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Bulletin of the Global Volcanism Network

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

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


Recently Published Bulletin Reports

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

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

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

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

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

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

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

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

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

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

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

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



Suwanosejima (Japan) — July 2019 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Small ash plumes continued during January through June 2019

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

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

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

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

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

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

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

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


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

Great Sitkin

United States

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

All times are local (unless otherwise noted)


Small steam explosions in early June 2019

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

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

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

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

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

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/).


Ibu (Indonesia) — July 2019 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


Ebeko (Russia) — July 2019 Citation iconCite this Report

Ebeko

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Klyuchevskoy (Russia) — July 2019 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Yasur (Vanuatu) — June 2019 Citation iconCite this Report

Yasur

Vanuatu

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); The Captain Cook Society (URL: https://www.captaincooksociety.com/home/detail/225-years-ago-july-september-1774); Royal Museums Greenwich (URL: https://collections.rmg.co.uk/collections/objects/13383.html); Wikimedia Commons, (URL: https://commons.wikimedia.org/wiki/File:The_Landing_at_Tana_one_of_the_New_Hebrides,_by_William_Hodges.jpg); Nick Page, Australia,Flickr: (URL: https://www.flickr.com/photos/152585166@N08/).


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

Bagana

Papua New Guinea

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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


Ambae (Vanuatu) — June 2019 Citation iconCite this Report

Ambae

Vanuatu

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

All times are local (unless otherwise noted)


Declining thermal activity and no explosions during February-May 2019

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

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

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

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

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Sangay (Ecuador) — July 2019 Citation iconCite this Report

Sangay

Ecuador

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

Information Contacts: Instituto Geofísico (IG-EPN), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


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

Kadovar

Papua New Guinea

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Tico Liu, Hong Kong (Facebook: https://www.facebook.com/tico.liu. https://www.facebook.com/photo.php?fbid=10155389178192793&set=pcb.10155389178372793&type=3&theater); Shari Kalt (Instagram user LuxuryTravelAdvisor: https://www.instagram.com/luxurytraveladviser/, https://www.instagram.com/p/BkhalnuHu2j/); Coral Expeditions, Australia (URL: https://www.coralexpeditions.com/, Facebook: https://www.facebook.com/coralexpeditions); Philip Stern (Facebook: https://www.facebook.com/sternph, https://www.facebook.com/sternph/posts/2167501866616908); Brad Scott, GNS Science Volcanologist at GNS Science, New Zealand (Twitter: https://twitter.com/Eruptn); Chaiyasit Saengsirirak, Bangkok, Thailand (Facebook: https://www.facebook.com/chaiyasit.saengsirirak, https://www.facebook.com/photo.php?fbid=2197513186969355).


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

Sarychev Peak

Russia

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

All times are local (unless otherwise noted)


Brief ash emission reported on 16 May 2019

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

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

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

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

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

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

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

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


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

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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Bulletin of the Global Volcanism Network - Volume 42, Number 12 (December 2017)

Managing Editor: Edward Venzke

Bogoslof (United States)

Explosions in July and August 2017; new lava dome visible 20-22 August destroyed by explosions that end on 30 August

Cleveland (United States)

Dome growth and destruction multiple times during January-November 2017

Dempo (Indonesia)

Phreatic explosion from the crater lake generates a dense ash plume in November 2017

Pacaya (Guatemala)

Pyroclastic cone in MacKenney crater grows above crater rim, January-September 2017

Sabancaya (Peru)

Continuous pulses of ash emissions for ten months, February-November 2017

Santa Maria (Guatemala)

Slow growth of new lava dome, persistent ash plumes, and nearby ashfall, January-October 2017

Sinabung (Indonesia)

Constant activity through September 2017, with ash plumes, block avalanches, and pyroclastic flows

Tungurahua (Ecuador)

Nearly constant ash emissions and frequent lahars during July-December 2015

Ulawun (Papua New Guinea)

Intermittent ash plumes during June-November 2017

Villarrica (Chile)

Lava lake level fluctuates and Strombolian activity persists during October 2016-November 2017



Bogoslof (United States) — December 2017 Citation iconCite this Report

Bogoslof

United States

53.93°N, 168.03°W; summit elev. 150 m

All times are local (unless otherwise noted)


Explosions in July and August 2017; new lava dome visible 20-22 August destroyed by explosions that end on 30 August

Intermittent eruptions from Bogoslof, 40 km N of the main Aleutian arc (BGVN 42:09, figure 2), have created and destroyed several distinct islands at the summit of this submarine volcano. Previous eruptions in 1927 and 1992 created lava domes that were subsequently heavily eroded, before the most recent eruption began in December 2016 (figure 16). Numerous explosions with ash plumes significantly changed the morphology of the island between December 2016 and March 2017. Ash plumes rose to over 10 km altitude during May-July 2017 multiple times. A lava dome briefly emerged in early June before it was destroyed by subsequent explosions. This report continues with an account of activity between July and December 2017. Eruptive activity ended on 30 August. Information comes primarily from the Alaska Volcano Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC).

Figure (see Caption) Figure 16. Worldview satellite image of Bogoslof collected at 2313 UTC on 12 June 2017, two days after a lava dome that appeared in the lagoon was destroyed. The circular embayments were formed by a series of more than 40 explosions that began in mid-December 2016. These explosions greatly reshaped the island as material was removed and redeposited as air fall. Vigorous steaming was visible from a region S of the most active vent areas in the lagoon. Lava extrusion produced a circular dome that first rose above the water on 5 June and grew to a diameter of ~160 m before being destroyed by an explosion early in the day on 10 June. Courtesy of AVO.

New explosions during 2, 4, 8, and 9-10 July 2017 produced ash plumes that rose from 6.1 to 11 km altitude. Although significant ash clouds were produced, there were no reports of ashfall in nearby communities. After almost a month of quiet, an eruption on 7 August created new tephra deposits, and extended the N shore of the island. This eruption created a significant SO2 plume that was recorded by satellite instruments. Intermittent pulses of tremor were recorded during mid-August. A new lava dome grew between 20 and 22 August to 160 m in diameter before it was destroyed in a series of explosions during 26-30 August. Thermal anomalies were observed in satellite data several times during September, and they tapered off into early October. Steam emissions were still visible in early November when the last weak thermal anomaly was reported. By early December, significant erosion had begun to change the island's shape, and only minor steam emissions were visible in clear satellite images.

Beginning at 1248 local time (AKDT) on 2 July 2017, a significant explosive event was detected in seismic and infrasound data, and observed in satellite imagery. The event lasted about 16 minutes, and produced an ash plume that rose to 11 km altitude and drifted E, passing N of Dutch Harbor. No explosions were reported the following day, but two events were detected in seismic, infrasound, and satellite data on 4 July. The first, at 1651, lasted 13 minutes and produced an eruption cloud that rose to 8.5 km altitude and drifted SE; the second 11-minute-long eruption began at 1907, and produced a small cloud that rose to 9.8 km altitude and drifted SE.

On the morning of 8 July 2017, an eruption with a total duration of 19 minutes began at 1015 AKDT and produced a volcanic cloud reaching an altitude of 9.1 km that drifted N. Overnight during 9-10 July Bogoslof erupted several times; the first two explosions during the 3-hour-long eruption produced a small ash cloud that rose to 6.1 km altitude and drifted SE, dissipating rapidly. Later on 10 July, an 8-minute-long eruption began at 1000 AKDT and a 15-minute-long eruption began at 1706 AKDT; neither produced a significant plume. None of the eruptions on 8, 9, or 10 July caused ashfall in local communities. Weakly elevated surface temperatures were observed in clear satellite images on 12 and 16 July.

Following almost a month of quiet, Bogoslof erupted again on 7 August 2017. The eruption was detected in seismic, infrasound, satellite, and lightning data. The eruption began at 1000 AKDT and lasted for about three hours, producing an ash plume that rose to 9.7 km altitude according to AVO, and drifted S over Umnak Island, then out over the Pacific Ocean. The Anchorage VAAC initially reported the plume at 10.4 km altitude moving S. A later pilot report noted an altitude of 12.2 km. Satellite measurements of sulfur dioxide (SO2) in the eruption cloud indicated the second highest mass of SO2 erupted since the onset of activity in December 2016 (figure 17). Satellite images of the island taken on 8 August showed new tephra deposits had surrounded the vent area, forming a new crater lake, and extending the N shore of the island by 250 m (figure 18).

Figure (see Caption) Figure 17. Although the data is coarsely pixelated, it is clear that a substantial SO2 plume emerged from Bogoslof during the 7 August eruption, as recorded by the OMPS instrument on the Suomio NPP satellite. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 18. Worldview true-color satellite image of Bogoslof acquired on 8 August 2017, one day after a 3-hour-long explosive eruption. Ashfall deposits have expanded the island towards the N as the result of the eruption and formed an enclosed crater lake. At the time of this satellite overpass, the level of the crater lake was below sea level. Previous events such as these (that formed a shallow crater lake) formed a deep crater that was subsequently filled by an influx of ocean water. Vigorous steaming was apparent from the likely site of the initial explosive event in mid-December 2016. Sediment coming from erosion of the island is seen offshore surrounding most of the island. A comparison with figure 16, above, shows the extent of new material added on 7 August. Data provided under the Digital Globe NextView License. Courtesy of AVO.

Several short-duration seismic and infrasound signals were detected at the stations on nearby islands on 9 August 2017. Weakly elevated surface temperatures and a minor steam plume were observed in satellite images. Two short pulses of tremor were seen in seismic data on 14 August, one lasting five minutes and the other lasting three minutes. Seismicity returned to background levels following the pulses and remained quiet until a series of small earthquakes the next morning. Seismicity again returned to background levels by the following afternoon, 16 August, and remained quiet through the rest of that week. Photographs taken during an overflight on 15 August indicated that the vent region, which had dried out during the 7 August eruption, had refilled with water (figure 19).

Figure (see Caption) Figure 19. An overflight of Bogoslof on 15 August 2017 showed the increase in area of the crater lake after the eruption of 7 August (see figure 18). View is to the SE. Courtesy of AVO.

Unrest continued during mid-August 2017, and available data suggested that a lava dome had formed within the intra-island lake just W of the 1992 lava dome. The new dome was first observed on 18 August, and during 20-22 August grew to about 160 m in diameter. Two small explosions were detected in infrasound data at 0410 AKDT on 22 August. These explosions did not produce any volcanic plumes recognizable in satellite data. Elevated surface temperatures were observed on 24 August along with a steam plume extending S about 17 km from the island. Satellite images showed elevated surface temperatures and a robust steam plume the next day drifting 70 km SE. A photo from a nearby low-altitude airplane on 26 August, taken shortly before the next explosion, confirmed the intense steam plume (figure 20) likely caused by the interaction of the new dome with seawater. Two MODVOLC thermal alerts were issued on 25 August, the first two since January 2017, and the last two for the year.

Figure (see Caption) Figure 20. Bogoslof volcano with a vigorous steam plume likely caused by interaction of the new, hot lava dome with seawater. Photo by Dave Withrow (NOAA/Fisheries), taken at about 1300 AKDT on 26 August aboard a NOAA twin otter (N56RF) aircraft while surveying harbor seals west of Dutch Harbor. They were 13 nautical miles (24 km) from Bogoslof when photo was taken looking E with a 400 mm lens. Courtesy of AVO.

An explosive eruption at 1629 AKDT on 26 August 2017 lasted for about four minutes and produced a cloud that was observed in satellite images drifting SE over southern Unalaska Island. Cloud-top temperatures seen in satellite data indicated that it rose as high as 7.3 km altitude. The Anchorage VAAC reported the plume at 8.2 km altitude several hours later. The eruption was observed in seismic, infrasound, and satellite data, and one lightning stroke was detected. Elevated surface temperatures persisted, suggesting to AVO scientists that the lava dome was possibly still present within the crater lake. Three short-duration eruptive events occurred during 27-28 August. On 27 August at 1508 AKDT a brief explosive event lasting about two minutes produced a volcanic cloud that reached about 7.9 km altitude and drifted SE. Another explosive eruption occurred at 0323 AKDT on 28 August and lasted about 25 minutes. Satellite imagery showed only a very small eruption cloud drifting ESE that dissipated quickly. The third event occurred at 1117 AKDT that morning and produced a small ash cloud that likely reached 9 km altitude before dissipating over the North Pacific Ocean. Modeling of ash fallout from the cloud indicated trace to minor ash fall over the Southern Bering Sea in the area just S of the volcano.

Elevated surface temperatures were noted in satellite data on 29 August, along with a steam plume drifting SSE, suggesting to AVO the presence of lava at the surface. An explosive eruption began the next morning at 0405 AKDT and continued intermittently for almost two hours. It produced an ash cloud that reached to about 6 km altitude and drifted SSE, dissipating over the southern Bering Sea and North Pacific Ocean area. A vapor plume extended about 65 km SSE later that day.

AVO reported on 8 September 2017 that available data suggested that the most recent lava dome, first observed on 18 August, was removed by the explosive eruptions of 27-30 August. In addition, a narrow isthmus of new land extended across the crater, bisecting it and creating two lakes. Elevated surface temperatures were recorded in a satellite images on 11, 14, 17, 19, and 23 September. Discolored water was visible in satellite images on 17 September and may have represented outflow from the crater. Elevated surface temperatures continued to be observed in satellite data during periods of clear weather into the first two weeks of October, and again briefly at the beginning of November. Several areas of steam emissions were visible in satellite imagery on 9 October (figure 21).

Figure (see Caption) Figure 21. Worldview-3 satellite image of Bogoslof Island acquired on 9 October 2017. The areas that exhibited active steam emission are highlighted with yellow and black dashed lines. Image data acquired with the Digital Globe NextView License. Courtesy of AVO.

