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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

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

Bezymianny (Russia) Ongoing thermal anomalies, gas-and-steam plumes, and lava dome growth during February-May 2019; strong explosion in mid-March

Nevados de Chillan (Chile) Small ash explosions and dome growth during December 2018-May 2019; ballistic ejecta deposited around the crater, with a pyroclastic flow in May



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/).


Bezymianny (Russia) — June 2019 Citation iconCite this Report

Bezymianny

Russia

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

All times are local (unless otherwise noted)


Ongoing thermal anomalies, gas-and-steam plumes, and lava dome growth during February-May 2019; strong explosion in mid-March

Volcanism at Bezymianny has been frequent since 1955. During the last reporting period, observations primarily consisted of moderate gas-and-steam emissions and thermal anomalies. Lava dome growth has been reported, as well as the effusion of several lava flows onto the dome flanks. Monitoring is the responsibility of the Kamchatka Volcano Eruptions Response Team (KVERT). Activity during February to mid-March 2019 consisted of predominantly moderate gas-and-steam emissions. Incandescent, hot avalanches from the lava dome, strong fumarolic activity, and a thermal anomaly began to occur in mid-March 2019. This reporting period includes activity from February-May 2019.

One explosion occurred during this reporting period. According to video data from KVERT and seismic data from the Kamchatka Branch of the Geophysical Service, on 15 March 2019 an explosion sent ash up to an altitude of 15 km. According to the KVERT Weekly Reports, satellite data showed large ash clouds from this eruption drifting several thousands of kilometers east from the volcano. The Volcano Observatory Notice for Aviation (VONA) issued by KVERT for this event described ash clouds to a distance of about 870 km. Ashfall was reported in Ust'-Kamchatsk (115 km E) on 15 March and Nikolskoe (350 km E) on 15-16 March 2019.

Beginning 15 March and continuing through May 2019, the number of hot avalanches from the lava dome top significantly increased, as well as the temperature of the thermal anomalies as reported by KVERT based on satellite data. Incandescent lava dome growth with extruding, viscous lava flows accompanying strong fumarolic activity and thermal anomalies continued in late April-May 2019 (figure 30).

Figure (see Caption) Figure 30. Fumarolic plume rising above at Bezymianny on 14 April 2019. Photo by A. Klimova, courtesy of the Institute of Volcanology and Seismology FEB RAS, KVERT.

MODIS infrared data processed by MIROVA showed stronger and more frequent thermal anomalies in mid-March 2019 compared to the typical thermal activity since late January and afterwards through May (figure 31). According to the MODVOLC algorithm, 11 hotspot pixels were recorded between February and May 2019.

Figure (see Caption) Figure 31. Thermal anomalies at Bezymianny for September 2018 through May 2019 as recorded by the MIROVA system (Log Radiative Power). Courtesy of MIROVA.

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

Information Contacts: 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/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences (KB GS RAS) (URL: http://www.emsd.ru/); 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/).


Nevados de Chillan (Chile) — June 2019 Citation iconCite this Report

Nevados de Chillan

Chile

36.868°S, 71.378°W; summit elev. 3180 m

All times are local (unless otherwise noted)


Small ash explosions and dome growth during December 2018-May 2019; ballistic ejecta deposited around the crater, with a pyroclastic flow in May

The current Nevados de Chillán eruption period began on 8 January 2018 with a phreatic explosion from the new Nicanor crater, within the Nuevo crater; a new dome was observed within this crater the next day. Dome growth continues with explosions that eject ash plumes and incandescent ejecta. This bulletin summarizes activity from December 2018 through May 2019 and is based on reports by Chile's Servicio Nacional de Geología y Minería (SERNAGEOMIN)-Observatorio Volcanológico de Los Andes del Sur (OVDAS) and satellite imagery.

Throughout December 2018 pulsating emissions from the Nicanor crater produced white plumes predominantly composed of water vapor, with occasional ash ejections giving the plume a gray appearance. Incandescence was frequently observed during the night due to the ejection of hot ballistic ejecta emplaced around the crater during explosions. After 11 months of observations, the dacite dome in the crater maintained a semi-stable extrusion rate of around 345 m3/day. Explosions were reported on 7, 17, 28, and 29 December.

Similar background activity continued through January with pulsating gas-and-steam plumes occasionally including ash, and incandescence observed during the nights due to hot ejecta around the crater. Explosions were recorded at 0500 and 1545 on 11 January, and on 13, 21, and 31 January (figures 33 and 34). During the night explosions and incandescent ejecta were observed impacting the area around the crater.

Figure (see Caption) Figure 33. An explosion at Nevados de Chillán on 11 January 2019. The explosion ejected incandescent blocks that impacted the flanks. The timestamp is at the top left of each image; screenshots are of footage courtesy of SERNAGEOMIN.
Figure (see Caption) Figure 34. An explosion at Nevados de Chillán on 31 January 2019 produced an ash plume from the Nicanor crater. Courtesy of SERNAGEOMIN.

Activity continued through February similar to previous months. The dome in the crater maintained a low extrusion, and activity alternated between dome growth and partial destruction during explosions. Steam-and-gas plumes with occasional ash content continued, with plumes reaching 1 km and drifting in multiple directions. Incandescence was observed during the night. Explosions were reported on 15 February.

During March through May, typical activity consisting of pulsating emission of steam plumes with occasional ash content, and incandescence at night, continued. Intermittent explosions associated with the partial destruction of the dome continued, with events reported on 1 March at 2323, and on 4, 7, and 8 March. Several explosions were reported during 8-9 and 23-30 April. Three explosions were reported on 3 May with one of them producing a 2-km-high ash plume and a pyroclastic flow on 10 May (figure 35). Additional explosions occurred on the 12 and 18 May.

Figure (see Caption) Figure 35. An explosion at Nevados de Chillán on 10 May 2019 produced an ash plume that rose to 2 km above the crater and a pyroclastic flow. The white plume in the bottom two images is steam from the interaction of the hot pyroclastic material and the snow. Screenshots are of a video courtesy of SERNAGEOMIN with timestamps indicated in the top left of each image.

