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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

Suwanosejima (Japan) Small ash plumes continued during January through June 2019

Great Sitkin (United States) Small steam explosions in early June 2019

Ibu (Indonesia) Frequent ash plumes and small lava flows active in the crater through June 2019

Ebeko (Russia) Continuing frequent moderate explosions though May 2019; ashfall in Severo-Kurilsk

Klyuchevskoy (Russia) Weak thermal anomalies and moderate Strombolian-type eruptions in September 2018-June 2019

Yasur (Vanuatu) Strong thermal activity with incandescent ejecta continues, February-May 2019

Bagana (Papua New Guinea) Infrequent thermal anomalies, no ash emissions, February-May 2019

Ambae (Vanuatu) Declining thermal activity and no explosions during February-May 2019

Sangay (Ecuador) Explosion on 26 March 2019; activity from 10 May through June produced ash plumes, lava flows, and pyroclastic flows

Kadovar (Papua New Guinea) Ash emissions and thermal anomalies during October 2018-April 2019; lava emissions at the E flank coast and summit area

Sarychev Peak (Russia) Brief ash emission reported on 16 May 2019

Nyiragongo (DR Congo) Lava lake remains active through May 2019; three new vents around the secondary cone



Suwanosejima (Japan) — July 2019 Citation iconCite this Report

Suwanosejima

Japan

29.638°N, 129.714°E; summit elev. 796 m

All times are local (unless otherwise noted)


Small ash plumes continued during January through June 2019

Suwanosejima is an active volcanic island south of Japan in the Ryuku islands with recent activity centered at Otake crater. The current eruption began in October 2004 and activity has mostly consisted of small ash plumes, ballistic ejecta, and visible incandescence at night. This report summarizes activity during January through June 2019 and is based on reports by the Japan Meteorological Agency (JMA), and various satellite data.

Thermal activity recorded by the MIROVA system was low through January and February after a decline in November (figure 36), shown in Sentined-2 thermal infrared imagery as originating at a vent in the Otake crater (figure 37). During January an explosive event was observed at 1727 on the 3rd, producing a gray plume that rose 600 m above the crater. A white gas-and-steam plume rose to 1.5 km above the crater and nighttime incandescence was observed throughout the month. Reduced activity continued through February with no reported explosive eruptions and light gray plumes up to 900 m above the crater. Incandescence continued to be recorded at night using a sensitive surveillance camera.

Figure (see Caption) Figure 36. MIROVA log radiative power plot of MODIS thermal infrared data at Suwanosejima during September 2018 through June 2019. There was reduced activity in 2019 with periods of more frequent anomalies during March and June. Courtesy of MIROVA.
Figure (see Caption) Figure 37. A Sentinel-2 thermal satellite image shows Suwanosejima with the active Otake crater in the center with elevated temperatures shown as bright orange/yellow. There is a light area next to the vent that may be a gas plume. False color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

There was an increase in thermal energy detected by the MIROVA system in mid-March and there was a MODVOLC thermal alert on the 15th. Occasional small explosions occurred but no larger explosive events were recorded. A white plume was noted on the 27th rising to 900 m above the crater and an event at 1048 on the 30th produced a light-gray plume that rose to 800 m. Incandescence was only observed using a sensitive camera at night (figure 38).

Figure (see Caption) Figure 38. Incandescence from the Suwanosejima Otake crater reflecting in clouds above the volcano. Courtesy of JMA (Volcanic activity of Suwanosejima March 2019).

No explosive events were observed through April. A white gas-and-steam plume rose to 1,200 m above the crater on the 19th and incandescence continued intermittently. Minor explosions were recorded on 5, 30, and 31 May, but no larger explosive events were observed during the month. The event on the 30th produced ash plume that reached 1.1 km above the crater. Similar activity continued through June with one explosive event occurring on the 2nd. Overall, there was a reduction in the number of ash plumes erupted during this period compared to previous months (figure 39).

Figure (see Caption) Figure 39. Observed activity at Suwanosejima for the year ending in July 2019. The black vertical bars represent steam, gas, or ash plume heights (scale in meters on the left axis), yellow diamonds represent incandescence observed in webcams, gray volcano symbols along the top are explosions accompanied by ash plumes, red volcano symbols represent large explosions with ash plumes. Courtesy of JMA (Volcanic activity of Suwanosejima June 2019).

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

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); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Great Sitkin (United States) — July 2019 Citation iconCite this Report

Great Sitkin

United States

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

All times are local (unless otherwise noted)


Small steam explosions in early June 2019

The Great Sitkin volcano is located about 40 km NE of Adak Island in the Aleutian Islands and has had a few short-lived eruptions over the past 100 years. Prior to the latest activity in early June 2019 described below, small phreatic explosions occurred in June and August 2018 (BGVN 43:09). An eruption in 1974 produced a lava dome in the center of the crater. The Alaska Volcano Observatory (AVO) is the primary source of information for this September 2018-June 2019 reporting period.

Low-level unrest occurred from September 2018 through February 2019 with slightly elevated seismic activity (figure 6). Small explosions were seismically detected by AVO on 30 October, 5 and 16 November, and 11 December 2018, but they were not seen in regional infrasound data and satellite data did not show an ash cloud.

On 1, 7, and 9 June 2019, AVO reported small steam explosions as well as slightly elevated seismic activity. Steam plumes and surficial evidence of an explosion were not observed during these events. On 18 June 2019 weakly elevated surface temperatures were recorded, field crews working on Adak observed some steam emissions, and a gas flight was conducted. Elevated concentrations of carbon dioxide detected above the lava dome were likely associated with the steam explosions earlier in the month (figures 7 and 8). From 23 June through the end of the month seismicity began to decline back to background levels.

Figure (see Caption) Figure 6. A steam plume was seen at the summit of Great Sitkin on 7 December 2018. Photo by Andy Lewis and Bob Boyd; courtesy of AVO/USGS.
Figure (see Caption) Figure 7. Some degassing was observed on the southern flank of the Great Sitkin during an overflight on 18 June 2019. Photo by Laura Clor; image courtesy of AVO/USGS.
Figure (see Caption) Figure 8. View of Great Sitkin with white plumes rising from the summit on 20 June 2019. Photo by Laura Clor, courtesy of AVO/USGS.

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

Information Contacts: 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/).


Ibu (Indonesia) — July 2019 Citation iconCite this Report

Ibu

Indonesia

1.488°N, 127.63°E; summit elev. 1325 m

All times are local (unless otherwise noted)


Frequent ash plumes and small lava flows active in the crater through June 2019

Ibu volcano on Halmahera island in Indonesia began the current eruption episode on 5 April 2008. Since then, activity has largely consisted of small ash plumes with less frequent lava flows, lava dome growth, avalanches, and larger ash plumes up to 5.5 km above the crater. This report summarizes activity during December 2018 through June 2019 and is based on Volcano Observatory Notice for Aviation (VONA) reports by MAGMA Indonesia, reports by Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and Badan Nasional Penanggulangan Bencana (BNPB), and various satellite data.

During December PVMBG reported ash plumes ranging from 200 to 800 m above the crater. There were 11 MODVOLC thermal alerts that registered during 1-12 December. An explosion on 12 January 2019 produced an ash plume that reached 800 m above the crater and dispersed to the S (figure 15). A report released for this event by Sutopo at BNPB said that Ibu had erupted almost every day over the past three months; an example given was of activity on 10 January consisting of 80 explosions. There were four MODVOLC thermal alerts through the month.

Figure (see Caption) Figure 15. An eruption at Ibu at 1712 on 21 January 2019 produced an ash plume that rose to 800 m above the crater. Courtesy of BNPB (color adjusted).

Throughout February explosions frequently produced ash plumes as high as 800 m above the crater, and nine MODVOLC thermal alerts were issued. Daily reports showed variable plume heights of 200-800 m most days throughout the month. Wind directions varied and dispersed the plumes in all directions. A VONA released at 1850 on 6 February reported an ash plume that rose to 1,925 m altitude (around 600 m above the summit) and dispersed S. Activity continued through March with the Darwin VAAC and PVMBG reporting explosions producing ash plumes to heights of 200-800 m above the crater and dispersing in various directions. There were ten MODVOLC alerts through the month.

Similar activity continued through April, May, and June, with ash plumes reaching 200-800 m above the crater. There were 12, 6, and 15 MODVOLC Alerts in April, May, and June, respectively.

Planet Scope satellite images show activity at a two vents near the center of the crater that were producing small lava flows from February through June (figure 16). Thermal anomalies were frequent during December 2018 through June 2019 across MODVOLC, MIROVA, and Sentinel-2 infrared data (figures 17 and 18). Sentinel-2 data showed minor variation in the location of thermal anomalies within the crater, possibly indicating lava flow activity, and MIROVA data showed relatively constant activity with a few reductions in thermal activity during January and February.

Figure (see Caption) Figure 16. Planet Scope natural color satellite images showing activity in the Ibu crater during January through June 2019, with white arrows indicating sites of activity. One vent is visible in the 21 February image, and a 330-m-long (from the far side of the vent) lava flow with flow ridges had developed by 24 March. A second vent was active by 12 May with a new lava flow reaching a maximum length of 520 m. Activity was centered back at the previous vent by 23-27 June. Natural color Planet Scope Imagery, copyright 2019 Planet Labs, Inc.
Figure (see Caption) Figure 17. Examples of thermal activity in the Ibu crater during January through May 2019. These Sentinel-2 satellite images show variations in hot areas in the crater due to a vent producing a small lava flow. Sentinel-2 false color (urban) images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 18. MIROVA log radiative power plot of MODIS thermal infrared at Ibu from September 2018 through June 2019. The registered energy was relatively stable through December, with breaks in January and February. Regular thermal anomalies continued with slight variation through to the end of June. Courtesy of MIROVA.

Geologic Background. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/).


Ebeko (Russia) — July 2019 Citation iconCite this Report

Ebeko

Russia

50.686°N, 156.014°E; summit elev. 1103 m

All times are local (unless otherwise noted)


Continuing frequent moderate explosions though May 2019; ashfall in Severo-Kurilsk

The Ebeko volcano, located on the northern end of the Paramushir Island in the Kuril Islands, consists of many craters, lakes, and thermal features and has been frequently erupting since late February 2017. Typical activity includes ash plumes, explosive eruptions, and gas-and-steam activity. The previous report through November 2018 (BGVN 43:12) described frequent ash explosions that sometimes caused ashfall in Severo-Kurilsk (7 km E). The primary source of information is the Kamchatka Volcanic Eruptions Response Team (KVERT). This report updates the volcanic activity at Ebeko for December 2018 through May 2019.

Frequent moderate explosive activity continued after November 2018. Volcanologists in Severo-Kurilsk observed explosions sending up ash, which drifted N, NE, and E, resulting in ash falls on Severo-Kurilsk on 28 different days between December 2018 and March 2019. On 25 December 2018 an explosion sent ash up to a maximum altitude of 4.5 km and then drifted N for about 5 km. Explosions occurring on 8-10 March 2019 sent ash up to an altitude of 4 km, resulting in ashfall on Severo-Kurilsk on 9-10 March 2019. An ash plume from these explosions rose to a height of 2.5 km and drifted to a maximum distance of 30 km ENE.

Satellite data analyzed by KVERT registered 12 thermal anomalies from December 2018 through May 2019. According to satellite data analyzed by MIROVA (Middle InfraRed Observation of Volcanic Activity), only one thermal anomaly was recorded from December 2018-May 2019, and no hotspot pixels were recognized using satellite thermal data from the MODVOLC algorithm.

Geologic Background. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); 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/).


Klyuchevskoy (Russia) — July 2019 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Weak thermal anomalies and moderate Strombolian-type eruptions in September 2018-June 2019

Klyuchevskoy has had alternating eruptive and less active periods since August 2015. Activity has included lava flows, a growing cinder cone, thermal anomalies, gas-and-steam plumes, and ash explosions. Though some eruptions occur near the summit crater, major explosive and effusive eruptions have also occurred from flank craters (BGVN 42:04 and 43:05). Intermittent moderate gas-and-steam and ash emissions were previously reported from mid-February to mid-August 2018. The Kamchatka Volcanic Eruptions Response Team (KVERT) is the primary source of information for this September 2018-June 2019 reporting period.

KVERT reported that moderate gas-and-steam activity, some of which contained a small amount of ash, and weak thermal anomalies occurred intermittently from the beginning of September 2018 through mid-April 2019. On 21-22 April 2019 webcam data showed a gas-and-steam plume extending about 160 km SE (figure 31). Moderate Strombolian-type volcanism began late April 2019 and continued intermittently through June 2019. On 11-12 June webcam data showed explosions that sent ash up to a maximum altitude of 6 km, with the resulting ash plume extending about 200 km WNW.

Figure (see Caption) Figure 31. Gas-and-steam plume containing some amount of ash rising from the summit of Klyuchevskoy on 22 April 2019. Photo by A. Klimova, courtesy of Institute of Volcanology and Seismology (IVS FEB RAS).

Thermal anomalies were noted by KVERT during two days in September 2018, six days in April 2019, eleven days in May 2019, and six days in June 2019. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed infrequent weak thermal anomalies December 2018 through early May 2019.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); 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/).


