the end of February 2006 (the end of this report), and produced visible ash plumes. Several small explosions during 16-21 November 2005 produced steam-and-ash clouds to low levels above the volcano. Explosions on 12 December 2005 resulted in small amounts of ash deposited in areas SW of the volcano.

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 high point of the complex) on the north and the historically active Volcán de Colima at the south. A group of late-Pleistocene cinder cones is located on the floor of the Colima graben west and east of the 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, producing thick debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions have destroyed the summit (most recently in 1913) and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Information Contacts: Observatorio Vulcanológico de la Universidad de Colima, Colima, Col., 28045, México (URL: https://portal.ucol.mx/cueiv/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).


Erta Ale (Ethiopia) — March 2006 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


Molten lava lake observations as late as 3 January 2006

Viviane Grandjean wrote of her observations at Erta Ale during 24 December 2005-3 January 2006 in Bulletin No. 57 of the Société de Volcanologie Genève. On 26 December she saw the lava lake through clouds of gas; its surface was calm, with incandescent lava visible through the broken chilled surface. The S pit crater had an estimated diameter of 170 m and vertical walls, and the lava lake was about 80 m in diameter. It seemed to shrink during the next days, one part appearing hardened and forming almost a second terrace. The plates of cooled surface lava were seen moving and converging amidst degassing lava. Lava fountains were periodically visible and generally outlined the borders of the lava lake under the rim.

On 27 December, the walls of the crater were estimated at about 50 m high, with a crater diameter of about 300 m. Members of the group descended into the crater to inspect a series of active hornitos near the N vents. At one end of the line a vent lined with sulfur opened. In the interior cavity of a smaller vent temperatures of about 800°C were measured. Degassing occurred generally in the area. Lava fountaining continued.

The lava lake appeared lower and calmer to observers on 28 December, with a potential second terrace still forming. Some group members descended into the crater again and observed rockfall and continued lava fountaining.

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

Information Contacts: Viviane Grandjean, c/o Société Volcanologique Européenne (SVE)-Société Volcanologique de Genève (SVG), Geneva, C.P.1, 1211 Geneva 17, Switzerland (URL: http://www.sveurop.org/).


Galeras (Colombia) — March 2006 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Heightened seismicity through April 2006; increased lava dome volume noted

Galeras was last reported on in BGVN 31:01. During the first weeks of November 2005 seismometers recorded tornillo earthquakes (long-period events with seismic traces that look like screws in profile and are currently thought to be related to pressurized fluid flow at shallow depth). Minor deformation was also recorded at Galeras. The earthquakes were similar to those that occurred before eruptions in 1992-93. On 24 November at 0246 seismic signals indicated the beginning of an eruption. Ash fell in the towns of Fontibon, San Cayetano, Postobon, and in north Pasto. Activity decreased by the next day, so the Alert Level was reduced. Thousands of people were evacuated during the week prior to the eruption. Gas emissions continued through December 2005 and January and February 2006. During 23 January to 6 February, the lava dome in the main crater continued to grow; strong degassing occurred in several sectors of the active cone and around the lava dome. Galeras remained at Alert Level 3 ("changes in the behavior of volcanic activity have been noted") through February 2006.

During the last week of February, seismic stations detected an average of 280 small earthquakes per day. On 26 February a shallow M 4.8 volcano-tectonic earthquake below the volcano was recorded at 1009, followed by 35 smaller earthquakes. SO2 flux of about 600 metric tons per day was measured during February. Steam and gas rose to ~ 700 m above the volcano.

During 27 February to 6 March an increase in the volume of the lava dome located in the main crater was observed. During March, seismicity at Galeras decreased in comparison to the previous several weeks and deformation was measured at the volcano. Plumes of mainly steam, gas, and small amounts of ash were emitted from the volcano and rose to a maximum height of 1.2 km above the volcano.

Due to an increase in tremor at Galeras beginning on the morning of 28 March 2006, INGEOMINAS raised the Alert Level from 3 to 2 (likely eruption in days or weeks). On 28 March, energetic signals and tremor began and seismic instruments detected very shallow low-energy hybrid signals, similar to ones recorded during 1991-1993 when dome emplacement occurred on the main crater's floor.

The increase in seismic energy ended on 29 March. The number of earthquakes beneath the volcano decreased during 28 March to 3 April (an average of 66 earthquakes was recorded daily), in comparison to the previous week (an average of 89 earthquakes was recorded daily). Steam columns rose up to ~ 500 m above the volcano and the outer layer of the lava dome at the volcano's summit cooled in comparison to previous weeks.

During 5-24 April, decreases were observed in seismicity, deformation, gas emissions, and temperatures. According to INGEOMINAS, most of the explosive eruptions at Galeras in the past 17 years occurred when parameters were at similarly low levels. In addition, the current lava dome has a significantly greater volume than the dome that was destroyed during an eruption in 1992. The volume of magma in the interior of the volcanic system is greater than during 1989-1993. Galeras remained at Alert Level 2.

Geologic Background. Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Long-term extensive hydrothermal alteration has contributed to large-scale edifice collapse on at least three occasions, producing debris avalanches that swept to the west and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid-Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.

Information Contacts: Diego Gomez Martinez, Observatorio Vulcanológico y Sismológico de Pasto (OVSP), INGEOMINAS, Carrera 31, 1807 Parque Infantil, PO Box 1795, Pasto, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html; 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.ospo.noaa.gov/Products/atmosphere/vaac/); El Pais (URL: http://elpais-cali.terra.com.co/paisonline/).


Ol Doinyo Lengai (Tanzania) — March 2006 Citation iconCite this Report

Ol Doinyo Lengai

Tanzania

2.764°S, 35.914°E; summit elev. 2962 m

All times are local (unless otherwise noted)


Unusual activity at summit crater during late March and early April 2006

Typical activity continued at Ol Doinyo Lengai from December 2005 through mid-March 2006. Unusual activity, including a large plume and significant lava overflows from the summit crater, occurred during late March and early April. Much of the following information was posted on websites maintained by Fred Belton or Chris Weber, or was contained in email from local sources or visitors relayed by Belton or Celia Nyamweru. None of the reports regarding the unusual March-April activity originated from sources close enough to describe the exact nature of the eruption.

