Logo link to homepage

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/).

Search Bulletin Archive by Publication Date

Select a month and year from the drop-downs and click "Show Issue" to have that issue displayed in this tab.

   

The default month and year is the latest issue available.

Scientific Event Alert Network Bulletin - Volume 13, Number 12 (December 1988)

Managing Editor: Lindsay McClelland

Asosan (Japan)

Minor ash emission

Atmospheric Effects (1980-1989) (Unknown)

1985-88 Hawaii aerosol data summarized

Colima (Mexico)

Bombs ejected; small ash clouds; new fumaroles

Fournaise, Piton de la (France)

Fissure eruption in N part of caldera

Kick 'em Jenny (Grenada)

Seismicity suggests submarine eruption

Kilauea (United States)

Continued lava flow into sea; tube breakouts upslope

Langila (Papua New Guinea)

Small Vulcanian explosion

Lengai, Ol Doinyo (Tanzania)

Lava continues to flow onto main crater floor

Lonquimay (Chile)

Fissure eruption produces tephra clouds and lava flow

Macdonald (Undersea Features)

Frequent eruptive seismicity in 1988

Manam (Papua New Guinea)

Ash and incandescent fragments; frequent B-type events

Rabaul (Papua New Guinea)

Decreasing seismicity; minor inflation

Ruapehu (New Zealand)

Crater lake eruption ejects ash and blocks

Ruiz, Nevado del (Colombia)

High-frequency seismicity drops; energy release still high

Siple (Antarctica)

Overflight shows no sign of recent eruption

Tokachidake (Japan)

Ash ejection; small pyroclastic flows and mudflow

Ulawun (Papua New Guinea)

Tremor and B-type events; vapor emission

White Island (New Zealand)

Minor ash emission; deflation; fumaroles cool

Yasur (Vanuatu)

Centuries-long Strombolian eruption continues from four vents



Asosan (Japan) — December 1988 Citation iconCite this Report

Asosan

Japan

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

All times are local (unless otherwise noted)


Minor ash emission

Ash ejection from [Crater 1] was observed on 28 December at 1420, during a field survey. The ash cloud rose 30 m above the crater rim. Red glow at vents and cracks in the crater floor had often been seen since 16 October. The number of isolated tremor episodes, counted from data recorded on a seismometer 0.8 km W of the crater, had gradually increased since the end of October, although the amplitude of continuous tremor episodes remained almost the same. No ash ejection was observed during a 31 December field survey.

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: JMA.


Atmospheric Effects (1980-1989) (Unknown) — December 1988 Citation iconCite this Report

Atmospheric Effects (1980-1989)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


1985-88 Hawaii aerosol data summarized

Lidar data from Mauna Loa, Hawaii continued to document the gradual decay in stratospheric aerosol density. No large volcanic aerosol injections have occurred since the November 1985 eruption of Ruiz. A small increase in aerosols was detected after the 9 May eruption of Banda Api, Indonesia, but effects on the stratosphere appear to have been brief. The cause of the small November peak at Mauna Loa is uncertain, but profile characteristics did not suggest that the material was from a new eruption.

Geologic Background. The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. 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 here.

Information Contacts: Thomas DeFoor, Mauna Loa Observatory, P.O. Box 275, Hilo, HI 96720 USA.


Colima (Mexico) — December 1988 Citation iconCite this Report

Colima

Mexico

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

All times are local (unless otherwise noted)


Bombs ejected; small ash clouds; new fumaroles

While working on a hazard map during October and November, geologists (A.L. Martín del Pozzo, C. Suarez Plascencia, R.M. Uribe, A.M. Soler, and G. Stoopes) observed that a section of the E part of the dome had caved in since their last visit at the end of January. A fumarole that had been seen since 1981 was not active in January, but its activity had resumed at an increased level by October and November, and there were two new vents that emitted vapor. On 13 November, the geologists noted three new bombs (1-, 3-, and 4-m-diameters) that had been ejected from the summit dome since January and fallen on the top of Volcancito, a parasitic cone 1 km NE of the summit. The bombs were porphyritic andesite with plagioclase, hornblende, and pyroxene phenocrysts of up to 5 mm. Univ of Guadalajara geologists climbed the volcano later in November and noted new fumarolic activity that had not been evident in April. From a highway 18-20 km E of the volcano on 22 December, Arizona State Univ geologists saw small explosions from the summit dome, producing puffs of steam and darker ash clouds, typical of recent activity at the volcano.

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

Information Contacts: Ana Lilian Martín del Pozzo, Instituto de Geofísica, UNAM, Ciudad Univ, Delegación Coyoacán; Julian A. Flores Diaz, Instituto de Geografía y Estadísticas, Univ de Guadalajara; Michael Sheridan and Gary Stoopes, Arizona State Univ, USA.


Piton de la Fournaise (France) — December 1988 Citation iconCite this Report

Piton de la Fournaise

France

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

All times are local (unless otherwise noted)


Fissure eruption in N part of caldera

The onset of the 14 December eruption, at 1303, followed 40 minutes of 1-Hz tremor. Data from the tilt network had allowed geologists to reach the field 2 hours earlier and provided an excellent forecast of vent location. Geologists heard (and saw through clouds) the opening of a 400-m fissure N of Faujas Crater that ejected 20-50-m fountains of aphyric basalt and built a new cone. A second fissure opened to the SW, but lava production was low. During the following days, a significant number of discrete seismic events accompanied vigorous tremor. Most seismic events were limited to the summit zone, but some were recorded in the N part of the caldera. Eruptive activity stopped suddenly on 29 December at 0150. Since then, seismic activity has progressively resumed.

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

Information Contacts: H. Delorme, P. Nerbusson, D. Vandamme, J. Delmond, and P. Taochi, OVPDLF; P. Bachelery, Univ de la Réunion; J. Dubois, J-L. Cheminée, A. Hirn, J. LePine; P. Blum, and J. Zlotnicki, IPGP.