Yasur (Vanuatu) — June 2019 Citation iconCite this Report

Yasur

Vanuatu

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

All times are local (unless otherwise noted)


Strong thermal activity with incandescent ejecta continues, February-May 2019

Yasur volcano on Tanna Island has been characterized by Strombolian activity with large incandescent bombs, frequent explosions, lava fountaining, and ash emissions for much of its known eruptive history. Melanesians from nearby islands are believed to have settled Tanna in about 400 BCE; it is now part of the nation of Vanuatu, independent since 1980. The Kwamera language (or Tannese) spoken on the SE coast of the island is thought to be the source of the name of the island. No known oral history describes volcanic activity; the first written English-language documentation of activity dates to 5 August 1774, when Captain James Cook saw "a great fire" on Tanna Island. Cook realized that it "was a Volcano which threw up vast quantities of fire and smoak and made a rumbling noise which was heard at a good distance" (The Captain Cook Society) (figure 51).

Figure (see Caption) Figure 51. Incandescence, steam, and dark ash from Yasur fill the sky in this sketch representing Captain James Cook's landing in the 'Resolution' at Tanna Island on 5 August 1774. The form of the volcano is behind the ship, the incandescence is in the upper right next to the ship's masts. "Landing at Tanna" by William Hodges, 1775-1776, National Maritime Museum, Greenwich, London. The Maritime Museum noted that this is one of a group of panel paintings produced by Hodges of encounters with islanders during the voyage, in which the European perception of each society at the time is portrayed. Image taken from Wikimedia Commons.

Based on numerous accounts from ships logs and other sources, volcanic activity has been continuous since that time. During periods of higher activity, multiple vents within the summit crater send ejecta 100 m or more above the crater rim, with large bombs occasionally landing hundreds of meters away. Continued activity during February-May 2019 is covered in this report with information provided by the Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD) which monitors the volcano and satellite data; photographs from tourists also provide valuable information about this remote location.

VMGD has maintained Alert Level 2 at Yasur since October 2016, indicating that it is in a major state of unrest. There is a permanent exclusion zone within 395 m of the eruptive vents where access is prohibited due to multiple hazards, primarily from large incandescent bombs up to 4 m in diameter which have been ejected from the vents onto the crater rim in the past, resulting in fatalities (BGVN 20:08).

Satellite and ground based information all support high levels of thermal activity during February -May 2019. MODVOLC thermal alerts were issued 11 times in February, 27 times in March, and 20 times each in April and May. The MIROVA graph also indicated the ongoing consistently high levels of thermal energy throughout the period (figure 52). Plumes of SO2 emissions are common from Vanuatu's volcanoes; newer higher resolution data available beginning in 2019 reveal a persistent stream of SO2 from Yasur on a near-daily basis (figure 53).

Figure (see Caption) Figure 52. The MIROVA graph of thermal energy at Yasur from 3 September 2018 through May 2019 indicates the ongoing activity at the volcano. Courtesy of MIROVA.
Figure (see Caption) Figure 53. The SO2 plumes from Yasur were persistent during January-May 2019 when they were visible many days of each week throughout the period. Top left: On 12 January plumes were visible drifting E from both Ambrym (top) and Yasur (bottom). Top right: Plumes drifted W from three Vanuatu volcanoes on 7 February, Gaua (top), Ambrym (middle) and Yasur (bottom). Bottom left: On 12 March N drifting plumes could be seen from Ambae (top) and Yasur (bottom). On 27 April, only Yasur had an SO2 plume drifting W. Courtesy of Goddard Space Flight Center.

Satellite imagery confirmed that the heat sources from Yasur were vents within the summit crater of the pyroclastic cone. Both northern and southern vent areas were active. On 7 March 2019 the N vent area had a strong thermal signal. Ten days later, on 17 March, similar intensity thermal anomalies were present in both the N and S vent areas (figure 54). On 6 April the S vent area had a stronger signal, and gas emissions from both vents were drifting N (figure 55). Satellite imagery from 21 May 2019 indicated a strong thermal signal inside the crater in the area of the vents, and included a weaker signal clearly visible on the inside E crater rim. Strong Strombolian activity or spatter sending large incandescent bombs as far as the crater rim are a likely explanation for the signal (figure 56), underscoring the hazardous nature of approaching the crater rim.

Figure (see Caption) Figure 54. Strong thermal anomalies from the crater of Yasur's pyroclastic cone seen in satellite images confirmed the ongoing high level of activity. Left: 7 March 2019, a strong thermal anomaly from the N vent area, shown with "Geology" rendering (bands 12, 4, 2). Right: 17 March 2019, thermal anomalies at both the N and S vent areas, shown with "Atmospheric Penetration" rendering (bands 12, 11, 8A). The crater is about 500 m in diameter. Sentinel-2 satellite imagery courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 55. Strong thermal anomalies (left) and gas emissions (right) at Yasur were captured with different bands in the same Sentinel-2 satellite image on 6 April 2019. Left: The thermal anomaly in the S vent area was stronger than in the N vent area, "Atmospheric Penetration" rendering (bands 12, 11, 8A). Right: Gas plumes drifted N from both vent areas, "Natural color" rendering (bands 4, 3, 2). The crater is about 500 m in diameter. Sentinel-2 satellite imagery courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 56. Thermal activity from the crater of Yasur on 21 May 2019 produced a strong thermal signal from the center of the crater and a weaker signal on the inside E crater rim, likely the result of hazardous incandescent bombs and ejecta, frequent products of the activity at Yasur. Left: "Atmospheric Penetration" rendering (bands 12, 11, 8A). Right: "Geology" rendering (bands 12, 4, 2). The crater is about 0.5 km in diameter. Sentinel-2 satellite imagery courtesy of Sentinel Hub Playground.

Tourists visit Yasur on a regular basis. A former lake on the N side of Yasur has left ripples in the sand deposits over older volcanic rocks on the N side of the volcano (figure 57) since it drained in 2000 (BGVN 28:01). Visitors are allowed to approach the S rim of the crater where incandescence from both the N and S vents is usually visible (figure 58). Incandescent spatter from the convecting lava in the vents is highly dangerous and unpredictable and often covers the inner slopes of the rim as well as sending bombs outside the crater (figure 59).

Figure (see Caption) Figure 57. The pyroclastic cone of Yasur viewed from the north on 6 May 2019. Ripples in volcaniclastic sand in the foreground are remnants of a lake that was present on the N side of the volcano until a natural dam breached in 2000. Copyrighted photo by Nick Page, used with permission.
Figure (see Caption) Figure 58. Two glowing vents were visible from the south rim of Yasur on 6 May 2019. The S vent area is in the foreground, the N vent area is in the upper left. Copyrighted by Nick Page, used with permission.
Figure (see Caption) Figure 59. Incandescent spatter at Yasur on 6 May 2019 sent fragments of lava against the inside crater wall and onto the rim. The convecting lava in the vent can be seen in the lower foreground. Copyrighted photo by Nick Page, used with permission.

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/); Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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/); The Captain Cook Society (URL: https://www.captaincooksociety.com/home/detail/225-years-ago-july-september-1774); Royal Museums Greenwich (URL: https://collections.rmg.co.uk/collections/objects/13383.html); Wikimedia Commons, (URL: https://commons.wikimedia.org/wiki/File:The_Landing_at_Tana_one_of_the_New_Hebrides,_by_William_Hodges.jpg); Nick Page, Australia,Flickr: (URL: https://www.flickr.com/photos/152585166@N08/).


Bagana (Papua New Guinea) — June 2019 Citation iconCite this Report

Bagana

Papua New Guinea

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

All times are local (unless otherwise noted)


Infrequent thermal anomalies, no ash emissions, February-May 2019

With historical eruptions reported back to 1842, Papua New Guinea's Bagana volcano on the island of Bougainville has been characterized by viscous andesitic lava flows down the steep flanks of its cone, along with intermittent ash plumes and pyroclastic flows. Ongoing thermal anomalies and frequent ash plumes have been typical of activity during the current eruption since it began in early 2000. Activity declined significantly in December 2018 and remained low through May 2019, the period covered in this report (figure 33). Information for this report comes primarily from satellite images and thermal data.

Figure (see Caption) Figure 33. The MIROVA plot of radiative power at Bagana from 1 September 2018 through May 2019 shows a marked decline in thermal activity during December 2018 after ash explosions and satellite observations of flows during the previous months. Courtesy of MIROVA.

The last ash emission at Bagana was reported on 1 December 2018 by the Darwin Volcanic Ash Advisory Center (VAAC). A Sentinel-2 satellite image showed a linear thermal anomaly trending NW from the summit on 14 December (BGVN 50:01). On 8 January 2019, an image contained a dense steam plume drifting E and a very faint thermal anomaly on the N flank a few hundred meters from the summit. A more distinct thermal anomaly at the summit appeared on 22 February 2019 (figure 34). A visitor to the region photographed incandescence on the flank, likely from the volcano, at dawn around 19 February 2019 (figure 35).

Figure (see Caption) Figure 34. Sentinel-2 satellite imagery revealed thermal anomalies at Bagana in January and February 2019. Left: a very faint thermal anomaly was N of the summit at the edge of the E-drifting steam plume on 8 January 2019. Right: A thermal anomaly was located at the summit, at the base of the NE-drifting steam plume on 22 February 2019. Sentinel-2 satellite images with "Atmospheric Penetration" rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 35. A visitor near Bagana spotted incandescence on the flank at dawn, possibly from a lava flow. Posted online 19 February 2019. Courtesy of Emily Stanford.

Two faint thermal anomalies were visible at the summit in satellite imagery on 19 March; a single one appeared on 29 March 2019 (figure 36). No thermal anomalies were recorded in Sentinel-2 images during April or May, but steam plumes and gas emissions were visible through cloud cover on multiple occasions (figure 37).

Figure (see Caption) Figure 36. Faint thermal anomalies at Bagana were recorded in satellite imagery twice during March 2019. Left: 19 March, two anomalies appear right of the date label. Right: 29 March, a small anomaly appears right of the date label. Sentinel-2 image rendered with "Atmospheric Penetration" (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 37. Steam and gas emissions at Bagana were recorded in satellite imagery during April and May 2019. Left: A steam plume drifted NW from the summit on 23 April, visible through dense cloud cover. Right: A gas plume drifted SW from the summit on 18 May. Sentinel-2 image with "Geology" rendering (bands 12, 4, 2). Courtesy of Sentinel Hub Playground.

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

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Emily Stanford (Twitter: https://twitter.com/NerdyBatLady, image posted at https://twitter.com/NerdyBatLady/status/1098052063009792001/photo/1).


Ambae (Vanuatu) — June 2019 Citation iconCite this Report

Ambae

Vanuatu

15.389°S, 167.835°E; summit elev. 1496 m

All times are local (unless otherwise noted)


Declining thermal activity and no explosions during February-May 2019

Ambae (Aoba) is a large basaltic shield volcano in the New Hebrides arc, part of the multi-island country of Vanuatu. Its periodic phreatic and pyroclastic explosions originating in the summit crater lakes have been recorded since the 16th century. A pyroclastic cone appeared in Lake Voui during November 2005-February 2006 (BGVN 31:12, figure 30); an explosive eruption from a new pyroclastic cone in the lake began in mid-September 2017 (BGVN 43:02). Activity included high-altitude ash emissions (9.1 km), lava flows, and Strombolian activity. Intermittent pulses of ash emissions during the following months resulted in extensive ashfall and evacuations; multiple communities were affected by lahars. The most recent episode of the eruption from July to September 2018 (BGVN 44:02) resulted in 11-km-altitude ash plumes and the evacuation of the entire island due to heavy ashfall and lahars. This report covers activity from February to May 2019, with information provided by the Vanuatu Geohazards Observatory of the Vanuatu Meteorology and Geo-Hazards Department (VMGD) and satellite data from multiple sources.

Activity diminished after the extensive eruptive phase of July-September 2018 when substantial ash plumes and ashfall resulted in evacuations. An explosion with an ash plume on 30 October 2018 was the last activity reported for 2018. Thermal alerts were reported by the Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC thermal alerts system through January 2019, and the Log Radiative Power graph prepared by the MIROVA project showed decreasing thermal anomalies into June 2019 (figure 92). Satellite images recorded in April and May 2019 (figure 93) showed the configuration of the summit lakes to be little changed from the previous November except for the color (BGVN 44:02, figure 89). No ash emissions or SO2 plumes were reported during the period. VMGD noted that the volcano remained at Alert Level 2 through May 2019 with a 2-km-radius exclusion zone around the summit.

Figure (see Caption) Figure 92. The MIROVA log radiative power plot for Ambae showed ongoing intermittent thermal anomalies from early September 2018 through May 2019. Courtesy of MIROVA.
Figure (see Caption) Figure 93. Satellite imagery in April and May 2019 showed little change in the configuration of lakes at the summit of Ambae since November 2018 (see BGVN 44:02, figure 89). Left: 24 April 2019. Right: 29 May 2019. Sentinel-2 satellite imagery with "Natural Color" rendering (bands 4, 3, 2); courtesy of Sentinel Hub Playground.

Geologic Background. The island of Ambae, also known as Aoba, is a massive 2500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

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/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Sangay (Ecuador) — July 2019 Citation iconCite this Report

Sangay

Ecuador

2.005°S, 78.341°W; summit elev. 5286 m

All times are local (unless otherwise noted)


Explosion on 26 March 2019; activity from 10 May through June produced ash plumes, lava flows, and pyroclastic flows

Sangay is the southernmost active volcano in Ecuador, with confirmed historical eruptions going back to 1628. The previous eruption occurred during August and December and was characterized by ash plumes reaching 2,500 m above the crater. Lava flows and pyroclastic flows descended the eastern and southern flanks. This report summarizes activity during January through July 2019 and is based on reports by Instituto Geofísico (IG-EPN), Washington Volcanic Ash Advisory Center (VAAC), and various satellite data.