Activity during 20 December 2005-13 March 2006. The local Masai guide William reported an eruption from hornito T49B during a visit on 20 December 2005. When David Bygott climbed the volcano on 22 December the crater was inactive. A recent narrow flow of pahoehoe lava from the NW flank of T49B had flowed across the NW crater rim overflow, and was still warm and making cracking noises. A wide pahoehoe-textured lava flow from T56B had mostly turned white and appeared to be several days to a week old.

On 4 January 2006 Bernhard Donth observed lava escaping from T49B; spatter and little flows went in all directions. One bigger lava flow had reached as far as the NW overflow. A report from Christian Mann of a climb on 10 January only noted degassing from T47. A photo taken that day from the summit showed a white and brown crater with no indication of recent activity. However, Belton noted that during the previous weeks lava had apparently filled up the large open vent of T56B and had flowed from there and possibly other locations onto the NE part of the crater floor.

Chris DeVries and a group of other students from McGill University visited during 25-26 February. Many hornitos were intermittently degassing. T58B was spattering a bit, and magma was heard sloshing around. A small ~ 10-m-long flow had erupted from this vent earlier in the day; it was still very black and hot. T57B had a large opening to its NW, but it did not appear that any recent flows had come from this opening. The base of this cone later ruptured, and the lava inside drained out quickly and violently; the flow proceeded to the E overflow.

Christoph Weber arrived with a film team at the crater on 2 February 2006. The tallest hornito (T49B) reached approximately 2,890 m elevation (measured with GPS), ~ 60 m above the crater floor at the NW overflow (figure 87). No recent eruption had occurred at T49B, but strong noisy degassing took place sometimes. Just E of T49B the hornito T56B had convecting lava deep inside and some days-old lava flows stretched from three different vents at T56B to the E overflow. After the major collapse of T56B in 2004, this hornito (at approximately 2,875 m elevation on 2 February) has nearly grown up again to its former shape and height. Also from T58C and the collapsed T58B hornito some days-old lava flows were found on the eastern slopes passing the old and weathered T37, T37B, and T45 cones.

Figure (see Caption) Figure 87. View of Ol Doinyo Lengai on 6 February 2006, looking NW at the central hornito cluster. Fresh lava flows are black. A person can be seen near the recent lava flow in front of T57B. Courtesy of C. Weber.

The caldera-shaped collapsed T58B had its flat floor at ~ 2,865 m elevation with four active vents inside. Lava convection was close to the surface of T58B and inside the tall T58C. At 1300 on 2 February a sudden increase of activity took place with two lava fountains at T58B lasting only some seconds. At the same time lava spilled from all T58B vents, a T58C flank vent, and a T56B vent. Lava spatter with lava flows inside T58B and up to ~ 150 m towards the E occurred over the following 3 days. On 6 and 7 February, higher activity occurred with lava outflow at T58C. During an observation flight on 13 February, Weber noticed new lava flows from T58B and T56B. Crater rim overflow measurements on 2 February 2006 were unchanged since August 2005 (BGVN 30:10).

Photographs taken by Michael Dalton-Smith from a plane on 13 March 2006 showed many small flows extending in all directions from the central cluster. The flow over the NW rim seemed to be confined to a channel and did not spread out until it was further down the mountain.

Unusual activity starting in late March. David Peterson saw a fairly obvious plume at the top of the mountain (figure 88) on 28 March. A day or two after that he heard reports of lava pouring down the volcano's sides with some residents moving out of Engare Sero as a result. Unconfirmed news reports in The Guardian on 1 April described a scene of "rumbling" noises with lava and ash discharges on 30 March that prompted hundreds to as many as 3,000 local residents to flee the area. Peterson also relayed that his colleague Habibu reported on 1 April that the lava flows had abated. Another friend, Achmed, noted that a river of lava extending from the crater to the base of the volcano was about the "width of a four lane highway" (12 m). An Agence France Presse news report, with quotes from Emmanuel Chausi, a conservation officer with the nearby Ngorongoro Conservation Area Authority (NCAA), claimed that "huge plumes of detritus" were ejected during the nights of both 2 and 3 April, but no lava was reported.

Figure (see Caption) Figure 88. A photograph, undated, but from the time period of the eruption, shows a white plume from Ol Doinyo Lengai. This is probably what started the rumor of a major eruption. Fred Belton saw a similar cloud on 15 July 2004 when lava vaporized a big area of plants on the E rim. Fred Belton received this photograph, taken from Basecamp Tanzania, on 9 April 2006.

Photos received from Dean Polley, taken 1 April, provide additional information about the eruption (figure 89). Based on these aerial photos, Belton's interpretation is that lava on 30 March must have erupted strongly from at or near the central cluster. A deep channel visible down the flank indicates a flow lasting some hours through a channel deepened by thermal erosion. A crater photo from Matt Jones also taken on 1 April (figure 90) confirmed that there had been recent strong activity from the T56B and T58C hornitos. C. Weber relayed that visitors who climbed the volcano later on (with guide Othman Swalehe ) reported a lava channel 5 m wide and 2.5 m deep, starting from the T58C hornito, following the flow field to the SW and then continuing outside the crater at the W overflow where there was a channel 8 m wide and 3 m deep. The collapsed hornito area at T56B and T58B measured about 30 m N-S and 15 m E-W with an active lava lake inside. The tall hornitos T58C (partly collapsed to the SE), T49B, and T57B were mostly not affected by the collapse, and the W part of T56B remained standing.

Figure (see Caption) Figure 89. Aerial photograph of Ol Doinyo Lengai looking approximately ESE showing the summit crater and lava overflows, 1 April 2006. Courtesy of Dean Polley.
Figure (see Caption) Figure 90. Photograph of the Ol Doinyo Lengai crater on 1 April 2006, looking NW at the central hornito cluster. The T58C hornito is completely split, with the south half removed. A significant portion of T56B is also missing. See figure 87 for a comparison with crater morphology on 6 February 2006 and identification of hornitos. Photo by Matt Jones, provided courtesy of F. Belton.

Michael Dalton-Smith flew over on 4 April and saw more recent black flows partially covering the gray flows from 30 March. When Dalton-Smith drove from Seronera to the crater on 4 April, he had a great cloud-free view. Using binoculars it appeared that there was a huge fountain out of one of the hornitos, and all hornitos had black plumes rising from them.