Satellite data from December 2018 through May 2019 recorded intermittent thermal energy, with an increase after February 2019 (figure 36). Thermal anomalies from MODIS instruments were detected by the MODVOLC system on 29 March and 17 May 2019 (two anomalies). A thermal anomaly in the Nicanor crater was persistent in Sentinel-2 data throughout this period.

Figure (see Caption) Figure 36. Thermal anomalies at the active Nicanor crater of the Nevados de Chillán complex. Top: Sentinel-2 thermal image of showing the location of the thermal anomaly (orange). Bottom: MIROVA log radiative power plot of MODIS thermal infrared data from September 2018 through May 2019. Thermal signatures are intermittent and increase after February 2019. Note that the black lines are not from the crater and are unlikely to be related to volcanic activity. Courtesy of Sentinel Hub Playground and MIROVA.

Geologic Background. The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height.

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

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Scientific Event Alert Network Bulletin - Volume 12, Number 06 (June 1987)

Managing Editor: Lindsay McClelland

Aira (Japan)

Explosions and ash emission continue; gas damages trees

Akutan (United States)

Summit incandescence; ash and steam emission

Arenal (Costa Rica)

Stronger explosions; ashfalls to 20 km W

Atmospheric Effects (1980-1989) (Unknown)

New stratospheric layer may be from forest fire smoke

Bagana (Papua New Guinea)

Lava flow remains active

Banda Api (Indonesia)

Small plume observed after large earthquake

Bandaisan (Japan)

Earthquake swarm

Cleveland (United States)

Lava flow and ash emission from summit crater

Erta Ale (Ethiopia)

Landsat data show two crusted lava lakes

Iliboleng (Indonesia)

Earthquakes increase; 300-m-high plume

Izu-Oshima (Japan)

Three earthquake swarms; intermittent tremor continues

Kilauea (United States)

Lava flow builds coast, destroys house; inflation resumes

Lokon-Empung (Indonesia)

Two ash explosions

Macdonald (Undersea Features)

Acoustic waves recorded from eruption

Mahawu (Indonesia)

Lake volume and temperature increase, seismicity rises

Manam (Papua New Guinea)

Violent Strombolian eruption; pyroclastic flows

Marapi (Indonesia)

Small explosions; ashfall on two cities

Okmok (United States)

Minor ash emission

Pavlof (United States)

Incandescent flow; summit glow; ash emission continues

Rabaul (Papua New Guinea)

Seismicity, deformation, and tilt low

Ruiz, Nevado del (Colombia)

Peak 1987 SO2 emission; seismicity declines

Sangeang Api (Indonesia)

Frequent explosions continue

Semeru (Indonesia)

Normal Vulcanian activity

Tacana (Mexico-Guatemala)

Steam output decreases; gas analyses

White Island (New Zealand)

Explosions weaken; inflation accelerates



Aira (Japan) — June 1987 Citation iconCite this Report

Aira

Japan

31.593°N, 130.657°E; summit elev. 1117 m

All times are local (unless otherwise noted)


Explosions and ash emission continue; gas damages trees

An explosion was recorded . . . at 1718 on 14 May, for the first time in 1.5 months. Only two explosions had been recorded since 23 January but quiet ash emission occurred about 20 times a month during those four months. The explosion did not cause any damage. Three explosions were recorded in June, on the 14th, 15th, and 19th. Volcanic gas mixed with rain damaged the island's orange orchard and trees in Kagoshima City . . . on 15 and 16 June. Maximum ash cloud height was 1,500 m on 5 and 13 June. 335 g/m2 of ash accumulated in June at [KLMO]. About 100-400 explosions have been recorded yearly since 1955, with 476 explosions in 1985 and 216 in 1986. Only 18 explosions have been recorded this year, 13 in January.

Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Information Contacts: JMA.


Akutan (United States) — June 1987 Citation iconCite this Report

Akutan

United States

54.134°N, 165.986°W; summit elev. 1303 m

All times are local (unless otherwise noted)


Summit incandescence; ash and steam emission

On about 22 June (± 1 day), a bright red glow from the summit was seen by a fisherman a considerable distance from the volcano in the Bering Sea. On 24 June a pilot reported that the large cinder cone within the summit caldera was sending ash SW at 1,300 m altitude. Two days later pilot H. Wilson (Peninsula Airways) observed a 300-m-high steam plume from the cinder cone and fresh-looking gray-black ash that extended below the snow line on the W flank. No significant eruptive activity was occurring during several sightings from March to early June.

Geologic Background. One of the most active volcanoes of the Aleutian arc, Akutan contains 2-km-wide caldera with an active intracaldera cone. An older, largely buried caldera was formed during the late Pleistocene or early Holocene. Two volcanic centers are located on the NW flank. Lava Peak is of Pleistocene age, and a cinder cone lower on the flank produced a lava flow in 1852 that extended the shoreline of the island and forms Lava Point. The 60-365 m deep younger caldera was formed during a major explosive eruption about 1600 years ago and contains at least three lakes. The currently active large cinder cone in the NE part of the caldera has been the source of frequent explosive eruptions with occasional lava effusion that blankets the caldera floor. A lava flow in 1978 traveled through a narrow breach in the north caldera rim almost to the coast. Fumaroles occur at the base of the caldera cinder cone, and hot springs are located NE of the caldera at the head of Hot Springs Bay valley and along the shores of Hot Springs Bay.

Information Contacts: J. Reeder, ADGGS.


Arenal (Costa Rica) — June 1987 Citation iconCite this Report

Arenal

Costa Rica

10.463°N, 84.703°W; summit elev. 1670 m

All times are local (unless otherwise noted)


Stronger explosions; ashfalls to 20 km W

During the first half of June, activity was at a relatively low level, with an average of four explosions daily (figure 12). A moderate increase was recorded beginning 17 June, with several significant explosions: 27 June, 1455; 28 June, 1503; and 29 June, 1655. These ejected substantial quantities of vapor, ash, and blocks. Ash clouds reached Tilaran, 20 km W of Arenal. Costa Rican geologists noted that such increases in activity have been a normal part of the current eruption.