After the December 2018 eruption there was a larger reduction in seismicity, down to one event per day. During January, February, and most of March there was no recorded activity and low seismicity until the Washington VAAC reported an ash plume at 0615 on 26 March. The ash plume rose to a height of around 1 km and dispersed to the SW as seen in GOES 16 satellite imagery as a dark plume within white meteorological clouds. There was no seismic data available due to technical problems with the station.

More persistent eruptive activity began on 10 May with thermal alerts (figure 30) and an ash plume at 0700 that dispersed to the W. An explosion was recorded at 1938 on 11 May, producing an ash plume and incandescent material down the flank (figure 31). Two M 2 earthquakes were detected between 3.5 and 9 km below the crater on 10 May, possibly corresponding to explosive activity. By 17 May there were two active eruptive centers, the central crater and the Ñuñurcu dome (figure 32).

Figure (see Caption) Figure 30. MIROVA log radiative power plot of MODIS thermal infrared at Sangay for the year ending June 2019. The plot shows the August to December 2018 eruption, a break in activity, and resumed activity in May 2019. Courtesy of MIROVA.
Figure (see Caption) Figure 31. An explosion at Sangay on 10 May 2019 sent ballistic projectiles up to 650 m above the crater at a velocity of over 400 km/hour, an ash plume that rose to over 600 m, and incandescent blocks that traveled over 1.5 km from the crater at velocities of around 150 km/hour. Screenshots are from video by IG-EPN.
Figure (see Caption) Figure 32. A photograph of the southern flank of Sangay on 17 May 2019 with the corresponding thermal infrared image in the top right corner. The letters correspond to: a) a fissure to the W of the lava flow; b) an active lava flow from the Ñuñurcu dome; c) the central crater producing a volcanic gas plume; d) a pyroclastic flow deposit produced by collapsing material from the front of the lava flow. Prepared by M. Almeida; courtesy of IG-EPN (special report No. 3 – 2019).

Activity at the central crater by 21 May was characterized by sporadic explosive eruptions that ejected hot ballistic ejecta (blocks) with velocities over 400 km/hour; after landing on the flanks the blocks travelled out to 2.5 km from the crater. Ash plumes reached heights between 0.9-2.3 km above the crater and dispersed mainly to the W and NW; gas plumes also dispersed to the W. The Ñuñurcu dome is located around 190 m SSE of the central crater and by 21 May had produced a lava flow over 470 m long with a maximum width of 175 m and an estimated minimum volume of 300,000 to 600,000 m3. Small pyroclastic flows and rockfalls resulted from collapse of the lava flow front, depositing material over a broad area on the E-SE flanks (figure 33). One pyroclastic flow reached 340 m and covered an area of 14,300 m2. During the 17 May observation flight the lava flow surface reached 277°C.

Figure (see Caption) Figure 33. A view of the ESE flanks of Sangay on 17 May 2019. The area within the black dotted line is the main area of pyroclastic flow deposition from the Ñuñurco Dome. Photo by M. Almeida; courtesy of IG-EPN (special report No. 4 – 2019).

At the end of June activity was continuing at the central crater and Ñuñurco Dome. At least three lava flows had been generated from the dome down the SE flank and pyroclastic flows continued to form from the flow fronts (figure 34). Pyroclastic material had been washed into the Upano river and steam was observed in the Volcán River possibly due to the presence of hot rocks. Ash plumes continued through June reaching heights of 800 m above the crater (figure 35), but no ashfall had been reported in nearby communities.

Figure (see Caption) Figure 34. Sentinel-2 natural color (left) and thermal (center) images (bands 12, 11, 4), and 1:50 000 scale maps (right) of Sangay with interpretation on the background of a 30 m numerical terrain model (WGS84; Zone 17S) (Prepared by B. Bernard). The dates from top to bottom are 17 May, 22 May, 27 May, 16 June, and 26 June 2019. Prepared by B. Bernard; courtesy IG-EPN (special report No. 4 – 2019).
Figure (see Caption) Figure 35. Plots giving the heights and dispersal direction of ash plumes at Sangay during May and June 2019. Top: Ash plume heights measures in meters above the crater. Bottom: A plot showing that the dominant dispersal direction of ash plumes is to the W during this time. Courtesy of IG-EPN (special report No. 4 – 2019).

Geologic Background. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Information Contacts: Instituto Geofísico (IG-EPN), Escuela Politécnica Nacional, 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); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Kadovar (Papua New Guinea) — May 2019 Citation iconCite this Report

Kadovar

Papua New Guinea

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

All times are local (unless otherwise noted)


Ash emissions and thermal anomalies during October 2018-April 2019; lava emissions at the E flank coast and summit area

Steeply-sloped Kadovar Island is located about 25 km NNE from the mouth of the Sepik River on the mainland of Papua New Guinea. The first confirmed historical eruption with ash plumes and lava extrusion began in early January 2018, resulting in the evacuation of around 600 residents from the N side of the approximately 1.4-km-diameter island (BGVN 43:03); continuing activity from October 2018 through April 2019 is covered in this report. Information was provided by the Rabaul Volcano Observatory (RVO), the Darwin Volcanic Ash Advisory Center (VAAC), satellite sources, and photos from visiting tourists.

Activity during March-September 2018. After the first recorded explosions with ash plumes in early January 2018, intermittent ash plumes continued through March 2018. A lava flow on the E flank extended outward from the island, extruding from a vent low on the E flank and forming a dome just offshore. The dome collapsed and regrew twice during February 2018; the growth rate slowed somewhat during March. A satellite image from 21 March 2018 was one of the first showing the new dome growing off the E flank with a thermal anomaly and sediment plumes in the water drifting N and E from the area. Thermal anomalies were visible at both the summit vent and the E-flank coastal dome in in April and May 2018, along with steam and gas rising from both locations (figure 19).

Figure (see Caption) Figure 19. Sentinel-2 satellite imagery of Kadovar provided clear evidence of thermal activity at the new E-flank coastal dome during March-May 2018. Sediment plumes were visible drifting N and E in the water adjacent to the coastal dome. The summit crater also had a persistent steam plume and thermal anomaly in April and May 2018. Left: 21 March 2018. Middle 10 April 2018. Right: 15 May 2018. Images all shown with "Geology" rendering using bands 12, 4, and 2. Courtesy of Sentinel Hub Playground.

A trip to Kadovar by tourists in mid-May 2018 provided close-up views of the dense steam plumes at the summit and the growing E-flank coastal dome (figures 20 and 21). The thermal anomaly was still strong at the E-flank coastal dome in a mid-June satellite image, but appeared diminished in late July. Intermittent puffs of steam rose from both the summit and the coastal dome in mid-June; the summit plume was much denser on 29 July (figure 22). Ash emissions were reported by the Darwin VAAC and photographed by tourists during June (figure 23) and September 2018 (BGVN 43:10), but thermal activity appeared to decline during that period (figure 24).

Figure (see Caption) Figure 20. A tourist photographed Kadovar and posted it online on 19 May 2018. Steam plumes rose from both the summit and the E-flank coastal dome in this view taken from the SE. Courtesy of Tico Liu.
Figure (see Caption) Figure 21. A closeup view of the E-flank coastal dome at Kadovar posted online on 19 May 2018 showed steam rising from several places on the dome, and dead trees on the flank of the volcano from recent eruptive activity. Courtesy of Tico Liu.
Figure (see Caption) Figure 22. The thermal anomaly was still strong at the E-flank coastal dome of Kadovar in a 14 June 2018 satellite image (left), but appeared diminished on 29 July 2018 (right). Intermittent puffs of steam rose from both the summit and the coastal dome on 14 June; the summit plume was much denser on 29 July. Sentinel-2 images both show "Geology" rendering using bands 12, 4, and 2. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 23. An ash plume rose from the summit of Kadovar and drifted W while steam and gas rose from the E-flank coastal dome, posted online 27 June 2018. Courtesy of Shari Kalt.
Figure (see Caption) Figure 24. Thermal activity at Kadovar for the year ending on 26 April 2019 was consistent from late April 2018 through mid-June 2018; a quiet period afterwards through late September ended with renewed and increased thermal activity beginning in October 2018. All distances are actually within 1 km of the summit of Kadovar, a DEM georeferencing error makes some locations appear further away. Courtesy of MIROVA.

Multiple satellite images during August and early September 2018 showed little or no sign of thermal activity at the E-flank coastal dome, with only intermittent steam plumes from the summit. A new steam plume on the eastern slope appeared in a 22 September 2018 image (figure 25). The Rabaul Volcano Observatory (RVO) reported explosive activity on the afternoon of 21 September. Noises of explosions were accompanied by dark gray and brown ash clouds that rose several hundred meters above the summit crater and drifted NW. Local reports indicated that the activity continued through 26 September and ashfall was reported on Blupblup island during the period. Ground observers noted incandescence visible from both the summit and the E-flank coastal dome.

Figure (see Caption) Figure 25. Steam plumes were seen in satellite images of Kadovar during August and early September 2018, but no thermal anomalies. Intermittent steam plumes rose from the summit vent on 28 August (left). A new dense steam plume originating mid-way down the E flank appeared on 22 September 2018 (right). Sentinel-2 images both show "Geology" rendering using bands 12, 4, and 2. Courtesy of Sentinel Hub Playground.

Activity during October-December 2018. Evidence of both thermal and explosive activity reappeared in October 2018 (figure 24). The Darwin VAAC reported intermittent ash plumes rising to 2.7 km altitude and drifting W on 1 October 2018. Low-level continuous ash emissions rising less than a kilometer and drifting W were reported early on 3 October. A higher plume drifted WNW at 2.4 km altitude on 7 October. Intermittent discrete emissions of ash continued daily at that altitude through 16 October, drifting NW or W. Ash emissions drifting NW and thermal anomalies at the summit were visible in satellite imagery on 2 and 12 October (figure 26). A brief ash emission was reported on 21 October 2018 at 2.4 km altitude drifting NE for a few hours. Intermittent ash emissions also appeared on 29 October moving SE at 1.8 km altitude. For the following three days ash drifted SW, W, then NW at 2.1 km altitude, finally dissipating on 1 November; the thermal anomaly at the summit was large and intense in satellite images on 27 October and 1 November compared with previous images (figure 27).

Figure (see Caption) Figure 26. Ash emissions drifting NW and thermal anomalies at the summit of Kadovar were visible in satellite imagery on 2 and 12 October 2018; no thermal activity was noted at the E-flank coastal dome. Sentinel-2 images both show "Geology" rendering using bands 12, 4, and 2. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 27. Strong thermal anomalies at the summit of Kadovar on 27 October and 1 November 2018 were not concealed by the steam plumes drifting SW and NW from the summit. Sentinel-2 images both show "Geology" rendering using bands 12, 4, and 2. Courtesy of Sentinel Hub Playground.

An ash explosion was photographed by tourists on a cruise ship on the afternoon of 6 November 2018 (figure 28). After the explosion, a dense steam plume rose from a large dome of lava near the summit at the top of the E flank (figure 29). Continuous ash emissions rising to 1.8 km altitude were reported by the Darwin VAAC beginning on 9 November 2018 moving WNW and lasting about 24 hours. A new ash plume clearly identifiable on satellite imagery appeared on 13 November at 2.4 km altitude moving E, again visible for about 24 hours. Another shipboard tourist photographed an ash plume on 18 November rising a few hundred meters above the summit (figure 30).

Figure (see Caption) Figure 28. An explosion at Kadovar photographed on the afternoon of 6 November 2018 sent a dense gray ash plume hundreds of meters above the summit drifting W; blocks of volcanic debris descended the flanks as well. View is from the S. Courtesy of Coral Expeditions, used with permission.
Figure (see Caption) Figure 29. Tourists on a cruise ship passed by Kadovar on 6 November 2018 and witnessed a steam plume drifting W from a large dome of lava near the summit at the top of the E flank after an ash explosion. Smaller steam plumes were visible in the middle and at the base of the E flank, but no activity was visible at the coastal dome off the E flank (lower right). View is from the SE. Courtesy of Coral Expeditions, used with permission.
Figure (see Caption) Figure 30. An ash plume rose at dusk from the summit of Kadovar and was witnessed by a cruise ship tourist on 18 November 2018. View is from the E; the E-flank coastal dome is a lighter area in the lower foreground. Courtesy of Philip Stern.

Low-level ash emissions were reported briefly on 28 November at about 1 km altitude moving SE. Intermittent puffs of ash were seen drifting WSW on 2 and 3 December at about 1.2 km altitude. They were the last VAAC reports for 2018. Two thermal anomalies were visible at the summit in satellite imagery on 26 November, they grew larger and more intense through 16 December when multiple anomalies appeared at the summit and on the E flank (figure 31).

Figure (see Caption) Figure 31. Multiple thermal anomalies near the summit of Kadovar grew larger and more intense between 26 November and 16 December 2018. Sentinel-2 images show "Geology" rendering using bands 12, 4, and 2. Courtesy of Sentinel Hub Playground.

Activity during January-April 2019. Multiple thermal anomalies were still visible at the summit in satellite imagery on 5 January 2019 as regular puffs of steam drifted SE from the summit, leaving a long trail in the atmosphere (figure 32). Additional imagery on 10 and 30 January showed a single anomaly at the summit, even through dense meteorologic clouds. A short-lived ash emission rose to 2.4 km altitude on 11 January 2019 and drifted E; it dissipated the next day. Multiple minor intermittent discrete ash plumes extended WNW at 3.0 km altitude on 18 January; they dissipated within six hours.

Figure (see Caption) Figure 32. Multiple thermal anomalies were visible in satellite imagery of Kadovar on 5 January 2019 as regular puffs of steam drifted SE from the summit. Sentinel-2 image shows "Geology" rendering using bands 12, 4, and 2. Courtesy of Sentinel Hub Playground.