A clear, high-resolution satellite image taken on 2 November showed continued steaming of the ground on the S side of the smaller crater lake. Weakly elevated surface temperatures consistent with a hot crater lake were last observed in clear nighttime satellite images on 10 November 2017. Imagery from 20 November showed warm regions in the crater lagoon and at the site of the steaming that had persisted for several months (see figure 21). AVO scientists noted that this was consistent with a slowly cooling, post-eruptive system, and was likely responsible for the occasional observation of slightly elevated surface temperatures in satellite data. The MIROVA graph of thermal anomalies supported the slow cooling trend observed by AVO after the last explosions on 30 August 2017 (figure 22).

Figure (see Caption) Figure 22. The last series of explosive events recorded at Bogoslof during 26-30 August 2017 coincided with the last significant thermal anomalies on the MIROVA graph (infrared MODIS data) that covers the year ending on 19 January 2018. Gradual tapering of thermal anomalies is consistent with AVO satellite observations of a cooling trend during September through early November. Courtesy of MIROVA.

More than sixty explosive events occurred between 20 December 2016 and 30 August 2017. The most energetic of these sent water-rich, volcanic ash clouds to altitudes exceeding 10.7 km. The resulting dispersed volcanic clouds impacted local and international aviation operations over portions of the North Pacific and Alaska. Although most of the volcanic ash fell into the ocean, trace amounts were twice deposited on the community of Unalaska and the Port of Dutch Harbor. The 2016-17 eruption greatly changed the morphology of Bogoslof Island. At its greatest extent, the area of the island increased to about three times its pre-eruption size. Nearly all of the new material on the island is unconsolidated pyroclastic fall and flow (surge) deposits. The deposits are highly susceptible to wave erosion and additional changes in the configuration of the island are likely. A satellite image from 3 December 2017 shows significant erosion of the island with the vent lagoon opened to the ocean on the north shore of the island (figure 23).

Figure (see Caption) Figure 23. Worldview-3 satellite image of Bogoslof Island on 3 December 2017. Erosion of the island by waves had removed substantial material, and no new eruptive material had been added to the island since the end of August 2017. The approximate area of the island in this image was 1.3 square kilometers. Image data acquired with the Digital Globe NextView License. Courtesy of AVO.

Geologic Background. Bogoslof is the emergent summit of a submarine volcano that lies 40 km north of the main Aleutian arc. It rises 1500 m above the Bering Sea floor. Repeated construction and destruction of lava domes at different locations during historical time has greatly modified the appearance of this "Jack-in-the-Box" volcano and has introduced a confusing nomenclature applied during frequent visits of exploring expeditions. The present triangular-shaped, 0.75 x 2 km island consists of remnants of lava domes emplaced from 1796 to 1992. Castle Rock (Old Bogoslof) is a steep-sided pinnacle that is a remnant of a spine from the 1796 eruption. Fire Island (New Bogoslof), a small island located about 600 m NW of Bogoslof Island, is a remnant of a lava dome that was formed in 1883.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: http://www.avo.alaska.edu/ ), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.dggs.alaska.gov/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845(URL: http://vaac.arh.noaa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Cleveland (United States) — December 2017 Citation iconCite this Report

Cleveland

United States

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

All times are local (unless otherwise noted)


Dome growth and destruction multiple times during January-November 2017

Dome growth and destruction accompanied by small ash explosions has been typical behavior at Alaska's Cleveland volcano in recent years (figures 20, 21, and 22). Located on Chuginadak Island in the Aleutians, slightly over 1,500 km SW of Anchorage, it has historical activity, including three large (VEI 3) eruptions, recorded back to 1893. The Alaska Volcano Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC) are responsible for monitoring activity and notifying air traffic of aviation hazards associated with Cleveland. This report provides a summary table of dome growth and destruction since 2013 (table 8), and details of continued activity from January through November 2017.

Figure (see Caption) Figure 20. A lava dome was growing at the summit of Cleveland on 4 August 2015. Concentric rings and radial fractures in the dome surface surrounded an elevated hot dome. Photo taken during the 2015 field season of the Islands of Four Mountains multidisciplinary project, work funded by the National Science Foundation, the USGS/AVO, and the Keck Geology Consortium. Courtesy of AVO.
Figure (see Caption) Figure 21. A 60-m-diameter lava dome was seen in this WorldView-1 satellite image from 25 May 2016 of Cleveland's summit crater. Image created by Rick Wessels, USGS. Image data copyright 2016 Digital Globe, NextView License. Courtesy of AVO.
Figure (see Caption) Figure 22. Thermal and photographic images of the lava dome that was growing in the summit crater of Cleveland on 26 July 2016. Top image is from a FLIR (Forward Looking InfraRed) camera, where warmer colors indicate hotter temperatures (scale is in Celsius); bottom image is a photograph of the summit crater, lava dome, and active fumaroles. AVO crew observed incandescence from the summit crater vent during this overflight. Courtesy of AVO.

Table 8. Observations of dome growth and other crater activity at Cleveland, 2013-2017. Data extracted from AVO reports.

Date Dome Observations
Jan-Feb 2013 New lava flow observed multiple times, 100 m across
4-6 May 2013 Explosions, ash cloud
 
Jun-Jul 2013 Elevated temperatures, satellite imagery
2-5 Oct 2013 Explosions
 
13 Nov 2013 Elevated surface temperatures near summit
25 Nov 2013 Explosion
 
28 Dec 2013 Strongly elevated surface temperature near summit
30 Dec 2013, 2 Jan 2014 Small ash cloud visible; explosion with ash plume
 
Jan-25 Feb 2014 Elevated surface temperatures near summit multiple times
25 Feb 2014 Two small explosions and ash clouds
 
7 Mar-4 Jun 2014 No detected activity
5 Jun 2014 Explosion
 
7 Jul 2014-Aug 2014 Intermittent weakly elevated surface temperatures at summit, vigorous steam plume, incandescence at summit during field visit
Late Aug-early Sep 2014 Elevated surface temperatures in satellite data
14, 24 Nov 2014 Vigorous steaming observed in webcam; Satellite image shows small lava dome in summit crater
5 Dec 2014-9 Jan 2015 Minor steaming and weakly elevated surface temperatures at summit
25, 28 Feb 2015 Weakly elevated surface temperatures at summit, low level steam plume observed
26 Mar 2015 Small steam plume, no further activity until 14 June
14 Jun 2015 Ash cover on upper flanks
 
17 Jun-21 Jul 2015 Elevated surface temperatures at summit
21 Jul 2015 Explosion
 
31 Jul, 4 Aug 2015 Strongly elevated surface temperatures at summit, photograph (figure 20) of lava dome in summit crater
6 Aug 2015 Small explosion
 
Aug-Oct 2015 Intermittent elevated surface temperatures at summit
29 Aug 2015 Seismic swarm
Sep-Nov 2015 No Reported Activity
Dec 2015 Elevated surface temperatures at summit
22-23 Dec 2015 Increased frequency of small VT events
 
Jan 2016 Elevated surface temperatures at summit
28 Feb 2016 Brief burst of small local earthquakes
 
Mar-1 April 2016 Elevated surface temperatures at summit
16 April 2016 Explosion
 
6 and 10 May 2016 Explosions
 
17-25 May 2016 Small lava dome observed (figure 21)
Jun-Jul 2016 Elevated surface temperatures at summit
26 Jul 2016 Lava dome observed (figure 22)
Aug-21 Oct 2016 Intermittent degassing, steam plumes, and elevated surface temperatures at summit
24, 28 Oct 2016 Explosion, ashfall observed
 
5 Nov 2016-23 Mar 2017 Elevated surface temperatures and intermittent steam emissions at summit. 3 Feb 2017 Satellite observation of lava dome
24 Mar 2017 Small explosion
 
Late Mar -15 May 2017 Elevated surface temperatures at summit crater; Dome observed 15 April
16 May 2017 Explosion
 
6-29 Jun 2017 Small, low-frequency earthquakes on 6 Jun, elevated surface temperatures at summit crater several times during June
4 Jul 2017 Explosion
 
7 Jul-21 Aug 2017 Elevated surface temperatures at summit crater; satellite (July 14-21) and photographic (July 25-26) observations of lava dome at summit (figure 23)
22 Aug 2017 Explosion
 
Late Aug-24 Sep 2017 Sporadic observations of elevated surface temperatures at summit crater
26, 28 Sep 2017 Explosions
 
28 Sep-Oct 2017 Elevated surface temperature at crater; lava effusion observed throughout October
28, 30 Oct 2017 Explosions
 
Early Nov 2017 Elevated surface temperatures at crater
14, 16 Nov 2017 Explosions

Lava dome extrusion may have been ongoing since early December 2016, when weakly elevated surface temperatures reappeared after the 24 October 2016 explosion. The lava dome was first observed in satellite imagery on 3 February 2017. Elevated surface temperatures were recorded throughout February and March 2017, and there was a small explosion on 24 March. Growth of a new dome was first observed on 15 April; it continued until being destroyed by an explosion on 16 May. Seismic data on 6 June and elevated temperatures on 7 June indicated growth of another dome, which continued until an explosion on 4 July 2017. There were multiple satellite and photographic observations of the growing dome during July and August; it was destroyed in an explosion on 22 August. Elevated surface temperatures were sporadically observed in early September. The next explosion took place on 26 September followed by two weaker ones on 28 September. Lava effusion was observed in satellite imagery throughout October. Small explosions on 28 and 30 October partly destroyed the lava dome. Elevated surface temperatures were recorded in early November along with small explosions on 14 and 16 November.

Activity during January-April 2017. While no activity was detected in infrasound or seismic data during January 2017, weakly elevated surface temperatures continued to be observed in infrequent clear satellite views (8 and 9 January), just as they were during 8-10 December and in infrared thermal data at the end of December (BGVN 42:04, figure 19). Low-level steam plumes were seen in clear views of the summit from the webcam during 15-19 and 21 January. Moderately elevated surface temperatures were observed in satellite data on 31 January 2017.

Satellite observations on 3 February 2017 confirmed the presence of a new lava dome at the bottom of the summit crater. The dome was about 70 m in diameter at that time, similar in size to previous domes. Observations in satellite imagery of weakly elevated surface temperatures at the summit continued during 7-9 February and during the last few days of the month. Minor steaming was seen in clear webcam images on 8 February. AVO noted that these observations were consistent with the presence of an active lava dome.

Minor steaming from the summit visible in clear webcam views, and slightly elevated surface temperatures in nighttime infrared satellite images, were present on several days during the first half of March. By the third week, surface temperatures were weakly to moderately elevated. At 0815 AKST (1615 UTC) on 24 March, a small explosion was detected in both seismic and infrasound (pressure sensor) data. This event was short-lived and similar to, if not smaller than, recent explosions. Cloud cover obscured observations by satellite. Slightly elevated surface temperatures were observed at the summit again during the last week of March.

No significant activity was detected in seismic, infrasound, or satellite data during the first two weeks of April 2017. A satellite image on 15 April, however, showed the presence of a small (less than 10-m-diameter) mound deep in the crater; the previous 75-m-diameter lava dome had been destroyed by the 24 March explosion. Satellite observations over the next several days indicated continued dome growth. Slightly elevated surface temperatures again appeared in a satellite view on 18 April. A satellite image on 23 April showed the dome partially filling the crater.

Activity during May-August 2017. Satellite images on 2 May showed that the lava dome was still active and had grown from about 15 m to more than 20 m in diameter. No further surface changes were evident on 8 May, indicating a pause or termination to the lava effusion. A short explosive eruption on 16 May at 1917 AKDT (17 May at 0317 UTC) was detected by local seismic instruments and lasted about 11 minutes. The resulting ash cloud rose to around 3.7-4.6 km altitude and was seen in satellite images to drift SW for about 5 hours. Satellite observations in the following days showed that the lava dome, built after the 24 March explosion, had been completely destroyed. Occasional clear webcam views showed steam emissions in the week following the 16 May explosion. Satellite imagery from 25 May suggested possible elevated surface temperatures at the summit while images from 26 May showed no change in the crater morphology since 16 May. No significant activity was detected in seismic or infrasound data for the remainder of May.

Evidence of possible lava effusion within the summit crater next appeared during the first week of June 2017. Small low-frequency earthquakes were detected on 6 June and elevated surface temperatures were observed in night-time satellite images on 7 June. Weakly elevated surface temperatures were observed in satellite images on 13, 19-23, and 29 June, and occasional clear webcam views of the summit showed light steaming. No activity was observed in seismic or infrasound data during the remainder of June.

A moderate explosive eruption lasting about ten minutes occurred early on the morning of 4 July at 0319 AKDT (1119 UTC). Elevated surface temperatures at the summit were visible after that on 7 and 14 July in satellite images, and occasional clear webcam views of the summit showed minor steaming. Satellite observations during 14-21 July revealed that a new dome, about 30 m in diameter and 10 m in height, had appeared at the bottom of the summit crater. Elevated surface temperatures were again observed on 22-24 July. New satellite observations between 21 and 28 July showed that the lava dome had reached about 42 m in diameter, with a slight inflation of its approximate height of 10 m. Minor steaming from the crater was seen in the webcam on 25 and 29-30 July; elevated surface temperatures were identified in satellite data on 30 July and 1 August. No activity was observed in seismic or infrasound data after the 4 July explosion for the remainder of the month.

