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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 09, Number 09 (September 1984)

Managing Editor: Lindsay McClelland

Atmospheric Effects (1980-1989) (Unknown)

Two years of lidar data from Germany summarized

Campi Flegrei (Italy)

More M > 3 events with wider distribution, but seismic energy release unchanged and uplift slows

Erebus (Antarctica)

Vigorous explosions, clouds, and incandescent tephra

Etna (Italy)

Lava flows, Strombolian activity and ash emission

Home Reef (Tonga)

Pumice from March eruption found 1,300 km to the WSW

Karangetang (Indonesia)

Seismicity and minor tephra emission since January; ash column and nuées ardentes in September

Kilauea (United States)

Episode 25; highest fountains of 1983-84 eruption; tephra

Long Valley (United States)

Seismicity at relatively low level and inflation

Manam (Papua New Guinea)

Ash-laden emissions, incandescence

Mayon (Philippines)

Explosive activity reintensifies; 73,000 evacuated

Rabaul (Papua New Guinea)

Seismicity, ground deformation rates decline

St. Helens (United States)

New lobe in collapse zone on composite dome

Ulawun (Papua New Guinea)

Mild strombolian eruption

Unzendake (Japan)

Earthquake swarm

Villarrica (Chile)

Brief ash eruption; increased seismicity



Atmospheric Effects (1980-1989) (Unknown) — September 1984 Citation iconCite this Report

Atmospheric Effects (1980-1989)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Two years of lidar data from Germany summarized

Lidar and balloon data showed that aerosols from the March-April 1982 eruption of El Chichón remain in the stratosphere. Despite the 15-km eruption clouds reported during the Mayon eruption, no new aerosol layers were detected. At Mauna Loa, Hawaii, integrated backscattering values were lower in September than in August. Cirrus clouds were abundant throughout the month, masking any upper tropospheric aerosols that might have been present. A sunrise during clear weather in early October did not show any apparent aerosol layers. At Hampton, Virginia, a very broad backscattering peak and somewhat increased integrated backscatter were measured 6 September, but a profile with a narrower peak on 19 September (the last measurement of the month) yielded integrated values lower than in August. September values from Fukuoka, Japan were similar to those from the last measurement in mid-July. April-June lidar data from Garmisch-Partenkirchen, Germany show a gradual decrease in backscattering from stratospheric aerosols. A 3-dimensional representation of the structure of the aerosol profile since early 1982 is shown in figure 8. Balloon data from Laramie, Wyoming have continued to show slow decay of the El Chichón aerosols. No material from Mayon was evident during a flight 6 October.

Figure with caption Figure 8. Development and gradual decay of the El Chichón aerosol cloud over Garmisch-Partenkirchen, West Germany, January 1982-March 1984. The aerosol profile structure is represented in three dimensions. Courtesy of Reinhold Reiter.

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: R. Reiter, Garmisch-Partenkirchen, W. Germany; T. DeFoor, MLO; M. Osborn, NASA; M. Fujiwara and M. Hirono, Kyushu Univ., Japan; J. Rosen, Univ. of Wyoming.


Campi Flegrei (Italy) — September 1984 Citation iconCite this Report

Campi Flegrei

Italy

40.827°N, 14.139°E; summit elev. 458 m

All times are local (unless otherwise noted)


More M > 3 events with wider distribution, but seismic energy release unchanged and uplift slows

"Activity at Campi Flegrei displayed some changes July-September. The monthly mean uplift velocity was in the range of 1.2 mm/day at Pozzuoli and

"Seismic energy release remained at the same level as in the past year. We observed a higher number of the most energetic events (M 3) than in past months (table 1). They are also no longer confined within the restricted area around Solfatara Crater, but instead occur all over the seismically active area.

Table 1. Magnitudes of the most energetic events in the Campi Flegrei area, July-September 1984.

Date Magnitude
01 Jul 1984 3.7, 3.5
11 Jul 1984 3.8
22 Aug 1984 3.6
29 Aug 1984 3.9, 3.8
12 Sep 1984 3.3
13 Sep 1984 3.2
28 Sep 1984 3.5, 3.7

"The temperatures of fumaroles in Solfatara Crater remained stable. The radon content of the water wells reached a minimum in the last year, with a slight increase again at the end of September.