Kick 'em Jenny (Grenada) — December 1988 Citation iconCite this Report

Kick 'em Jenny

Grenada

12.3°N, 61.64°W; summit elev. -185 m

All times are local (unless otherwise noted)


Seismicity suggests submarine eruption

"Seismographs throughout the eastern Caribbean recorded strong underwater acoustic signals 29-30 December 1988. The first signals began at approximately 1550 on 29 December. Onset of the signals was extremely emergent, so their point of origin could not be determined precisely, but their pattern of arrivals and amplitudes suggested an origin in the southern Lesser Antilles. The most likely source was thought to be Kick-'em-Jenny . . . . When last surveyed in 1982, the summit of this volcano was 160 m below sea level. The initial signals persisted for approximately 56 minutes.

"A shorter but more intense signal was recorded on the 29th between 1722 and 1750. At this time, residents of Sauteurs on the N coast of Grenada felt strong ground vibrations and heard a deep rumbling sound. Although observers in full view of the location of the volcano had been alerted by this time, no disturbance of the sea surface was noted. Vibrations were felt and heard as far away as Martinique, 250 km to the N. Georges Boudon from the Martinique volcano observatory was scuba diving off the N coast of Martinique at the time and distinctly heard the underwater signal.

"A third explosion occurred at about 0500 on 30 December. Onsets for this event were much more distinct and it was confirmed that Kick-'em-Jenny was the source. Lt. Col. Glen Mignon of the Grenada Defence Force surveyed the site from a vessel of the Grenada Coast Guard on the morning of 30 December but no disturbance of the sea surface was visible [but see 14:5]. No further explosions have been recorded as of 2 January but as a precautionary measure small vessels have been advised to keep 5 km clear of the volcano until further notice."

References. Shepherd, J.B., and Robson, G.R., 1967, The source of the T-phase recorded in the eastern Caribbean on October 24, 1965: Bulletin of the Seismological Society of America, v. 57, p. 227-234.

Sigurdsson, H. and Shepherd, J.B., 1974, Amphibole-bearing basalts from the submarine volcano Kick-'em-Jenny in the Lesser Antilles Island Arc: BV, v. 38, p. 891-910.

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

Information Contacts: J. Shepherd, UWI; Lt. Col. G. Mignon, Grenada; C. Antenor-Habezac, Observatoire Volcanologique de la Guadeloupe.


Kilauea (United States) — December 1988 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Continued lava flow into sea; tube breakouts upslope

Kilauea continued to erupt in December. Lava traveled through the tube system to the coast, continuing to build an active lava bench at sea level. Seismic stations > 10 km away detected minor bench collapses at 1804-1825 on 2 December and 2129-2150 on the 14th. These destroyed 10% and 20% of the total bench area. A series of lava breakouts from the main tube system at 440 and 330 m elevation began on the 10th and continued throughout the month. Lava (mostly low volumes of pahoehoe) repeatedly broke from the tube system, branched into several flows, and stagnated after the flow fronts reached ~100 m elevation. The lava flowed over and E of the main 1986-88 field, posing no threat to property. The Kupaianaha lava pond level averaged 20 m below the rim during the month.

Low-level tremor continued . . . near Pu`u `O`o and Kupaianaha. The signal pattern varied from steady amplitude sustained for many days to recurring bursts at intervals of a few minutes or hours. Rockfalls were detected at Pu`u `O`o throughout the month. Shallow microearthquakes continued at an average rate in the summit region and along the rift zone. Most of the 17 largest earthquakes (M 2.5-4.3) were located along the S flank of Kilauea and the SE flank of Mauna Loa at intermediate depths of ~5-15 km.

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

Information Contacts: C. Heliker and R. Koyanagi, HVO.


Langila (Papua New Guinea) — December 1988 Citation iconCite this Report

Langila

Papua New Guinea

5.525°S, 148.42°E; summit elev. 1330 m

All times are local (unless otherwise noted)


Small Vulcanian explosion

"Low-level activity continued in December. Weak to moderate white emissions with occasional grey ash clouds were released from Crater 2. Weak rumbling noises were heard 28-31 December. A Vulcanian explosion on the 4th ejected an ash column that rose a few hundred metres and resulted in light ashfall to the SE. Crater 3 remained inactive throughout the month. Seismic activity remained at a low level with <10 events/day near the end of the month."

Geologic Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: H. Patia and P. Lowenstein, RVO.


Ol Doinyo Lengai (Tanzania) — December 1988 Citation iconCite this Report

Ol Doinyo Lengai

Tanzania

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

All times are local (unless otherwise noted)


Lava continues to flow onto main crater floor

When geologists visited . . . 22-25 November, most of the crater floor had been covered by lava erupted since the end of June. A new 13-m-high cone (T11) was emitting aa lava onto the active crater floor (F7 and F9 in figure 11) and into the depression S of the saddle (F8) within an overflow channel 3 m deep and3/min and temperatures from [>582 -593°C]. A shimmer of heat and irregular gas blasts were observed from the E side of T4/T7, the site of lava lake activity and the source of small flows in June. T9 had grown and merged with T5, a site of minor activity in June. A number of fresh hornitos had formed W of T5, the largest being 1.5 m high (H4).

On 23 November at 0800, black lava continued to bubble within T11, but its flows had stopped and the overflow channel appeared blocked. During the night, a hornito (H4) W of T5 had emitted two pahoehoe flows that moved NW, one reaching the NW crater wall (F10 and F11, figure 11). Gas blasts continued from T4/T7, becoming more frequent that evening.

Figure (see Caption) Figure 11. Sketch map of Ol Doinyo Lengai's crater viewed from the W rim on 23 November 1988. Diameter of the active crater is 236 m. The N rim at the top of C1 is 45 m above the crater floor. Height of the S slope of the central saddle is 4.5 m. Courtesy of C. Nyamweru

The next day at 0510, an eruption began W of T5, forming hornito H5 that was 1.5 m high and 1.1 m in diameter. At 0540, a new vent (T5B) opened on the SW slope of T5, emitting spatter and a thin fluid lava flow (F12) that extended a few tens of meters. Emission rates averaged ~0.1 m3/minute and temperatures ranged from [>579 to 593°C]. A gas-emitting pinnacle on the N side of T4/T7 spattered fresh lava, building a new cone. Another new cone that formed in the center of T11 ejected lava to 10 m. A small vent on the W side of T8 had ejected fresh spatter and glowed at depth.