Slow growth of the lava dome in the summit crater continued during the first few days of August 2017. Satellite observations showed that the dome surface area increased by about 75%, and covered an area of approximately 2,100 m2 (45 x 50 m) by 4 August. The height of the dome also increased due to intrusion of new lava. Elevated surface temperatures were observed in satellite data along with steam emissions from the summit crater seen in webcam images during periods of clear weather for the first few days of August, and again during 7-8 August. The small lava dome was observed during an overflight on 17 August (figure 23).

Figure (see Caption) Figure 23. A small lava dome grew inside the summit crater of Cleveland on 17 August 2017. Photo by Janet Schaefer, courtesy of AVO/ADGGS (Alaska Volcano Observatory/Alaska Division of Geological & Geophysical Surveys).

Minor degassing from the summit was seen in satellite and webcam images during 20-21 August. No explosive (ash-producing) activity was detected in seismic, infrasound, or webcam data in August until a 1-minute-long explosion on 22 August 2017 at 1043 AKDT (1843 UTC). Satellite data from 24 August indicated that the explosion destroyed the lava flow on the crater floor that had effused during July-August 2017. Explosion debris was evident on the crater floor, but no other changes to the summit area or flanks were noted. The 22 August explosion was detected by seismic and infrasound (air pressure) sensors, but no ash clouds were seen in satellite data. Nothing unusual was detected in seismic, infrasound, or satellite data for the remainder of August, except that elevated surface temperatures were observed sporadically in satellite data, suggesting that lava was present within the crater. A weak vapor plume was also sometimes visible at the summit in webcam images.

Activity during September-November 2017. Weakly elevated surface temperatures were observed in satellite data on 5 and 14 September 2017, along with minor steaming reported on 11, 17-19, and 22-24 September. These observations suggested to AVO the continued presence of lava in the crater. A small, short (three-minute-long) explosion was detected on local seismic and infrasound sensors at 1747 AKDT on 25 September (0147 on 26 September UTC) that produced a small volcanic cloud visible in satellite data about 30 minutes later with a height estimated at below 4.6 km altitude. Two weaker explosions were subsequently detected in infrasound and seismic data on 28 September (0516 and 0558 AKDT, 1319 and 1358 UTC), although no visible ash clouds were associated with these events. Weakly elevated surface temperatures during 28-30 September suggested that lava was present in the summit crater; a weak plume emanating from the crater could be seen when the summit was cloud-free.

Lava effusion in the crater was again noted in satellite data beginning on 30 September, forming a low dome that covered an area of about 4,200 m2 by 1 October 2017. Low-resolution satellite data from 6 October showed highly elevated surface temperatures, suggesting that slow growth of the dome continued. The dome doubled in size between 1 and 11 October when it appeared to cover an area of about 8,300 m2 and had approximate dimensions of 95 x 115 m. The number and intensity of elevated surface temperatures seen in satellite imagery declined during 7-13 October.

Satellite data from 15 October showed that the lava dome covered an area of about 9,500 m2 with dimensions of 100 x 125 m. There was no significant change in the size of the lava dome between 15 and 19 October based on satellite image analysis. On 16 October, satellite imagery revealed moderately elevated surface temperatures, and the webcam provided views of a small steam plume. Satellite data showed that the lava dome had grown further to about 110 x 140 m by 23 October and that surface temperatures were moderately elevated on 22 and 24 October. Small steam plumes were seen in webcam views during 22- 24 October. Small explosions on 28 and 30 October partly destroyed the dome within the summit crater. This was followed by slightly to moderately elevated surface temperatures occasionally observed in satellite imagery through the end of the month.

Moderately elevated surface temperatures were consistently observed in satellite imagery throughout the first half of November, suggesting new lava at or near the surface. Seismic and infrasound sensors detected a signal associated with low-level emissions shortly after midnight on 12 November. Two small explosions were also detected by the sensors on 14 and 16 November. These events were less energetic than those seen previously, and no volcanic cloud was observed following either explosion. A number of small earthquakes were detected on 14 November. Satellite observations of the summit indicated that a dome remained in the crater, and that the explosions were sourced from a vent in the middle of the dome. The satellite data showed no significant changes for the second half of November; although the volcano was obscured by cloud cover much of the time.

The infrared MIROVA thermal data for 2017 provided evidence that generally coincided with the satellite thermal observations of persistent heat production from dome growth throughout the year (figure 24).

Figure (see Caption) Figure 24. Infrared MODIS satellite data plotted with the MIROVA system shows intermittent thermal pulses from Cleveland for the year ending on 18 January 2018. Many of the spikes in thermal energy correspond to periods of satellite and photographic observation of dome growth. Courtesy of MIROVA.

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

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.dggs.alaska.gov/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845 USA (URL: http://vaac.arh.noaa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Dempo (Indonesia) — December 2017 Citation iconCite this Report

Dempo

Indonesia

4.016°S, 103.121°E; summit elev. 3142 m

All times are local (unless otherwise noted)


Phreatic explosion from the crater lake generates a dense ash plume in November 2017

Activity at Dempo on Sumatra in recent years has consisted of brief phreatic eruptions, most recently single-day events on 25 September 2006 (BGVN 34:03) and 1 January 2009 (BGVN 34:01). There were no additional reports from the Center of Volcanology and Geological Hazard Mitigation (CVGHM), also known as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), until a brief episode of unrest in late April 2015, Another typically short phreatic explosion took place on 9 November 2017.

Activity during 2015. On 29 April the Alert Level was raised to 2 (on a scale of 1-4) by PVMBG following observations of diffuse white-gray plumes on 27 April rising to 50 m above the crater. Seismicity had increased during April compared to the previous month (figure 5). A Detik news report on 30 April quoted the PVMBG Head of the Western Volcano Field of Observation and Investigation, Hendra Gunawan, as saying that there had been tremor recorded over the previous four days. No ashfall was reported by PVMBG, and a phreatic eruption was only mentioned in the 29 April notice as a potential danger.

Figure (see Caption) Figure 5. Seismicity recorded at Dempo from 1 January to 29 April 2015. The types of earthquakes reported are HBS (Hembusan, puff or emission events), Trm (tremor), VB (shallow volcanic type B), VA (volcanic type A), TL (local tectonic), and TJ (distant tectonic). Courtesy of PVMBG.

Observers reported that during 1 June-9 September 2015 no plumes were seen and seismicity was low. On 10 September PVMBG lowered the Alert Level to 1.

Activity during 2017. Staff at the PVMBG Dempo observation post reported that no plumes rose from the crater during January and February 2017, but some diffuse white plumes during 1 March-4 April rose no higher than 50 m. Seismicity increased significantly above background levels from 21 March to 4 April (figure 5). On 5 April PVMBG raised the Alert Level to 2 based on visual and seismic data, but did not report any phreatic eruptions.

Figure (see Caption) Figure 6. Seismicity recorded at Dempo from 31 December 2016 to 6 April 2017. The types of earthquakes reported are HBS (Hembusan, puff or emission events), TRE (tremor), VB (shallow volcanic type B), VA (volcanic type A), TL (local tectonic), and TJ (distant tectonic). Courtesy of PVMBG.

According to PVMBG a three-minute-long phreatic eruption began at 1651 on 9 November 2017 and generated a dense ash plume that rose to 4.2 km altitude, about 1 km above the crater rim, and drifted S. Ashfall and sulfur gases were reported in villages on the S flanks, but there was no damage to property or injuries. The Alert Level remained at 2, with a 3-km-diameter exclusion zone; the Aviation Color Code was at Yellow.

Geologic Background. Dempo is a prominent stratovolcano that rises above the Pasumah Plain of SE Sumatra. The andesitic volcanic complex has two main peaks, Gunung Dempo and Gunung Marapi, constructed near the SE rim of a 3 x 5 km caldera breached to the north. The Dempo peak is slightly lower, and lies at the SE end of the summit complex. The taller Marapi cone was constructed within a crater cutting the older Gunung Dempo edifice. Remnants of seven craters are found at or near the summit, with volcanism migrating WNW over time. The large, 800 x 1100 m wide historically active crater cuts the NW side of the Marapi cone and contains a 400-m-wide lake located at the far NW end of the crater complex. Historical eruptions have been restricted to small-to-moderate explosive activity that produced ashfall near the volcano.

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/); Detiknews (URL: https://news.detik.com/).


Pacaya (Guatemala) — December 2017 Citation iconCite this Report

Pacaya

Guatemala

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

All times are local (unless otherwise noted)


Pyroclastic cone in MacKenney crater grows above crater rim, January-September 2017

Activity since 1961 at Pacaya has been characterized by extensive lava flows, bomb-laden Strombolian explosions, and ash plumes emerging from MacKenney crater and several vent fissures, impacting communities in the vicinity; several million people live within 50 km. After a few months of quiet, intermittent ash plumes and incandescence in early June 2015 marked the beginning of the latest eruptive episode, which has been ongoing since that time. Observations of incandescence increased during the second half of 2015, and the presence of a new pyroclastic cone, about 15 m in diameter at the center of MacKenney crater, was confirmed in mid-December 2015.

Strombolian activity from the cone continued throughout 2016. It was most active during June and July, depositing new ejecta onto the flanks. Although it had quieted down by the end of the year, persistent degassing, steam plumes, and occasional incandescence were still observed from the new cone. It had filled much of the crater by December 2016. This report describes the continued growth of the pyroclastic cone during January-September 2017, as well as new lava flows that emerged during February and March. Information was provided primarily by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH) and satellite thermal data.

The pyroclastic cone inside MacKenney crater continued to grow sporadically during January-September 2017. Weak explosions in January produced ejecta 15 m above the top of the cone as steam and gas emissions rose about 400 m above the crater rim. By early February the top of the cone had risen to 10 m above the crater rim. Ejecta ranging in size from millimeters to 50 cm rose up to 25 m above the cone. Three small lava flows emerged from the crater in early February and flowed down the NW flank a few hundred meters before cooling. Growth of the cone continued more slowly during March-August, but incandescence was still observed, and weak explosions deposited tephra around the sides of the cone. Increased explosive activity during August reduced the height of the cone to slightly below the crater rim, but renewed explosions during September built it back up again to 10 m above the rim a few weeks later.

During January 2017, activity increased slightly compared with December 2016, and included degassing, tremors, incandescence, and weak explosions from MacKenney crater. Steam-and-gas plumes rose to around 400 m above the crater rim and generally drifted about 5 km before dissipating. Incandescence in the crater grew more visible towards the end of the month; ejecta from the pyroclastic cone within crater rose as much as 15 m above the crater rim. Seismic RSAM values also increased from a maximum of 2,500 to 3,500 units. The first MODVOLC thermal alert since 10 April 2016 appeared on 10 January 2017. Eight more alerts appeared during January, every few days for the rest of the month.

Degassing during February 2017 sent plumes slightly higher to 500 m above the crater . The top of the pyroclastic cone had risen to about 10 m above the crater rim by early February, as compared to about 10 m below the crater rim a year earlier in February 2016 (figure 78). Ejecta from the cone ranged in size from millimeters to 50 cm, and rose to heights of 10-25 m above the top of the cone with constant activity (figure 79).

Figure (see Caption) Figure 78. The pyroclastic cone inside MacKenney Crater at Pacaya grew substantially between February 2016 (upper photo) and 2 February 2017 (lower photo). View is to the NW with the 2010 fissure at the back, right side of the crater. Courtesy of INSIVUMEH (Reporte mensual, febrero 2017; Informe mensual de la actividad del Volcán Pacaya, junio 2017).
Figure (see Caption) Figure 79. Ejecta from the top of the pyroclastic cone inside MacKenney crater at Pacaya ranged in size from millimeters to approximately 50 cm, and was thrown tens of meters from the summit on 2 February 2017. Courtesy of INSIVUMEH (Reporte mensual, febrero 2017).

Three small lava flows were reported during February 2017, first emerging from the NW side of the crater from the fissure created during 2010 on 9 February 2017 and flowing NW towards Cerro Chino. Incandescent material was ejected 30-50 m above the crater rim and filled much of the crater. Lava travelled as far as 300 m down the NW flank. The dimensions of the flows were variable, but by the end of the month they were about 50 m long and 20 m wide. Ten MODVOLC thermal alerts were issued during February, indicating that activity was high inside and around the summit crater.

Steam plumes during March and April 2017 rose as high as 600 m above the crater rim. Lava flowed tens of meters outside the crater rim a few times at the end of March. The growth of the pyroclastic cone continued with Strombolian explosions of 10-25 m above the top of the cone during this time, and incandescence visible on clear nights. It was possible to see the new cone above the crater rim from the NW and W flanks (figure 80). Rumblings from the explosive activity were reported within 5 km of the cone. Although the three MODVOLC thermal alerts issued during the first week of March were the last through at least September 2017, weak explosions and nighttime incandescence continued during May as the pyroclastic cone continued to grow.

Figure (see Caption) Figure 80. The top of the new pyroclastic cone inside MacKenney crater at Pacaya was visible from the edge of nearby Cerro Chino crater, about 1 km NW, beginning in February 2017. Courtesy of INSIVUMEH (Reporte mensual, febrero 2017).

By June 2017, the steam plumes were rising about 800 m above the crater rim. The height of the pyroclastic cone remained at about 10 m above the crater rim, but continued to grow in volume and produce abundant steam and gas (figure 81). Similar emissions were reported during July, however, incandescence was only occasionally observed at night.

Figure (see Caption) Figure 81. Abundant steam and gas emerged from the upper part of the pyroclastic cone inside MacKenney crater at Pacaya on 17 June 2017. The dome rose height remained at about 10 m above the crater rim, shown in the lower left foreground. Courtesy of INSIVUMEH (Informe mensual de la actividad del Volcán Pacaya, junio 2017).