Figure (see Caption) Figure 12. Daily number of Arenal's volcanic earthquakes recorded at station FOR, June 1987. Courtesy of ICE.

Geologic Background. Conical Volcán Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1670-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. Arenal lies along a volcanic chain that has migrated to the NW from the late-Pleistocene Los Perdidos lava domes through the Pleistocene-to-Holocene Chato volcano, which contains a 500-m-wide, lake-filled summit crater. The earliest known eruptions of Arenal took place about 7000 years ago, and it was active concurrently with Cerro Chato until the activity of Chato ended about 3500 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. An eruptive period that began with a major explosive eruption in 1968 ended in December 2010; continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows characterized the eruption from vents at the summit and on the upper western flank.

Information Contacts: R. Barquero and Guillermo Alvarado, ICE.


Atmospheric Effects (1980-1989) (Unknown) — June 1987 Citation iconCite this Report

Atmospheric Effects (1980-1989)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


New stratospheric layer may be from forest fire smoke

An apparently new aerosol layer was detected at the base of the stratosphere on lidar and balloon data. The source of the aerosols was uncertain. No large explosive eruptions were documented in the weeks before the layer was first observed in early June. However, large forest fires that burned from about 6 to 22 May in N China produced extensive clouds of smoke that were tracked for thousands of kilometers on NOAA weather satellite imagery. One major smoke plume moved over Kamchatka, then covered most of the Gulf of Alaska before advancing over Canada's Yukon Territory. Another extended into the Arctic Basin in streamers several hundred kilometers wide and thousands of kilometers long. A third major zone of smoke entered a low pressure area and could be traced as far as Ellesmere Island, just W of northern Greenland.

Instruments on a balloon launched near Laramie, WY on 29 May detected strong particle enhancement from ground level through the tropopause into the lower stratosphere. Highest values were measured between 10 km and the top of the layer at about 13 km, with concentrations of particles larger than 0.15 µm exceeding 10/19cm3, compared to recent lower stratospheric values of about 0.5/cm3. Concentrations remained above 5/cm3 throughout the troposphere, increasing to more than 10/19cm3 near ground level. More than a month later (8 July), the next balloon flight from Laramie detected no unusual tropospheric material, but an aerosol layer extended from the tropopause at 11 km to about 14 km. Counts of particles larger than 0.15 µm reached 3/cm3. The layer was relatively smooth and the distribution of particle sizes suggested that it was probably several weeks old (figure 42). The ratios of the number of particles of 0.15 µm diameter to those of 0.25 µm size was somewhat less than 10 on 29 May, decreasing to about 5 on 8 July. Smaller particles are generally expected from biomass burning, typically yielding ratios of the 0.15/0.25 µm size fractions greater than 10, compared to values of 2-5 for eruption-generated aerosols.

Figure with caption Figure 42. Plots of concentrations of particles with radii >0.15 µm counted from balloons launched from Laramie, WY on 29 May and 8 July 1987. Note that the x axis is a logarithmic scale. The 8 July tropopause was at about 11 km altitude.

Lidar at Hampton, VA detected a distinct layer between the tropopause (13 km) and 15 km altitude on 10 June (figure 43). Eight days later, remnants of the layer were still present, but it was not evident on 25 or 29 June.

Figure with caption Figure 43. Lidar data from various locations, showing altitudes of aerosol layers. Note that some layers have multiple peaks. Backscattering ratios from Fukouka, Japan, are for the Nd-YAG wavelength of 1.06 µm; all others are for the ruby wavelength of 0.69 µm. Integrated values show total backscatter, expressed in steradians-1, integrated over 300-m intervals from 16-33 km at Mauna Loa and from the tropopause to 30 km at Hampton, Virginia. Altitudes of maximum backscattering ratios and coefficients are shown for each layer at Mauna Loa.

A strong but thin layer at the tropopause (15.6 km) was observed 19 May by lidar at Mauna Loa, Hawaii, and the upper troposphere was very turbid during the next measurement, on 26 May. Each of the five June lidar measurements at Mauna Loa showed a small layer at the base of the stratosphere, most strongly on 16 June. The upper troposphere remained turbid through June. On 11 June a very strong scattering layer that had not been present 2 days earlier appeared just above the tropopause at Fukuoka, Japan. A similar but weaker layer was detected again on 25 June, but was not evident on 16, 22, or 26 June. Late on 10 July, lidar at Garmisch-Partenkirchen, West Germany measured minor peaks at 12.5 and 14 km, probably near the tropopause, with scattering ratios estimated at 1.2-1.3. The next day, peaks of the same intensity were observed at 14 and 16 km, and on 12 July there was a peak of the same scattering ratio at 15 km.

Integrated backscatter data from Mauna Loa, January 1985-June 1987, show a rapid decline in the aerosol produced by the 1982 El Chichón eruption, a sudden increase in June 1985 from an unknown source, then a decline until the appearance of the Ruiz aerosol in December 1985. A gradual increase was observed through much of 1986, then values have diminished for most of the first half of 1987.

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

Information Contacts: David Hofmann and James Rosen, Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 USA; William Fuller and Mary Osborn, NASA Langley Research Center, Hampton, VA 23665 USA; Thomas DeFoor, Mauna Loa Observatory, P. O. Box 275, Hilo, HI 96720 USA; Motowo Fujiwara, Physics Department, Kyushu University, Fukuoka 812, Japan; Horst Jäger, Fraunhofer-Institut für Atmosphärische Umweltforschung, Kreuzeckbahnstrasse 19, D-8100 Garmisch-Partenkirchen, West Germany; Will Gould, NOAA/NESDIS, World Weather Building, Camp Springs, MD 20746, USA.


Bagana (Papua New Guinea) — June 1987 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)


Lava flow remains active

Activity continued at a steady moderate level throughout June. Strong white vapour emissions were occasionally tinged with brown or grey ash. Several aerial inspections and close-up ground observations suggested that most of the emitted ash was derived from debris avalanches from the summit area where a mound of lava filled the crater. Rock slides were common at the edges of the active lava flow on the N to NW flanks. Occasional incandescent ejections from the summit were reported by a schoolteacher living near the S base of the volcano. Glow from the summit was reported often, although volcanologists camped at the E base of the volcano on 17-18 June did not observe any summit incandescence.