Geologic Background. The symmetrical Ol Doinyo Lengai is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent stratovolcano, known to the Maasai as "The Mountain of God," rises abruptly above the broad plain south of Lake Natron in the Gregory Rift Valley. The cone-building stage ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatitic and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra ejections and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater and occasionally down the upper flanks. The depth and morphology of the northern crater have changed dramatically during the course of historical eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater. Long-term lava effusion in the summit crater beginning in 1983 had by the turn of the century mostly filled the northern crater; by late 1998 lava had begun overflowing the crater rim.

Information Contacts: Frederick Belton, Developmental Studies Department, PO Box 16, Middle Tennessee State University, Murfreesboro, TN 37132, USA (URL: http://oldoinyolengai.pbworks.com/); Christoph Weber, Volcano Expeditions International, Muehlweg 11, 74199 Untergruppenbach, Germany (URL: http://www.v-e-i.de/); Bernhard Donth, Waldwiese 5, 66123 Saarbruecken, Germany; Celia Nyamweru, Department of Anthropology, St. Lawrence University, Canton, NY 13617, USA; Guardian News, Arusha, Tanzania (URL: http://www.ippmedia.com/); Agence France Presse (URL: http://www.afp.com/).


Lokon-Empung (Indonesia) — March 2006 Citation iconCite this Report

Lokon-Empung

Indonesia

1.358°N, 124.792°E; summit elev. 1580 m

All times are local (unless otherwise noted)


Steaming and seismically active during January-October 2005

The twin volcanoes of Lokon and Empung exhibited low levels of activity during 2005. Table 9 is a summary of reported gas emissions and number of volcanic earthquakes during 2005.

Table 9. Summary of activity at Lokon-Empung during 2005, indicating the height and composition of plumes observed and the numbers of earthquakes recorded. Data courtesy of CVGHM.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Plume height Plume color and composition
18 Jan-24 Jan 2005 9 75 -- --
24 Jan-30 Jan 2005 3 88 35 m white gas
02 May 2005 3 44 -- --
09 May 2005 3 139 50 m white gas
26 Sep-02 Oct 2005 6 117 15 m white gas
03 Oct-09 Oct 2005 5 126 25 m white gas

Geologic Background. The twin volcanoes Lokon and Empung, rising about 800 m above the plain of Tondano, are among the most active volcanoes of Sulawesi. Lokon, the higher of the two peaks (whose summits are only 2 km apart), has a flat, craterless top. The morphologically younger Empung volcano to the NE has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century, but all subsequent eruptions have originated from Tompaluan, a 150 x 250 m wide double crater situated in the saddle between the two peaks. Historical eruptions have primarily produced small-to-moderate ash plumes that have occasionally damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred. A ridge extending WNW from Lokon includes Tatawiran and Tetempangan peak, 3 km away.

Information Contacts: Dali Ahmad, Hetty Triastuty, Nia Haerani and Suswati, Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).


Mayon (Philippines) — March 2006 Citation iconCite this Report

Mayon

Philippines

13.257°N, 123.685°E; summit elev. 2462 m

All times are local (unless otherwise noted)


Eruptions resume in February 2006 after a 2-year hiatus

Since the previous report in December 2004 (BGVN 29:12) Mayon had remained quiet until 21 February 2006. On that day the Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that a minor explosion at 0941 produced an ash plume that rose ~ 500 m above the volcano's crater and drifted SW. Ash was deposited on the upper slopes of the volcano. The ash emission was accompanied by a small explosion-type earthquake, recorded only by seismographs around the volcano.

Prior to the explosion PHIVOLCS had seen an increase in seismicity at the volcano. Between 1545 on 20 February and 0520 on 21 February, there were 147 low-frequency earthquakes recorded, a number considerably above the five or fewer events per day normally detected. Seismicity also indicated some minor rockfalls, which probably resulted from lava blocks detaching from the summit. Steaming was observed. No incandescence was visible at the crater due to clouds obscuring the volcano.

PHIVOLCS reported that about nine earthquakes related to explosive activity took place at Mayon around 23 February. Cloudy conditions prevented visual observations, but the seismic events detected probably signified minor ash explosions. This was supported by reports from local residents who heard rumbling. The seismic network also recorded two low-frequency earthquakes associated with shallow magma movement. The SO2 flux averaged 1,740 metric tons per day (t/d), similar to values obtained during the last measurements on 28 November 2005. The flux was well above the usual 500 t/d measured at the volcano. Mayon remained at Alert Level 2, with a 6-km-radius Permanent Danger Zone in effect. At this point the possibility of more violent eruptions triggered warnings to tourists and the public in general to remain outside of the danger zone.

Geologic Background. Beautifully symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the Philippines' most active volcano. The structurally simple edifice has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions date back to 1616 and range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, PHIVOLCS Building, C.P. Garcia Avenue, Univ. of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/).


Miyakejima (Japan) — March 2006 Citation iconCite this Report

Miyakejima

Japan

34.094°N, 139.526°E; summit elev. 775 m

All times are local (unless otherwise noted)


Ash emissions in February 2006; declining SO2 flux

According to a news report, there was a minor eruption at Miyake-jima on 17 February 2006 that consisted of small ash emissions. Residents of the island were warned that there could be gas emissions and mudslides. The Geological Survey of Japan (AIST) website reported that the SO2 flux at Miyake-jima averaged about 2,000-5,000 tons per day in January 2006 (figure 22). The previous activity took place in November-December 2004, ending on 9 December 2004 when minor eruptions were reported after a two-year lull. As of mid-April 2006 no further activity had been reported.

Figure (see Caption) Figure 22. Sulfur dioxide (SO2) flux monitoring of Miyake-jima by COSPEC V was conducted from 26 August 2000, peaking in early 2000 at values well over 100,000 metric tons per day and dropping off slowly after that. Daily monitoring was performed by the Japanese Meteorological Agency and Geological Survey of Japan.

Geologic Background. The circular, 8-km-wide island of Miyakejima forms a low-angle stratovolcano that rises about 1100 m from the sea floor in the northern Izu Islands about 200 km SSW of Tokyo. The basaltic volcano is truncated by small summit calderas, one of which, 3.5 km wide, was formed during a major eruption about 2500 years ago. Parasitic craters and vents, including maars near the coast and radially oriented fissure vents, dot the flanks of the volcano. Frequent historical eruptions have occurred since 1085 CE at vents ranging from the summit to below sea level, causing much damage on this small populated island. After a three-century-long hiatus ending in 1469, activity has been dominated by flank fissure eruptions sometimes accompanied by minor summit eruptions. A 1.6-km-wide summit caldera was slowly formed by subsidence during an eruption in 2000; by October of that year the crater floor had dropped to only 230 m above sea level.