The Royal New Zealand Air Force released images of eruptive activity on 10 February 2019 (figure 33). Satellite imagery in February was largely obscured by weather; two thermal anomalies were barely visible through clouds at the summit on 14 February. The Darwin VAAC reported an ash emission at 1.8 km altitude drifting ESE on 16 February; a similar plume appeared on 21 February that also dissipated in just a few hours.

Figure (see Caption) Figure 33. The Royal New Zealand Air Force released images of an ash plume at Kadovar on 10 February 2019. Courtesy of Brad Scott.

Satellite imagery on 1 March 2019 confirmed a strong thermal anomaly from the summit and down the E flank almost to the coast. A month later on 5 April the anomaly was nearly as strong and a dense ash and steam plume drifted N from the summit (figure 34). A tourist witnessed a dense steam plume rising from the summit on 4 April (figure 35). Multiple discrete eruptions were observed in satellite imagery by the Darwin VAAC on 9 April at 1.2-1.5 km altitude drifting SE. The thermal anomaly at the summit persisted in satellite imagery taken on 15 April 2019.

Figure (see Caption) Figure 34. A strong thermal anomaly appeared from the summit down the E flank of Kadovar on 1 March 2019 (left). A month later on 5 April the strong anomaly was still present beneath a dense plume of ash and steam (right). Sentinel-2 imagery shows "Geology" rendering with bands 12, 4, and 2. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 35. A dense steam plume is shown here rising from the summit area of Kadovar, posted online on 4 April 2019. View is from the N. Courtesy of Chaiyasit Saengsirirak.

Geologic Background. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. Kadovar is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. The village of Gewai is perched on the crater rim. A 365-m-high lava dome forming the high point of the andesitic volcano fills an arcuate landslide scarp that is open to the south, and submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. No certain historical eruptions are known; the latest activity was a period of heightened thermal phenomena in 1976.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); 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/); Tico Liu, Hong Kong (Facebook: https://www.facebook.com/tico.liu. https://www.facebook.com/photo.php?fbid=10155389178192793&set=pcb.10155389178372793&type=3&theater); Shari Kalt (Instagram user LuxuryTravelAdvisor: https://www.instagram.com/luxurytraveladviser/, https://www.instagram.com/p/BkhalnuHu2j/); Coral Expeditions, Australia (URL: https://www.coralexpeditions.com/, Facebook: https://www.facebook.com/coralexpeditions); Philip Stern (Facebook: https://www.facebook.com/sternph, https://www.facebook.com/sternph/posts/2167501866616908); Brad Scott, GNS Science Volcanologist at GNS Science, New Zealand (Twitter: https://twitter.com/Eruptn); Chaiyasit Saengsirirak, Bangkok, Thailand (Facebook: https://www.facebook.com/chaiyasit.saengsirirak, https://www.facebook.com/photo.php?fbid=2197513186969355).


Sarychev Peak (Russia) — June 2019 Citation iconCite this Report

Sarychev Peak

Russia

48.092°N, 153.2°E; summit elev. 1496 m

All times are local (unless otherwise noted)


Brief ash emission reported on 16 May 2019

Located on Matua Island in the central Kurile Islands of Russia, Sarychev Peak has historical observations of eruptions dating back to 1765. Thermal activity in October 2017 (BGVN 43:11) was the first sign of renewed activity since a major eruption with ash plumes and pyroclastic flows in June 2009 (BGVN 34:06). The following month (November 2017) there was fresh dark material on the NW flank that appeared to be from a flow of some kind. After that, intermittent thermal anomalies were the only activity reported until explosions with ash plumes took place that lasted for about a week in mid-September 2018 (figure 24). Additional explosions in mid-October were the last reported for 2018. A single ash explosion in May 2019 was the only reported activity from November 2018 to May 2019, the period covered in this report. Information is provided by the Sakhalin Volcanic Eruption Response Team (SVERT) and the Kamchatka Volcanic Eruptions Response Team (KVERT), members of the Far Eastern Branch, Russian Academy of Sciences (FEB RAS), and from satellite data.

Figure (see Caption) Figure 24. Multiple ash plumes were observed at Sarychev Peak during September 2018. Left: 13 September. Right: 18 September. Photos by S. A. Tatarenkov, courtesy of IMGG FEB RAS.

Satellite imagery in mid-September and early October 2018 showed gas emissions from the summit vent, and a weak thermal anomaly in October (figure 25). KVERT lowered the Aviation Color Code from Orange to Yellow on 1 November 2018, and SVERT released a VONA on 12 November 2018 lowering the Aviation Color Code from Yellow to Green after the ash emissions in October.

Figure (see Caption) Figure 25. Minor gas emissions were visible at Sarychev Peak in satellite imagery in mid-September and early October 2018; a possible weak thermal anomaly appeared in the summit vent in October. Top left: 13 September. Top right: 18 September. Bottom left: 8 October. Bottom right: 11 October. The 13 September image uses "Natural Color" rendering (bands 4, 3, 2) and the other images use "Geology" rendering (bands 12, 4, 2). Sentinel-2 satellite imagery courtesy of Sentinel Hub Playground.

Sentinel-2 satellite instruments in March, April, and May 2019 acquired images that showed dark streaks in the snow-covered peak radiating out from the summit vent in various directions. As the spring snows melted, more dark streaks appeared. It is unclear whether the streaks represent fresh ash, particulates from gas emissions in the snow, or concentrated material from earlier emissions that were exposed during the spring melting (figure 26). No further activity was reported until the Tokyo VAAC noted an eruption on 16 May 2019 that produced an ash plume which rose to 2.4 km altitude and drifted S. It was visible in satellite imagery for 3 or 4 hours before dissipating. SVERT reported the ash plume visible up to 50 km SE of the island. They also noted that weak thermal anomalies had been seen in satellite data on 10, 12, and 17 May 2019.

Figure (see Caption) Figure 26. Streaks of brown radiate outward from the summit vent at Sarychev Peak in Sentinel-2 satellite imagery taken during March-May 2019. The exact material and timing of deposition is unknown. Top left: 17 March. Top middle: 14 April. Top right: 19 April. Bottom left: 29 April, Bottom middle: 6 May. Bottom right: 26 May 2019. Sentinel-2 images with "Natural Color" rendering using bands 4,3, and 2. Courtesy of Sentinel Hub Playground.

Geologic Background. Sarychev Peak, one of the most active volcanoes of the Kuril Islands, occupies the NW end of Matua Island in the central Kuriles. The andesitic central cone was constructed within a 3-3.5-km-wide caldera, whose rim is exposed only on the SW side. A dramatic 250-m-wide, very steep-walled crater with a jagged rim caps the volcano. The substantially higher SE rim forms the 1496 m high point of the island. Fresh-looking lava flows, prior to activity in 2009, had descended in all directions, often forming capes along the coast. Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits. Eruptions have been recorded since the 1760s and include both quiet lava effusion and violent explosions. Large eruptions in 1946 and 2009 produced pyroclastic flows that reached the sea.

Information Contacts: Institute of Marine Geology and Geophysics, Far Eastern Branch of the Russian Academy of Sciences, (FEB RAS IMGG), 693 022 Russia, Yuzhno-Sakhalinsk, ul. Science 1B (URL: http://imgg.ru/ru); Sakhalin Volcanic Eruption Response Team (SVERT), Institute of Marine Geology and Geophysics, Far Eastern Branch, Russian Academy of Science, Nauki st., 1B, Yuzhno-Sakhalinsk, Russia, 693022 (URL: http://www.imgg.ru/en/, http://www.imgg.ru/ru/svert/reports); Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Nyiragongo (DR Congo) — May 2019 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Lava lake remains active through May 2019; three new vents around the secondary cone

Since at least 1971 scientists and tourists have observed a lava lake within the Nyiragongo summit crater. Lava flows have been a hazard in the past for the nearby city of Goma (15 km S). The previous report (BGVN 43:06) of activity between November 2017 and May 2018 described nearly daily record of thermal anomalies due to the active lava lake and lava fountaining, gas-and-steam plumes, and the opening of a new vent within the crater in February 2016. Monthly reports from the Observatoire Volcanologique de Goma (OVG) disseminate information regarding the volcano's activity. This report updates the activity during June 2018-May 2019.

OVG noted that the level of the lava lake changes frequently, and was lower when observed on October 2018, 12 April 2019, and 12 May 2019. According to data from the OVG, on 15 April 2019 the secondary cone that formed in February 2016 produced lava flows and ejecta. In addition, at least three other vents formed surrounding this secondary cone. During most of April 2019 the lava lake was still active; however, beginning on 12 April 2019, seismic and lava lake activity both declined.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data continues to show almost daily, strong thermal anomalies every month from June 2018 through 24 May 2019 (figure 66). Similarly, the MODVOLC algorithm reports a majority of the hotspot pixels (2,406) occurring within the lava lake at the summit crater (figure 67).

Figure (see Caption) Figure 66. Thermal anomalies at Nyiragongo for June 2018 through 24 May 2019 as recorded by the MIROVA system (Log Radiative Power) were frequent and strong. Courtesy of MIROVA.
Figure (see Caption) Figure 67. Map showing the number of MODVOLC hotspot pixels at Nyiragongo from 1 June 2018 to 31 May 2019. Nyiragongo (2,423 pixels) is at the bottom center; Nyamuragira volcano (342 pixels) is about 13 km NW. Courtesy of HIGP-MODVOLC Thermal Alerts System.

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

Information Contacts: Observatoire Volcanologique de Goma (OVG), Goma, North Kivu, DR Congo (URL: https://www.facebook.com/Observatoire-Volcanologique-de-Goma-OVG-180016145663568/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

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Bulletin of the Global Volcanism Network - Volume 28, Number 10 (October 2003)

Managing Editor: Edward Venzke

Alaid (Russia)

Volcanic tremor detected beginning on 31 October

Asosan (Japan)

Phreatic eruptions during 10-14 July cause ashfall 14 km away

Bezymianny (Russia)

Rapid decrease in activity following the 26 July eruption

Cereme (Indonesia)

Volcanic seismicity that began in March increased in October

Fuego (Guatemala)

Explosive eruptions and lava flows through October

Gamalama (Indonesia)

Small ash explosions August to early October; seismicity normal by mid-October

Ijen (Indonesia)

Shallow volcanic earthquakes and continuous tremor recorded in October

Karangetang (Indonesia)

White gas emissions and glow during October, but decreased seismicity

Krakatau (Indonesia)

Increased volcanic seismicity in August

Lewotobi (Indonesia)

Explosions and ashfall during June-July; seismicity stops in early September

Lokon-Empung (Indonesia)

Small gas plume; high but variable shallow volcanic seismicity

Masaya (Nicaragua)

Fumarole temperatures unchanged; landslides, incandescence in Santiago crater

Miyakejima (Japan)

Continued seismicity and regular gas-and-steam plumes

Nyamuragira (DR Congo)

Long-period earthquake swarms

Nyiragongo (DR Congo)

Lava lake growing through pit-wall collapses; environmental damage

Pacaya (Guatemala)

Frequent steam plumes

San Cristobal (Nicaragua)

Intermittent ash emissions between August 2002 and September 2003

Santa Maria (Guatemala)

Explosions, pyroclastic flows, and night glow in October

Semeru (Indonesia)

Frequent ash explosions continue through October

Sheveluch (Russia)

Ash eruptions, lava dome growth, steam plumes, and thermal anomalies

Soputan (Indonesia)

Ash explosion and lava flows on 31 August

Soufriere Hills (United Kingdom)

Low-level seismicity; ash venting 30 September-1 October

Unnamed (Tonga)

Pumice rafts from September-October 2001 eruption reach eastern Australia



Alaid (Russia) — October 2003 Citation iconCite this Report

Alaid

Russia

50.861°N, 155.565°E; summit elev. 2285 m

All times are local (unless otherwise noted)


Volcanic tremor detected beginning on 31 October

On 4 November 2003 the Level of Concern Color Code was raised to Yellow due to volcanic tremor that began on 31 October. Weak seismicity continued through 7 November. Volcanic tremor during this time was 0.5-3.3 x 10-6 mps, and a large number of weak local events were registered. On satellite images the volcano was obscured by clouds all week.

The Kamchatkan Volcanic Eruption Response Team notes that Alaid is characterized by two types of eruptions: central crater eruptions and lateral eruptions. Central crater eruptions are stronger and more dangerous then the lateral ones. The strongest central crater eruptions of Alaid were in February 1793, June 1854, July 1860, 1894, and April 1981. The April 1981 eruption sent an ash plume to 8,000-9,000 m altitude that extended for more than 1,500 km (SEAN 06:04 and 06:05). Two eruptions in 1933-1934 and 1972 (CSLP Cards nos. 1405, 1406, 1410, and 1518) ejected ash columns 3 km high.

Satellite imagery indicated possible activity in March 1982 (SEAN 07:03 and 12:04), 3 December 1996 (BGVN 21:12), and 23 August 1997 (BGVN 22:09).

Geologic Background. The highest and northernmost volcano of the Kuril Islands, 2285-m-high Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached widely to the south. Alaid is the northernmost of a chain of volcanoes constructed west of the main Kuril archipelago. Numerous pyroclastic cones dot the lower flanks of this basaltic to basaltic-andesite volcano, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest in the Kuril Islands during historical time.

Information Contacts: Anastasia Tranbenkova, 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.