An experiment with paint marks on the central part of the lava flow and adjacent marks on the levee banks indicated that the speed of the flow at ~1,200 m elevation was only 1-2 m/day. At this elevation the flow channel is ~20-30 m wide and possibly 10 m deep. These measurements indicate a flow rate of 200-600 m3/day or ~105 m3/year. The total volume of the flow since 1975 is ~106 m3.

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: C. McKee and P. Lowenstein, RVO.


Banda Api (Indonesia) — June 1987 Citation iconCite this Report

Banda Api

Indonesia

4.523°S, 129.881°E; summit elev. 596 m

All times are local (unless otherwise noted)


Small plume observed after large earthquake

A M 6.7 tectonic earthquake occurred 150 km SE of Banda Api on 17 June (preliminary epicenter 5.58°S, 130.88°E). Activity consisting of a white plume, reaching 100 m above Banda Api's crater, was reportedly observed after the earthquake. However, photographs taken during a climb to the crater 24-26 April showed no plume or gas emission.

Geologic Background. The small island volcano of Banda Api is the NE-most volcano in the Sunda-Banda arc and has a long period of historical observation because of its key location in the Portuguese and Dutch spice trade. The basaltic-to-rhyodacitic volcano is located in the SW corner of a 7-km-wide mostly submerged caldera that comprises the northernmost of a chain of volcanic islands in the Banda Sea. At least two episodes of caldera formation are thought to have occurred, with the arcuate islands of Lonthor and Neira considered to be remnants of the pre-caldera volcanoes. A conical peak rises to about 600 m at the center of the 3-km-wide Banda Api island. Historical eruptions have been recorded since 1586, mostly consisting of Strombolian eruptions from the summit crater, but larger explosive eruptions have occurred and occasional lava flows have reached the coast.

Information Contacts: VSI.


Bandaisan (Japan) — June 1987 Citation iconCite this Report

Bandaisan

Japan

37.601°N, 140.072°E; summit elev. 1816 m

All times are local (unless otherwise noted)


Earthquake swarm

An earthquake swarm began 16 June, with 155 events recorded that day by the seismograph 2 km SSE of the summit (table 1). Epicenters were mainly concentrated 10 km SW. Seismicity decreased to

Table 1. Daily number of felt earthquakes at Wakamatsu Observatory, 10 km W of the epicentral area of the Bandai swarm, June 1987.

Date Felt Events
16 Jun 1987 7
17 Jun 1987 2
18 Jun 1987 1
21 Jun 1987 2
23 Jun 1987 2

Geologic Background. One of Japan's most noted volcanoes, Bandaisan rises above the north shore of Lake Inawashiro. This complex is formed of several overlapping andesitic stratovolcanoes, the largest of which is Obandai. Kobandai volcano, which collapsed in 1888, was formed about 50,000 years ago. Obandai volcano was constructed within a horseshoe-shaped caldera that formed about 40,000 years when an older volcano collapsed, forming the Okinajima debris avalanche, which traveled to the SW and was accompanied by a plinian explosive eruption. The last magmatic eruption took place more than 25,000 years ago, but four major phreatic eruptions have occurred during the past 5000 years, two of them in historical time, in 806 and 1888. Seen from the south, Bandaisan presents a conical profile, but much of the north side of the volcano is missing as a result of the collapse of Ko-Bandai volcano during the 1888 eruption, in which a debris avalanche buried several villages and formed several large lakes.

Information Contacts: Japan Meteorological Agency (JMA).


Cleveland (United States) — June 1987 Citation iconCite this Report

Cleveland

United States

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

All times are local (unless otherwise noted)


Lava flow and ash emission from summit crater

On 19 June pilot T. Madsen (Aleutian Airways) observed minor bluish-brown ash rising to 2,000-2,500 m altitude and drifting SE for as much as 50 km. Later that day (about 1300) Madsen observed continued fine ash emissions. Fresh ash was seen on all flanks of the volcano but was concentrated on the ESE flank. Two or three large hot rocks fell from the summit onto the ESE flank during his observations.

Pilot Harold Wilson (Peninsula Airways) observed Mt. Cleveland several times between 22 and 29 June. At 1600 on 22 June a steam plume was rising ~300 m above the summit and fresh black ash covered most of the volcano; snow had fallen in the region in the last week. At noon the next day incandescent lava was visible in the cracks of a 30-m-diameter dome-like feature within the summit crater. A narrow lava flow extended down the ESE slope and ponded at the base of the volcano. Blocks were thrown to 30 m above the vent and steam rose ~450 m above the summit. Numerous photos were taken. The "dome" incandescence and steam emission remained visible through 26 June. On 27 June the volcano was obscured by steam and clouds. Wilson noted that the activity was the most intense he had ever seen at Mt. Cleveland since he began flying in the region in 1980.

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: J. Reeder, ADGGS.


Erta Ale (Ethiopia) — June 1987 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


Landsat data show two crusted lava lakes

The following is abstracted from Rothery and others (1988). Landsat TM data acquired 5 January 1986 show both lakes. The northern one had shrunk to no more than 60 m across and the S lake was ~150 m in diameter. Temperatures derived from the data suggest that the lakes were quiescent with cool (< 400°C) crust. Incandescent cracks at ~1,150°C occupied < 0.4% of the surface area.

Reference. Rothery, D.A., Francis, P.W., and Wood, C.A., 1988, Volcano monitoring using short wavelength infrared data from satellites: JGR, v. 93, no. B7, p. 7993-8008.

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

Information Contacts: D. Rothery, Open Univ.


Iliboleng (Indonesia) — June 1987 Citation iconCite this Report

Iliboleng

Indonesia

8.342°S, 123.258°E; summit elev. 1659 m

All times are local (unless otherwise noted)


Earthquakes increase; 300-m-high plume

Since 20 June, a plume has risen as much as 300 m above the summit. The number of shallow volcanic earthquakes increased to ~20/day 20-25 June, compared to 1/day previously. No eruptive activity has been reported since November.