INSIVUMEH reported increased activity during August 2017 with the frequency of Strombolian explosions increasing to 5-7 per hour, and higher RSAM units recorded to 4,000; some material was ejected as high as 75 m above the crater rim, generating block avalanches as far as 100 m down the W flank. Explosions during 11 August reduced the height of the pyroclastic cone inside the crater such that it was no longer visible from the flank. Moderate to strong explosions were recorded a number of times during the month (figure 82).

Figure (see Caption) Figure 82. A thermal image of MacKenney crater at Pacaya on 18 August 2017 shows Strombolian activity at the summit. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Pacaya, Semana del 19-25 de Agosto de 2017).

Seismic and explosive activity remained high during September 2017. Two significant events were recorded. On 5 September RSAM values peaked at 5,000 units and remained elevated for about six hours before dropping back to average values around 2,000. This corresponded with a period of rebuilding of the pyroclastic cone within the crater. INSIVUMEH reported Strombolian explosions ejecting material as high as 100 m above the crater rim during 21-22 September. The second event lasted for about three days during 23 and 26 September when there was an increase in the rate of explosions, registering up to 40 per hour. After destruction of part of the cone during August, it was rebuilt to a level about 10 m above the crater rim again during this time.

Infrared thermal data generally agrees well with observations of increased activity and lava flows during January-March 2017 (figure 83). However, reports from INSIVUMEH indicate that explosive activity continued at the pyroclastic cone during April-September, although only the largest events during August and September created thermal signals that were captured in the MIROVA data.

Figure (see Caption) Figure 83. MIROVA graph of infrared MODIS data for the year ending on 15 October 2017 at Pacaya shows the thermal signature associated with lava flows and explosive activity during January through March 2017. Although increased explosive activity was reported in August and September, the thermal signal was much smaller. Courtesy of MIROVA.

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Sabancaya (Peru) — December 2017 Citation iconCite this Report

Sabancaya

Peru

15.787°S, 71.857°W; summit elev. 5960 m

All times are local (unless otherwise noted)


Continuous pulses of ash emissions for ten months, February-November 2017

Activity that began in 1986 at Sabancaya was the first recorded in over 200 years. During the last period of substantial ash eruptions between 1990 and 1998 ashfall deposits up to 4 cm thick were reported 8 km E of the volcano. Intermittent seismic unrest and fumarolic emissions characterized activity from late 2012 through October 2016, with a few possible minor ash emissions unconfirmed during this period, and probable SO2 plumes.

Hybrid seismic events, related to the movement of magma, and SO2 emissions increased noticeably during September and October 2016. An explosive eruption period with numerous ash plumes began on 6 November 2016 and has continued throughout 2017. Continuous ash emissions with plume heights exceeding 10 km altitude were often recorded through February 2017. Thermal anomalies were first measured in satellite data in early November 2016, along with numerous significant SO2 plumes (BGVN 42:05). Details of the continuing eruptive activity at Sabancaya from February-November 2017 are discussed in this report with information from the two Peruvian observatories that monitor the volcano: Instituto Geofisico del Peru - Observatoria Vulcanologico del Sur (IGP-OVS), and Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico) (OVI-INGEMMET). Aviation reports and notices come from the Buenos Aires Volcanic Ash Advisory Center (VAAC), and satellite data is reported from several sources.

Images from December 2016. An expedition to Sabancaya during 9-18 December 2016 by photographer Martin Rietze recorded numerous ash emissions and the impacts of the ongoing eruption on the region (figures 31-36). Similar activity continued throughout 2017.

Figure (see Caption) Figure 31. Gas and a dense ash plume rose above Sabancaya during 12-15 December 2016 in this view taken 6.5 km NNE of the volcano. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 32. A column of ash drifted E from Sabancaya during 12-15 December 2016 while a cloud cap condensed on top of the plume. Image taken from 6.5 km NNE of the summit. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 33. An ash plume fanned out to the E from Sabancaya during 12-15 December 2016. Image taken from 15 km E. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 34. Sabancaya lies in the saddle between the older volcanic complexes of Ampato to the S (left) and Hualca Hualca to the N (right) in this view taken from 15 km E. It is the only one of the three to have erupted during the Holocene. An ash plume rose from Sabancaya during 12-15 December 2016, while ash from an earlier pulse is visible drifting S over Ampato. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 35. Trace amounts of ashfall from Sabancaya covered the region 10 km W of the volcano during 12-15 December 2016. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 36. An ash-and-steam plume rose vertically from Sabancaya during 12-15 December 2016 while a meteor streaked across the nighttime sky in this image taken 6.5 km NNE of the summit. Photo copyright by Martin Rietze, used with permission.

Summary of activity, February-November 2017. The persistent eruptive activity during February-November 2017 can be visualized by the continuous MIROVA plot of Log Radiative Power during this time (figure 37). The Buenos Aires VAAC issued 1,174 VAAC reports for Sabancaya during February-November 2017, with over 100 recorded each month (table 1). Tens of explosions were reported daily by OVI-INGEMMET and IGP-OVS throughout the period. Ash plumes usually rose to the 9-11 km altitude range (3,000-5,000 m above the summit), and drifted 30-50 km in many directions before dissipating. MODVOLC thermal alerts were reported between 2 and 16 times every month, and satellite data registered SO2 plumes with values greater than two Dobson Units multiple days each month (figure 38).

Figure (see Caption) Figure 37. MODIS infrared satellite data plotted by MIROVA for the 12 months ending 19 January 2018 show the continuous signature of thermal activity from Sabancaya during that time. Courtesy of MIROVA.

Table 1. Eruptive activity at Sabancaya, February-November 2017. Compiled using data from IGP-OVS/OVI-INGEMMET reports, the Buenos Aires VAAC, HIGP, and NASA GSFC.

Month VAAC Reports Avg Daily Explosions by week Max Plume Heights (m above crater) Plume Drift MODVOLC Alerts Days with SO2 over 2 DU
Feb 2017 108 58, 23, 19, 42 3,000-4,300 40 km, NW, N, S, SE, SW 6 12
Mar 2017 122 44, 36, 36, 37, 41 2,500-4,800 30-40 km, S, NW, SW, N 4 8
Apr 2017 113 27, 37, 36, 33 3,000-3,200 40 km NW, NE, SE, W, N 16 11
May 2017 117 41, 38, 39, 41 2,800-4,200 30-40 km NE, E, SE 4 3
Jun 2017 104 47, 31, 26, 15, 5 1,500-3,700 30-40 km E, SE, SW, S 4 5
Jul 2017 127 10, 19, 24, 40 3,500-5,500 40-50 km NW, S, E, N, SE 2 13
Aug 2017 124 65, 41, 46, 44 3,200-4,200 30-50 km N, SE, NW, S 12 10
Sep 2017 118 38, 29, 45, 45 2,500-3,500 30-40 km SE, E, NE 6 5
Oct 2017 120 42, 41, 47, 43 3,100-3,900 35-60 N, NW, W, S, SE, NE, E 9 8
Nov 2017 121 57, 66, 82, 78, 69 3,300-4,200 40-50 km N, NE, E, SE, NW, SW 11 10
Figure (see Caption) Figure 38. Numerous significant SO2 plumes were captured by the OMI instrument on the Aura satellite for Sabancaya during February-November 2017. Plumes drifted SSE on 4 March, 22 March, 30 July, and 6 August 2017 (top four images), and SW and W on 9 October and 10 November 2017 (bottom two images). The red pixels indicate values of Dobson Units (DU) greater than 2. Courtesy of NASA Goddard Space Flight Center.

Activity during February-November 2017. IGP-OVS and OVI-INGEMMET monitor seismicity, inflation and deflation, SO2 emissions, and visual activity with webcams from several locations around Sabancaya (figure 39). Ash plumes during February 2017 rose to heights of 3,000-4,300 m above the summit (figure 40). The average number of daily explosions decreased from 53 the first week to 19 the third week, and then increased to 42 during the last week. Ash plumes drifted up to 40 km in numerous directions.

Figure (see Caption) Figure 39. Stations where IGP-OVS and OVI-INGEMMET monitor seismicity (red), inflation and deflation (green), SO2 emissions (orange), and their webcam locations (yellow) for Sabancaya. Courtesy of IGP-OVS and OVI-INGEMMET weekly reports.
Figure (see Caption) Figure 40. Ash emission from Sabancaya, 12 February 2017. View from the OVI-INGEMMET webcam located near Coporaque, about 30 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 06 al 12 de febrero de 2017).

During March 2017 the number of daily explosions was very consistent averaging each week between 36 and 44 events. Maximum ash plume heights ranged from 2,500 to 4,800 m and drifted 30-40 km to either the NW or SW (figure 41). Ash fell in Pinchollo (20 km N) and Cabanaconde (22 km NW) during the last few days of the month.

Figure (see Caption) Figure 41. Ash emission from Sabancaya, 12 March 2017. Taken from OVI-INGEMMET webcam located about 4 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 06 al 12 de marzo de 2017).

Ash fell during the first week of April in Pinchollo, Maca (20 km NE) and Chivay (32 km NE). Plume heights during the month were slightly lower, ranging from 3,000-3,200 m and drifted 40 km in several directions. The frequency of daily explosions decreased slightly from March to an average each week ranging from 27 to37. The Buenos Aires VAAC reported that diffuse ash plumes drifted 100 km E on 9 April.

The frequency of daily explosions increased slightly during May; weekly averages ranged from 38 to 41. Plume heights were somewhat higher, at 2,800-4,200 m, and drifted 30-40 km in many directions (figure 42). There was a notable decrease during June 2017 in the number of daily explosions from an average during the first week of 47 to an average of only five at the end of the month. Deflation was observed in the GPS data after 21 June. Plume heights ranged from 1,500 to 3,700 m.

Figure (see Caption) Figure 42. On 20 May 2017 the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image of repeated puffs of ash rising from Sabancaya and drifting E. Courtesy of NASA Earth Observatory.

Activity increased steadily during July 2017. Daily explosions rose from an average of 10 during the first week to 40 the last week; ash plume heights were up to 5,000 m during those weeks (figures 43, 44) and drifted 50 km or more generally NW and SE. Ash plumes during the third week affected communities N of the volcano, including the villages of Cabanaconde, Pinchollo, Lari (20 km NE), Madrigal (20 km NE), Ichupampa (23 km NE), Maca and Achoma (21 km NE). Winds changed to the S on 22 July, so ashfall then affected Lluta (30 km SW), Huanca (75 km SSE), and some parts of Arequipa (80 km SSE).

Figure (see Caption) Figure 43. Ash and gas emission from Sabancaya rose several kilometers above the summit on 9 July 2017 in this OVI-INGEMMET image from their webcam located near Coporaque, about 30 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 03 al 09 de julio de 2017).
Figure (see Caption) Figure 44. On 26 July 2017, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured this natural-color image of an ash plume drifting E from Sabancaya. The rising ash cast a shadow on the ground below. Courtesy of NASA Earth Observatory.

After averaging 65 explosions per day during the first week of August 2017, activity declined slightly to weekly averages of 41-46 explosions per day for the rest of the month. Plume heights ranged from 3,200 to 4,200 m and drifted generally 30-50 km NW or SE. During September 2017 activity was much the same. Plume heights ranged from 2,500-3,500 m, and drifted 30-40 km SE or NE. The weekly averages of daily explosion frequency varied between 29 and 45 events.

A noteworthy difference in activity occurred during October 2017, when there were tremors with ash emissions lasting for more than three hours per day during the last two weeks of the month. Daily explosion frequency averaged from 41 to 47 each week, and plume heights ranged from 3,100 to 3,900 m (figure 45). A few plumes drifted as far as 60 km during the third week of the month.

Figure (see Caption) Figure 45. A large ash and gas plume rose from Sabancaya on 21 October 2017 in this view from the OVI-INGEMMET webcam located near Coporaque, about 30 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 16 al 22 de octubre de 2017).

During November 2017 the number of daily explosions increased from an average of 57 the first week to 82 by the third week, decreasing to 69 at the end of the month. Plume heights remained at 3,300-4,200 m, drifting 40-50 km in several directions. Tremors with ash emissions lasted 1-2 hours most days.

Geologic Background. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Information Contacts: Observatorio Volcanologico del INGEMMET, (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa (URL: http://ovi.ingemmet.gob.pe); Instituto Geofisico del Peru, Observatoria Vulcanologico del Sur (IGP-OVS), Arequipa Regional Office, Urb La Marina B-19, Cayma, Arequipa, Peru (URL: http://ovs.igp.gob.pe/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Martin Rietze (URL: http://www.mrietze.com/).


Santa Maria (Guatemala) — December 2017 Citation iconCite this Report

Santa Maria

Guatemala

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

All times are local (unless otherwise noted)


Slow growth of new lava dome, persistent ash plumes, and nearby ashfall, January-October 2017

The dacitic Santiaguito lava-dome complex on the W flank of Guatemala's Santa María volcano has been growing since 1922. The youngest of the four vents in the complex, Caliente, has been actively erupting with ash explosions, pyroclastic, and lava flows for more than 40 years. During July-September 2016, daily weak ash emissions were punctuated weekly by stronger emissions that sent ash plumes to altitudes of 3.3-6 km, and numerous pyroclastic flows were reported (BGVN 42:07). A new lava dome appeared in October and had filled half of the crater by years end; the frequency of explosions increased to 25-35 per day by December 2016. Guatemala's INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meterologia e Hidrologia) and the Washington VAAC (Volcanic Ash Advisory Center) provided regular updates on the continuing activity during the time period of this report from January-October 2017.