Information Contacts: Japan Meteorological Agency (JMA), Volcanological Division, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan (URL: http://www.jma.go.jp/); A. Tomiya, Geological Survey of Japan (AIST), 1-1 Higashi, 1-Chome Tsukuba, Ibaraki 305-856, Japan (URL: https://staff.aist.go.jp/a.tomiya/miyakeE.html); Kazahaya Kohei, Geological Survey of Japan (URL: https://staff.aist.go.jp/kazahaya-k/miyakegas/COSPEC.html); Earthquake Research Institute (ERI), University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-0032, Japan.


Montagu Island (United Kingdom) — March 2006 Citation iconCite this Report

Montagu Island

United Kingdom

58.445°S, 26.374°W; summit elev. 1370 m

All times are local (unless otherwise noted)


January 2006 visit documenting steam and new lava flows

Recent volcanism on Montagu Island was discovered based on satellite information (BGVN 30:11). Thanks to a visit from the South African icebreaker MV SA Agulhas, the first photographs of the island are now available, taken from just offshore. The Agulhas is an Antarctic supply and oceanographic research vessel built in the late 1970s; it is affiliated with the South African Department of Environmental Affairs and Tourism, Antarctica and Islands Division. She left Cape Town on 1 December 2005, and her journey was the focus of several reports (e.g., Hunter, 2005). The westerly position of pack ice during the course of this voyage enabled the Agulhas to visit Penguin Bukta, an indentation (bay) in the coastal ice shelf (figure 13).

Figure (see Caption) Figure 13. A map indicating the location of Montagu island with respect to features in the region. The pack ice is mobile and the position shown refers to conditions on 10 January 2006 as mapped by satellite radar (NASA/JAXA). Courtesy of Ian Hunter, South African Weather Service.

The Agulhas departed Penguin Bukta on 8 January to deploy drifting weather buoys and to install an automatic weather station on South Thule island at the extreme S end of the South Sandwich Islands. Besides the usual hazards of Antarctic travel and navigation, the South Sandwich Islands were the scene of some severe undersea earthquakes as the Agulhas entered those waters. This was of concern because such earthquakes can cause significant bathymetric change. The US Geological Survey posted detailed information on two large 2006 earthquakes to the E of the islands. The first, on 2 January, had M 7.3 and, fortunately, a moderately deep focal depth of 46 km.

The ship reached offshore of the remote, uninhabited Montagu island in mid-January 2006 (figures 14 and 15). These pictures were forwarded to the Smithsonian by Ian Hunter who received them from Frikkie Viljoen (the ice navigator), and Dave Hall (the ship's Master) after the Agulhas returned from Antarctica on 19 February 2006.

Figure (see Caption) Figure 14. Lava from Montagu Island eruption entering the sea. The photo was taken on 13 January 2006 from the SA Agulhas while lying to the N of the Island. The geometry of the setting given here is based on the MODIS photo taken on 9 September 2005 (BGVN 30:11) that clearly indicates the lava flow streaming N into the sea. Courtesy of Dave Hall and Frikkie Viljoen, SA Agulhas, and Ian Hunter, South African Weather Service.
Figure (see Caption) Figure 15. Photo taken on 13 January 2006 from the SA Agulhas from N of Montagu Island showing the lava field formed by the recent eruption. Courtesy of Dave Hall and Frikkie Viljoen, SA Agulhas, and Ian Hunter, South African Weather Service.

In an e-mail message to Hunter on the return leg of the voyage (on 16 January), Hall noted the following. "By now you will have heard that we successfully deployed the new weather station at Thule Island and had a good look at the eruption on Montagu. We got to within 1.5 miles [2.4 km] of the lava flow, but it was strangely disappointing. Although it was during the evening it was still full daylight so the lava flow was just the same colour as the surrounding rock, not dramatic at all! The most visible feature was the steam plume as the hot lava entered the sea. The top of the island was covered in cloud but that did part long enough to get a quick sighting of the summit, emitting the smoke and ash cloud."

John Smellie of the British Antarctic Survey reported hearing from a Falklands contact that an RAF flight sent at Christmas 2005 had taken photos and reported the eruption was "over." In addition, there could also be first-hand news from a yacht that was to be in the area during January 2006.

Reference. Hunter, Ian, (12 January) 2006, International Support for the SA Agulhas's mission in Antarctica, in Ports & Ships, Shipping News?reporting from the harbours of South Africa & Southern Africa (URL: http://www.ports.co.za/didyouknow/)

Geologic Background. The largest of the South Sandwich Islands, Montagu consists of a massive shield volcano cut by a 6-km-wide ice-filled summit caldera. The summit of the 10 x 12 km wide island rises about 3000 m from the sea floor between Bristol and Saunders Islands. Around 90% of the island is ice-covered; glaciers extending to the sea typically form vertical ice cliffs. The name Mount Belinda has been applied both to the high point at the southern end of the summit caldera and to the young central cone. Mount Oceanite, an isolated 900-m-high peak with a 270-m-wide summit crater, lies at the SE tip of the island and was the source of lava flows exposed at Mathias Point and Allen Point. There was no record of Holocene or historical eruptive activity until MODIS satellite data, beginning in late 2001, revealed thermal anomalies consistent with lava lake activity that has been persistent since then. Apparent plumes and single anomalous pixels were observed intermittently on AVHRR images during the period March 1995 to February 1998, possibly indicating earlier unconfirmed and more sporadic volcanic activity.

Information Contacts: Ian T. Hunter, South African Weather Service, Private Bag X097, Pretoria 0001, South Africa (URL: http://www.weathersa.co.za/); Department of Environmental Affairs and Tourism, Antarctica and Islands Division, Private Bag X447, Pretoria 0001, South Africa; John Smellie, British Antarctic Survey, Natural Environment Research Council, High Cross, Madingly Road, Cambridge CB3 0ET, United Kingdom (URL: https://www.bas.ac.uk/).


Poas (Costa Rica) — March 2006 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Small phreatic eruption on 24 March 2006, the first since 1994

Poás was last reported on in BGVN 28:09, covering the period from September 2001 to December 2002. The focus of activity at Poás during that time was the main crater and its fumaroles, and its low-pH, variably colored lake.