Geologic Background. Iliboleng stratovolcano was constructed at the SE end of Adonara Island across a narrow strait from Lomblen Island. The volcano is capped by multiple, partially overlapping summit craters. Lava flows modify its profile, and a cone low on the SE flank, Balile, has also produced lava flows. Historical eruptions, first recorded in 1885, have consisted of moderate explosive activity, with lava flows accompanying only the 1888 eruption.

Information Contacts: VSI.


Izu-Oshima (Japan) — June 1987 Citation iconCite this Report

Izu-Oshima

Japan

34.724°N, 139.394°E; summit elev. 758 m

All times are local (unless otherwise noted)


Three earthquake swarms; intermittent tremor continues

Three earthquake swarms occurred in May. The first, 15 km NW of the island, lasted from 6 to about 20 May. It was followed by two weaker swarms; in the SE part of the volcano 22-26 May, and near the summit from 22 May to mid-June (figure 7). About 89 shocks were recorded at the Oshima weather station during the 6-20 May swarm (figure 8), the largest a M 5.1 event at 0635 on 11 May. Swarms have occurred in that area one or two times a year since 1978, most recently in October 1986.

Figure (see Caption) Figure 7. Earthquake swarms in Oshima area, May 1987. Epicentral areas are shaded. Courtesy of JMA.
Figure (see Caption) Figure 8. Daily seismicity of the earthquake swarm NW of Oshima, 5-31 May 1987. Courtesy of JMA.

The 22-26 May swarm was the first increase in seismicity in the SE part of the island since the eruption. The largest event, at 0626 on 23 May, had a magnitude of 3.0 and was felt at the weather station. Seismicity in the SE part of the island had decreased steadily and exponentially since the 1986 eruption (figure 9).

Figure (see Caption) Figure 9. Daily seismicity in SE part of Oshima Island, 10 December 1986 to 10 June 1987. Courtesy of JMA.

An increase in summit-area microearthquakes also began on 22 May. Recorded events increased from about 20/day February-May, to ~40/day after 22 May, and to 100 daily after 29 May; the number of events decreased in mid-June. Steady microearthquake activity had continued near the summit since February, when observation by seismograph began in the area (figure 10). Tremor that began 1 January was intermittently recorded throughout May and June. Tremor episodes generally occurred at regular intervals of 1-2 hours and lasted for about 30 minutes. Beginning 14 May their regularity decreased, intervals between episodes grew from several hours to 20 hours, and episode durations increased to 60-300 minutes (figure 11). The regular tremor interval resumed on 7 June but toward the end of June became irregular again. Long-duration tremor episodes of more than 10 hours were often recorded. Weak steam emission continued at the summit of Miharayama, the central cone, producing about 50-m plumes. Steam rose steadily 0-5 m from craters that had formed on the N-flank fissure in the 1986 eruption.

Figure (see Caption) Figure 10. Daily seismicity in the summit area of Oshima, 20 February-10 June 1987. Courtesy of JMA.
Figure (see Caption) Figure 11. Duration of volcanic tremor at Oshima, January-June 1987. Courtesy of JMA.

Geologic Background. Izu-Oshima volcano in Sagami Bay, east of the Izu Peninsula, is the northernmost of the Izu Islands. The broad, low stratovolcano forms an 11 x 13 km island and was constructed over the remnants of three dissected stratovolcanoes. It is capped by a 4-km-wide caldera with a central cone, Miharayama, that has been the site of numerous historical eruptions. More than 40 parasitic cones are located within the caldera and along two parallel rift zones trending NNW-SSE. Although it is a dominantly basaltic volcano, strong explosive activity has occurred at intervals of 100-150 years throughout the past few thousand years. Historical activity dates back to the 7th century CE. A major eruption in 1986 produced spectacular lava fountains up to 1600 m height and a 16-km-high subplinian eruption column; more than 12,000 people were evacuated from the island.

Information Contacts: JMA.


Kilauea (United States) — June 1987 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Lava flow builds coast, destroys house; inflation resumes

Lava continued to emerge along the S coast from the tube system . . . . On 4 June lava again entered the ocean, and continued to flow into the sea until late in the month. It was more active 10-24 June than at any time since it entered the ocean, flowing at an increased rate, generating steam clouds and black sand, and forming pillow lavas. The flow front was ~700 m wide as it entered the ocean and extended at least 50 m from the old shore. The flow into the ocean declined 25-26 June and stopped between the 27th and the 30th.

Although no aerial photos have been taken, and no estimate made of the amount of new land added to the island, figure 50 shows the ~1.5 km of new shoreline.

Figure (see Caption) Figure 50. Sketch map of the S coast of Hawaii showing Kilauea's March-June lava flows and the approximate position of the new shoreline.

From 1 to 6 June, lava threatened the two remaining houses in the kipuka formed in November, and on the 6th, one was destroyed. From 8 June, lava threatened to bury the remains of an historic church established by Father Damien, a famous Hawaiian cleric, and a beach house off the edge of the November 1986 flow margin. By the end of the month, the old church was surrounded by 3-4 m of lava. On the 29th, a lobe of the lava flow covered another 200 m of highway reconstructed after the November-December blockage. It flowed across the highway and moved E, funneling into a small graben behind the beach house. Inland, at the shield surrounding the vent, activity remained about the same. The level of the lava pond fluctuated between overflowing and 5 m below the rim. Tumescence on the N flank of the shield has continued but at a reduced rate.

On 25 June at 2146 a moderate seismic event occurred, associated with partial collapse of the conduit at Pu`u `O`o, the sole source of lava production from 13 June 1983 to 19 July 1986. When part of the conduit wall collapsed, the conduit was enlarged from 10 to 30-40 m in diameter. Bright red magma was sighted ~100 m down in the inactive vent, before it crusted over. There was a high rate of microshocks caused by rockfalls from the conduit walls and resulting structural readjustments within the cone.

Harmonic tremor continued at low level . . . near the eruption site. The number of shallow short-period earthquakes remained nearly constant at average levels. There was a swarm of intermediate-depth long-period events during the second week of June (figure 51).

Figure (see Caption) Figure 51. Kilauea's activity, January-June 1987, showing summit tilt, short- and long-period earthquakes, carbon/sulfur ratio of summit gases, MgO content of lavas, and estimated lava volume.