Activity at the Caliente dome was very consistent from January through October 2017. A lava dome that began growing during October 2016 continued to slowly increase in size. Its growth generated constant steam and gas emissions that rose 100-500 m above the dome, and daily explosions with ash that generally rose to 2.8-3.3 km altitude (200-800 m above the dome). Ashfall was reported almost daily in villages and farms within 5-12 km S and SW, including San Marcos Palajunoj, Loma Linda, Monte Bello, El Patrocinio, La Florida, El Faro, Patzulin, and others. There were 15-35 explosions per day throughout this time. As the lava dome within the Caliente summit crater increased in size, more block avalanches were observed traveling tens of meters down the flanks of Caliente, outside the crater rim. Several lahars affected the major drainages during May-October.

Fifteen to twenty small to moderate daily explosions with ash emissions were typical for the Caliente dome complex during most of January 2017, in addition to constant blue and white gas emissions from the top of the lava dome. This same pattern continued throughout February, when the new dome inside the summit crater continued to grow (figure 63). By March, the dome was large enough that occasional block avalanches of fresh lava reached outside the summit crater, and descended a few tens of meters onto the flanks; the lava dome, growing since October 2016, had not quite filled the crater (figure 64).

Figure (see Caption) Figure 63. The lava dome inside the summit crater of Caliente grew noticeably between 17 January and 28 February 2017 at Santa María in this view to the S. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA FEBRERO 2017).
Figure (see Caption) Figure 64. Ash and steam rises during an explosion from the new lava dome inside the summit crater of the Caliente dome of Santa María. Recently ejected blocks are steaming on the flanks close to the webcam on 19 March 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA MARZO 2017).

By April 2017 the number of daily explosions had increased to 25-30, with similar energy levels and ash plume heights as earlier in the year. The Cabello de Ángel River continued downcutting through the 2014-2015 lava flows (figure 42, BGVN 41:09) creating a new channel that was 15-50 m deep (figure 65). During May, the number of daily explosions ranged from 9 to 26 (figure 66), and block avalanches from the new lava dome traveled short distances down the flanks. Two lahars were reported in May; on 6 May a lahar 30 m wide and 2.5 m deep descended the Cabello de Ángel drainage (a tributary of the Nimá I river on the S flank) carrying branches, tree trunks, and blocks up to 2 m in diameter. A smaller lahar on 31 May traveled down the Nimá I drainage and dragged smaller blocks and tree trunks down the channel.

Figure (see Caption) Figure 65. The Cabello de Ángel river cuts new channels through the 2014-2015 lava flows on the SE flank of Caliente dome at Santa María during April 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA ABRIL 2017).
Figure (see Caption) Figure 66. A moderate explosion on 30 May 2017 from Santiaguito at Santa María sends an ash plume to 2.6 km altitude that then drifted SW. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA Mayo 2017).

Explosions during June 2017 continued at the rate of 14-36 per day, with ash plumes rising to 2.7-3.3 km altitude (figure 67). Juvenile material continued to fill and overtop the crater rim, creating weak block avalanches down the flanks. Increased precipitation during June resulted in five lahars descending the Cabello de Ángel, Nimá I, and San Isidro drainages on 1, 5, 7, 9, and 16 June. They ranged in size from 15 to 25 m wide and 1 to 1.5 m high, and transported blocks 1-2 m in diameter. A larger lahar on 1 June that traveled down the Cabello de Ángel drainage was 30 m wide and 2 m high.

Figure (see Caption) Figure 67. An ash plume at Santa María's Santiaguito complex on 21 June 2017 rises to 2.9 km. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA Junio 2017).

Similar explosive activity continued during July. On 5 July, a moderately-sized lahar descended the Cabello de Ángel drainage, a tributary of the Nimá I river. Near the El Faro estate, the lahar was 30 m wide and 1 m deep, and carried blocks 50 cm in diameter. On 14 July, another lahar traveled down the Nimá I drainage, which is a tributary of the Samalá. By August the summit crater of Caliente was nearly filled with the new lava dome, and overflows of block avalanches were more frequent, mostly traveling down the E flank (figure 68). A moderately-sized lahar descended the Nimá I drainage on 9 August.

Figure (see Caption) Figure 68. Fresh block avalanches were visible covering an area about 126 m wide and 246 m long near the summit of Caliente at Santa María when images from 31 July (left) and 2 August 2017 (right) were compared. Most of the block avalanches traveled down the east flank (A), but smaller avalanches traveled shorter distances down the NE flank (B). Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 29 de julio al 04 de agosto de 2017).

Explosions with ash plumes rising hundreds of meters above the crater rim continued daily during September and October, and sent block avalanches down the NE and SE flanks of the dome. INSIVUMEH reported that on 11 October 2017 a 12-m-wide and 1.5-m-high lahar descended the Cabello de Ángel and the Nimá I drainages, carrying blocks up to 1 m in diameter. On 13 October, the seismic network detected moderate-to-strong lahars in the Cabello de Ángel and the Nimá I drainages triggered by heavy rain.

Relatively few VAAC reports were issued for Santa María during 2017 compared with the previous two years. The Washington VAAC observed an ash plume in satellite imagery drifting 15 km W at 4.6 km altitude on 14 January. Morning visible imagery on 1 February showed an ash plume 25 km SW at 3.8 km altitude. An ash emission was observed on 27 February a few kilometers WSW at or slightly above the summit. Multiple small puffs of ash extended 55 km WSW of the summit on 9 March, at 4.6 km altitude. An ash plume was centered 15 km NW of the summit at 3.8 km altitude and rapidly dissipating on 4 April. The next VAAC observation, on 2 June, was a small puff of ash located 30 km S of the summit. On 6 September, possible volcanic ash was drifting SW of the summit at 4.3 km altitude.

Infrared MODIS satellite data suggest low-level, persistent activity at Santa María throughout January-October 2017 (figure 69). This is consistent with photographs of a slowly growing lava dome at the summit, and persistent low-energy explosions with ash emissions and block avalanches during the year. There were no MODVOLC thermal anomalies during this time.

Figure (see Caption) Figure 69. Infrared MODIS thermal data graphed through the MIROVA system indicates a low but persistent level of thermal activity at Santa María for the year ending on 8 June 2017. This is consistent with the observations of a slowly growing lava dome inside the summit crater. Courtesy of MIROVA.

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/ ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Sinabung (Indonesia) — December 2017 Citation iconCite this Report

Sinabung

Indonesia

3.17°N, 98.392°E; summit elev. 2460 m

All times are local (unless otherwise noted)


Constant activity through September 2017, with ash plumes, block avalanches, and pyroclastic flows

Indonesia's Sinabung volcano, located on North Sumatra, had its first confirmed Holocene eruption between 27 August and 18 September 2010; ash plumes rose up to 2 km above the summit, and falling ash and tephra caused fatalities and thousands of evacuations (BGVN 35:07). It remained quiet after the initial eruption until 15 September 2013, when a new eruption began that has continued for over three years. Details of events during October 2016-September 2017 are covered in this report. Information is provided by, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), referred to by some agencies as CVGHM, the Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Centre (VAAC), and the Badan Nacional Penanggulangan Bencana (National Disaster Management Authority, BNPB).

Summary of activity during November 2013-September 2016. Thousands of evacuations took place during November and December 2013 when ash plumes reached heights between 6 and 11 km altitude multiple times. Ashfall from hundreds of pyroclastic flows in January 2014 covered communities in the region. Lava flows emerged from the summit in mid-January 2014 and traveled down the S flank. Pyroclastic flows on 1 February 2014 killed 17 people in the village of Sukameriah, located 3 km S of the summit (BGVN 39:01). The lava flow had advanced 2.5 km from the summit by 6 April 2014. Lava flows, ash plumes, and pyroclastic flows persisted throughout 2014 and 2015. Ash plumes generally rose up to about 5 km altitude, and pyroclastic flows traveled up to 4.5 km from the summit throughout this period (BGVN 39:10). Repeated lava dome growth and destruction was also reported by PVMBG during this time (BGVN 40:10).

Increases in lava dome volume and instability during June 2015 again led to evacuations of thousands living within 7 km of the volcano. Ash deposits were common in the communities up to 10-15 km away. Similar activity continued into 2016, with tens of pyroclastic flows affecting nearby communities during many months. In April 2016, over 9,000 people remained in evacuation centers. Ash plumes were reported 3-8 times each month by the Darwin VAAC between April and October 2016, with plume altitudes ranging generally from 3-5.5 km. Several fatalities were reported during May 2016 (BGVN 42:02). A lahar passed through Kutambaru village, 20 km NW of Sinabung, on 9 May and killed one and injured four people. A pyroclastic flow on 21 May 2016 killed 7 people in the village of Gamber, 4 km SE from the summit. Ashfall was reported during July 2016 more than 50 km NE, and incandescent lava was visible up to a kilometer from the summit. Continuous pyroclastic flows were reported on 25 August 2016, with an ash plume observed at 6.1 km altitude the following day.

Summary of activity during October 2016-September 2017. Ash plumes, block avalanches, and pyroclastic flows were all nearly constant at Sinabung throughout this period (table 7). The number of explosions recorded every month ranged from 37 (March 2017) to 105 (June 2017). The number of Volcanic Observatory Notices to Airmen (VONAs) each month ranged from 34 (September 2017) to 93 (June 2017). The Darwin VAAC reported ash plumes on 17 or more days every month of 2017 through September. Thermal anomaly signals also persisted throughout, likely caused primarily by dome growth and incandescent block avalanches.

Table 7. Ash plumes and explosions reported for Sinabung, October 2016-September 2017. Data from Darwin VAAC and PVMBG reports.

Month Days with Ash Plume Reports Ash Plume Altitudes (km) Ash Plume Drift Explosions reported (PVMBG) Number of VONA's issued (MAGMA) Comments
Oct 2016 5, 12, 26, 28-29, 31 3.4-4.6 km SE, E, SSE, NE -- -- --
Nov 2016 1, 2, 6, 11, 13, 14, 20, 29, 30 3.4-5.8 km E, W, E, NE, SE -- -- Multiple brief explosions; pyroclastic flows observed 1, 2 Nov
Dec 2016 15, 17, 19-21, 26, 27, 29-31 3.0-6.1 km SSE, E, S, SE, NW, S, SW -- -- Hotspot visible in satellite images on 30 Dec
Jan 2017 1, 8-15, 17-20, 22, 24, 26-31 3.4-5.5 km WSW, W, E, ESE, SW 101 58 Ash 50 km E and 75 km NE on 8 Jan; hot spot in satellite imagery 10 Jan
Feb 2017 1-14, 16-22, 24-26, 28 3.0-5.5, 6.7, 7.4 km SSE, S, NE, E, SE, SW, WSW, W 88 70 4 Feb explosion caused ash plume to 7.4 km altitude
Mar 2017 1, 2, 5, 7-18, 21, 22, 24, 25, 27, 29 3.0-5.5 km WNW, NW, SSE, NNW, W, S, SW, NE, N, E, ESE 37 34 Highest plumes, on 17 and 18 March, rose to 5.5 km altitude and drifted W and WSW
Apr 2017 5, 7, 9-20, 22, 24-30 3.0-5.5, 8.4 km ESE, E, SE, WNW, SSE, SSW, W, SW, WSW, NNE, S 104 58 Large explosion on 9 April, ash plume reported by a ground observer to 8.4 km altitude, drifting SE
May 2017 2-12, 14-17, 19-20, 23-31 3.4-8.8 km WSW, WNW, NW, SW, S, E, SE, NE, ESE, W, ENE 87 58 Series of large explosions during 17-20 May, several plumes rose to altitudes between 6.1 and 8.8 km
Jun 2017 1-27, 29, 30 2.7-5.5, 6.4 km NE, N, WNW, ENE, ESE, SE, SW, W, S, E, NW, NE, SSW, SSE 105 93 --
Jul 2017 2-3, 6, 8-11, 14, 15, 17-31 2.7-6.1 km ESE, NW, ENE, E, SE, W, WSW, SSW, ENE, NE 91 64 --
Aug 2017 1, 2, 6-10, 12, 16, 23-29, 31 2.7-5.5, 6.4 km ENE, SE, E, S, W, ESE, WNW, NNW, WSW 61 76 Large explosion on 2 Aug with ashfall in many places; Hotspots reported 6, 7 Aug
Sep 2017 1, 3, 7, 8, 12-16, 18, 22, 23, 25-29 3.0-5.5, 6.1-6.4 km ENE, WSW, E, W, NW, SE, ESE, SW 55 34 --

Activity during October 2016-September 2017. The visiting head of PVMGB observed an ash plume from an explosion on 28 September 2016. Ash emissions continued at Sinabung, with multiple aviation advisories issued by the Darwin VAAC through the end of 2016. Explosions generated ash plumes that rose to altitudes of 3.0-6.1 km, and drifted in multiple directions during the last quarter of 2016 (table 7). Pyroclastic flows were observed several times during November (figure 28), and a hotspot was visible in satellite imagery on 30 December.

Figure (see Caption) Figure 28. A large pyroclastic flow descended the E flank of Sinabung on 29 November 2016 in this view taken a few kilometers SE of the volcano. . Courtesy of Sadrah Peranginangin.

Activity during January 2017 was dominated by incandescent block avalanches (figure 29). PVMBG reported 101 ash-bearing explosions with plumes rising up to 1 km above the summit, and pyroclastic flows that traveled up to 3 km ESE and 500 m S. A You Tube video captured a pyroclastic flow and ash plume on 17 January 2017. Ash plumes were reported by the Darwin VAAC on 21 days during the month with plume heights ranging from 3.4-5.5 km altitude.

Figure (see Caption) Figure 29. Block avalanches descended the E flank of Sinabung many times during January 2017, including at 0134 local time on 17 January, as seen looking to the WSW. Courtesy of Endro Lewa.