A field team from Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA) visited Poás on 25 January 2006 and found that the level of the volcano's hot acidic crater lake had risen in comparison to the previous month. Sustained rainfall during the previous months caused the water level to rise by ~ 4 m. The area of the lake increased by ~ 20%. Flooding occurred in relatively flat areas to the N, E, and SE. The shoreline extended about 150 m toward the SE. Scattered fumaroles and hot spots at the N base of the lava dome were flooded. Increased steaming was visible from the National Park. The average lake temperature remained at 22°C, with hot spots near the rim reaching up to 80°C. OVSICORI-UNA staff noted that in the past an increase in lake level during a rainy period has been followed by a decrease during the drier months of February to April.

On 24 March 2006 around noon, the first eruptions since 1994 began at Poás. The small, phreatic eruptions originated from the bottom of the volcano's Caliente Lake and dispersed mud, gas, and acid rain toward the S and SW parts of the crater. Witnesses described a sudden emission of water and sediments S of the lake. Roaring was heard in a nearby tourist area and weak earthquakes were felt. The strongest eruption occurred on the night of 24 March, when ejected volcanic material reached 200 m high and acid rain showered park headquarters, located 800 m S of the crater. During 25 March at least 8 eruptions took place. Due to the likelihood of more explosions the local National Emergencies Agency temporarily closed the park.

OVSICORI-UNA staff visited the E side of the volcano on 25 March and confirmed that water, blocks, and sediments from the bottom of the lake had been ejected. Several dozens of impact craters were seen with diameters between 15 and 60 cm, extending E as far as 700 m (figure 80). During 22-27 March, harmonic tremor was recorded. On the 27th, there was a reduction in seismicity and it returned to normal levels. No deformation was measured at the volcano. A news article reported that the area around the volcano was closed to visitors.

Figure (see Caption) Figure 80. Photo of the E side of Poás, annotated with observations made by OVSICORI-UNA staff. Impact craters ranged in size from a few cm to 70 cm; blocks ranged from a few cm to 50 cm and were scattered randomly over the area investigated. Blocks of fine-grained lake sediments were also observed and collected. The material collected was interpreted as pre-existent solid material from the bottom of the lake that has been heavily altered by the action of hot acidic fluids during the last 12 years. Photo courtesy of Eliecer Duarte Gonzalez, OVSICORI-UNA.

Following the eruptions that began on 24 March, seismicity at Poás decreased by 27 March and harmonic tremor that was recorded during the heightened activity ceased.

On 1 April 2006, OVSICORI-UNA staff visited Caliente Lake and its surroundings. During this visit the widening of the lake perimeter was confirmed as well as the emplacement of lake sediments and pre-existent blocks from both the bottom of the lake and its walls. Fracturing of the dome's N wall was also confirmed. The lake temperature was 54°C, with a pH of 0.63. The water was light gray due to the great quantity of suspended sediments. The park surrounding the volcano was reopened on 1 April.

Geologic Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: Eliecer Duarte Gonzalez, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica. (URL: http://www.ovsicori.una.ac.cr/); Rafael Barquero, Red Sismiológica Nacional, Sección de Sismología, Vulcanología y Exploración Geofisica, Escuela Centroamericana de Geología, Universidad de Costa Rica, Aptdo. 560-2300, Curridabat, San José, Costa Rica.


Raoul Island (New Zealand) — March 2006 Citation iconCite this Report

Raoul Island

New Zealand

29.27°S, 177.92°W; summit elev. 516 m

All times are local (unless otherwise noted)


Eruption on 17 March 2006 preceded by 5 days of earthquakes; 1 fatality

An eruption took place on 17 March 2006 at Raoul Island, killing one person. Brad Scott, New Zealand Institute of Geological and Nuclear Sciences (GNS), reported that on the evening of 12 March 2006 earthquakes began near Raoul Island. More than 200 earthquakes were recorded in the first 24 hours, with many of the larger events felt on the island. Earthquakes continued throughout the week, but the numbers gradually decreased.

An eruption from the Green Lake crater, within the Raoul caldera (figure 2), began at 0821 on 17 March. Other than the precursory seismicity, no water-level or temperature changes were observed, even only 24 hours before the eruption. Based on data from the seismograph on the island, the eruption appears to have continued for up to 30 minutes, although the most intense part of the eruption lasted for only 5 to 10 minutes. Following the eruption, the rate of earthquake activity doubled, but by 23 March the number of earthquakes was reduced to 10-20 per day. No thermal anomalies were detected by the MODIS satellite system during March 2006.

Figure (see Caption) Figure 2. Maps of Raoul Island taken from New Zealand governmental publications issued considerably prior to the 2006 eruption. A) Sketch map of the entire island (from Lloyd and Nathan, 1981). B) A second sketch map showing key areas of volcanism during the past 4,000 years (from Latter and others, 1992). C) A more detailed view of Raoul caldera and the cratered interior of the island, with contour lines at 20 m intervals (from Lloyd and Nathan, 1981). The northern caldera contains three small lakes: Blue Lake (1.17 km2, about 40% overgrown), Green Lake (160,000 m2), and Tui Lake (5,000 m2, drinking water quality). The island's high point is Moumoukai (516 m). Unfortunately, the current report mentions a few other features undisclosed on these maps. Courtesy of GNS.

The 2006 eruption blew over mature trees out to ~ 200 m and deposited dark gray mud and large ballistic blocks. Many of the steep crater margins had post-eruption collapses marked by fresh landslides.

The New Zealand Department of Conservation evacuated five staff members from the island, but one worker, taking water-temperature measurements at Green Lake at the time of the eruption, was killed. Devastation left by the eruption thwarted efforts to find the missing worker (figure 3). A news story reported that the missing man left around 0730 on 17 March to walk to Green Lake. An hour later the volcano erupted.

Figure (see Caption) Figure 3. Photo reportedly taken by the rescue helicopter pilot John Funnell of the area affected by the volcanic eruption on Raoul Island, 17 March 2006. AP Photo; photo credit to John Funnell.