Asosan (Japan) — October 2003 Citation iconCite this Report

Asosan

Japan

32.884°N, 131.104°E; summit elev. 1592 m

All times are local (unless otherwise noted)


Phreatic eruptions during 10-14 July cause ashfall 14 km away

Recent noteworthy activity at Aso consisted of elevated tremor in August 2002 and a phreatic eruption in July 2003. Seismicity recorded by the Japan Meteorological Agency (JMA) between January 2000 and April 2003 (table 8) was generally constant, with continuous volcanic tremor every month in addition to isolated tremor events. The number of tremor events was high through October 2000, during April 2002, and from August 2002 through March 2003. Also during this extended period, white plumes were observed approximately once a month, with two or more plumes occurring in July, October, and December 2002, and February and March 2003. These plumes were usually less than 500 m high.

Table 8. Seismicity at Aso between January 2000 and April 2003. The seismograph station is located ~13 km W of the summit. Courtesy of JMA.

Month Number of volcanic earthquakes Number of volcanic tremors
Jan 2000 19 1,466
Feb 2000 16 926
Mar 2000 73 1,232
Apr 2000 -- --
May 2000 39 537
Jun 2000 30 802
Jul 2000 29 1,234
Aug 2000 21 2,104
Sep 2000 36 1,445
Oct 2000 38 1,448
Nov 2000 43 202
Dec 2000 33 129
Jan 2001 51 60
Feb 2001 161 739
Mar 2001 76 537
Apr 2001 40 81
May 2001 40 85
Jun 2001 99 188
Jul 2001 84 282
Aug 2001 60 471
Sep 2001 40 86
Oct 2001 91 32
Nov 2001 52 17
Dec 2001 45 5
Jan 2002 38 5
Feb 2002 59 20
Mar 2002 20 20
Apr 2002 114 1,138
May 2002 91 14
Jun 2002 191 36
Jul 2002 238 37
Aug 2002 153 4,413
Sep 2002 144 1,438
Oct 2002 103 1,440
Nov 2002 652 3,391
Dec 2002 154 8,496
Jan 2003 122 6,981
Feb 2003 178 4,183
Mar 2003 92 1,965
Apr 2003 70 474

Activity during August 2002. For the first time since 1992, isolated volcanic tremor events occurred at a rate of more than 300 events/day in Naka-dake Crater 1. These events were recorded between 5 and 21 August and totalled nearly 4,000 (table 9), with the highest number, 340 events, on 15 August. During this period, the water temperature of the pool in the crater remained between 57 and 60°C. On 14 August, infrared cameras measured the maximum temperature of the southern crater wall at 307°C; this increased to 314°C the following week.

Table 9. Daily number of isolated volcanic tremor events at Aso, August 2002. Courtesy of Japan Meteorological Agency.

Date Isolated tremor events
05 Aug 2002 129
06 Aug 2002 238
07 Aug 2002 241
08 Aug 2002 137
09 Aug 2002 244
10 Aug 2002 304
11 Aug 2002 315
12 Aug 2002 335
13 Aug 2002 299
14 Aug 2002 336
15 Aug 2002 340
16 Aug 2002 287
17 Aug 2002 257
18 Aug 2002 208
19 Aug 2002 162
20 Aug 2002 104
21 Aug 2002 37 as of 1100

Activity during July 2003. JMA reported on 11 July 2003 that tephra had fallen at Aso that morning. According to the report, a tremor event with an intermediate amplitude was recorded at 1718 on 10 July. Staff from the Aso Weather Station confirmed that small amounts of tephra had been newly deposited at Hakoishi-Toge (Hakoishi Pass), ~ 6 km ENE of the Nakadake crater. Kazunori Watanabe (Kumamoto University) and other geologists surveyed the deposit on 11 July and estimated the total mass of ejected material at roughly 130 tons. Ash was deposited as far as 14 km from the crater. A small amount of fresh vesicular glass particles were noted in the ejecta under the microscope. According to Yasuaki Sudo (Aso Volcanological Laboratory, Kyoto University), who inspected the crater area, the event was a small phreatic eruption of mud. The deposit consisted of wet ash aggregates and was ~ 1 mm thick, even at the crater rim. A spray of mud was blown off the crater rim by strong winds to 10 km from the crater.

Seismic signals implied a series of small phreatic eruptions between 12 and 14 July. Then on 27 July continuous volcanic tremor started around 1400. Observations that day noted that the water in Crater 1 was gray and boiling in the center; the temperature of the water was 76°C.

Geologic Background. The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 CE. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

Information Contacts: Volcanological Division, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan (URL: http://www.jma.go.jp/); Volcano Research Center, Earthquake Research Institute (ERI), University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html); Kazunori Watanabe, Kumamoto University, 40-1, Kurokami 2-chome, Kumamoto 860-8555, Japan; Hitoshi Yamasato and N. Uchida, Japan Meteorological Agency (JMA), Fukuoka District Meteorological Observatory, 1-2-36 Oohori, Chuo-ku, Fukuoka 810-0052, Japan; Tomoki Tsutsui and Yasuaki Sudo, Aso Volcanological Laboratory, Kyoto University, Choyo, Aso, Kumamoto, 869-1404, Japan.


Bezymianny (Russia) — October 2003 Citation iconCite this Report

Bezymianny

Russia

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

All times are local (unless otherwise noted)


Rapid decrease in activity following the 26 July eruption

A large explosive eruption of Bezymianny on 26 July 2003 sent an ash plume 8-11 km high and 86 km long (BGVN 28:07). A later KVERT report noted that the active eruption phase lasted ~ 4 hours after beginning on 2057. Longer plumes on 27 July extended to 192 km, 217 km and ~ 250-300 km W of the vent. Probable pyroclastic deposits were identified on the SE flank.

No seismicity was registered during 27 July-3 August. The Color Code was lowered from Red to Orange on 28 July, and reduced to Yellow on 1 August. A 1-2-pixel thermal anomaly was detected on 1 August, and observers saw gas-and-steam plumes extending ~ 15 km NW on 2 August. On 8 August the hazard status was returned to Green. Clouds frequently obscured the volcano, but another gas-and-steam plume extended SE on 19 August when a 2-pixel thermal anomaly was also noted on satellite imagery. No further seismicity was recorded through 22 August, although large volcanic tremor at nearby Kliuchevskoi volcano would have masked smaller events.

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

Information Contacts: Olga 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.


Cereme (Indonesia) — October 2003 Citation iconCite this Report

Cereme

Indonesia

6.892°S, 108.4°E; summit elev. 3078 m

All times are local (unless otherwise noted)


Volcanic seismicity that began in March increased in October

Data from the Volcanological Survey of Indonesia (VSI) indicated a tectonic and volcanic earthquake at Cereme on 25 March, followed by one more volcanic event on 28 March. Activity picked up on 2 April with three more volcanic events, with 17 events through 14 April. Daily highs of 8 and 11 events were recorded on 24 April and 3 May, respectively (2-4 May had 22). Seismicity remained generally low (0-3/day) until 29 events occurred on 7 October.

After a felt earthquake on 7 October, volcanic earthquakes increased. This increased seismicity was accompanied by elevated visually observed activity, resulting in the hazard status being upgraded to Alert Level 2 on 13 October. Seismic activity during 6-12 October consisted of 46 deep volcanic earthquakes and 15 shallow volcanic earthquakes; 36 deep volcanic events occurred the following week of 13-19 October. There was a felt earthquake on 19 October that lasted for 95.5 seconds (35 mm amplitude). Seismic activity declined during 20-26 October, when only seven deep volcanic earthquakes were recorded. The temperature measured at the Sangkan Hurip hotspring in late October was 48°C, unchanged from previous measurements.

Geologic Background. The symmetrical stratovolcano Cereme, also known as Ciremai, is located closer to the northern coast than other central Java volcanoes. A steep-sided double crater elongated in an E-W direction caps 3078-m-high Gunung Cereme, which was constructed on the northern rim of the 4.5 x 5 km Geger Halang caldera. A large landslide deposit to the north may be associated with the origin of the caldera, although collapse may rather be due to a voluminous explosive eruption (Newhall and Dzurisin, 1988). Eruptions, relatively infrequent in historical time, have included explosive activity and lahars, primarily from the summit crater.

Information Contacts: Dali Ahmad, Hetty Triastuty, Nia Haerani, and Suswati, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).


Fuego (Guatemala) — October 2003 Citation iconCite this Report

Fuego

Guatemala

14.473°N, 90.88°W; summit elev. 3763 m

All times are local (unless otherwise noted)


Explosive eruptions and lava flows through October

Explosive and effusive activity, last reported through January 2003 (BGVN 28:01) has continued through October 2003. Plumes identified on satellite imagery between April and September 2003 were described in aviation advisories issued by the Washington Volcanic Ash Advisory Center (VAAC). Regular reports of daily activity provided by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH) on their website have been summarized for many days in the second half of October.

Activity during April-September 2003. The Washington VAAC reported that on 28 April 2003 Fuego generated intermittent ash eruptions. One cloud was observed at ~ 7 km altitude moving SW at 19-29 km/hour. On 2 May the VAAC reported possible ash around the summit, but as of 1515, none was visible. INSIVUMEH indicated that although Fuego was active with explosions, most ash was confined to near the summit.

On 29 June INSIVUMEH reported a moderate eruption during 1745-2200 that consisted mainly of lava effusion. Lava flows were observed on the E flank, in the Lajas, Jute, and Barranca Honda ravines. Avalanches generated sounds similar to a locomotive, with strong rumblings and acoustic waves. Fuego's Observatory 2, on the SW flank, reported 2 cm of ashfall. Ashfall also occurred in San Pedro Yepocapa, Patulul Suchitepequez, Cocales, and villages W and SW of the volcano. At about 2335 there was a reduction in seismic activity at the Fuego 3 station.

INSIVUMEH reported on 1 July that explosive activity continued with weak to sometimes strong explosions ejecting grayish ash up to 900 m above the crater, with occasional degassing sounds and rumblings. Pyroclastic-flow material moved into the W-flank Seca and Santa Teresa valleys, 1.5 km from the village of Sangre de Cristo. A pyroclastic flow was reported by the Washington VAAC at 1130 on 9 July. INSIVUMEH reported strong explosions with ash to 2 km above the summit, a plume extending 5-7 km W, and ashfall to the W and SW. GOES-12 imagery showed a 3.7-km-wide plume extending ~ 11 km W.

The Washington VAAC reported on 7 August that a brief puff of ash was ejected at about 1600; the small plume moved to the NW and dissipated by 1745. On 28 September the Washington VAAC, based on visible and multi-spectral IR techniques, reported an ash eruption at about 1100. This plume, which was ~ 5 x 5 km, moved S toward the coast and was no longer discernable on imagery by 1400. A second ash emission between 1415 and 1432, with an approximate altitude of 6 km, was partially obscured by clouds.

Activity during 15-30 October 2003. On 15 October INSIVUMEH reported the continuation of eruptive activity, with degassing and small rumbling sounds. Incandescence was seen above the crater at night. The ejected ash was dispersed around the volcanic edifice. A small eruption that began at 0007 on 17 October ended at 0040 after five moderate explosive pulses, each 2-3 minutes in duration, generated thick columns of grayish ash ~ 1,500 m high. Before and after this eruptive event moderate and strong explosions caused rumbling and shock waves felt at the OVFGO and FG2 observatories. Small incandescent avalanches moved towards the Santa Teresa valley.

Harmonic tremor was registered at the FG3 station at 1630 on 20 October. On 21 October, INSIVUMEH reported explosions after 0350. The majority were strong, expelling abundant incandescent material. Ash columns caused small and moderate avalanches, mainly in the Santa Teresa and Trinidad valleys, and occasionally in the Taniluyá. Shock waves were felt by communities around the volcano. Slight ashfall occurred in the Morelia and Santa Lucia villages located 7 and 10 km, respectively, SSW of the active crater.

On 23 October, INSIVUMEH reported moderate, weak and occasionally strong explosions producing grayish and blackish plumes up to one km high. Moderate and strong explosions generated rumbling and lava flows that traveled toward the Santa Teresa and Trinidad valleys. Ashfall occurred in the upper portion of the Fuego-Acatenango complex. At 0945 a strong explosion, lasting 1.5 minutes, produced a thick ash cloud that reached a height of ~ 1 km and dispersed to the SW. Two short pulses lasting 45-60 minutes between 1200-1300 and 1800-1900 on 23 October generated a series of 7-9 moderate explosions that produced a grayish column to ~ 1 km over the central crater.

A strong explosion at 0910 on 27 October was preceded by five moderate explosions at intervals of 3-7 minutes that produced gas clouds and ash 700 m high. The first event produced a heavy ash column of a height of ~ 1 km which dispersed to the SW. An explosion at 0625 caused a pyroclastic flow toward the Trinidad and Santa Teresa valleys, and produced light ashfall in the village of Sangre de Cristo. On 29 October INSIVUMEH reported predominantly weak and moderate explosions 1-3.5 minutes long with gas-and-ash columns up to 1 km high. The last of these produced ashfall, shock waves felt at OVFGO, and avalanches of incandescent material toward the Santa Teresa and Trinidad valleys.

On 30 October an effusive eruption during 2300-0600 produced incandescent lava fountains 75-100 m high with pulses of 5-6 minutes, changing to fountains ~ 50 m high and 15-20 minutes long. A short lava flow descended SW from the crater rim, reaching ~ 250 m in length and splitting into three short branches. Short avalanches and pyroclastic flows descended to the top of the Santa Teresa valley. The eruption produced moderate to weak sounds lasting ~ 2 minutes. At dawn, a thick fumarolic plume was observed blowing NW. There was no ash emission during this activity, but at 0625 hours a small explosion sent a column of gas and ash ~ 400 m high. The seismic station at FG3 registered harmonic tremor (2-4 mm amplitude).