The E-W tiltmeter at Kilauea's summit indicated an inflationary trend following almost a month of gradual deflation. The level of tilt remained low relative to the peak of inflation prior to E-48 (19 July 1986).

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

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


Lokon-Empung (Indonesia) — June 1987 Citation iconCite this Report

Lokon-Empung

Indonesia

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

All times are local (unless otherwise noted)


Two ash explosions

Lokon-Empung generally remained quiet during May and June, with only two ash explosions, on 10 and 13 May. Ash columns rose ~750 m above Tompaluan Crater. Explosions began in March 1986, but have been infrequent for the last few months.

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

Information Contacts: VSI.


Macdonald (Undersea Features) — June 1987 Citation iconCite this Report

Macdonald

Undersea Features

28.98°S, 140.25°W; summit elev. -39 m

All times are local (unless otherwise noted)


Acoustic waves recorded from eruption

An eruption was detected by acoustic waves (T-phase) received by RSP stations 6-7 July. Explosions began around 0100 on 6 July and were followed by continuous noise of variable level, with episodes of stronger intensity. The 27.5 hour crisis [but see 12:09] was . . . comparable to the November 1980 eruption in duration and intensity.

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

Information Contacts: J. Talandier, LDG Tahiti.


Mahawu (Indonesia) — June 1987 Citation iconCite this Report

Mahawu

Indonesia

1.352°N, 124.865°E; summit elev. 1299 m

All times are local (unless otherwise noted)


Lake volume and temperature increase, seismicity rises

A 100-m white plume was first seen emerging from the summit crater on 17 April (12:04). A similar whitish plume was continuously present above the summit in May and June. Both tectonic and volcanic earthquakes had increased at the end of April and continued to be recorded in May and June. By 30 June, the crater lake volume had increased to 45,000 m3 and water temperature had increased to 48°C.

Geologic Background. The elongated Mahawu volcano immediately east of Lokon-Empung volcano is the northernmost of a series of young volcanoes along a SSW-NNE line near the margin of the Quaternary Tondano caldera. Mahawu is capped by a 180-m-wide, 140-m-deep crater that sometimes contains a small crater lake, and has two pyroclastic cones on its N flank. Historical activity has been restricted to occasional small explosive eruptions recorded since 1789. In 1994 fumaroles, mudpots, and small geysers were observed along the shores of a greenish-colored crater lake.

Information Contacts: VSI.


Manam (Papua New Guinea) — June 1987 Citation iconCite this Report

Manam

Papua New Guinea

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

All times are local (unless otherwise noted)


Violent Strombolian eruption; pyroclastic flows

"A short-lived phase of violent Strombolian activity occurred at Southern Crater on 30 June, producing pyroclastic flows, minor lava flows, and moderate scoria and ashfalls. This activity followed moderate Strombolian activity that had peaked between 10 and 24 June.

"Weak to moderate Strombolian activity similar to that of late May occurred at Southern Crater in early June. Incandescent lava was ejected several times/minute and ejecta reached maximum heights of ~200 m. The ash content of emissions was low. Activity began to increase about 3 June and reached a peak on 10-12 June when lava was ejected to ~800 m and blue vapour was strongly emitted. A temporary increase in ash emission on 15 June fed a 800-m-high curved plume that extended ~1 km. Between 10 and 24 June, seismicity fluctuated at a moderate-high level before declining. During the latter part of this period, lava ejections rose a few hundred meters and an ash column up to 500 m high crowned the summit. A small scoria cone (~20 m) formed around the active vent in Southern Crater. Small debris avalanches from the cone's flanks flowed into the SW and SE valleys.

"Although there were visible and seismic indications of declining activity in late June, a sharp increase in activity took place on 30 June. Seismicity began increasing in the morning and Strombolian activity strengthened progressively. At 2140, activity suddenly culminated in 2 exceptionally large ejections of lava that reached over 500 m height. A continuous eruption of a >2-km-high ash column followed.

"Eyewitnesses on mainland New Guinea saw cascades of glowing lava fragments descending into the SW valley during the 30 June eruption. Vivid lightning was observed, first only at the base of the eruption column, then after a few minutes throughout the dense eruption cloud. The cloud was blown ~20 km W in the following hour and lightning discharges continued in and around the cloud every few seconds.

"A mild roaring accompanied the eruption which generated several pyroclastic flows that descended ~2.5 km into the SW valley and ~3.5 km into the SE valley. The flows were 20-30 m wide and overlapped near their source, but with distance flow width narrowed to 10-20 m. Most flows were 1-2 m thick. The clasts in the flow deposits were generally small, the largest ~30 cm. However, large accidental blocks up to 5 m in diameter were picked up by a stronger flow in the SE valley.

"Airfall scoria was concentrated in a narrow sector downwind of the eruption column. The deposit was ~2 km wide on the W coast, ~5 km from the source. The maximum scoria thickness was ~30 mm and the largest scoria clasts were ~60 mm, with an average of ~10 mm. The scoria clasts were highly vesicular and contained small olivine phenocrysts, appearing to be basaltic in composition. Small rafts of scoria were observed offshore on the morning of 1 July, but most had sunk by later that day. Ashfall continued after the scoria fall had ended. The dispersal axis during ashfall migrated N (~1 km at the W coast), relative to the dispersal axis of the scoria fall, indicating a slight wind shift. The maximum ash thickness was ~5 mm. Very light ashfall took place on Boisa Island ~12 km NW of the summit, and near Awan on the mainland ~20 km W of Manam. No human injuries resulted from the scoria fall but some birds were reported to have been killed and some food gardens were damaged.

"Two minor lava flow sources were identified at the scoria cone at the top of Southern Crater. One flowed through a chute into the SW valley, where the lava flow broke up as it cascaded down the valley headwall. The other flow appeared to breach the scoria cone's E flank but may have been partially welded scoria. A lobate flow was emplaced on the upper part of the talus fan heading into the SE valley. The flows may only have been active for a short time.