On the 25th, [the inner] T11 cone was 2 m high. Lava bubbled gently within H5. Several new small pahoehoe flows had formed below T5B during the night and a flow continued in the morning. This lava encircled a fumarole near the base of the crater's E wall. Loud firecracker-like explosions were heard when lava flowed into the fumarole.

Further Reference. Dawson, J.B., Pinkerton, H., Norton, G.E., and Pyle, D.M., 1990, Physicochemical properties of alkali carbonatite lavas; data from the 1988 eruption of Oldoinyo Lengai, Tanzania: Geology, v. 18, p. 260-263.

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

Information Contacts: C. Nyamweru, Kenyatta Univ; J. Dawson, Univ of Edinburgh; H. Pinkerton and G. Norton, Univ of Lancaster; D. Pyle, Cambridge.


Lonquimay (Chile) — December 1988 Citation iconCite this Report

Lonquimay

Chile

38.379°S, 71.586°W; summit elev. 2832 m

All times are local (unless otherwise noted)


Fissure eruption produces tephra clouds and lava flow

On Christmas Day, after more than 2 weeks of increasing seismicity, an eruption began at the NE foot of the volcano. Vigorous tephra emission fed a large eruption column that produced substantial ashfalls E of the volcano, and a lava flow advanced ~4.5 km.

Felt earthquakes and subterranean noises began 7 December. Several of the shocks reached intensities between IV and V, with magnitudes of 4.2-4.6. Some were registered at Santiago, 800 km away. About 200 earthquakes were felt during the 3 days prior to the start of the eruption, some of intensity VI. One was felt at Temuco, 110 km from the volcano, on 24 December.

The eruption began at 1615 the next day, with a strong ejection of gas and water vapor. Early in the eruption, about eight small vents were active along a fissure ~800 m long, 3.5 km from the summit. Its N60°E trend was similar to the orientation of previous Holocene and historic monogenetic eruptive centers that had produced lava domes and andesitic/dacitic block lava flows. Within a few hours, activity was concentrated at two principal vents. The eruption was dominated by gas emission during its first 36 hours. Moderate Strombolian activity from several vents was reported on 26 December. The next day, gas and tephra rose several thousand meters from the two main vents, feeding a plume that was blown E by mid-level winds. The plume was first detected on NOAA weather satellite images at 1100, when it extended 70 km E at roughly 5.5 km altitude, and remained evident in clear weather during the following weeks (table 1). Viscous lava began to flow N and NE from the fissure on 27 December at about noon.

Table 1. Observations of plumes from Lonquimay on NOAA weather satellite imagery, 27 December 1988-17 January 1989.

Date Time Direction / Length Weather and/or Height
27 Dec 1988 1100-1200 70 km E, diffuse about 5.5 km
27 Dec 1988 up to 1700 dense to 50-80 km diffuse to 350 km cirrus developing
28 Dec 1988 a.m. dense ~70 km ENE diffuse to 160 km very diffuse to 68°W periodic pulses freezing temp, 500-250 mbars
28 Dec 1988 1430 dense 50-80 km, S of E cloudy
29 Dec 1988 0900 two plumes (v-shaped and diffuse) --
29 Dec 1988 1200 denser plume to 175 km E 100 km wide at 125 km very diffuse to 500 km --
30 Dec 1988 a.m. dense to 150 km (10 km wide) diffuse to 425 km 65 km at widest point weather front approaching
30 Dec 1988 p.m. 100 km, more diffuse --
31 Dec 1988 1400 dense to 95 km E, 15-60 km wide; apparently weakening --
31 Dec 1988 1900 plume length increased by 2x; 250 km E, 50 km wide --
02 Jan 1989 1430 dense to 250 km, very diffuse to 500 km; 25 km wide at 250 km, due E, 40 km/hr wind speed --
03 Jan 1989 -- 120 km long, 12 km wide; thin as far as 400 km; across continent at least 5.5 km; -10°C
04 Jan 1989 1300 new eruption pulse (more dense) --
04 Jan 1989 1500 starting to separate from volcano -34°C, about 9 km
04 Jan 1989 1600 weakened (more diffuse); fully separated from volcano; dense to 95 km, 35 km wide; 25 km thick, 120 km SE --
05 Jan 1989 1400-1600 still erupting; not as strong; 100-120 km SE cloudy
06 Jan 1989 through 1750 moderate density, 150 km E or N of E; diffuse to 400 km --
08 Jan 1989 0500 new eruption pulse --
08 Jan 1989 1000 dense, 20-30 km wide, 135 km NE --
10 Jan 1989 a.m. dense to 200 km SE; diffuse to 500-600 km --
10 Jan 1989 0630-0700 eruption pulse --
10 Jan 1989 0700-0800 -- -5°C, 5.5-6 km
10 Jan 1989 1430-1730 dense to 105 km ESE, 45 km wide; diffuse to 200-290 km --
12 Jan 1989 -- -- cloudy
13 Jan 1989 -- no eruption evident clear
14-15 Jan 1989 2300-0300 little or no plume evident (on IR) clear
15 Jan 1989 0330-0400 possible weak eruption --
15 Jan 1989 0420 plume on visible image; dense to 150 km NE, diffuse to 350 E --
16 Jan 1989 0900 dense to 100-130 km ENE-NE; diffuse to 150-180 km; 20-30 km wide (visible image) --
17 Jan 1989 0931 very diffuse ENE to 300-360 km clear

A second phase, characterized by strongly explosive phreatomagmatic activity, began on 27 December at 1820 with the violent ejection of a column of gas and tephra, primarily andesite-dacite ash, that reached 9 km altitude in 5 minutes. The activity was concentrated in the upper vent, at 1,680 m elevation, which became the principal eruptive center. Two similar explosions followed, separated by intervals of approximately an hour. Oscar González-Ferrán estimated that the velocity of ejection reached between 250 and 350 km/hour. The next day, activity was nearly continuous, with alternating 15-20-minute periods of higher and lower explosivity ejecting spatter, bombs, lapilli, scoria, and ash. The cone over the main vent had reached 50 m height and 80 m in diameter (table 2). As the crater grew, it developed a horseshoe shape, open to the NE (downslope).

Table 2. Growth of Lonquimay's new Navidad cone, 28 December 1988-4 January 1989. Courtesy of Hugo Moreno Roa.