Near-daily ash plumes from 88 explosive events during February 2017 rose to heights of 500-5,000 m above the summit (3.0-7.5 km altitude), and pyroclastic flows traveled 3.5 km E and 1 km S. The Darwin VAAC reported ash emissions on all but three days of the month. A large explosion on 4 February sent an ash plume to 7.4 km altitude that then drifted SE (figure 30), and on 9 February a large ash plume drifted WSW at 6.7 km altitude.

Figure (see Caption) Figure 30. Photo of an ash plume at Sinabung on 4 February 2017 that rose more than 5 km above the summit and slowly drifted SE. Photo taken from Kabanjahe, about 13 km SE. Courtesy of Sadrah Peranginangin.

Block avalanches continued to travel 500-2,000 m down the ESE flank during March 2017. Ash plume heights ranged from 500 to 3,000 m above the summit (3.0-5.5 km altitude) during the 37 explosion events reported by PVMBG (figure 31). Pyroclastic flows traveled 2.5 km down the S flank. The highest plumes of the month were recorded on 17 and 18 March; they rose to 5.5 km altitude and drifted W and WSW. The Darwin VAAC reported ash plumes during 21 days of the month.

Figure (see Caption) Figure 31. Photo of an ash plume at Sinabung on 29 March 2017 at 1548 local time, in this view looking W. Courtesy of Igan S. Sutawijaya.

During April 2017, block avalanches were observed traveling between 800 and 3,500 m down the SSE flank (figure 32), and 104 explosions were recorded by PVMBG. Ash plumes from these explosions rose to heights of 800 to 3,500 m above the summit. Pyroclastic flows descended 2.8 km down the S flank. A large explosion on 9 April reported in a VONA by a ground observer sent an ash plume to 8.4 km altitude, drifting SE. Pyroclastic flows were also observed on the SE flank. The Darwin VAAC reported ash plumes on 22 days of the month.

Figure (see Caption) Figure 32. Pyroclastic flows descended the S flank (left) and block avalanches descended the E flank of Sinabung near midnight on 4 April 2017, while a small explosion took place at the summit. Image taken from a small village a few kilometers from the base of the SE flank. Courtesy of Sadrah Peranginangin.

Ash plumes rose between 500 and 6,000 m above the summit during May 2017. Eighty-seven explosive events were recorded (figure 33), and block avalanches were observed traveling 500-1,500 m down the S and SE flanks. The Darwin VAAC reported ash plumes on 26 days during the month. A series of large explosions during 17-20 May resulted in several plumes that rose to altitudes between 6.1 and 8.8 km, in addition to numerous others at lower altitudes between 3.7 and 5.8 km. As of late May, over 9,000 people were still displaced from the volcano, living in either shelters or evacuation camps, according to BNPB.

Figure (see Caption) Figure 33. Strombolian activity at the summit of Sinabung on 1 May 2017. Courtesy of Sadrah Peranginangin.

Incandescent block avalanches and pyroclastic flows were persistent during June 2017. They moved down the SE and S flanks up to 2,500 m. PVMBG reported 105 explosive events with plume heights ranging from 500-4,000 m above the summit (figure 34). The largest explosions of the month, on 17 June, generated ash plumes that rose to 6.4 km altitude and drifted 15 km SW. The Darwin VAAC reported ash emissions every day except for 28 June.

Figure (see Caption) Figure 34. Ash plume rose from Sinabung on 26 June 2017. The view is from a small village about 7 kilometers ENE of the summit. Courtesy of Endro Lewa.

PVMBG reported 91 explosive events during July 2017 that produced ash plumes that rose 500-3,500 m above the summit. They also noted four pyroclastic flows that traveled 1-3 km down the S and SE flanks. Block avalanches continued on the S and E flanks, traveling as far as 3 km. The Darwin VAAC issued reports on 24 days during July. The largest explosions occurred on 20 and 23 July when ash plumes rose to 5.8 and 6.1 km altitude and drifted WSW, ENE, and SE (figure 35).

Figure (see Caption) Figure 35. A large ash plume from Sinabung rose more than 5 km above the summit on 20 July 2017. The view is from a small village about 7 kilometers ENE of the summit. Courtesy of Endro Lewa.

Although fewer explosive events (61) were reported during August, block avalanches continued to travel 500-2,300 m down the SE flank. Ash plumes rose 500-2,000 m above the summit; 22 pyroclastic flows traveled up to 4.5 km down the SE flank. The Darwin VAAC issued reports of ash emissions on 17 days of the month.

A large explosion on 2 August sent ash emissions to 5.5-6.4 km altitude (figure 36). The S-drifting plume brought ashfall to the communities of the Ndokum Siroga District (SE), Simpang (7 km SE), Gajah (8 kmE), Kabanjahe (13 km SE), and Naman Teran (5 km NE) (figures 37 and 38). PVMBG reported that the explosions of 2 August destroyed the lava dome at the summit, which had grown since April 2017 to about 2.3 million m3 in size before the explosion (figure 39). The volume of the lava dome was an estimated 23,700 m3 on 6 August, after the explosions.

Figure (see Caption) Figure 36. Photo showing the large eruption from Sinabung on 2 August 2017, with a dark ash plume and pyroclastic flows. Image taken 5 kilometers E of the summit, looking W. Courtesy of Endro Lewa.
Figure (see Caption) Figure 37. Many communities were affected by ashfall and pyroclastic flows from the large explosion at Sinabung on 2 August 2017. This village is located near the base of the E flank. Courtesy of Endro Lewa.
Figure (see Caption) Figure 38. A village on the SE flank of Sinabung, was covered with ash on 3 August 2017 after a large eruption the previous day that sent a column of ash to 4.2 km altitude and a pyroclastic flow down the adjacent slope, destroying vegetation in its path. Courtesy of Xinhuanet (Xinhua/YT Haryono).
Figure (see Caption) Figure 39. The dome at Sinabung on 3 August 2017 one day after its destruction in a large explosion. The volume according to PVMBG was 2.3 million cubic meters in early July and measured only 23,700 cubic meters after the explosion. Courtesy of Endro Lewa.

The explosions also produced pyroclastic flows that traveled SE and E 2.5-4.5 km and reached the Laborus river, increasing the size of a natural dam on the river that had been evolving from previous deposits. Ashfall was also reported to the E and NE at Berastagi (12 km E). Hot spots were recorded in satellite imagery on 6 and 7 August. Additional ash plumes to similar altitudes (5.5-6.4 km) were reported several other times during August (figure 40 and 41).

Figure (see Caption) Figure 40. An explosion at Sinabung on 8 August 2017. The ash plume rises 2,000 m and a pyroclastic flow descends the E flank in this view from a small village about 7 km ENE of the summit. Courtesy of Endro Lewa.
Figure (see Caption) Figure 41. Ash and steam plumes and block avalanches at Sinabung on 25 August 2017 in this view from a small village about 7 km ENE of the summit. Courtesy of Endro Lewa.

The impact of numerous pyroclastic flows on the SE and E flanks during 2016-2017 caused a natural dam to form on the Laborus River near Desa Sukanalu and Kutanonggal Village (figure 42). The estimate of the area covered by water behind the dam was over 100,000 m2 prior to the early August explosions, about one-tenth the size of Lake Laukawar, located further upstream.

Figure (see Caption) Figure 42. A natural dam on the Laborus River (right, 'Bendungan Laborus') was created by numerous pyroclastic flows; the lake area was 123,000 square meters prior to the 2-3 August explosions. Courtesy of PVMBG (Kegiatan Gunungapi Sinabung Pasca Letusan 2-3 Agustus 2017, 22 August 2017).

Activity diminished only slightly during September 2017. PVMGB reported 55 explosive events with ash plumes that rose 500-4,000 m above the summit (figure 43). Block avalanches fell 500-1,500 m down the SE flank, and five pyroclastic flows were observed in the same area which traveled 1.5 – 2.0 km. Reports of ash emissions were issued by the Washington VAAC on 17 days of the month. The highest ash plume during the month rose to 6.4 km altitude on 25 September.

Figure (see Caption) Figure 43. A lava dome and ash plume at the summit of Sinabung on 17 September 2017. Courtesy of Sadrah Peranginangin.

Thermal anomalies. Thermal anomalies persisted throughout October 2016-September 2017. MODVOLC thermal alerts were reported 1-10 times every month except for June 2017. The MIROVA system recorded persistent low to moderate radiative power (figure 44) consistent with the dome growth, explosions, and block avalanches reported by PVMBG.

Figure (see Caption) Figure 44. Thermal anomaly data shown on a MIROVA graph of log Radiative Power at Sinabung for the year ending 18 December 2017. Persistent intermittent pulses of thermal energy are consistent with dome growth and block avalanches reported by PVMBG. Courtesy of MIROVA.

References: Associated Press, 2017, Raw: Indonesia's Sinabung Volcano Spews Hot Ash (URL: https://www.youtube.com/watch?v=R3KhjpHVeaw), posted to YouTube 17 January 2017.

Geologic Background. Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

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 (URLs: http://www.vsi.esdm.go.id/, https://magma.vsi.esdm.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/); 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/); Xinhua News (URL: http://news.xinhuanet.com/english/2017-08/03/c_136497362.htm); Igan S. Sutawijaya (URL: https://www.facebook.com/igansutawijaya/); Endro Lewa (URL: https://www.instagram.com/endro_lewa/); Sadrah Peranginangin (URL: https://www.facebook.com/sadrah.peranginangin).


Tungurahua (Ecuador) — December 2017 Citation iconCite this Report

Tungurahua

Ecuador

1.467°S, 78.442°W; summit elev. 5023 m

All times are local (unless otherwise noted)


Nearly constant ash emissions and frequent lahars during July-December 2015

Eight distinct episodes of activity occurred at Ecuador's Tungurahua from November 2011 through December 2014 that included 10-km-high ash plumes, Strombolian activity, pyroclastic flows, lahars and a lava flow (BGVN 42:05). Another distinct eruptive episode, during April and May 2015, consisted primarily of persistent ash emissions (BGVN 42:08). Abundant rainfall during the first half of 2015 led to numerous lahars, some of which disrupted travel on local roads. Continuing activity from July through December 2015 is described below based on information provided by the Observatorio del Volcán Tungurahua (OVT) of the Instituto Geofísico (IG-EPN) of Ecuador, and aviation alerts from the Washington Volcanic Ash Advisory Center (VAAC).

After the last ash emissions reported in mid-May 2015, only minor emissions of steam with no ash rising to 500 m above the crater were reported during June. However, activity increased again during July, when ashfall was reported nearly every day at the lookout stations around Tungurahua, and several larger explosions produced ash plumes that rose as high as 7.5 km altitude, about 2.5 km above the summit. Frequent rains during July resulted in lahars in six different drainages. Multiple explosions during August caused ash plumes and ashfall in communities within 20 km several times every week with the highest plume rising to 8.5 km altitude. A similar pattern continued during September 2015, with longer periods of seismic tremor, persistent ash emissions, and Strombolian activity that sent block avalanches down the flanks. The number and intensity of explosions increased in October; multiple explosions every week resulted in ashfall in communities within 25 km, mostly to the NW, and low-energy Strombolian activity persisted throughout the month. The strongest explosions of the period began with a series of seismic tremors on 10 November that persisted for nine days; daily ash plumes rose to between 7 and 8 km altitude, with the highest plume reported rising to at least 9.1 km altitude. Several millimeters of ashfall were reported in the nearby communities and at lookout stations, and the ash plume was recognized in satellite data more than 250 km from the summit before dissipating. Activity tapered off by the end of November, and only weak steam emissions were reported during December 2015.

Activity during July-September 2015. Persistent steam plumes in July rose up to 500 m above the summit crater and drifted generally W, often carrying small quantities of ash. Several lookout stations in communities located within 20 km NW and SW reported ashfall almost every day, including Choglontús (13 km WSW), Bilbao, and El Manzano (8 km SW). Other stations that reported ashfall during the month included Palitahua, Mocha, Chacauco, and Pillate. IG-EPN reported explosions with larger ash plumes on 3, 12, and 14 July that rose as high as 7.5 km (figure 86). Increased seismicity on 21 and 22 July was associated with emissions that caused ashfall in most of the reporting locations.

Figure (see Caption) Figure 86. An ash plume rises 1 km above the summit crater at Tungurahua on 3 July 2015. Courtesy of OVT, IG-EPN, photo by P. Espin (Informe No. 802, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 30 de junio al 07 de julio de 2015).

The Washington VAAC reported the ash plume on 3 July extending 25 km WSW from the summit at 5.2 km altitude (200 m above the crater); they also detected a faint hotspot in satellite imagery. They reported an ash plume extending 35 km WSW late in the day at 6.4 km on 14 July visible in satellite imagery (figure 87). An ash plume reported by the Washington VAAC on 31 July was moving SW at 6.7 km altitude.

Figure (see Caption) Figure 87. One of several explosions on 14 July 2015 at Tungurahua created an ash plume that rose at least 2 km above the summit and drifted W. Courtesy of OVT, IG-EPN, photo by F. Vasconez (Informe No. 803, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 07 de julio al 14 de julio de 2015).

Lahars were reported during 5-7, 18-19, 22-23, and 29-30 July in the Chontapamba, Rea, Achupashal, Juive, Pondoa and Puela river drainages. Heavy rain on 18 and 19 July generated mudflows in the Juive, Pondoa and La Pampa ravines. Blocks 40 cm in diameter were reported in the Puela River on 22 July, and blocks 1 meter in diameter were reported in the Chontapamba river on 29 July.