"Southern Crater activity decayed rapidly following the end of the violent Strombolian phase. No incandescent lava ejections were seen after 2300 on 30 June, but thick ash clouds continued to be released throughout the following day. Seismicity had returned to the levels of late May by about 7 July. Main Crater emitted vapour and possibly ash and showed weak fluctuating glow throughout June. Main Crater glow appeared brighter after activity at Southern Crater declined at about 2300 on the 30th. No significant changes in tilt were observed in June, although readings tended to be somewhat erratic.

"Aerial Inspections in early July indicated that there had been no rise of magma in Main Crater, which was at least 100 m wide, 70 m deep, and funnel-shaped. White and blue vapours were being emitted from an incandescent vent of ~10x3 m at the base of the crater. Southern Crater activity at this time consisted of 3-6 weak Strombolian ejections/minute, rising to the level of the rim from the 60-m-deep base of the funnel-shaped crater. Thin orange-brown ash emissions from Southern Crater and the blue and white vapours from Main Crater rose gently to ~200 m above the summit before being blown W and dispersing ~2-3 km downwind."

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

Information Contacts: C. McKee and P. Lowenstein, RVO.


Marapi (Indonesia) — June 1987 Citation iconCite this Report

Marapi

Indonesia

0.38°S, 100.474°E; summit elev. 2885 m

All times are local (unless otherwise noted)


Small explosions; ashfall on two cities

Small explosions occurred on 25 and 30 May, and 1, 5, 7, 9, 10, and 11 June, with column heights reaching 1 km above the summit. A light dusting of ash fell on Bukittinggi, [15] km NW [of the summit], and Padang, [65] km [SSW]. The previous activity at Marapi occurred 15 January.

Geologic Background. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2000 m above the Bukittinggi plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Information Contacts: VSI.


Okmok (United States) — June 1987 Citation iconCite this Report

Okmok

United States

53.43°N, 168.13°W; summit elev. 1073 m

All times are local (unless otherwise noted)


Minor ash emission

Peninsula Airways pilot H. Wilson noted a bluish-gray haze just ESE of Okmok Caldera on 10 June at 1600, although clouds obscured the volcano. On 18 June at about 1500, Jay Brian Carribaburu (Peninsula Airways) observed minor ash emission from a cinder cone in the SW part of the caldera. Steam and ash were being continuously emitted from the cinder cone when T. Madsen (Aleutian Airways) flew by on 19 June at 1140. Steam and ash rose to 2,100 m (~1 km above the summit) and drifted ~11 km SW. Several large blasts of ash occurred during Madsen's observations. On 23 June, Wilson saw steam with minor ash rising to 500 m above the active cone.

Geologic Background. The broad, basaltic Okmok shield volcano, which forms the NE end of Umnak Island, has a dramatically different profile than most other Aleutian volcanoes. The summit of the low, 35-km-wide volcano is cut by two overlapping 10-km-wide calderas formed during eruptions about 12,000 and 2050 years ago that produced dacitic pyroclastic flows that reached the coast. More than 60 tephra layers from Okmok have been found overlying the 12,000-year-old caldera-forming tephra layer. Numerous satellitic cones and lava domes dot the flanks of the volcano down to the coast, including 1253-m Mount Tulik on the SE flank, which is almost 200 m higher than the caldera rim. Some of the post-caldera cones show evidence of wave-cut lake terraces; the more recent cones, some of which have been active historically, were formed after the caldera lake, once 150 m deep, disappeared. Hot springs and fumaroles are found within the caldera. Historical eruptions have occurred since 1805 from cinder cones within the caldera.

Information Contacts: J. Reeder, Alaska Division of Geological and Geophysical Surveys (ADGGS).


Pavlof (United States) — June 1987 Citation iconCite this Report

Pavlof

United States

55.417°N, 161.894°W; summit elev. 2493 m

All times are local (unless otherwise noted)


Incandescent flow; summit glow; ash emission continues

The eruption . . . continued in June. On 7 June at 1601 pilot Richard Williams (Peninsula Airways) saw an incandescent flow (probably lava) that had descended to 1,200 m elevation on the NNE flank. Ash was rising to 600 m above the volcano from the NE near-summit vent, drifting S. Forty minutes later the ash plume reached 760 m. Residents of Nelson Lagoon, 80 km NE, reported a bright red glow from the summit throughout the night. On 9 June at 1153 a pilot reported only steam emission from the NE near-summit vent.

The following day at 1419 the U.S. Coast Guard reported that gray ash was being emitted from the active vent and 7 hours later pilot Harold Wilson (Peninsula Airways) saw (and photographed) gray then black-gray ash emission. A plume rose to 760 m above the NE vent and drifted 2 km W. The black-gray ash emission was intermittent and lasted for about 15 minutes. Only minor steam emission was reported on 11 June but dark ash emission had resumed on 12 June at 1602 when Chuck Nickerson and George Wooliver (Reeve Aleutian Airways) passed the volcano.

A lava or debris flow seen from 25 km away during the afternoon of 2 June was reported in 12:5. That evening from 2130 to 2200 Marsha Brown (FAA, Cold Bay) saw an incandescent flow move down the NNE flank. Richard Williams observed the incandescent flow from Nelson Lagoon (80 km NE) and estimated that it extended almost 1/3 of the way down the volcano.

Geologic Background. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.

Information Contacts: J. Reeder, ADGGS.


Rabaul (Papua New Guinea) — June 1987 Citation iconCite this Report

Rabaul

Papua New Guinea

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

All times are local (unless otherwise noted)


Seismicity, deformation, and tilt low

A low level of activity continued in June with 128 caldera earthquakes recorded. Most of the 19 located events occurred on the NW part of the caldera seismic zone. Ground deformation rates remained low, although levelling measurements showed an uplift of 10 mm in the NE part of the caldera between 29 April and 23 June. Tilt changes were small with a maximum change of 5-10 µrad of inflation in the E part of the caldera (Greet Harbour area).

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

Information Contacts: C. McKee and P. Lowenstein, RVO.