Date Height (m) Diameter (m)
28 Dec 1988 50 80
30 Dec 1988 60 150
31 Dec 1988 100 250
01 Jan 1989 110 250
02 Jan 1989 180 250
04 Jan 1989 above 200 300

Some 60 hours after the large explosion on 27 December, the third phase began, characterized by substantial lava production (table 3) accompanied by strong magmatic degassing. Vigorous explosions produced shock waves and a large amount of ash, while an andesitic block lava flow crept very slowly NNE. Two lobes were active, the longer to the E. The rate of lava effusion was estimated at ~4 x 105 m3/day through 4 January, with the flow front advancing 20-25 m/hour.

Table 3. Dimensions of the lava flow from Lonquimay, 28 December 1988-4 January 1989. Courtesy of Hugo Moreno Roa.

Date Length (km) Thickness (m) Surface Area (km2) Volume (x 106 m3)
28 Dec 1988 1.8 10 1.0 10
30 Dec 1988 3.0 10 1.5 15
31 Dec 1988 3.3 10 2.2 22
02 Jan 1989 4.0 10 2.5 25
04 Jan 1989 4.5 10 3.0 30

Three seismographs from the Univ of Chile were installed by Sergio Barrientos, Hector Masone, and Oscar González-Ferrán ~27 hours after the onset of the eruption (between 2100 on 26 December and 0400 on the 27th): LON1, on the flank of Cerro Cautín, 4 km from the eruptive center; LON2, in Pinitos Malalcahuello, 11 km away; and LON3 in Quebrada Guamachuco, 12 km from the vent (figure 1). When seismic recording began, activity was very intense, with ~50 events every 3 hours (figure 2). However, seismic activity declined rapidly between 40 and 120 hours after the start of the eruption. Initial analysis of the seismograms showed that the epicenters were concentrated in the immediate eruption area. Geologists therefore believed that eruptive activity was unlikely to propagate SE toward the main crater of Lonquimay or to another point on the eruptive fissure.

Figure (see Caption) Figure 1. Sketches of Lonquimay showing activity during the initial phase during 25-26 December 1988 (top) and in early January 1989 (bottom). In December the new eruptive fissure emitted water vapor, blocks, and fragments of older lava. Positions of newly installed seismic stations LON1, LON2, and LON3 are also indicated. The January sketch depicts the plume rising several thousand meters above the 200-m-high pyroclastic cone and extending tens of kilometers downwind; the lava flow has reached 3.5 km length. Courtesy of O. González-Ferrán.
Figure (see Caption) Figure 2. Number of seismic events recorded in 3-hour periods, 27 December 1988-7 January 1989, by Univ of Chile seismic station LON3, 12 km from the vent. Arrows label changes in eruptive activity. Courtesy of O. González-Ferrán.

The effusive phase continued during the following week, with strong magmatic degassing. Explosive activity was intense and nearly continuous with vigorous emission of gas and ash, generating a column that usually remained between 5,000 and 7,000 m altitude (figure 3). The plume was generally very consistent in both altitude and direction, toward the SE.

Figure (see Caption) Figure 3. Daily altitude of the gas-tephra column from Lonquimay, in meters above sea level, 25 December 1988-7 January 1989. Courtesy of O. González-Ferrán.

Satellite imagery showed dense plumes extending as much as 250 km and more diffuse material was occasionally evident to 500 km from the volcano (figure 4). The plumes generally were of insufficient density to yield precise blackbody temperatures (and thus infer plume height from satellite data). However, correlations of estimated plume temperatures and directions of drift with data from nearby radiosondes agreed well with altitude estimates by field geologists. Winds caused sporadic rotation and shearing of the eruption column at 2,000-3,000 m altitude, producing ashfall to the SW and NE (figure 5). On 4 January at 1500, during a period of increased atmospheric humidity, geologists observed that the plume became cauliflower-shaped and a thunderstorm developed within it. An acidic rain began to fall, probably of pH 3-4. The estimated volume of the mixture of gas and pyroclastics, principally ash, was on the order of 8 x 1011 m3 as of mid-January. Lava emission was slow and not very voluminous, with the block flow reaching a length of around 3.5 km by 8 January.

Figure (see Caption) Figure 4. Images from data collected by the AVHRR on the NOAA-11 polar orbiting satellite, 29 December 1988 at 1530, 1.1 km resolution (top) and 2 January 1989 at 1530, 4 km resolution (bottom). One of the five spectral channels on the AVHRR (channel 4) senses thermal radiation, and was used to determine plume temperatures of around 0°C on both images. Correlation of this temperature and the direction of plume movement with radiosonde data indicate that the plume is at an altitude of about 5 km on both images. Courtesy of G. Stephens.
Figure (see Caption) Figure 5. Cumulative ash deposition from the Lonquimay eruption as of 13 January 1989. Courtesy of O. González-Ferrán.

Explosive activity declined noticeably on 6 January at a little before 0400, and had practically ended by 0500. The column of gas and pyroclastics disappeared, with ejection limited to some incandescent blocks. Resumption of activity began with small emissions of gas and pyroclastics every 15 minutes until 0730, to heights that did not exceed 200 m. A new vent-clearing phase then began, consisting of strong emission of ash and soot-like material, without magmatic degassing or ejection of incandescent blocks. Satellite images had shown decreased activity on 5 January, but moderate plumes were evident with diffuse material to 400 km from the volcano on the 6th. Explosive activity continued during the following 24 hours, to altitudes that increased to some 3,000-4,000 m, accompanied by strong explosions. During this phase the plume continued to drift primarily ENE. The lava flow remained stationary.

The number of seismic events had noticeably decreased from the first week of the eruption. During the more effusive activity of 2-8 January, only 210 shocks were registered. No changes or migrations of the epicentral area were observed, with the sole exception of a brief shift toward the SW sector of the volcano (Quebrada de Guamachuco area). This ended quickly and was not repeated. The seismic net was temporarily reinforced by another four seismographs, one with three components, contributed by the Instituto Nacional de Prevención Sísmico de San Juan, Argentina (INPRES) and brought to the region by geologist Nestor Weidmann. This equipment operated 4-9 January before it was returned to its base in San Juan.