There were fewer events with ash emissions during August compared to July. A lahar sent 40-cm-diameter blocks down the Mapayacu ravine on 14 August. Two explosions on 15-16 August caused ashfall in Choglontus, Manzano, and Chontapamba. Small lahars from the Rea and Romero drainages blocked the Baños-Penipe road on 16 August. An explosion on 18 August sent an ash plume WSW and caused ashfall in Choglontus; the next day reddish ash and steam emissions around 1000 local time caused ashfall again in Choglontus. Black ashfall was reported there on 22 August. Increased seismic activity with several explosions on 25 August was accompanied by ash plumes that caused ashfall in Chontapamba, Pillate, Bilbao, and Juive Grande. Gray ash was reported in Chinchicoto and Yanayacu, and thick black ash was reported in Rumipamba, Pingili and Mocha. Fine-grained gray ash was reported in Mocha on 27 August.

The Washington VAAC reported occasional emissions of gas and minor volcanic ash on 1 August 2015. A pilot report of an ash plume rising to 7 km altitude and drifting W on 15 August was not detected in satellite imagery due to weather clouds, although ashfall was reported within 15 km of the summit. Another pilot report on 20 August noted an ash plume to 8.5 km altitude. The altitude of an ash plume spotted drifting W on 25 August was estimated to be between 7.6 and 9 km. Ongoing emission of gas and possible minor ash was reported on 30 August at 6.7 km altitude moving W; the faint plume later detected in satellite imagery was moving WNW and extended about 50 km from the summit.

Mudflows from substantial rain on 1 and 7 September 2015 affected the Achupashal ravine and again disrupted travel on the Baños-Penipe road (figure 88). An ash plume on 2 September reached 3 km above the crater and drifted NW, causing ashfall in Pillate, Quero, Santuario, La Galera and El Rosario. Asfall was reported the next day in El Manzano and Choglontus. The Washington VAAC reported the ash plume at 8 km altitude on 2 September; the satellite imagery showed it extending 15 km WNW.

Figure (see Caption) Figure 88. The Baños-Penipe road is frequently damaged by lahars in the Quebrada de Achupashal at Tungurahua, making travel difficult. The muddy water on 7 September 2015 washed out the road again. Courtesy of OVT, IG-EPN, photo by B. Bernard at 1359 local time (Informe No. 811, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 01 de septiembre de 2015 al 08 de septiembre).

Moderate to high amounts of ash characterized the emissions on 11 September 2015 (figure 89). The plumes rose 2 km above the crater, drifted W and caused slight ashfall in Chonglontus and El Manzano. Only Chonglontus reported additional ashfall the next day. The Washington VAAC initially reported the ash plume at 7.3 km altitude extending 40 km SW on 11 September. About 6 hours later, the leading edge of the plume was dissipating about 170 km SW. This was followed by a new ash plume late in the day that rose to 5.8 km altitude and drifted 15 km WSW from the summit. Slight incandescence was reported on 13 September along with minor ash and steam emissions that were moving W at 7.6 km altitude.

Figure (see Caption) Figure 89. An ash plume drifts W from Tungurahua on 11 September 2015. Courtesy of OVT, IG-EPN, photo by S. Santamaria (Informe No. 811, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 08 de septiembre de 2015 al 15 de septiembre).

Constant emission of moderate amounts of ash on 19 September 2015 created an ash plume that rose to 2 km above the crater and drifted NW. Ashfall was reported in El Manzano and Pillate. An explosion late in the day rattled structures in Pondoa, and was followed by observations of incandescence at the crater shortly after midnight. Ashfall was reported to the W in Pillate, El Manzano, Bilbao, Motilones, Chontapamba, and Choglontus the following day. Ongoing emissions were not visible in satellite imagery due to weather clouds. A sudden deflation in the deformation data was recorded on 19 September. Similar deflation events preceded major explosions in July 2013 and February 2014.

Several hours of seismic tremor on 27 September produced an ash-rich plume and incandescent blocks which descended the W flank. This was followed by additional explosions and periods of tremor, some lasting for more than an hour (figure 90), that produced ash plumes drifting SW. Ashfall was reported in the towns of Manzano, Choglontus, Cahuají, and Palictahua. Additional ashfall was reported the next day in Choglontus and Manzano. The Washington VAAC spotted a faint ash plume moving W in multispectral imagery on 27 September, and another plume at 6.7 km altitude moving slowly NW the next day around noon. New fumaroles not previously observed below the W flank of the crater were observed on 29 September for the first time.

Figure (see Caption) Figure 90. Lengthy tremors that registered at the seismic station RETU coincided with ash-rich plumes and incandescent blocks at Tungurahua between midnight and noon local time on 27 September 2015. Courtesy of OVT, IG-EPN (Informe No. 814, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 22 al 29 de septiembre de 2015).

Activity during October-December 2015. Tremors were followed by a significant explosion on 4 October 2015 that produced ash emissions and block avalanches that traveled down the W flank. Ashfall reports were issued from the communities of Manzano, Choglontus, and Cahuají, all located to the SW. The Washington VAAC reported the ash plume 35 km WSW of the summit at 9.1 km altitude. Seismic activity increased beginning on 8 October. On 11 October, four explosions produced Strombolian-style activity with incandescent blocks traveling down the Chomtapamba and Achupashal ravines, an ash plume rising 2 km above the crater, and ashfall in regions to the NW and SW including Manzano, Choglontus, Puela and Mocha. The Washington VAAC reported the ash plume extending W from the summit at 7.9 km altitude. Around 2000 local time, the ash plume resembled a large mushroom cloud, and loud noises were reported from Cusua. There were numerous reports of incandescent blocks and explosions heard on the N and E flanks during the evening and overnight into the next morning (figure 91). Ashfall was again reported in Choglontus on 13 October.

Figure (see Caption) Figure 91. Incandescent blocks descend the upper flank of Tungurahua at 1909 local time on 11 October 2015. Courtesy of OVT, IG-EPN, photo by E. Telenchana (Informe No. 816, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 06 al 13 de octubre de 2015).

An explosion in the early morning hours of 14 October was heard at all of the stations around the volcano. It was followed by ashfall in Choglontus. An ash emission on 19 October rose 1 km above the crater and drifted W and SW, producing ashfall in Choglontus, Bilbao, Pillate, and Cotaló. The Washington VAAC reported the plume extending 55 km NW of the summit at 6.7 km altitude. The next day, ongoing seismic data suggested frequent diffuse ash emissions. A plume was detected in multispectral data at 7.6 km altitude radiating E and rapidly dissipating. That afternoon (20 October), ashfall was reported in the Punzupala area. Ashfall continued from daily emissions for the next week with the most ashfall reported from Manzano, Choglontus, Bilbao, and Chacauco. Communities with trace amounts of ashfall included Ambato, Quero, Cevallos, Huachi, Chiquicha, Huambaló, Cotaló, and Pillate.

Incandescent material was observed traveling more than 1,000 m down the W flank from an explosion on 25 October. Local television reported ashfall in Ambato, Cevallos, Quero, and parts of Mocha and Tisaleo later that day. Swarms of LP earthquakes followed by episodes of ash emissions and low-energy Strombolian activity continued for the remainder of the month and into early November, causing sporadic ashfall in nearby villages. A small lahar was reported in the La Pampa ravine on 30 October.

An emission on 2 November 2015 created an ash plume that rose about 1.5 km above the crater and drifted E and NE; small quantities of ash were reported in the upper Runtun area. Incandescence at the summit crater from Strombolian activity was observed that night and for several days following. Heavy rains on 7 November caused mudflows in the Romero, Pingullo, and Achupashal ravines, and a larger lahar with meter-size blocks in the Chontapamba ravine. The Washington VAAC noted a dark emission from the volcano drifting W on 8 November at 5.5 km altitude.

A new series of tremors beginning on 10 November, coincided with more than a week of continuous ash emissions which reached 3.5 km above the crater and drifted in several directions. Incandescence was observed at night, and incandescent blocks descended generally up to 500 m down the NW, N, and E flanks during this period (figure 92).The Washington VAAC first reported an ash plume at 7.6 km altitude late in the evening on 10 November and continued with a constant series of reports for the next nine days. Most of the plumes were reported between 7 and 8 km altitude, drifting generally W (figure 93). The ash plumes produced heavy black ashfall in Manzano, Choglontus, Bilbao, Mocha, Quero, Cotaló, Tisaleo, Penipe and Cevallos. An ash plume was visible about 130 km W by midday on 11 November, and the plume had reached 8.2 km altitude. Loud noises were reported numerous times from the nearby communities for several days. On 12 November the Washington VAAC reported volcanic ash observed in satellite data extending 200 km WNW at 9.1 km altitude. Ashfall was heavy enough on 14 November to cause tree branches near Choglontus to bend under the weight of the ash.

Figure (see Caption) Figure 92. Strombolian activity from the summit of Tungurahua causes incandescent blocks to fall 500 m down the flanks of on 14 November 2015. Courtesy of OVT, IG-EPN, photo by V. Valverde (Informe No. 821, Síntesis seminal del estado del Volcán Tungurahua, Semana: 10 al 17 de noviembre de 2015).
Figure (see Caption) Figure 93. A dense ash plume rises from the summit of Tungurahua and drifts W on 17 November 2015. A small pyroclastic flow is visible on the NW flank (right side of image). Courtesy of OVT, IG-EPN, photo by S. Santamaria (Informe No. 822, Síntesis seminal del estado del Volcán Tungurahua, Semana: 17 al 24 de noviembre de 2015).

A plume on 15 November 2015 rose more than 5 km above the crater (10 km altitude), according to IG-EPN, and sent blocks about 1,000 m down the flanks. On 18 November, the Washington VAAC reported a narrowing plume extending 270 km W from the summit. The largest ashfalls occurred during the night of 18-19 November. Strombolian activity sent blocks 800 m down the flanks during the night, and a strong "jet" was observed in the eastern part of the crater. Incandescent material was observed from two eruptive vents late on 18 November. Five millimeters of ash were reported from the solar panels at the Tablor station on 19 November, deposited in less than 24 hours (figure 94). IG-EPN reported this event as one of the most significant ashfall events since 2010; many crops and livestock animals were affected. Dense ash emissions tapered off after 19 November, and smaller, less dense plumes rose 2 km above the crater on 22-23 November. The University of Hawaii's MODVOLC system issued thermal alerts for Tungurahua on 15 (2) and 19 (3) November, the only time during 2015. Significant sulfur dioxide (SO2) emissions were captured by the OMI instrument on the Aura Satellite during the mid-November episode from 11-19 November (figure 95).

Figure (see Caption) Figure 94. A 5-mm thick layer of ash was deposited on the solar panels of the Tablon station at Tungurahua in less that 24 hours on 19 November 2015. Courtesy of OVT, IG-EPN, photo by S. Santamaria (Informe No. 822, Síntesis seminal del estado del Volcán Tungurahua, Semana: 17 al 24 de noviembre de 2015).
Figure (see Caption) Figure 95. Substantial SO2 plumes originating from Tungurahua were recorded by the OMI instrument on the Aura satellite during 10-19 November 2015. Top left: the plume from Tungurahua drifts WSW while a smaller plume from Cotopaxi is visible about 90 km N on 10 November. Top right: the plume from Tungurahua drifts WNW on 12 November at the bottom of the image, a much smaller plume drifts W from Cotopaxi immediately above it, and a third SO2 plume is visible drifting WSW from Nevado del Ruiz in Columbia 750 km NNE. Lower left: a larger plume on 14 November drifts WSW from Tungurahua and probably includes some gas from Cotopaxi. Lower right: a large plume from Tungurahua disperses W on 17 November for well over 500 km. Courtesy of NASA Goddard Space Flight Center.

A seismic swarm with 33-35 events per hour began on 25 November, and tapered off to 3-5 events per hour by 30 November 2015. There was no increase in surface activity during the swarm, but rather a gradual decrease, with no significant ashfall reported during the last week of November. Activity diminished significantly during December 2015. Weak steam emissions that reached no higher than 500 m above the crater were typical. Seismicity remained low, and there were no reports of ash emissions or ashfall in the area.

Geologic Background. Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Information Contacts: Instituto Geofísico (IG), 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/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Ulawun (Papua New Guinea) — December 2017 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)


Intermittent ash plumes during June-November 2017

Activity at Ulawun has been characterized by intermittent seismic activity and weak ash emissions. The last significant episode was during October-November 2016 (BGVN 41:12). This report summarizes the next eruption, which began on 11 June 2017 and continued sporadically at least through October 2017. Data were provided by the Rabaul Volcano Observatory (RVO) and Darwin Volcanic Ash Advisory Centre (VAAC).

RVO reported that during 1 May-23 June 2017, white plumes rose from Ulawun. Seismicity was low and dominated by small low-frequency earthquakes, although RSAM values slowly increased and then spiked on 13 June. Ash emissions began on 11 June and then became dense during 21-23 June. Volcanic ash advisories from the Darwin VAAC warned of ash plumes from between 24 June and 3 November 2017 (table 5); no further volcanic ash warnings were issued after 3 November. Plumes generally rose to altitudes of 2.4-3 km, or a maximum of 700 m above the summit.

Table 5. Ash plumes from Ulawun during January-November 2017, based upon analyses of satellite imagery. Courtesy of Darwin VAAC.

Dates Plume altitude (km) Plume drift
24-26 Jun 2017 3 W
28 Jun 2017 2.7 W
04-08 Aug 2017 2.4-2.7 NW, W, and SW
09-10 Aug 2017 2.4 NW, W
17-18 Aug 2017 2.7 W
31 Aug-01 Sep 2017 2.7 SW, W, NW, and N
05 Sep 2017 2.7 SW
25 Sep 2017 3 WSW
26-27 Oct 2017 2.4 130 km S and SE
03 Nov 2017 3 NNE

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: 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/); 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.