Volcano monitoring of the Raoul crater lakes started after the 1964 eruption, as these lakes responded measurably before that event, consistent with a long-lived hydrothermal system. There are low-temperature (boiling-point) fumaroles in the vicinity of Green Lake and minor seepages of hydrothermal brine from the system (boiling hot springs) along Oneraki Beach, outside of the caldera. The gases have strong hydrothermal signatures (as opposed to proximal magmatic). As such, they do not suggest single-phase vapor transport directly from a magmatic source to the surface, but rather are indicative of the presence of boiling hydrothermal brine at depth. GNS has no quantitative data from Denham Bay (offshore to the W of the island, but scientists from the organization found boiling-point (100° C) steaming ground on the steep crater walls, and gas and water seeps in the sea. Historical observations of volcanic eruptions from this caldera (and Raoul caldera) point to the likely existence of a sizable active system residing there.

Still and video footage taken of the post-eruptive scene on 17 March 2006 showed many new craters and reactivation of 1964 craters. The main steam columns were derived from Crater I, Marker Bay, and Crater XI. Fumarolic activity appeared near the mouth of Crater Gully and the stream that drains from Crater V. The area NW of Bubbling Bay, where there had been a fumarole, contained a crater about 20-30 m across.

In the main body of Green Lake there were two areas of strong upwelling. One occurred near the end of the peninsula S of Crater XII (a promontory that had been explosively removed). Jagged rocks were visible in the lake where it had been 2-4 m deep. There was also a new feature about 200-300 m N of Green Lake's Crater XII (figure 2B); the new feature included a moat near the edge of the crater floor, which contained a vigorously active vent. Green Lake's surface did not appear elevated at the time of the post-eruption 17 March observations.

Sulfur dioxide (SO2) was detected by satellite about 5 hours after the 17 March eruption (figure 4). SO2 data was collected by the Aura Ozone Monitoring Instrument (OMI), which is affiliated with the University of Maryland, the US National Aeronautics and Space Administration (NASA), the Royal Netherlands Meteorological Institute (KNMI), and the Finnish Meteorological Institute (FMI). The highest SO2 values stood over and adjacent to the island and reached as high as two Dobson Units (DU, figure 4). Simon Carn noted that the total mass of SO2 in figure 4 was ~ 200 tons. Subsequent observations did not detect further SO2 discharge.

Figure (see Caption) Figure 4. Atmospheric sulfur dioxide (SO2) detected by the Aura/OMI satellite about 5.65 hours after the Raoul Island eruption's onset on 17 March 2006. (The eruption onset was at about 0821 local time and this SO2 observation was at about 1358 local time (0158 UTC).) Image courtesy of Simon Carn, the OMI SO2 group at the University of Maryland, and NASA/KNMI/FMI.

An aerial inspection on 21 March made from a Royal New Zealand Air Force Orion aircraft allowed excellent views of both the Raoul and Denham Bay calderas. Visible steam discharge from the vents had declined significantly owing to a 6-8 m rise in Green Lake's water level and the consequent drowning of most of the active vents. The lake level did not appear to have reached overflow level. Landsliding and collapse also blocked Crater I. Vigorous upwelling and gas discharge was still obvious through Green Lake, which appeared very warm.

There was no evidence of further eruptions since 17 March, nor was there any evidence that activity had occurred from the 1964 craters adjacent to Crater Gully (i.e. craters III, IV, and VI-X). However, many new craters formed at the mouth of Crater Gully where hot bare ground had been present. There was a possible NE-trend through the vents from Crater Gully to NE of Crater XII. In 1964 the craters aligned along three parallel fractures that tended NW. Heightened activity was not confined to the lake.

In Denham Bay GNS scientists observed a weak plume of discolored water approximately coincident with the vent area. There was evidence of hydrothermal seepage along most of the beach (milky discoloration indicating mixing of hydrothermal brine and seawater). There were also discharges in the rocky bay halfway between Hutchison Bluff and the NW end of Denham beach (figure 2A). If these are confirmed as hydrothermal seepages, they represent a significant rise in the surface of the hydrothermal fluids in the system, consistent with that observed in the caldera.

On 23 March 2006, the GNS reported that scientists who flew over noted that the hydrothermal system under the island showed signs of over-pressuring. GNS volcanologist Bruce Christenson stated, "From our aerial observations, it is clear that the heat, gas, and water that are discharging into Green Lake are making this part of the volcano's hydrothermal system unstable." Several new steam vents opened in and around Green Lake during the eruption and some old ones had reactivated. Many of these were drowned as a result of lake-level rise. According to Christenson, "one explanation for the increased hydrothermal activity is that it is being driven by the intrusion of magma at depth."

Steve Sherburn of GNS reported on 24 March on the GeoNet website (the New Zealand GeoNet Project provides real-time monitoring and data collection for rapid response and research into earthquake, volcano, landslide, and tsunami hazards) that over the last few days the level of earthquake activity at or close to Raoul Island had continued to decline to a current level of only 5-10 earthquakes per day, most of which were probably too small to be felt on the island. There is no unequivocal seismic evidence for magma movement (such as the strong volcanic tremor observed before the 1964 eruption). Careful seismic monitoring of Raoul Island will continue.

Brad Scott reported on 3 April 2006 that activity continued to decline in the Green Lake crater area. The most recently available photographs showed the water level continuing to rise slowly in Green Lake, but it had not reached overflow level. Over the last few days the level of earthquake activity at or close to Raoul Island continued to decline and in early April there were only 2-5 earthquakes per day being recorded.

References. Latter, J.H.; Lloyd, E.F.; Smith, I.E.M.; and Nathan, S., 1992, Volcanic hazards in the Kermadec Islands, and at submarine volcanoes between Southern Tonga and New Zealand: Volcanic Hazards Information Series, no. 4 (CD 303), New Zealand Ministry of Civil Defence, 45 p. (Booklet) ISBN 0-477-07472-3Lloyd, E.F., and Nathan, S., 1981, Geology and tephrochronology of Raoul Island, Kermadec Group, New Zealand: New Zealand Geological Survey Bulletin, no. 95, 105 p. (includes map in back pocket).

Geologic Background. Anvil-shaped Raoul Island is the largest and northernmost of the Kermadec Islands. During the past several thousand years volcanism has been dominated by dacitic explosive eruptions. Two Holocene calderas exist, the older of which cuts the center the island and is about 2.5 x 3.5 km wide. Denham caldera, formed during a major dacitic explosive eruption about 2200 years ago, truncated the W side of the island and is 6.5 x 4 km wide. Its long axis is parallel to the tectonic fabric of the Havre Trough that lies W of the volcanic arc. Historical eruptions during the 19th and 20th centuries have sometimes occurred simultaneously from both calderas, and have consisted of small-to-moderate phreatic eruptions, some of which formed ephemeral islands in Denham caldera. An unnamed submarine cone, one of several located along a fissure on the lower NNE flank, has also erupted during historical time, and satellitic vents are concentrated along two parallel NNE-trending lineaments.