Associated with the decline in activity on 6 January was a sequence of strong shocks, some with maximum intensities of IV-V. These were interpreted to be related to the collapse of the roof of the magma chamber as magma column pressure diminished, coinciding with the observed vent-clearing phase. Between 8 and 14 January, a strong increase in seismicity was recorded, while eruptive activity remained at a medium-low level. On 12 January at 0011, a M 4.6 shock reached an estimated intensity of V-VII in the epicentral area, causing landslides, slumping of roads, and broken windows in houses. A shock registered 24 hours later reached M 5.0, larger than the events on 25 December.

On 8 January, the activity continued to increase and was entering a magmatic degassing phase, with an increase in lava block and spatter emission accompanied by strong explosions that caused expansive air waves. González-Ferrán noted that the compositional characteristics of the ejecta had changed from the more viscous and silicic (andesite-dacite) initial phase to a more fluid andesite. Satellite imagery showed continued plume production through 10 January. Clouds then obscured the area until 13 January, when no plume was evident throughout the day despite clear weather. A distinct plume was next detected on 15 January at 0420, with dense material extending 150 km from the volcano. Plume emission was continuing as of 17 January.

Moyra Gardeweg and Jorge Muñoz (SERNAGEOMIN) reported that bombs were of andesite to basaltic andesite composition with plagioclase, pyroxene, and olivine phenocrysts in a pale brown glassy groundmass. L. López-Escobar and J. Martínez (Univ of Chile) noted that ash collected at the town of Lonquimay (20 km from the vent) had an SiO2 content of 57.78% and a bomb collected near the cone, 59.21%, similar to the 59.49% in a sample from the lava flow extruded 100 years ago.

The principal risk for the population continues to be ashfall and gases that have particularly affected the region SE of the vent (Pueblo de Lonquimay, areas around the Cordillera de las Raices and upper Bio-Bio, to the Troyo zone; ashfall also extends into Argentina). The ashfall caused by low-altitude wind shearing occurred to the SSW, affecting the Malalcahuello region and the upper part of the Cautín river toward Guamachuco. The total population affected in Chile was ~10,000, of which ~2,000 were evacuated. The National Emergency Office, The Regional Intendancy, and the National Health Service conveyed immediate medical assistance, distributed protective masks, and issued emergency instructions. The agricultural and livestock authorities have provided information to help protect farm animals, which include ~100,000 cattle and sheep.

Participants in fieldwork included Sergio Barrientos, Hector Masone, Carlos Droguett, and O. González-Ferrán (Univ de Chile), Maurice and Katia Krafft (Equipe Vulcain, Cernay, France), Patricio Acevedo (Dept de Física, Univ de la Frontera, Temuco), Jaime Abarzua (Administrador, Reserva Malalcahuello, CONAF), and E. Casanova (Jefe, Oficina Emergencia, Victoria).

Geologic Background. Lonquimay is a small, flat-topped, symmetrical stratovolcano of late-Pleistocene to dominantly Holocene age immediately SE of Tolguaca volcano. A glacier fills its summit crater and flows down the S flank. It is dominantly andesitic, but basalt and dacite are also found. The prominent NE-SW Cordón Fissural Oriental fissure zone cuts across the entire volcano. A series of NE-flank vents and scoria cones were built along an E-W fissure, some of which have been the source of voluminous lava flows, including those during 1887-90 and 1988-90, that extended out to 10 km.

Information Contacts: O. González-Ferrán and H. Moreno, Univ de Chile; S. Kusselson, O. Karst, G. Swanson, M. Ruminsky, and A. Powell, SAB; G. Stephens, NOAA/NESDIS.


Macdonald (Undersea Features) — December 1988 Citation iconCite this Report

Macdonald

Undersea Features

28.98°S, 140.25°W; summit elev. -39 m

All times are local (unless otherwise noted)


Frequent eruptive seismicity in 1988

Seismicity . . . was substantially more vigorous in 1987 and particularly in 1988 than in previous years since 1977 (figure 1). Acoustic T-waves generated from a submarine eruption 11-17 November 1988 were the most intense since the Polynesian Seismic Research station began to collect data more than 25 years ago. Since the end of the 3-18 September eruption nearly continuous weak seismicity from Macdonald was detected 26 September-5 October, 12-24 October, and 12-14 December, and weaker more sporadic explosions 25-29 December.

Figure (see Caption) Figure 1. Histogram showing hours of detected activity at Macdonald Seamount from 1977-88. Arrows indicate explosive onsets of eruptions. [Data from a figure in 13:05 and a table in 13:12 are incorporated into this figure originally printed in 14:01]. Courtesy of J. Talandier.

Geologic Background. Discovered by the detection of teleseismic waves in 1967, Macdonald seamount (also known as Tamarii seamount) rises from a depth of about 1800 m to within 27 m of the sea surface at the eastern end of the Austral Islands. The alkali-basaltic submarine volcano marks the site of a hotspot that was the source of the Austral-Cook island chain. The summit of the seamount, named after volcanologist Gordon Macdonald, consists of a flat plateau about 100 x 150 m wide with an average depth of about 40 m. The summit plateau is capped with spatter cones that form steep-sided pinnacles. Most eruptions have been seismically detected, but in 1987 and 1989 pumice emission was observed from research vessels. Pumice rafts observed in the South Pacific in 1928 and 1936 may also have originated here.

Information Contacts: J. Talandier, LDG Tahiti.


Manam (Papua New Guinea) — December 1988 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Ash and incandescent fragments; frequent B-type events

"Activity . . . remained at a low level throughout December. Both Southern and Main Craters released white vapours at weak to moderate rates. Emissions from Southern Crater were often ash-bearing and were accompanied by thick blue vapours on the 13th. Deep rumbling noises from Southern Crater were heard 1-12, 15, and 23-27 December, accompanied by weak ejections of incandescent lava fragments on the 3rd and 4th. Weak fluctuating glow from Southern Crater was observed 1-8 and 11 December. Seismicity remained at a low to moderate level with 700-1,100 B-type volcanic events recorded daily. Sub-continuous low-amplitude tremor was also recorded throughout the month. No significant tilt changes were detected."

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: H. Patia and P. Lowenstein, RVO.