Villarrica (Chile) — December 2017 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Lava lake level fluctuates and Strombolian activity persists during October 2016-November 2017

Historical eruptions at Chile's Villarrica (figure 35), documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Lava flows emerging from the glacier-covered summit created deadly lahars in 1964 and 1971 (CSLP 95-71); a similar event in late 1984 led to evacuations and no fatalities occurred. Since then, an intermittently active lava lake has been the source of explosive activity, incandescence, and thermal anomalies. Renewed activity in early December 2014 was followed by a large explosion on 3 March 2015 that included a 9-km-altitude ash plume. Significant thermal anomalies from continued Strombolian activity at the lava lake and small ash emissions persisted through October 2016 (BGVN 41:11). Activity has continued during October 2016-November 2017, with information provided primarily by the Southern Andes Volcano Observatory, (Observatorio Volcanológico de Los Andes del Sur, OVDAS) part of Chile's National Service of Geology and Mining (Servicio Nacional de Geología y Minería, SERNAGEOMIN), and Projecto Observación Villarrica Internet (POVI), part of the Fundacion Volcanes de Chile, a research group that studies volcanoes across Chile.

Figure (see Caption) Figure 35. View of Villarrica from the town of Villarrica located 30 km NW on 10 November 2016. The active lava vent was also photographed the same day (see figure 41). Courtesy of Cristian Gonzalez G.

Steam-and-gas emissions rising 200-1,000 m above the summit were observed throughout the period. The lava lake level inside the summit crater changed elevation by as much as 15 m during October 2016. Fluctuations of several meters up and down each month were reported through February 2017, and again in October 2017. Persistent minor gas-and-ash emissions, with small blocks and lapilli ejected onto the crater rim, were captured by the webcams and observed by visitors near the summit every month. Strombolian explosions and a "lava jet" sent ejecta more than 100 m above the crater rim during February 2017, and incandescent material rose 60 m above the crater rim on 1 July. Increased seismicity was detected during November 2017.

Activity during October-December 2016. Weak emissions of steam, gases, and volcanic ash near the summit were visible in the webcam during October 2016. The Buenos Aires Volcanic Ash Advisory Center (VAAC) noted a pilot report of an ash plume moving NNW on 20 October 2016 at 3.7 km altitude, slightly less than a kilometer above the summit. OVDAS reported that during the month, steam plumes rose less than 700 m and incandescence was visible at night when weather conditions permitted viewing of the summit. The MODVOLC thermal anomaly system issued 11 alerts during October. During several visits to the summit that month, POVI scientists observed that the lava lake had risen 15 m (figure 36) to a level that had been previously observed on 18 December 2015, 29 January, 28 March, and 18 September 2016. A small pyroclastic cone was visible inside the summit crater on 28 October (figure 37); by 30 October, most of it had collapsed and molten lava was again visible at the center (figure 38).

Figure (see Caption) Figure 36. Between 17 and 27 October 2016, the lava lake rose about 15 meters inside the summit crater of Villarrica, reaching a similar level observed on 18 December 2015, 29 January, 28 March, and 18 September 2016. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 37. A small pyroclastic cone is visible at the bottom of the summit crater at Villarrica on 28 October 2016 (red arrows). On the left slope sub-parallel annular fissures are visible (yellow arrows), indicating the imminent collapse of the nested structure. The white arrows point to residue precipitated from gas emissions. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 38. The nested cone visible on 28 October had collapsed by 30 October 2016 at Villarrica, and incandescent lava was visible inside the vent. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).

During November and December 2016, steam emissions rose only 400 m above the crater and incandescence was only occasionally visible in the webcams at night. Thermal activity detected by satellite, however, was relatively high; MODVOLC issued twelve thermal alerts during November and nine during December. The repeated growth and destruction of small pyroclastic cones within the summit crater was well documented by several visits of POVI scientists to the summit (figures 39 and 41). They also collected bombs ejected near the crater rim (figure 40), and observed persistent minor ash-and-gas emissions (figure 42).

Figure (see Caption) Figure 39. A new pyroclastic cone grows inside the summit crater of Villarrica on 7 November 2016, days after the collapse of the previous cone on 28 October. Black spatter from lava splashes stand out on the exposed slope. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 40. A piece of ejecta collected at the edges of the summit crater at Villarrica on 9 November 2016. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 41. The pyroclastic cone at the summit crater of Villarrica photographed on 7 November had partially collapsed by 10 November 2016, the same day of the photograph showing a quiet, clear summit (figure 35). The splashes of lava rose no more than 10 m above the crater floor. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 42. A small ash emission of rose from the summit of Villarrica on 17 November 2016 around 1050 local time. The larger image was taken by climbers, and the inset images are from the webcam. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).

Observations by POVI scientists during December 2016 included continued evidence of cone creation and destruction in the vent (figure 43), and small lava fountains (figure 44). Strombolian explosions with bombs were recorded by the webcam on 1, 2, and 3 December. Bombs were ejected more than 50 m above the crater rim, some as large as 1.5 m in diameter. Between 2 and 3 December they observed an 8-10 m drop of the lava in the vent, leaving behind a circular depression with a small incandescent chimney on the NNW side. The webcam captured ash emissions on 2, 14, 15, 18, and 19 December.

Figure (see Caption) Figure 43. The partial collapse of the nested semicircular cone, reported by POVI on 30 November, was evident by 2 December 2016 inside the summit crater of Villarrica. The active vent is about 10-15 m in diameter. On the left wall of the crater the debris of a small recent landslide is visible above the lava. Courtesy of POVI (Informe Preliminar, Comportamiento del Volcán Villarrica, 01 al 31 de Diciembre 2016).
Figure (see Caption) Figure 44. A small Strombolian explosion created a lava fountain inside the summit crater of Villarrica on 8 December 2016. Courtesy of POVI (Informe Preliminar, Comportamiento del Volcán Villarrica, 01 al 31 de Diciembre 2016).

Activity during January-May 2017. OVDAS reported nighttime incandescence and steam emissions less than 250 m high during January 2017. They were higher in February, rising 700 m above the crater rim. Six MODVOLC thermal alerts were issued in January and one in February.

Volcanologists from POVI reported an increase in activity during February (figure 45), including a sudden collapse of about 10 m of much of the material in the lava pit on 9 February, after which a new rise began almost immediately (figure 46). During 10-15 February, explosions from a narrow vent sent lava fountains and ejecta more than 100 m high (figures 47). On 13 February, they witnessed powerful "lava jets" that rose 150 m (figure 48); bombs up to a meter in diameter were ejected 50 m from the vent and spatter covered much of the inner walls of the crater. Between 5 and 26 February, pyroclastic debris raised the level of the bottom of the crater by 10-12 m (figure 49).

Figure (see Caption) Figure 45. An increase in thermal and explosive activity was apparent between 1 and 5 February 2017 at the summit crater of Villarrica. Recently deposited lapilli (L) between 2-64 mm were scattered around the funnel shaped crater on 5 February (right). Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 46. Fresh lava spattered on the inner wall of the summit crater at Villarrica on 11 February 2017, during a new rise in the magma level after a collapse two days earlier. The diameter of the active vent had increased significantly during the previous 24 hours. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 47. Lava fountains exceeded 100 meters above the crater rim at Villarrica on 13 February 2017. Images captured just after midnight show the first explosion (lower right) at 0023 local time, followed two minutes later by the upper image, and another explosion (lower left) about 20 minutes later. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 48. The active vent in the summit crater of Villarrica was about 7 m in diameter on 13 February 2017, and sporadically emitted powerful and noisy "lava jets" more than 150 m high. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 49. Between 5 and 26 February 2017, the level of the bottom of the summit crater at Villarrica rose by about 10-12 m. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).

During March 2017, OVDAS reported steam-and-gas emissions rising 1,000 m. They issued a special report on 23 March indicating an increase in the gas plume height and the occurrence of sporadic explosions of ballistic material that remained within the summit crater. Single MODVOLC thermal alerts were issued on 7 and 14 March 2017.

Nighttime incandescence and steam plumes rising to 550 m characterized activity reported by OVDAS during April 2017. Only a single MODVOLC thermal alert was issued on 4 April. Steam plumes were reported to only 250 m above the crater rim during May along with incandescence at night, but there were seven MODVOLC thermal alerts on four different days; 1 (2), 19 (3), 20, and 29 May.

Activity during June-November 2017. OVDAS reported low levels of activity during June 2017, with incandescence at night and steam plumes rising no higher than 170 m. Only a single MODVOLC thermal alert was issued on 20 June. On a visit to the summit crater on 5 June, POVI scientists observed a 10-m-diameter vent at the bottom of the crater, and lapilli fragments 2-64 mm in diameter distributed around the crater rim. A second visit on 19 June revealed increased explosive activity at the bottom of the crater, ash deposits on the inner walls of the crater, and more lapilli around the mouth of the crater (figure 50). POVI webcams recorded a significant increase in the intensity of incandescence from the summit crater on 24 June 2017 (figure 51).

Figure (see Caption) Figure 50. An increase in explosive activity with respect to that observed on 5 June was noted by POVI scientists on a visit to the summit crater of Villarrica on 19 June 2017. Fresh ash deposits and lapilli appeared on the snow around the crater rim (yellow arrows). Courtesy of POVI (Volcán Villarrica, Resumen del Comportamiento, Observado en Junio 2017).
Figure (see Caption) Figure 51. A significant increase in the intensity of the incandescence emitted from the summit crater at Villarrica was observed in the webcams during the night of 23-24 June 2017. The upper images show the incandescence in the early evening of 23 June, and the lower images were taken just after midnight on 24 June 2017 from the POVI webcam. Courtesy of POVI (Volcán Villarrica, Resumen del Comportamiento, Observado en Junio 2017).

On 1 July 2017, POVI captured a webcam image of Strombolian explosions that sent incandescent material 60 m high from the summit crater. OVDAS reported steam plumes rising no more than 550 m and incandescence at night during July; there were no reported MODVOLC thermal alerts that month, and only a single alert on 30 August. OVDAS reported steam plumes during August rising to 150 m, sporadic ash and larger pyroclastic emissions around the crater rim, and nighttime incandescence.

Activity decreased during September and October 2017, with continued steam emissions rising 300-500 m, minor ash emissions around the crater rim, and nighttime incandescence. Two MODVOLC thermal alerts were issued, on 4 and 16 September, and none during October. POVI scientists visited the summit during October 2017 and noted that the vent remained active, especially after 22 October. They observed that at least half of the inner walls of the crater were covered with fresh ash and lapilli, concentrated on the W, S, and NE sides. They estimated that the active vent was about 8 m in diameter, approximately 100 m down inside the crater (figure 52). The bottom of the crater appeared about 4 m higher than it was on 26 September 2017, and the vent diameter had expanded by 2 m. Ash and lapilli fragments were found around the edge of the crater on 15, 22, and 25 October. Ejections of small fragments of lava were captured by the webcam on 22 and 23 October.

Figure (see Caption) Figure 52. A panoramic image of the summit crater at Villarrica, looking S on 15 October 2017, showed pyroclastic material covering much of the inner surface of the crater wall. The vent was estimated to be about 8 m in diameter, at a depth of 100 m. Courtesy of POVI (Seguimiento y Estudio del Comportamiento, Volcán Villarrica, Octubre 2017).

OVDAS reported that during November 2017, the webcams near the summit showed evidence of low intensity, predominantly white degassing to low altitudes (100 m above the summit). Nighttime incandescence associated with occasional explosions around the crater were typical. They also noted that long-period (LP) seismicity increased in both energy amplitude and frequency during the last few days of the month. A gradual increase in RSAM values began on 15 November with a continuous tremor signal. A 4.1 magnitude event was reported on 24 November located 2.6 km ESE of the summit at a depth of 1.8 km. A single MODVOLC thermal alert was reported on 28 November.

Seismicity and thermal anomalies. Seismicity at Villarrica during October 2016-November 2017 was relatively stable (figure 53), although it varied between about 2,500 and 6,500 events per month, with over 90% recorded as LP events, and only a few VT (volcano-tectonic) events. The highest frequency values occurred in May (5,749) and November 2017 (6,484).

Figure (see Caption) Figure 53. Chart of the frequency of seismic events at Villarrica, October 2016-November 2017. LP are Long-Period events, and VT are Volcano-Tectonic events. Data courtesy of OVDAS, SERNAGEOMIN monthly reports.

Infrared data graphed by the MIROVA system (figure 54) indicated the continuous but decreasing frequency and intensity of thermal anomalies at Villarrica between November 2016 and November 2017.

Figure (see Caption) Figure 54. Infrared data graphed by the MIROVA system indicated the continuous but decreasing frequency and intensity of thermal anomalies at Villarrica between November 2016 and November 2017. Courtesy of MIROVA.

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

Information Contacts: Servicio Nacional de Geología y Minería, (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Proyecto Observación Villarrica Internet (POVI) (URL: http://www.povi.cl/); 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://hotspot.higp.hawaii.edu/; http://modis.higp.hawaii.edu/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php?lang=es); 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/); Cristian Gonzalez G., flickr (URL:https://www.flickr.com/photos/cg_fotografia/), photo used under Creative Commons license (https://creativecommons.org/licenses/by-nd/2.0/).

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

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

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

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



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

False Report of Mount Pinokis Eruption

Philippines

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


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

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

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

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

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


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

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

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

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Elgon (Uganda) — December 2005

Elgon

Uganda

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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