Geologic Background. Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3763-m-high Fuego and its twin volcano to the north, Acatenango. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at Acatenango. In contrast to the mostly andesitic Acatenango, eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH), Ministero de Communicaciones, Transporto, Obras Públicas y Vivienda, 7a. Av. 14-57, zona 13, Guatemala City 01013, Guatemala (URL: http://www.insivumeh.gob.gt/).


Gamalama (Indonesia) — October 2003 Citation iconCite this Report

Gamalama

Indonesia

0.8°N, 127.33°E; summit elev. 1715 m

All times are local (unless otherwise noted)


Small ash explosions August to early October; seismicity normal by mid-October

A series of explosive eruptions on 31 July 2003 produced ashfall and pyroclastic flows (BGVN 28:07). Several small ash explosions occurred throughout August and September (BGVN 28:09). Activity was similar during 29 September-5 October 2003, with white gas emissions rising 25-100 m and some small ash explosions. Volcanic seismicity consisted of one deep earthquake, two shallow earthquakes, and 24 emission events. Activity remained low the following week, 6-12 October, with gas emissions rising 25-50 m. The number of daily seismic events this week had returned to normal levels, so the hazard status was downgraded to Alert Level 1 (on a scale of 1-4) on 13 October.

Geologic Background. Gamalama is a near-conical stratovolcano that comprises the entire island of Ternate off the western coast of Halmahera, and is one of Indonesia's most active volcanoes. The island was a major regional center in the Portuguese and Dutch spice trade for several centuries, which contributed to the thorough documentation of Gamalama's historical activity. Three cones, progressively younger to the north, form the summit. Several maars and vents define a rift zone, parallel to the Halmahera island arc, that cuts the volcano. Eruptions, recorded frequently since the 16th century, typically originated from the summit craters, although flank eruptions have occurred in 1763, 1770, 1775, and 1962-63.

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


Ijen (Indonesia) — October 2003 Citation iconCite this Report

Ijen

Indonesia

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

All times are local (unless otherwise noted)


Shallow volcanic earthquakes and continuous tremor recorded in October

The hazard status of Ijen was upgraded to Alert Level 2 (on a scale of 1-4) on 8 October. Seismicity the week of 6-12 October comprised four deep volcanic earthquakes, 21 shallow volcanic earthquakes, one emission event, and continuous tremor (0.5-2 mm amplitude). Only 16 shallow volcanic earthquakes were recorded the following week, along with continuous tremor (0.5-2 mm amplitude). Continuous tremor (0.5-4 mm amplitude) was recorded during 20-26 October, a week when the number of shallow volcanic events increased to 30. Gas plumes emitted from the crater rose up to 150 m high during October.

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

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


Karangetang (Indonesia) — October 2003 Citation iconCite this Report

Karangetang

Indonesia

2.781°N, 125.407°E; summit elev. 1797 m

All times are local (unless otherwise noted)


White gas emissions and glow during October, but decreased seismicity

Explosive activity has been common at Karangetang in recent years, producing ashfall and lava avalanches as recently as May and June 2003 (BGVN 28:05 and 28:07). However, Karangetang was not included in reports by the Volcanological Survey of Indonesia (VSI) between 16 June and 28 September 2003. A report for the week of 29 September-5 October indicated that there had been a decrease in multiphase and emissions earthquakes compared to the previous week (table 9). At that time white gas emissions were observed rising 400 m above the S crater and 50 m above the N crater. Red glow was seen at night over the S crater that week. No lava avalanches occurred. Similar observations were reported through 19 October. Although surface observations of activity were consistent, seismic data showed that shallow volcanic earthquakes increased and emission events decreased during 6-19 October. The hazard status remained at Alert Level 2 (on a scale of 1-4) through at least 19 October.

Table 9. Seismicity at Karangetang during 2 June-19 October 2003. No data was available between 16 June and 28 September. Courtesy of VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Multiphase Emission Tectonic
02 Jun-08 Jun 2003 11 348 233 46 26
09 Jun-15 Jun 2003 32 438 228 21 20
29 Sep-05 Oct 2003 15 84 50 121 38
06 Oct-12 Oct 2003 19 103 33 74 32
13 Oct-19 Oct 2003 18 135 54 72 33

Geologic Background. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi island. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

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


Krakatau (Indonesia) — October 2003 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 813 m

All times are local (unless otherwise noted)


Increased volcanic seismicity in August

A report of activity at Krakatau for the period 18-24 August was provided by the Volcanological Survey of Indonesia. There was increase in volcanic earthquakes during this time, while tectonic earthquakes decreased. No visual observations were made due to foggy weather. Seismicity consisted of 12 deep volcanic earthquakes, 56 shallow volcanic earthquakes, and three tectonic events. The hazard status was at Alert Level 2 (on a scale of 1-4).

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: Dali Ahmad, Hetty Triastuty, and Nia Haerani, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).


Lewotobi (Indonesia) — October 2003 Citation iconCite this Report

Lewotobi

Indonesia

8.542°S, 122.775°E; summit elev. 1703 m

All times are local (unless otherwise noted)


Explosions and ashfall during June-July; seismicity stops in early September

Explosive ash eruptions from the summit crater of Lewotobi sent dark gray plumes 300-350 m high between 2 June and 13 July. Detonation sounds accompanied explosions on 3, 5, and 6 June. Ash fell in the villages of Bawalatang, Duang, and Boru in early June, and was reported at the volcano observatory post in early July. Ash explosions continued during 14-20 July with plumes rising 150 m above the summit. Poor weather conditions prevented observations in late July, although seismic records indicated continued activity; no reports were available for August. In early September an ash plume was reported to rise 25 m above the crater.

Seismicity during June and July was dominated by emissions events, but included tremor, explosion, and shallow volcanic earthquakes (table 2). Early September seismicity consisted of a high number of shallow volcanic events and some deep volcanic earthquakes, but all seismicity ceased after 3 September. Only four tectonic earthquakes were detected after this date, during 6-19 October. The 29 September-5 October report noted an ash plume rising to 25 m above the crater, but over the next two weeks the 25-m-high plume was described as gas emissions. The hazard status was downgraded to Alert Level 1 (on a scale of 1-4) the week of 13-19 October.

Table 2. Seismicity at Lewotobi, 2 June-19 October 2003. Note that no seismicity was recorded after 3 September 2003. Courtesy of VSI.

Date Deep Volcanic Shallow Volcanic Explosion Emission Tremor Tectonic
02 Jun-08 Jun 2003 0 13 7 29 20 12
09 Jun-15 Jun 2003 0 24 -- 40 33 9
30 Jun-06 Jul 2003 0 8 14 26 11 3
07 Jul-13 Jul 2003 0 16 10 52 4 1
14 Jul-20 Jul 2003 4 17 19 24 10 4
21 Jul-27 Jul 2003 1 10 5 25 5 4
28 Jul-03 Aug 2003 0 9 8 20 6 3
01 Sep-03 Sep 2003* 27 257 0 0 0 5

Geologic Background. The Lewotobi "husband and wife" twin volcano (also known as Lewetobi) in eastern Flores Island is composed of the Lewotobi Lakilaki and Lewotobi Perempuan stratovolcanoes. Their summits are less than 2 km apart along a NW-SE line. The conical Lakilaki has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has erupted only twice in historical time. Small lava domes have grown during the 20th century in both of the crescentic summit craters, which are open to the north. A prominent flank cone, Iliwokar, occurs on the E flank of Perampuan.

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


Lokon-Empung (Indonesia) — October 2003 Citation iconCite this Report

Lokon-Empung

Indonesia

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

All times are local (unless otherwise noted)


Small gas plume; high but variable shallow volcanic seismicity

The hazard status at Lokon-Empung throughout the report period of 2 June-19 October was at Alert Level 2 (on a scale of 1-4). Between 2 June and 5 October a white gas plume consistently rose 25-50 m above Tompaluan crater. The gas plume rose slightly higher, to 75 m, during the following two weeks. Seismicity remained above normal background levels during this time, with some variation (table 7). Shallow volcanic earthquakes increased in late July, but by September the weekly count was lower than in early July, eventually reaching a low the week of 15-21 September when no such events were detected. Seismicity quickly returned to high values of 138-209 shallow events per week in October.

Table 7. Seismicity at Lokon-Empung, 2 June-19 October 2003. Data was not available for 16-29 June and 04-31 August. Courtesy of VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Tectonic
02 Jun-08 Jun 2003 13 45 20
09 Jun-15 Jun 2003 25 88 27
30 Jun-06 Jul 2003 18 81 19
07 Jul-13 Jul 2003 17 48 15
14 Jul-20 Jul 2003 9 91 19
21 Jul-27 Jul 2003 25 232 21
28 Jul-03 Aug 2003 16 157 10
01 Sep-07 Sep 2003 11 44 11
08 Sep-14 Sep 2003 7 36 20
15 Sep-21 Sep 2003 12 0 22
22 Sep-28 Sep 2003 34 22 20
29 Sep-05 Oct 2003 33 209 24
06 Oct-12 Oct 2003 5 159 14
13 Oct-19 Oct 2003 24 138 14

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


Masaya (Nicaragua) — October 2003 Citation iconCite this Report

Masaya

Nicaragua

11.984°N, 86.161°W; summit elev. 635 m

All times are local (unless otherwise noted)


Fumarole temperatures unchanged; landslides, incandescence in Santiago crater

This report summarizes the activity at Masaya during June-September 2003. Activity was generally constant, with fumarole temperature measurements similar to those from previous months (BGVN 28:08). In June, July, and August, during visits made every two weeks, Jaime Cárdenas of Masaya Volcano National Park measured the fumarole temperatures at the Comalito and San Fernando craters (table 4). No changes were observed from previous months. During these months, seismic tremor remained constant with 20 units RSAM. No earthquakes were registered, but on both 21 June and 21 July landslides were reported in the Santiago crater. In September, temperatures obtained from the Santiago crater with a Pyrometer were 187°C and 123°C. It was noted during this visit that the lava sounded like ocean waves, and incandescence was observed at night. Temperatures at El Comalito remained moderate.

Table 4. Temperatures recorded at the El Comalito (EC) and San Fernando (SF) fumaroles of Masaya, 10 June-22 September 2003. All temperatures are in degrees Celsius. Courtesy INETER.

Date EC 1 EC 2 EC 3 EC 4 EC 5 EC 6 SF 1 SF 2 SF 3 SF 4
10 Jun 2003 65.4 74.5 76.8 72.5 73.4 60.2 59.2 54.8 57.2 55.8
28 Jun 2003 66.4 75.4 78.4 73.6 73.8 60.4 60.2 55.6 58.8 56.7
12 Jul 2003 55 76 78.2 74 73.6 60 60 60.2 59.5 57
26 Jul 2003 66.8 78.4 79.4 75.6 74.2 61 61.2 61.4 60.2 58.2
15 Aug 2003 66.6 78.2 79.5 76 74.5 61.5 59.7 59.7 57.2 56.2
29 Aug 2003 67.8 75.6 76.6 74.8 76.4 64.2 59.3 57.4 56.9 57
22 Sep 2003 68.6 72.3 68.3 65.2 -- -- -- -- -- --

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is 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 twin volcanoes of Nindirí and Masaya, 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 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. 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 cause health hazards and crop damage.

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


Miyakejima (Japan) — October 2003 Citation iconCite this Report

Miyakejima

Japan

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

All times are local (unless otherwise noted)


Continued seismicity and regular gas-and-steam plumes

Volcanic activity at Miyake-jima since the eruption during the summer of 2000 (BGVN 25:07) has continued at lower levels through August 2003. The flux of SO2 gas remained high (~ 4, 000-9, 000 tons/day), and has been nearly constant since October 2002 (figure 20). A compilation of seismic data and plume observations through April 2003 (table 3) documents this continuing activity. Plume heights following the June-September 2000 activity have not been greater than 2.2 km above the summit (table 3), and their color has been described as white or grayish white.

Figure (see Caption) Figure 20. SO2 flux at Miyake-jima during August 2000-August 2003. Triangles along the timeline indicate explosions. Courtesy of the Geological Survey of Japan and the Japan Meteorological Agency.

Table 3. Summary of seismicity and plume observations at Miyake-jima, January 2000-April 2003. All reported plumes originated from the summit crater, and were described as either white (W), light white (LW), grayish white (GW), or gray (G). No months during this time had more than six plumes observed on any single day. Data courtesy of JMA.