Rabaul (Papua New Guinea) — December 1988 Citation iconCite this Report

Rabaul

Papua New Guinea

4.271°S, 152.203°E; summit elev. 688 m

All times are local (unless otherwise noted)


Decreasing seismicity; minor inflation

"Seismicity continued to decrease in December to a total of 131 recorded earthquakes. Events averaged 4/day with highest counts at 12 on the 22nd and 23rd. Only three events could be located; two at the SW tip of Matupit Island and one near the S part of Blanche Bay's entrance. Ground deformation rates remained low. At Greet Harbour's entrance, EDM data showed continued slight expansion (8 ppm) and tilt stations in this area showed inflationary changes of up to 6 µrad."

Geologic Background. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.

Information Contacts: H. Patia and P. Lowenstein, RVO.


Ruapehu (New Zealand) — December 1988 Citation iconCite this Report

Ruapehu

New Zealand

39.28°S, 175.57°E; summit elev. 2797 m

All times are local (unless otherwise noted)


Crater lake eruption ejects ash and blocks

The longest recorded period of low Crater Lake temperatures was interrupted by a moderate eruption on 8 December. Earthquakes started at 0843 that morning after a month of weak seismicity [but see 14:01]. The third event, at 0903, was followed by the onset of 2-Hz tremor. Just 1-2 minutes before the 6th and strongest earthquake (M [3.6]) at [1011], white steam clouds rose in 2-3 pulses to a short distance above the crater lake before being blown NE by strong winds. No ash was evident in the clouds but a thin veneer of dark gray wet ash extended 1.1 km NE of the crater lake (figure 8). Swirling patterns and feathered edges in the airfall zone suggested deposition from a turbulent cloud. Most blocks fell within 100 m of the lake, producing many impact and melt craters up to 1 m across. Most of the blocks consisted of altered andesite; no juvenile bombs were found. No fresh glass was evident in samples of fine-grained tephra. The ash was dominantly silty silica particles and aggregates mixed with solid sulfur globules and spheroids, plus a few fine andesite grains and plagioclase fragments. Ash and water on the upper Whangaehu Glacier formed a small mudflow, only a few meters wide, that extended ~500 m downslope.

Figure (see Caption) Figure 8. Ashfall (stippled), mudflow (arrows), and sites of greatest block concentrations (stars) from the 8 December 1988 eruption of Ruapehu.

Lake temperature was 13.7°C the day after the eruption, only slightly above the record low of 9° measured during previous fieldwork on 14 November. Only minor deformation changes had occurred since 14 November. Semi-continuous to continuous 2-Hz tremor was observed on seismic records through 12 December, and 8-10 low-frequency earthquakes occurred 9-10 December.

Geologic Background. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The 110 km3 dominantly andesitic volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake, is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys.

Information Contacts: I. Nairn, P. Otway, B. Scott, and C. Wood, NZGS Rotorua; S. Sherburn and B. Christenson, DSIR Chemistry, Wairakei.


Nevado del Ruiz (Colombia) — December 1988 Citation iconCite this Report

Nevado del Ruiz

Colombia

4.892°N, 75.324°W; summit elev. 5279 m

All times are local (unless otherwise noted)


High-frequency seismicity drops; energy release still high

The number and energy release of high-frequency seismic events at Ruiz continued to decline in December, while low-frequency seismicity was similar to previous months (figure 22). Total seismic energy release remained substantially elevated (figure 23). There were two main clusters of high-frequency events, one roughly 4 km E of the crater at ~2.5 km depth, the second 3 km SW of the volcano at ~2 km depth. Brief increases in tremor intensity occurred more often in December, but their energy was low. No significant deformation was measured during the month. The rate of SO2 emission averaged ~1,220 t/d.

Figure (see Caption) Figure 22. Number of seismic events/month at Ruiz (left) and monthly seismic energy release (right) for high-frequency (top) and low-frequency events (bottom), January-December 1988. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 23. Daily seismic energy release at Ruiz, July 1985-December 1988. Courtesy of INGEOMINAS.

Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


Siple (Antarctica) — December 1988 Citation iconCite this Report

Siple

Antarctica

73.43°S, 126.67°W; summit elev. 3110 m

All times are local (unless otherwise noted)


Overflight shows no sign of recent eruption

Further analysis of satellite images by geologists strongly suggested that the plumes originated from the volcano's summit, rather than its base. On 30 December, Philip Kyle and William McIntosh conducted an aerial inspection of the snow-covered volcano. The weather was clear except for low clouds below 500 m, around the mountain's base. No fresh ash, new craters, disruptions to the snowpack, or other evidence of recent explosive volcanism were observed. Although appearing identical to known eruption clouds, Kyle believes that the Mt. Siple plumes resulted from meteorological effects.

Geologic Background. Mount Siple is a youthful-looking shield volcano that forms an island along the Pacific Ocean coast of Antarctica's Marie Byrd Land. The massive 1,800 km3 volcano is truncated by a 4-5 km summit caldera and is ringed by tuff cones at sea level. Its lack of dissection in a coastal area more susceptible to erosion than inland volcanoes, and the existence of a satellite cone too young to date by the Potassium-Argon method, suggest a possible Holocene age (LeMasurier and Thomson 1990). Its location on published maps is 26 km NE of the actual location. A possible eruption cloud observed on satellite images on 18 September and 4 October 1988 was considered to result from atmospheric effects, after low-level aerial observations revealed no evidence of recent eruptions.

Information Contacts: P. Kyle, New Mexico Institute of Mining & Technology.


Tokachidake (Japan) — December 1988 Citation iconCite this Report

Tokachidake

Japan

43.418°N, 142.686°E; summit elev. 2077 m

All times are local (unless otherwise noted)


Ash ejection; small pyroclastic flows and mudflow

Tokachi-dake's first large eruption since 1962 followed more than two months of gradually increasing seismicity. The number of recorded earthquakes began to build in late September, totaling 43 in October and 93 in November compared to the typical background level of 10-20 events/month (figure 2). Stronger seismicity from 19 November was followed by emission of a 1,200-m white plume on the 22nd from crater 62-2, one of a line of vents formed during the 1962 eruption. Occasional episodes of volcanic tremor, the first in more than a year, had been recorded since 4 October and became more frequent in early December. Eruptive activity followed through most of December.