Information Contacts: Brad Scott, Institute of Geological and Nuclear Sciences (GNS), Wairakei Research Centre, 114 Karetoto Road, Taupo, New Zealand (URL: http://www.geonet.org.nz/, http://www.gns.cri.nz/).


Tinakula (Solomon Islands) — March 2006 Citation iconCite this Report

Tinakula

Solomon Islands

10.386°S, 165.804°E; summit elev. 796 m

All times are local (unless otherwise noted)


Eruption; increased thermal anomalies during February-April 2006

According to Simon Carn, volcanic activity at Tinakula appears to have begun on 12 February 2006, with a small explosion followed by degassing. He noted some significant SO2 emissions on 14 February, as well as small plumes from Ambrym and Aoba. As of 16 February, there was still a small SO2 signal from Tinakula, but it was no bigger than that from Ambrym or Aoba. Andrew Tupper noted from visible MTSAT (Multi-functional Transport Satellite) images and an Aqua MODIS (Moderate Resolution Imaging Spectroradiometer) screen shot that a plume on 14 February was moving NNE at ~ 10 km/hour and appeared to be not far above summit level; the plume did not register on the IR imagery. MTSAT is a dual-mission satellite for the Japan Ministry of Land, Infrastructure, and Transport and the Japan Meteorological Agency performing an air traffic control and navigation, as well as a meteorological, functions.

On 27 February, Thomas Toba of the Solomon Islands government wrote to Herman Patia of the Rabaul Volcano Observatory, confirming Tinakula activity. Toba contacted authorities from the Temotu Provincial Headquarters who confirmed that there were several small explosions from this volcano around early to middle February 2006.

Satellite thermal-sensor data (using the MODVOLC alert-detection algorithm) revealed a period of thermal anomalies on the uninhabited island of Tinakula during cloud-free intervals in early to mid-February 2006 (table 1). The anomalies were particularly numerous on 11 February. The information was extracted from the MODIS Thermal Alerts website maintained by the Hawai'i Institute of Geophysics and Planetology (HIGP) (see also BGVN 29:06 and 28:01). The satellites used were Aqua and Terra MODIS. Confirmation of the volcanic source of the anomalies was not broadly distributed until late March 2006.

Table 1. MODVOLC thermal anomalies at Tinakula for mid-February through mid-April 2006. Since the start of monitoring by MODIS satellite sensors on 8 May 2001, no thermal anomalies had been measured at Tinakula before 11 February 2006. Courtesy of University of Hawai'i Institute of Geophysics and Planetology MODIS Hotspot Alert website.

Date Time (UTC) Pixels Satellite
11 Feb 2006 1125 6 Terra
11 Feb 2006 1425 10 Aqua
11 Feb 2006 2350 3 Terra
12 Feb 2006 0240 4 Aqua
13 Feb 2006 2340 3 Terra
15 Feb 2006 1500 2 Aqua
18 Feb 2006 1430 2 Aqua
03 Mar 2006 2325 1 Terra
06 Mar 2006 1430 1 Aqua
08 Mar 2006 1120 1 Terra
08 Mar 2006 1420 2 Aqua
13 Mar 2006 1135 1 Terra
15 Mar 2006 1425 1 Aqua
20 Mar 2006 1145 1 Terra
09 Apr 2006 1420 1 Aqua
14 Apr 2006 1135 1 Terra
16 Apr 2006 1125 2 Terra
16 Apr 2006 1425 1 Aqua
18 Apr 2006 1410 3 Aqua
19 Apr 2006 1455 1 Aqua

Geologic Background. The small 3.5-km-wide island of Tinakula is the exposed summit of a massive stratovolcano at the NW end of the Santa Cruz islands. Similar to Stromboli, it has a breached summit crater that extends from the summit to below sea level. Landslides enlarged this scarp in 1965, creating an embayment on the NW coast. The satellitic cone of Mendana is located on the SE side. The dominantly andesitic volcano has frequently been observed in eruption since the era of Spanish exploration began in 1595. In about 1840, an explosive eruption apparently produced pyroclastic flows that swept all sides of the island, killing its inhabitants. Frequent historical eruptions have originated from a cone constructed within the large breached crater. These have left the upper flanks and the steep apron of lava flows and volcaniclastic debris within the breach unvegetated.

Information Contacts: Hawai'i Institute of Geophysics and Planetology (HIGP), School of Ocean and Earth Science and Technology, University of Hawai'i at Manoa, 1680 East-West Road, POST 602, Honolulu, HI 96822 (URL: http://modis.higp.hawaii.edu); Simon Carn, University of Maryland Baltimore County (UMBC), Joint Center for Earth Systems Technology (JCET), Total Ozone Mapping Spectrometer (TOMS) Volcanic Emissions Group, 1000 Hilltop Circle, Baltimore, MD 21250; Andrew Tupper, Darwin Volcanic Ash Advisory Centre, Bureau of Meteorology, Australia (URL: http://www.bom.gov.au/info/vaac/); Thomas Toba, Ministry of Energy, Water, and Minerals Resources, Honiara, Solomon Islands; Herman Patia, Rabaul Volcano Observatory, P.O. Box 386, Rabaul, Papua New Guinea.


Ubinas (Peru) — March 2006 Citation iconCite this Report

Ubinas

Peru

16.355°S, 70.903°W; summit elev. 5672 m

All times are local (unless otherwise noted)


Ash eruption beginning 25 March 2006; heightened seismicity since November 2004

Ubinas began erupting ash on 25 March 2006. Since mid-2005 a small increase in fumarolic activity had been seen during visits to the crater by personnel from the Instituto Geofísico del Perú (IGP), UNSA local university, and the Instituto Geologico, Minero y Metalurgico (INGEMMET); it was also reported by local authorities. Increased fumarolic emissions described by INGEMMET were reported on 18 January 2006 by Diario Digital Sur Noticias. Fumaroles started to make strong jet noises, and seismic activity increased, in February 2006. The eruption that began on 25 March, described below, has continued through at least late April.