Month Volcanic earthquakes Max. Plume Height (km) (date) Plume Color (date)
Jan 2000 2 -- --
Feb 2000 4 -- --
Mar 2000 1 -- --
Apr 2000 No JMA report received this month
May 2000 3 -- --
Jun 2000 > 13,840 -- --
Jul 2000 > 24,494 1.5 (8, 14) W (8) colored (14, 15)
Aug 2000 > 10,175 14 (18) Mix of white and colored almost daily all after 10th
Sep 2000 146 3.5 (26) frequently above 1 W (almost daily), C (3, 24, 27)
Oct 2000 16 2.7 (10) W
Nov 2000 5 2.5 (26) W
Dec 2000 6 2.0 (22, 27) W
Jan 2001 214 1.8 (22, 31) W, GW (11)
Feb 2001 260 2.0 (17) W
Mar 2001 299 2.0 (2, 16, 24) W, GW (19)
Apr 2001 191 2.0 (4) W
May 2001 707 2.2 (6) W, G (27)
Jun 2001 192 2.2 (10) W, G (3, 10)
Jul 2001 249 1.6 (16, 21) W, G (10)
Aug 2001 306 2.0 (24, 25, 27, 28) W
Sep 2001 234 3.0 (16) W
Oct 2001 116 1.5 (16, 21, 22, 24, 29, 31) W, GW
Nov 2001 124 2.0 (20) W, GW (1)
Dec 2001 123 1.7 (29) W
Jan 2002 41 2.0 (6) W, GW
Feb 2002 88 1.7 (14) W, GW
Mar 2002 71 1.2 (16, 28) W, GW (31)
Apr 2002 104 1.0 (10) W, GW (2, 3)
May 2002 265 1.5 (29) W
Jun 2002 176 0.8 (9) W, GW (15)
Jul 2002 78 0.8 (27) W
Aug 2002 45 1.0 (3) W
Sep 2002 57 1.5 (4) W
Oct 2002 47 1.0 (6, 30) W, GW (8)
Nov 2002 55 1.0 (6, 29) W
Dec 2002 66 0.8 (28) W
Jan 2003 202 1.0 (25) W
Feb 2003 313 0.8 (13) W
Mar 2003 212 1.2 (28) W
Apr 2003 450 1.0 (28) W

The number of monthly earthquakes was very low (1-4/month) until late June through early September 2000. Except for 5 May 2001 when 447 volcanic earthquakes occurred, daily totals have been less than 50. Monthly earthquake totals since August 2000 have been less than 300, except for May 2001 (707) and April 2003 (450). Volcanic tremor also began in July 2000 and became continuous in September 2000. Tremor through April 2003 totaled less than 500 events per month, except for May 2001, when 1, 362 events were recorded (444 on the 22nd). The unusually high seismicity noted in May 2001 corresponded to a period of continuous steam plumes with abundant SO2 content (BGVN 27:03), after which SO2 flux declined (figure 2).

Seismicity at Miyake-jima is recorded by three seismographs maintained by the Japan Meterological Agency (JMA): station "A" is ~ 1.9 km NNE of the summit at 530 m elevation, station "AKOC" is ~ 4.6 km W at 42 m elevation, and station "RST" is ~ 1.9 km SSE at 463 m elevation.

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/); Akihiko Tomiya, Geological Survey of Japan, AIST, 1-1 Higashi, 1-Chome Tsukuba, Ibaraki 305-8567, Japan (URL: https://staff.aist.go.jp/a.tomiya/tomiyae.html).


Nyamuragira (DR Congo) — October 2003 Citation iconCite this Report

Nyamuragira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


Long-period earthquake swarms

During the 3-month period from 2 August to 8 November 2003, seismicity in the Nyamuragira area was dominated by long-period (LP) events localized along a main NNE-SSW fracture between Nyamuragira and Nyiragongo volcanoes. Intermittent swarms of LP events (60-80 events each time) occurred on Nyamuragira two to three times per week. A larger swarm was observed on 23 July (100 LP events). This activity remained fairly stable for the whole period. Earthquakes related to fracturing continued, mainly S of Nyiragongo (N of Lake Kivu ) and NE of Nyamuragira. No noticeable deformation change has been recorded along the fracture system.

Geologic Background. Africa's most active volcano, Nyamuragira, is a massive high-potassium basaltic shield about 25 km N of Lake Kivu. Also known as Nyamulagira, it has generated extensive lava flows that cover 1500 km2 of the western branch of the East African Rift. The broad low-angle shield volcano contrasts dramatically with the adjacent steep-sided Nyiragongo to the SW. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Historical eruptions have occurred within the summit caldera, as well as from the numerous fissures and cinder cones on the flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Historical lava flows extend down the flanks more than 30 km from the summit, reaching as far as Lake Kivu.

Information Contacts: Observatoire Volcanologique de Goma, Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo.


Nyiragongo (DR Congo) — October 2003 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Lava lake growing through pit-wall collapses; environmental damage

During the 3-month period from 2 August to 8 November 2003, volcanic activity was concentrated inside the Nyiragongo crater. An almost permanently boiling lava lake occupies the crater at the depth of 700 m. Although the level of the lake inside the crater seems to remain constant, its size is slowly growing due to collapses of the pit walls. Degassing has been significant, marked by a large gas plume above the crater which is generally blown W by the prevailing winds and extends several tens of kilometers. The impact of this activity on the environment is growing; inside the National Park, a 50 km2 area of forest was totally destroyed by volcanic gases and acid rains, and a zone with 50% destruction covers more than 700 km2, affecting crops such as potatoes, corn, beans, and bananas. In the same areas significant fluoride pollution has been detected, and tanks collecting rain water are showing fluoride concentrations up to 23 mg/l (WHO tolerance = 1.5 mg/l).

In the Nyiragongo area, long-period events are commonly detected but at reduced number and are mainly located NW and SW of the volcano. Seismicity is largely dominated by permanent tremor generated by the activity of the lava lake. Earthquakes related to fracturing continue, mainly S of Nyiragongo and NE of Nyamuragira (~ 15 km NW of Nyiragongo). No noticeable deformation change has been recorded along the fracture system between the two volcanoes.

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

Information Contacts: Observatoire Volcanologique de Goma, Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo.


Pacaya (Guatemala) — October 2003 Citation iconCite this Report

Pacaya

Guatemala

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

All times are local (unless otherwise noted)


Frequent steam plumes

Although incandescence from the long-term lava lake ended after June 2001, SO2 emission rates remained high when measured in January 2002 (BGVN 27:07). On 30 May 2002, the Washington Volcanic Ash Advisory Center (VAAC) received a report from Guatemala City indicating that Pacaya was active. Satellite imagery showed possible low-level ash near the summit. A very thin SW-drifting plume was again visible in satellite imagery on 17 June 2002, but the composition of the plume was unknown. A faint hotspot at the summit was also visible on infrared imagery. Visual observation on the afternoon 24 August 2002 from the SW showed copious white steam emissions from the summit crater (figure 34).

Figure (see Caption) Figure 34. View of Pacaya looking NNE on 24 August 2002. Only white steam emissions were visible. Courtesy of Jacquelyn Gluck.

The Washington VAAC reported that on 5 July 2003 at 0715, a very thin ash and/or gas plume was visible on satellite imagery at an altitude of ~ 3 km extending ~ 7.5 km SW. By 1430 the plume was no longer visible, possibly obscured by thunderstorm clouds in the area. INSIVUMEH reported that only steam was emitted. Visible imagery on 9 August 2003 showed a narrow plume below 3 km altitude extending SW from the volcano, but its composition was unknown.

Reports provided by INSIVUMEH during the latter half of October 2003 indicated that during 15-21 October constant steam and abundant emissions of water and gas were being blown to the NNW and W of the volcano. These emissions continued through the end of the month. On 23 October, during periods of visibility, observers saw a line of off-white smoke across the S flank, which was dispersed in the area of the lava field near the Chupadero and the Caracol rivers. The next day observers saw a heavy column of off-white smoke rising ~ 600 m over the MacKenney crater. The plume continued through 27 October, but only to a height of ~ 400 m. The heavy gaseous cloud continued at the same height through 30 October.

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), 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); 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/); Jacquelyn Gluck, Global Volcanism Program, Smithsonian Institiution, Washington DC, 20560, USA.


San Cristobal (Nicaragua) — October 2003 Citation iconCite this Report

San Cristobal

Nicaragua

12.702°N, 87.004°W; summit elev. 1745 m

All times are local (unless otherwise noted)


Intermittent ash emissions between August 2002 and September 2003

This report summarizes the recorded activity at San Cristóbal during August 2002-September 2003. Reports from Instituto Nicaragüense de Estudios Territoriales (INETER) include observations from frequent visits to the volcano.

August-December 2002. During August-December 2002, abundant gas emanations were accompanied by small gas explosions. Incandescence was frequently observed. Seismicity was relatively high, but fluctuated from month to month (table 2). On 12 August, ash emissions with columns up to 800 m high were observed. More ash explosions were reported on 17 and 21 August. Gas emissions and small ash explosions continued in September, and incandescence was observed during 1-7 September. A strong explosion was reported on 6 October, and a dark gas column was observed. Throughout the month gas emissions were abundant, occasionally with columns to 600 m high. Temperatures at the South Point and El Zopilote fumaroles increased in October from the previous month. Gas emissions and ash explosions continued in November and December, with increased activity on 22 November and 16 December. Trees and fruit plants were affected by the gases in the community of Las Banderas. At the end of December, a volcano observer discovered that the path to the volcano was blocked by a deposit of sand-sized material.

Table 2. Number of earthquakes at San Cristóbal between August 2002 and June 2003. No data was available during November 2002 due to technical problems. Courtesy of INETER.

Month Number of earthquakes
Aug 2002 2,183
Sep 2002 2,792
Oct 2002 1,017
Nov 2002 --
Dec 2002 200-250 / day
Jan 2003 5,671
Feb 2003 2,595
Mar 2003 5,329
Apr 2003 1,713
May 2003 5,491
Jun 2003 4,855

January-March 2003. Activity decreased in the first few months of 2003. No changes were observed in the crater in January, and temperatures increased only at two fumaroles; those temperatures were low again in February. On 19 February the observer heard loud sustained noises and noted that the crater walls were colored green and yellow, indicating the presence of sulfur.

April-September 2003. Between April and September, fumarole temperatures were measured on each of the monthly visits to San Cristóbal, and showed very little change. The highest temperatures were generally found at South Point and were between 91 and 95°C. At El Munecho temperatures varied between 81 and 91°C, and at El Conejo between 77 and 86°C. Temperatures remained moderate at the other fumaroles.

Gas emissions were noted in particular between 20 and 23 April, days on which there were small increases in tremor; on 10 May gas emissions were strong enough to impede a visit. Activity increased in June, with abundant ash and gas emissions noted on 17 and 21 June. On 21 June incandescence was noted, and strong rumbling was heard in the evening. On 13 July gas emissions were dense, followed during 14-23 July by a dark column. Seismicity dropped from more than 350 events per day to 69 events on 3 July. By 9 July, only eight events per day were recorded; tremor remained constant at 35 RSAM units.

Gas emissions remained constant through August and September, with reports of gas explosions during a visit on 10 August and abundant gases during the 17 September visit. The strong noises and sounds of gas pressure being released decreased over these months, and no noise was noted on the September visit. Seismicity was very low in August and September, with no earthquakes and very low tremors in August, and only six earthquakes in September.

Geologic Background. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Information Contacts: Virginia Tenorio, Emilio Talavera, and Martha Navarro, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/).


Santa Maria (Guatemala) — October 2003 Citation iconCite this Report

Santa Maria

Guatemala

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

All times are local (unless otherwise noted)


Explosions, pyroclastic flows, and night glow in October

Long term eruptive activity at the Santiaguito lava-dome complex of Santa María has continued during 2003 following lahars, explosions, and pyroclastic flows reported during much of 2002 (BGVN 28:05). Plumes identified on satellite imagery between February and September 2003 were described in aviation advisories issued by the Washington Volcanic Ash Advisory Center (VAAC). Regular reports of daily activity provided by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH) on their website have been summarized for many days in the second half of October.

Satellite observations, February-September 2003. Based on GOES-8 imagery the Washington VAAC reported that explosions occurred during the evening of 16 February 2003 and the following morning. Plumes rose to 600 m above the summit, forming an ash plume that was visible on satellite imagery. Imagery from GOES-12 indicated an eruption at about 1330 on 23 July. The plume moved W and had largely dissipated by 1615 after extending ~ 80 km. Washington VAAC reported that the volcano had been active in recent days and that INSIVUMEH had reported an ash column rising to ~ 4.6 km altitude, causing ashfall on farms W of the summit.

The Washington VAAC identified another ash cloud in GOES-12 imagery on 14 August from 0715 through 0745 that was ~ 25 km long and 5 km wide. On 28 September the Washington VAAC reported an ash emission, again based on GOES-12 imagery, that reached an estimated 4.3 km altitude. By 1532 the plume appeared to have detached from the summit and begun to slowly dissipate.

Activity observed during October 2003. Weak and moderate explosions on 15 October continued to expel gray ash to heights of 300-600 m, dispersing to the W and SW. At night blocks of incandescent lava were seen down to the base of the Caliente dome. On 17 October, as during 16 October, most of the nearly 50 explosions were considered moderate, generating avalanches of block lava and ash on the SSW flanks and NE of the Caliente cone. However, at 1745 on 16 October, a strong explosion caused the collapse of a sector of the SW flank of the crater, forming a pyroclastic flow that lasted more than 3 minutes and stopped as it neared the front of the active lava flow ~ 4 km S of Santiaguito.

On 21 October, explosions sent gas-and-ash columns 200-700 m high, which were dispersed by winds to the W, causing slight ashfall of very fine particles to fall in the dome complex. During the night of 22-23 October incandescence on the edge of the crater rim of Caliente cone was observed. Avalanches lasting 3-4 minutes continued with abundant block lava and ash descending primarily down the SSW flank with a minor component to the NE. The ash columns tended to be carried W, causing fine ashfall in sparsely populated mountainous areas. On 24 October there were 26 moderate explosions, 41 weak ones, and about 20 avalanches of lava blocks and ash originating from the S edge of the lava dome in the Caliente cone crater and from the edge of the active lava flow.

During the night of 27 October incandescence along the edge of the lava dome was observed, and weak white fumarolic emissions reached ~ 200 m above the crater in the morning; explosions and avalanches persisted. On 29 October, predominantly moderate and weak explosions produced columns 200-700 m high, and very fine ash fell in nearby mountainous areas. Many of the moderate explosions produced avalanches of block lava and ash to the NE and SW. On 30 October, three small collapses of large blocks occurred from the crater rim, and more than a dozen avalanches, each preceded by explosions and lasting 2-3 minutes, produced abundant fine ash that partially covered the S flank.