Figure (see Caption) Figure 2. Monthly recorded earthquakes (top), number of volcanic tremor episodes (middle), and height of highest observed cloud (bottom) at Tokachi, 1965-88. Courtesy of JMA.

Snow darkened by ash was first noticed on 5 December. A gray plume rose 200 m on 10 December and ash again fell near the crater. No gray plumes had been seen since 1962 from JMA's Tokachi-dake Observatory, [5.8] km NW of the crater, although bad weather has often prevented observation, especially in winter when the crater is only visible about once a week. Tremor episodes were more frequent after 11 December. Light gray to gray plumes were again observed 11-12 December. Darkened snow was seen from the air the morning of the 13th, extending ~1 km N from crater 62-2, and Observatory personnel saw a gray to dark gray plume emerging from the crater from about 1430 to 1600 that day.

A vigorous phreatic eruption from crater 62-2 began at roughly 0600 on 16 December. The eruption was preceded by an earthquake at 0524 that was felt at intensity III (JMA scale) in Fukiage, 3 km W of the crater. Volcanic tremor was recorded between 0603 and 0611 but weather clouds obscured the crater and the start time of the eruption remains uncertain. Ash began to fall at Ikeda, 80 km SE of the volcano, at around 0700. A similar sequence began on 18 December at 0838 with an earthquake felt in Fukiage at intensity I, followed by 21 minutes of volcanic tremor. Clouds again obscured the volcano, but ashfall began around 0900 at towns as much as 30 km E of the volcano.

An earthquake on 19 December at 2148 (intensity I in Fukiage) marked the onset of phreatomagmatic activity from crater 62-2 that was accompanied by a long period of high-amplitude volcanic tremor. People near the volcano saw an incandescent column and a dark volcanic cloud. A small mudflow, generated by snowmelt, moved ~600 m down the NW flank, reaching 1,400 m elevation. Yoshio Katsui noted that a pyroclastic surge had melted snow in an area of 500 x 800 m. Although the highest ash cloud seen from the Observatory reached only 300 m, ash reached Abashiri and Kitami on the NE coast of Hokkaido, 150 km from the volcano. Weak volcanic tremor continued intermittently the next day and a light gray to gray plume was rising 200-400 m during the morning. Slight ashfalls were reported to 35 km from the volcano on the 21st and to 15 km 22-23 December. Periods of volcanic tremor continued.

A larger phreatomagmatic eruptive episode began at 2212 on 24 December, accompanied by an earthquake. An incandescent column rose 200 m and the 1-km ash cloud contained lightning. A pyroclastic flow advanced 1 km NW but there was no mud flow and no property was damaged. At 2232, the mayor of Kami-Furano instructed residents of 3 inhabited areas within 15 km W of the crater to evacuate; 2 minutes later, the evacuation of the Shirogane area, 6 km NW, was requested by the mayor of Biei. Population of the four affected areas is about 800. Vigorous eruption resumed at 0049, feeding similar columns of ash and incandescent tephra. JMA Observatory personnel saw a glowing flow descend to the NW. Volcanic tremor was recorded 0049-0315 and 0332-0340. Tremor and emission of a gray plume continued intermittently during the day. Ashfalls extended 80 km SE. A morning overflight revealed a somewhat enlarged 62-2 crater, but other craters and fumarolic areas appeared unchanged. Fieldwork by Katsui and others documented a pyroclastic flow 1 km long with a maximum temperature of 92°C at 50 cm depth, 60 hours after the eruption.

An earthquake at 0527 on 30 December, felt at intensity 1 at Fukiage, marked renewed eruptive activity. Weather clouds prevented observations but ash fell 30 km SE. Evacuation of the Kami-Furano area was cancelled 31 December, but was continued for Shirogane residents. Red glow and ejection of a black cloud were observed from the JMA Observatory on 1 January at 0212. The eruption seemed small and only nearby ashfalls were reported.

Activity resumed briefly on 8 January at 1938. An incandescent column was seen for a short time but weather obscured the volcano from JMA Observatory staff. Ash fell on towns to a few tens of kilometers SW of the volcano but no damage was reported. An earthquake was recorded at the beginning of the 8 January activity, probably an explosion shock of the type common in earlier explosive episodes. Volcanic tremor followed for about 10 minutes, and geologists presumed that the eruption ended as tremor ceased.

Of the three types of JMA official volcano information releases, the most serious (Volcanic Activity Information) is issued when volcanism is considered to be dangerous to people. VAI releases appeared three times during the eruption, all during the 24-25 December activity, while Extra Volcano Information reports were produced 23 times in November and December for activity judged less hazardous.

Geologic Background. Tokachidake volcano consists of a group of dominantly andesitic stratovolcanoes and lava domes arranged on a NE-SW line above a plateau of welded Pleistocene tuffs in central Hokkaido. Numerous explosion craters and cinder cones are located on the upper flanks of the small stratovolcanoes, with the youngest Holocene centers located at the NW end of the chain. Frequent historical eruptions, consisting mostly of mild-to-moderate phreatic explosions, have been recorded since the mid-19th century. Two larger eruptions occurred in 1926 and 1962. Partial cone collapse of the western flank during the 1926 eruption produced a disastrous debris avalanche and mudflow.

Information Contacts: JMA.


Ulawun (Papua New Guinea) — December 1988 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Tremor and B-type events; vapor emission

"During most days in December, the summit crater was covered by clouds. When the weather was clear, moderate to strong white vapour emissions were observed. Seismicity was mainly characterized by bands of low-amplitude, high-frequency, harmonic tremor. The daily average of tremor bands was 8, and the mean total duration was 15 hours/day. The tremor bands were accompanied by B-type volcanic events that increased in number and amplitude during the last week of the month."

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the north coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: H. Patia and P. Lowenstein, RVO.


White Island (New Zealand) — December 1988 Citation iconCite this Report

White Island

New Zealand

37.52°S, 177.18°E; summit elev. 321 m

All times are local (unless otherwise noted)


Minor ash emission; deflation; fumaroles cool

During 2 December fieldwork, geologists observed continued emission of fine red ash from Hitchhiker vent, similar to October and November. Near the vent, ~55 mm of ash had accumulated since 16 November, but only 1-2 mm of new ash had been deposited ~250 m to the SE. No fresh magma was detected in the ash; vesicular scoria fragments were last noted on 14 October. The new fumarole on the W floor of 1978 crater, first seen on 16 November, was emitting a jet of high-pressure white vapor at about a 45° angle. Small fumaroles were also noted for the first time on the floor of the western subcrater, below the 1914 landslide scar.