On 25 March farmers from Querapi village, 4 km from the crater, noted ash deposits on crops. A few millimeters of ash was deposited and quickly removed by rain. The volcano had been mostly cloud-covered during the previous few weeks, but on 27 March residents of Querapi noted a column of ash at 1430. On 30 and 31 March teams from IGP, UNSA, and INGEMMET visited the volcano (figure 2). Although there had been constant snow over the previous days, the summit was completely gray from ashfall. The ash thickness on rocks 2 km NW of the crater was 3 mm, just inside the summit crater there was about 1 cm, and at the inner pit crater edge there was 2 cm. Thick ash surrounded a new 30-m-wide vent in the crater base. This crater was emitting constant ash and gas with larger pulses approximately every 15 minutes. Near the edge of the pit crater were large numbers of flat circular mud discs up to 15 cm in diameter, many with central solid cores. These grew smaller and less frequent with distance. It is thought these are either huge accretionary lapilli, generated in storm clouds above Ubinas, or products of wet eruptions from the new vent. The crater area is dangerous and frequently smothered in ash clouds, so observations remain sketchy.

Figure (see Caption) Figure 2. Photo of Ubinas on 31 March 2006 showing an eruption plume rising from the summit crater. Photo by the Perúvian Civil Defense taken from Moquegua city, provided courtesy of the Associated Press.

Ash emissions through 10 April covered local villages and damaged crops. Clear crop damage was visible around the village of Querapi, with potato and alfalfa leaves and flowers blemished in spots. This is the critical growing time for the crop, and thus any damage is serious for the local farmers. Cattle have been seen suffering from diarrhea.

Short periods of seismic recordings have been made at a site 2,500 m NW of the crater rim. On 20 November 2004 only 16 local events were recorded over 12 hours. In February 2005 there where 96 events over the same time period. Over 12 hours on 27 March 2006 there were 115 events. During this last interval, low-amplitude tremor events lasting 3 minutes on average were recorded, as well as long-period (LP) events. Over the 12 hours of observation the following events were recorded: 62 LP, 18 LP with precursors, 10 volcano-tectonic (VT), five VT with precursors, and 20 tremor events.

Geologic Background. A small, 1.4-km-wide caldera cuts the top of Ubinas, Perú's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one of Holocene age about 1,000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Information Contacts: Orlando Macedo, Observatorio de Cayma-Arequipa, Instituto Geofísico del Perú at Arequipa city (IGP-Arequipa), Urb. La Marina B-19, Cayma, Arequipa, Perú; Jersy Marino, Instituto Geologico, Minero y Metalurgico (INGEMMET), Perú; Benjamin van Wyk, Laboratoire Magmas et Volcans (LMV), OPGC, France; Jean-Philippe Métaxian, Laboratire de Geophysique Interne et Tectonophysique-Univ de Savoie, France; Perúvian Civil Defense (URL: http://www.indeci.gob.pe/); Diario Digital Sur Noticias, Tacna, Perú (URL: http://www.surnoticias.com/); Associated Press (URL: http://www.ap.org/).


Veniaminof (United States) — March 2006 Citation iconCite this Report

Veniaminof

United States

56.17°N, 159.38°W; summit elev. 2507 m

All times are local (unless otherwise noted)


Modest ash emissions during September 2005-22 April 2006

On 7 September 2005, the Alaska Volcano Observatory (AVO) noted several minor bursts of ash from the volcano during the afternoon. Ash bursts continued to occur through at least 9 September, with ash rising less than 3 km altitude, and with the ash confined to the caldera. Over the following 2 weeks, minor ash emission continued at a rate of 1-5 events per day based on interpretations of seismic data. AVO reported that it was likely that diffuse ash plumes rose to heights less than ~ 3 km and were confined to the summit caldera. Cloudy weather during 16-23 September prohibited web-camera and satellite observations of Veniaminof, but seismic data indicated diminishing activity. On 28 September seismicity had remained at background levels for over a week, and there was no evidence to suggest that minor ash explosions were continuing.

On 4 November 2005, a low-level minor ash emission occurred from the intracaldera cone beginning at 0929. Ash rose a few hundred meters above the cone, drifted E, and dissipated rapidly. Minor ashfall was probably confined to the summit caldera. During the previous 2 weeks, occasional steaming from the intracaldera cone was observed. Very weak seismic tremor and a few small discrete seismic events were recorded at the station closest to the active cone. However, AVO reported that there were no indications from seismic data that a significantly larger eruption was imminent.

On the morning of 3 March 2006 ash again rose a few hundred meters above the intracaldera cone, drifted E, and dissipated rapidly. Ashfall was expected to be minor and confined to the summit caldera. Seismicity was again low and did not indicate that a significantly larger eruption was imminent. Over the week of 5-10 March, seismicity was low but slightly above background.

On the morning of 10 March, AVO received a report from a pilot of low-level ash emission from the intracaldera cone. Clear web-camera views on 9 March showed small diffuse plumes of ash extending a short distance from the intracaldera cone. The Anchorage Volcanic Ash Advisory Center (VAAC) reported a steam/ash plume noted on web-cam and satellite on 13 March 2006 at 0500Z (12 March 2006 at 2000 hours local), moving NNW at 9.2 km/hr and falling to the land surface. Web-cam images on 22 March showed a very diffuse steam-and-ash plume that was confined to the summit caldera, and on 24 March showed a steam-and-ash plume drifting from the summit cone at a height of less than 2.3 km. This level of activity was similar to that on 23 March, but higher than activity on 21 and 22 March, when a very diffuse steam-and-ash plume was confined to the summit caldera.

The flow of seismic data from Veniaminof stopped on the evening of 21 March 2006, and the problem was expected to continue until AVO staff could visit the site to repair the problem. Absent seismic data, the volcano could potentially still be monitored in other ways such as using web-camera and satellite images. Imagery was obscured by cloudy weather after 21 March. On 26 March 2006, a pilot reported a small ash plume rising above the volcano. Low-altitude ash emissions from Veniaminof were visible during 31 March to 7 April. On 6 April, a pilot reported an ash plume at a height of 3 km. AVO stated in its weekly report of 14 April 2006 that the seismicity at Veniaminof remained low but above background. Internet camera and satellite views had been obscured by cloudy weather, and AVO lacked new information about ash clouds or activity.

Geologic Background. Veniaminof, on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, and Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.avo.alaska.edu/); Charles R. Holliday, Air Force Weather Agency (AFWA), Offutt Air Force Base, NE 68113.

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/).