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (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); Washington VAAC, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/).


Semeru (Indonesia) — October 2003 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Frequent ash explosions continue through October

Frequent ash explosions at Semeru during 29 September-26 October 2003 produced white-gray ash plumes 400-500 m over the summit. The hazard status remained at Alert Level 2 (on a scale of 1-4) during this time. Although tectonic earthquakes, tremor events, shallow volcanic earthquakes, and avalanches were all detected seismically, the record was dominated by explosions (table 14). Explosions over this 4-week period averaged 95 per day, or one every 15 minutes.

Table 14. Seismicity at Semeru, 29 September-26 October 2003. Four shallow volcanic earthquakes were also detected during 6-12 October. Courtesy of VSI.

Date Explosion Avalanche Tremor Tectonic
29 Sep-05 Oct 2003 636 20 9 4
06 Oct-12 Oct 2003 567 10 -- 7
13 Oct-19 Oct 2003 687 19 22 4
20 Oct-26 Oct 2003 768 16 3 11

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

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


Sheveluch (Russia) — October 2003 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Ash eruptions, lava dome growth, steam plumes, and thermal anomalies

Eruptive activity continued during August-October 2003, including growth of a lava dome in the active crater. Seismicity remained above background levels, and weak, shallow earthquakes were recorded throughout the period. Slightly higher seismic activity was recorded on 30 October with magnitudes in the range of 2.0-2.4. Short-lived eruptions each week sent ash-and-gas plumes to heights of 100-1,500 m above the dome. Thermal anomalies were often recorded by US and Russian satellites.

Weak volcanic tremor was detected during 22-31 August. Tremor was accompanied by gas-and-steam plumes as high as 800 m during 26-27 August, and 2-4-pixel thermal anomalies on 26-30 August. Small thermal anomalies (1-4 pixels) and 500-800-m-high steam plumes were common through 19 September, with an 11-pixel anomaly on the 18th. Similar small thermal anomalies and plumes appeared again during 25-30 September. Thermal anomalies continued to be detected during 1-4, 7-8, 10-12, 16-20, 26, and 29-30 October. Steam plumes were also common, with varying heights of 100-800 m. Small steam plumes and a 1-pixel anomaly occurred 2-3 November.

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

Information Contacts: Olga 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.


Soputan (Indonesia) — October 2003 Citation iconCite this Report

Soputan

Indonesia

1.112°N, 124.737°E; summit elev. 1785 m

All times are local (unless otherwise noted)


Ash explosion and lava flows on 31 August

Increased activity during 18-22 July 2003 at Soputan consisted of frequent ash explosions and large glowing lava avalanches (BGVN 28:08). Seismicity from August through mid-October was dominated by avalanche events, with a few tectonic earthquakes (table 4). White gas emissions in this period were commonly seen rising 25-50 m above the crater, but were also reported as high as 1,000 m in late August and September. On 31 August there was ash explosion accompanied by ejection of incandescent material. The ash column reached 1,000 m above the summit. Lava flowed 750 m down the SW slope, and some descended to the N. Volcanic tremor that week (18-31 August) had an amplitude of 10-38 mm. The hazard status remained at Alert Level 2 (on a scale of 1-4) through 19 October.

Table 4. Seismicity at Soputan, 18 August-19 October 2003. Courtesy of VSI.

Date Avalanche Earthquakes Tectonic Earthquakes
18 Aug-31 Aug 2003 71 --
29 Sep-05 Oct 2003 80 12
06 Oct-12 Oct 2003 30 8
13 Oct-19 Oct 2003 62 9

Geologic Background. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano is located SW of Riendengan-Sempu, which some workers have included with Soputan and Manimporok (3.5 km ESE) as a volcanic complex. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

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


Soufriere Hills (United Kingdom) — October 2003 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Low-level seismicity; ash venting 30 September-1 October

Activity at Soufriére Hills remained at a relatively low level from mid-September into early November 2003. Seismicity consisted mostly of hybrid earthquakes and rockfall signals (table 49). Access continues to be prohibited to some areas after the major dome collapse and explosive activity of 12-13 July 2003 (BGVN 28:08), and there is a maritime exclusion zone around the S part of the island extending 3.7 km beyond the coastline from Trant's Bay in the E to Isles Bay on the W coast.

Table 49. Summary of seismic activity at Soufriére Hills, 5 September-7 November 2003. No volcano-tectonic earthquakes were recorded during this period, but one long-period rockfall event occurred 23-31 October. Courtesy of the Montserrat Volcano Observatory.

Date Rockfall Long-period Hybrid
05 Sep-12 Sep 2003 2 3 27
12 Sep-19 Sep 2003 9 4 20
19 Sep-26 Sep 2003 13 1 20
26 Sep-03 Oct 2003 4 -- 241
03 Oct-10 Oct 2003 1 -- 15
10 Oct-17 Oct 2003 12 -- 9
17 Oct-24 Oct 2003 8 2 12
24 Oct-31 Oct 2003 11 2 19
31 Oct-07 Nov 2003 8 -- 16

During the week of 12-19 September, no growth of the new lava dome was observed. Activity was at a slightly higher level during the week of 26 September-3 October, especially hybrid earthquakes, most of which occurred in a swarm between 1100 and 2100 on 27 September. Some of the hybrids could be located at 2-4 km depth. A period of low-amplitude tremor was also recorded between 0800 on 30 September and 0400 on 1 October coincident with vigorous ash venting, which resulted in ash clouds reaching 2,000-2,500 m altitude and drifting W over Plymouth. Observations on 30 September and 3 October suggested that no new dome growth had occurred.

From 3 October to 7 November, activity returned to a low level. A period of low-amplitude tremor was recorded between 3 and 8 October, and some mudflow signals were also recorded during periods of heavy rain. The tremor coincided with light ash venting. Visibility was poor during this period, so no direct observations of the summit area were possible. The dome was observed clearly on 23 October and a volume survey was carried out from Galways and Perches Mountains. The small dome that extruded in July 2003 had not grown further and appeared to be stagnant, with alteration and degradation occurring such that it appears to be breaking up. The pit crater associated with the explosions of July 2003 had widened slightly, although this was thought to be due to passive slumping of material. Sulfur dioxide and hydrogen chloride emission rates were high during several days around 13-15 October and on 22 October (table 50). An observation flight on 28 October yielded clear views of the scar area and the W scar wall. No changes were observed in the morphology of the scar and no new lava was observed in the vent area.

Table 50. Gas emissions at Soufriere Hills, 5 September-7 November 2003. Hydrogen chloride emissions are calculated from hydrogen chloride to sulfur dioxide mass ratios measured in the volcanic plume using Fourier transform infrared. Values are in metric tons/day. Courtesy of the Montserrat Volcano Observatory.

Date SO2 emissions (tons/day) HCI emissions (tons/day)
12 Sep-19 Sep 2003 700-900 230-300
19 Sep-26 Sep 2003 500-600 --
26 Sep-28 Sep 2003 400-500 --
28 Sep-01 Oct 2003 900-1,200 --
04 Oct 2003 3,100 --
05 Oct 2003 1,900 --
06 Oct-08 Oct 2003 800-1,200 --
04 and 07 Oct 2003 -- 600-1,000
10 Oct-12 Oct 2003 600-800 --
13 Oct 2003 1,900 --
16 Oct 2003 720 --
17 Oct-24 Oct 2003 950-1,200 --
22 Oct 2003 1,850 1,500
24 Oct-27 Oct 2003 800-900 --
28 Oct-31 Oct 2003 400-600 --
31 Oct-07 Nov 2003 800-1,350 --

According to the Washington VAAC, on 1 November resuspended ash was seen in satellite imagery. The ash was moving N to NNW at ~10 km/hour from Montserrat between Nevis and Antigua, and the resuspended ash was concentrated in a narrow plume.

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

Information Contacts: Montserrat Volcano Observatory (MVO), Mongo Hill, Montserrat, West Indies (URL: http://www.mvo.ms/); 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/).


Unnamed (Tonga) — October 2003 Citation iconCite this Report

Unnamed

Tonga

18.325°S, 174.365°W; summit elev. -40 m

All times are local (unless otherwise noted)


Pumice rafts from September-October 2001 eruption reach eastern Australia

A felsic shallow marine explosive eruption from a previously unknown volcano along the Tofua volcanic arc (Tonga) in September-October 2001 (BGVN 26:11 and 27:01) produced floating pumice rafts in Fiji in November 2001, approximately one month after it occurred. These sea-rafted pumice are the only recorded output of this subaqueous eruption at a remote location where direct observations are limited.

A new influx of sea-rafted pumice reached the eastern coast of Australia in October 2002 (figure 4), approximately one year after the eruption was first indicated by seismic activity and pumice stranding in Fiji. Pumice was stranded along at least two-thirds (>2,000 km) of the coastline of eastern Australia, extending from N of Townsville to Sydney. Typical amounts of pumice initially stranded on beaches were 500-4,000 individual clasts per m2; a minimum volume estimate of pumice deposited along the eastern Australian coastline is 1.25 x 105 m3. Most stranded pumice clasts are 1-5 cm diameter, although some outsized clasts are up to 10 cm. Many clasts were fouled by a variety of organisms, and dark algal coverings were common to all clasts that concealed the primary character of the pumice (figure 5). This is in contrast to pumice stranded on beaches in Fiji ~ 1 month after the eruption, which were clean of fouling organisms. Fouling organisms include algae, Bryozoa, serpulid worms, corals and, oysters with goose barnacles particularly abundant.

Figure (see Caption) Figure 4. Map of the southwest Pacific Ocean showing the location of the unnamed volcano in the Tofua volcanic arc that erupted in September-October 2001 producing the pumice rafts. The general dispersal trajectory of the sea-rafted pumice is shown by the dashed line, and the pumice reached the eastern Australian coastline ~ 1 year after the eruption. Courtesy of Scott Bryan.
Figure (see Caption) Figure 5. Closeup of beached pumice clasts from the unnamed volcano in the Tofua volcanic arc fouled by algae and goose barnacles (Lepas pectinata). Courtesy of Scott Bryan.

The pumice have a low phenocryst content (< 5% modal) with the phenocryst assemblage consisting of calcic plagioclase (An88-74), pigeonite (En45 Fs46 Wo9), augite (En35 Fs29 Wo36), and titanomagnetite. Preliminary petrographic observations in dicate that the pumice is compositionally homogenous, although there is considerable variation in vesicularity within and between clasts. Tubed pumice is a minor but distinctive clast type. The pumice, like previously stranded pumice on the Great Barrier Reef (Bryan, 1968, 1971), is low-K dacite in composition (table 2), characterized by low alkalis and high iron and silica. This composition is similar to other pumice-forming eruptions from the Tonga region (Bryan, 1968).

Table 2. Major element data on sea-rafted pumice clasts from eastern Australia, 2002. Samples HI1 and GC1: major element data for whole pumice clasts determined by the atomic absorption method of silicate rock analysis using Inductively-Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) at the University of Queensland. Samples P1 and P2 (n=3 for both): averaged pumice glass compositions analysed at the Centre for Microscopy & Microanalysis, University of Queensland, using a JEOL 8800-L (wavelength dispersive) electron microprobe. Analyses were performed with an accelerating voltage of 15 kV and with a probe current of 15 nA and a probe diameter of 10 microns to avoid volatilisation of alkali elements. Courtesy of Scott Bryan and Alex Cook.

Element HI1 GC1 P1 P2
SiO2 71.30 65.90 66.84 67.33
TiO2 0.36 0.58 0.51 0.50
Al2O3 12.80 12.31 12.29 12.16
Fe2O3^T 5.50 9.88 -- --
FeO^T -- -- 8.05 8.04
MnO 0.10 0.18 0.16 0.15
MgO 1.07 1.43 0.93 0.92
CaO 4.34 5.77 5.40 5.23
Na2O 3.45 3.20 2.71 2.80
K2O 0.90 0.60 0.71 0.72
P2O5 0.18 0.15 0.18 0.20
BaO -- -- 0.03 0.05
SrO -- -- 0.17 0.16
LOI 0.92 1.87 -- --
Raw Total 99.50 99.80 97.99 98.27

References. Bryan, W.B., 1968, Low-potash dacite drift pumice from the Coral Sea: Geological Magazine, v. 105, p. 431-439.

Bryan, W.B., 1971, Coral Sea drift pumice stranded on Eua Island, Tonga, in 1969: Geological Society of America Bulletin, v. 82, p. 2799-2812.

Geologic Background. A submarine volcano along the Tofua volcanic arc was first observed in September 2001. The newly discovered volcano lies NW of the island of Vava'u about 35 km S of Fonualei and 60 km NE of Late volcano. The site of the eruption is along a NNE-SSW-trending submarine plateau with an approximate bathymetric depth of 300 m. T-phase waves were recorded on 27-28 September 2001, and on the 27th local fishermen observed an ash-rich eruption column that rose above the sea surface. No eruptive activity was reported after the 28th, but water discoloration was documented during the following month. In early November rafts and strandings of dacitic pumice were reported along the coast of Kadavu and Viti Levu in the Fiji Islands. The depth of the summit of the submarine cone following the eruption determined to be 40 m during a 2007 survey; the crater of the 2001 eruption was breached to the E.

Information Contacts: Scott Bryan, Department of Geology & Geophysics, Yale University, PO Box 208109, New Haven CT 06520 8109 USA; Alex Cook, Queensland Museum, PO Box 3300, South Brisbane, Queensland 4101 Australia.

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


Central Chile and Argentina


Estero de Parraguirre


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/).