A deformation survey showed that subsidence had occurred in a broad zone, centered roughly 150 m E of Hitchhiker vent, since the previous measurements on 15 June. Magnetic data showed positive changes exceeding 200 nT in the same general area, interpreted to show significant cooling centered at 100-150 m depth. Temperatures of fumaroles in and near the area of subsidence had dropped substantially since June (Blue Duck, 775°C in June/565° in December; Donald Mound, 420/354°; Noisy Nellie, 280/226°). Seismicity has remained similar since mid-October, characterized by medium- to high-frequency volcanic tremor and microearthquakes. Maximum daily numbers of A-type (4) and B-type (23) events were associated with three small explosion earthquakes on 17-18 October.

Geologic Background. Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes; the summit crater appears to be breached to the SE, because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project.

Information Contacts: J. Cole, Univ of Canterbury, Christchurch; I. Nairn, B. Scott, P. Otway, and D. Christoffel, NZGS Rotorua; B. Christenson, DSIR Chemistry, Wairakei.


Yasur (Vanuatu) — December 1988 Citation iconCite this Report

Yasur

Vanuatu

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

All times are local (unless otherwise noted)


Centuries-long Strombolian eruption continues from four vents

". . . The gas and ash plume discharged from the volcano is carried by the prevailing SE trade winds across the central parts of the island. During 1987 and 1988, vegetation in areas downwind from the volcano has been affected by gas, ash, and acid rain from the plume, causing damage to residents' gardens and coffee plantings in the centre of the island. The volcanic damage added to and accentuated that caused by a succession of three cyclones in 1987-88. Werner Giggenbach, Ian Nairn, and Bradley Scott of the New Zealand DSIR visited Tanna for two weeks in September 1988. The investigation was coordinated and funded by the New Zealand Ministry of Foreign Affairs.

"Although frequently visited by tourists, eruptive activity at Yasur has not been studied in detail since a 1959 seismic study by Blot and Tazieff. Activity between 1959 and 1978 was briefly described by Carney and Macfarlane (New Hebrides Government Geological Survey Regional Report, 1979).

"Explosive eruptions were frequent at Yasur during our 6-14 September observation period, with four vents active in the three main subcraters, and continuous steam emission from a 5th vent high on the W crater wall. This steam vent had formed since the last available aerial photography in September 1986. A gas plume was continuously emitted from a small active lava lake in the central subcrater, with intermittent gas discharges during explosive eruptions from the other three vents. All these gas discharges combined to produce a continuous and voluminous gas plume that extended downwind from the volcano. Discussions with local people, observations made by tourists in past years, and comparisons with published and unpublished photographs have indicated that eruptive activity was at a relatively high level during our inspection, probably with more frequent explosions from more active vents than was usual prior to 1987. The volcanic plume also now appears to be larger and more constant than typical of earlier dry seasons.

"Eruption observations (including video camera recordings) correlated with our seismic recordings have enabled the seismicity to be used as a continuous record of eruptive activity, and provide the only quantitative data on comparative activity and gas discharge. During an inspection in April-May 1959, Blot and Tazieff recorded an average of 5 explosion earthquakes/hour, at a time when Yasur was fairly quiet. During our September 1988 observations, an average rate of 21.5 explosion earthquakes/hour was recorded. Each explosion results from the discharge of volcanic gas, while the high level of recorded volcanic tremor is correlated with the continuous gas discharge through the lava lake. We infer that the gas discharge was considerably higher in September 1988 than in 1959. Many of the explosions occurred as sharp detonations, often preceded by 'flashing arcs' (atmospheric shock waves) visible in the steam and gas haze within the crater, and felt as a sharp slap by observers on the crater rim.

"The present subcraters are deep (estimated at ~250 m below the S crater rim by parallax bar heighting of aerial photographs, and angle/distance measurements to the central lava lake) with near-vertical walls. Although the most violent explosions threw bombs high above the crater rim, these were on near-vertical trajectories, so that nearly all the bombs fell back into the crater.

"During earlier periods of increased eruptive activity, such as in 1975, many bombs were thrown over the crater rim, probably due to a shallower and more gently sloping crater configuration. The frequent explosions now occurring may also be less violent due to greater gas discharge and magma convection rates maintaining higher temperatures, and thus lower viscosities and yield strengths in the uppermost parts of the magma columns. The only bomb observed to be thrown over the crater rim was sampled while still hot, and has a composition similar to that of bombs ejected in 1934 and 1975. This suggests that no major change in magma composition has accompanied the recent volcanic gas damage problems.

"Gas samples collected from the plume crossing Yasur crater rim contained SO2 and HCl gases at concentrations between 3 and 9 ppm. The mass discharge rate of volcanic gases was not measured but our visual comparison of plume size with other volcanoes suggests that the Yasur discharge rate was between 400 and 800 tons/day SO2. This output and gas composition are typical of other volcanoes around the Pacific rim. SO2 and HCl are removed from volcanic plumes by rainout of condensing steam within the plume, rainfall through the plume, and adsorbed onto ash falling from the plume. Studies elsewhere have shown that damage to vegetation is most likely to have resulted from acids dissolved in water, most effectively applied to foliage as light rain or mist and accentuated by the presence of fine ash particles. These mechanisms appear to have caused the vegetation damage.

"Radiocarbon samples collected from Yasur pyroclastic fall deposits downwind . . . suggest that . . . continuous small-scale Strombolian activity has been in progress for the last 800 years, with at least two discrete subplinian scoria fall eruptions occurring between 1,400 and 800 years BP."

References. Blot, C., Chaigneau, M., and Tazieff, H., 1960, Nouvelles-Hebrides (Mars-Mai 1959): BV, v. 23, p. 207-210.

Geology of Tanna, Aneityum, Futuna and Aniwa. 1978: 1:100,000 New Hebrides Geological Survey Sheet 11.

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: I. Nairn, NZGS Rotorua.

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 (SEAN 22:08) False Report of Mount Pinokis Eruption

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (SEAN 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/).