Nevado del Ruiz (Colombia) — June 1987 Citation iconCite this Report

Nevado del Ruiz

Colombia

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

All times are local (unless otherwise noted)


Peak 1987 SO2 emission; seismicity declines

Low- and high-frequency earthquakes continued at moderate levels after 16 June. Tremor fluctuated but remained weak, reaching a maximum amplitude of 2 mm at the Olleta reference station (4 km W of Arenas crater). The rate of SO2 emission measured by COSPEC reached 5,640 t/d on 17 June, the highest value of 1987. Emission rates then declined to an average of 1,000 t/d for the rest of the month. Little change in deformation was measured.

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

Information Contacts: A. Acevedo, INGEOMINAS, Manizales.


Sangeang Api (Indonesia) — June 1987 Citation iconCite this Report

Sangeang Api

Indonesia

8.2°S, 119.07°E; summit elev. 1949 m

All times are local (unless otherwise noted)


Frequent explosions continue

Eruptive activity continued during May and June with ~50 explosions/day . . . . Plumes reached ~600 m above the crater rim. No earthquakes accompanied the explosions.

Geologic Background. Sangeang Api volcano, one of the most active in the Lesser Sunda Islands, forms a small 13-km-wide island off the NE coast of Sumbawa Island. Two large trachybasaltic-to-tranchyandesitic volcanic cones, 1949-m-high Doro Api and 1795-m-high Doro Mantoi, were constructed in the center and on the eastern rim, respectively, of an older, largely obscured caldera. Flank vents occur on the south side of Doro Mantoi and near the northern coast. Intermittent historical eruptions have been recorded since 1512, most of them during in the 20th century.

Information Contacts: VSI.


Semeru (Indonesia) — June 1987 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Normal Vulcanian activity

. . . Vulcanian activity during May and June.

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

Information Contacts: VSI.


Tacana (Mexico-Guatemala) — June 1987 Citation iconCite this Report

Tacana

Mexico-Guatemala

15.132°N, 92.109°W; summit elev. 4064 m

All times are local (unless otherwise noted)


Steam output decreases; gas analyses

On 11 April a team of Italian scientists inspected the craters and fumaroles produced by the explosion. A steam column more than 100 m high was being emitted, but total steam output appeared to have decreased. The largest fumarole had a temperature of 89.3°C. Analysis of samples from that fumarole gave the following results (in volume percent): CO2, 1.07; H2O, 98.7; H2S, 0.15; N2, 0.019; H2, 0.00082; CH2, 0.00015; NH4, 0.000037; B, 0.00020; O2, 0.000016. The volcanologists interpreted the composition as resulting from the interaction of a convective flow of deep origin with a shallow aquifer. This interpretation appeared to correlate with the mainly phreatic character of the more recent activity, inferred from the deposits. The scientists felt that phreatic explosions of weak intensity could provide a sufficient trigger for dangerous landslides because of the volcano's steep slopes.

Geologic Background. Tacaná is a 4064-m-high composite stratovolcano that straddles the México/Guatemala border at the NW end of the Central American volcanic belt. The volcano rises 1800 m above deeply dissected plutonic and metamorphic terrain. Three large calderas breached to the south, and the elongated summit region is dominated by a series of lava domes intruded along a NE-SW trend. Volcanism has migrated to the SW, and a small adventive lava dome is located in the crater of the youngest volcano, San Antonio, on the upper SW flank. Viscous lava flow complexes are found on the north and south flanks, and lobate lahar deposits fill many valleys. Radial drainages on the Guatemalan side are deflected by surrounding mountains into the Pacific coastal plain on the SW side of the volcano. Historical activity has been restricted to mild phreatic eruptions, but more powerful explosive activity, including the production of pyroclastic flows, has occurred as recently as about 1950 years ago.

Information Contacts: M. Martini, Univ di Firenze, Italy.


White Island (New Zealand) — June 1987 Citation iconCite this Report

White Island

New Zealand

37.52°S, 177.18°E; summit elev. 321 m

All times are local (unless otherwise noted)


Explosions weaken; inflation accelerates

Tephra emission and seismicity declined after the vigorous explosive activity of 13-22 May. Eruption (E-type) sequences were recorded on most seismograms between 22 May and 7 June. The largest event, at 1508 on 4 June, was accompanied by an eruption column clearly visible from the Bay of Plenty coast,>50 km away. Weak medium-frequency volcanic tremor was recorded 22-24 and 26 May, and lower-amplitude tremor bands, each lasting 4-10 hours, have dominated the background of most records since then. The number of low-frequency B-type earthquakes ranged from 3 to 15/day, but amplitudes were considerably lower than earlier in the year.

Geologists visited the crater on 11 June for the first time since the mid-May explosions. Only gas and minor ash emission was occurring from the active (Hitchhiker) vent on the floor of Congress Crater. Ballistic blocks probably ejected by the May explosions had fallen >700 m from the vent, and formed impact craters 0.5 m in diameter within 50 m of the coast (at Crater Bay). Since the 12 May visit, 900 mm of tephra had fallen at a site 60 m ESE of the rim of Congress Crater, but deposits thinned rapidly farther from the vent. All of the examined lapilli- to block-sized ejecta was lithic material, most altered, but some unaltered dense black andesite lava was found. The volume of the May-June tephra was in the order of 105 m3, about half of the total volume of 1987 ejecta.

Rapid local inflation, centered ~200 m ESE of the vent (in the Donald Mound area) occurred between the 12 May and 11 June levelling surveys. Maximum uplift was 29 mm, compared to 7 mm the previous month. Magnetic data showed a sharp (-100 nT) anomaly N of Donald Mound and a broader +100 nT anomaly to the SE. The NZGS interpreted the combined deformation/magnetic data to suggest that local heating was occurring at depths of 200-300 m.

During a brief visit on 30 June, a steam plume containing a little ash rose from the vent, but less vigorously than on 11 June. No new ejecta were evident near the crater rim, but heavy rains within the previous 2-3 days had disrupted the ground surface.

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

Information Contacts: I. Nairn and B. Scott, NZGS Rotorua.

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

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

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (SEAN 30:12) Elgon

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



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

False Report of Mount Pinokis Eruption

Philippines

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


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

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

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

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

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


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

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

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

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Elgon (Uganda) — December 2005

Elgon

Uganda

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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