"The decrease in the uplift velocity during constant seismic energy release does not support the idea that uplift velocity is closely related to the occurrence of larger earthquakes. On the contrary, in this last period we have observed higher-energy events. They often occur as double events (1 July, 29 August and 28 September; table 1). The area that was previously affected by swarms of low-energy events (1 km W of Pozzuoli) is now also affected by high-energy events. We do not know if this pattern of activity indicates a higher risk of eruption."

Geologic Background. Campi Flegrei is a large 13-km-wide caldera on the outskirts of Naples that contains numerous phreatic tuff rings and pyroclastic cones. The caldera margins are poorly defined, and on the south lie beneath the Gulf of Pozzuoli. Episodes of dramatic uplift and subsidence within the dominantly trachytic caldera have occurred since Roman times. The earliest known eruptive products are dated 47,000 yrs BP. The caldera formed following two large explosive eruptions, the massive Campanian ignimbrite about 36,000 BP, and the over 40 km3 Neapolitan Yellow Tuff (NYT) about 15,000 BP. Following eruption of the NYT a large number of eruptions have taken place from widely scattered subaerial and submarine vents. Most activity occurred during three intervals: 15,000-9500, 8600-8200, and 4800-3800 BP. Two eruptions have occurred in historical time, one in 1158 at Solfatara and the other in 1538 that formed the Monte Nuovo cinder cone.

Information Contacts: G. Luongo and R. Scandone, OV; F. Barberi, Univ. di Pisa.


Erebus (Antarctica) — September 1984 Citation iconCite this Report

Erebus

Antarctica

77.53°S, 167.17°E; summit elev. 3794 m

All times are local (unless otherwise noted)


Vigorous explosions, clouds, and incandescent tephra

"Brief reports from technical staff operating seismic instruments at Scott Base and infrasonic equipment at McMurdo Sound indicate a significant change in eruptive activity at Mt. Erebus. Activity associated with the lava lake has consisted of quiet degassing with emission of ~230 t/d of SO2 and 21 t/d of aerosol particles. Two to six small Strombolian eruptions occurred per day, often ejecting bombs of anorthoclase phonolite onto the crater rim, ~220 m above the lava lake.

"The reports indicate that starting on 13 September a number of large explosions were recorded by the IMESS network situated on the volcano, by infrasonic detectors in Windless Bight (~29 km away), by the WWSSN seismograph at Scott Base (37 km distant), and by a tidal gravimeter at South Pole station (~1,400 km from Mt. Erebus). Previous Strombolian activity has generally been too weak to record except on the IMESS seismic stations.

"From 13 to 19 September, the volcano was very active with 8-19 large explosions (recorded on WWSSN, IMESS, and infrasound instruments) per day, decreasing to 2-8/day 20-25 September, then increasing again to 12-27 explosions per day 26-29 September. Numerous mushroom-shaped clouds were reported, and were estimated to rise as much as 2 km above the summit. Observers at McMurdo, 37 km SW of the volcano, reported hearing explosions on 16 September at 0459, and 26 September at 1133 and 1135. Slight earth tremors were also felt there. On 17 September at 1010, a bright summit glow was observed from McMurdo Sound. Six minutes later, incandescent bombs were ejected to ~600 m above the summit; observers at Butter Point, 70 km from the volcano, reported seeing incandescent tephra from this explosion, which produced one of the larger infrasonic and seismic signals of the eruption sequence.

"Ash covered the NW side of the volcano down to 3,400 m elevation. Fumaroles around the summit crater showed a substantial increase in activity. A 300-500-m-high very narrow plume was observed lower on the E flank (1,800 m?). Observers suggested that it might have been a geyser."

Geologic Background. Mount Erebus, the world's southernmost historically active volcano, overlooks the McMurdo research station on Ross Island. It is the largest of three major volcanoes forming the crudely triangular Ross Island. The summit of the dominantly phonolitic volcano has been modified by one or two generations of caldera formation. A summit plateau at about 3,200 m elevation marks the rim of the youngest caldera, which formed during the late-Pleistocene and within which the modern cone was constructed. An elliptical 500 x 600 m wide, 110-m-deep crater truncates the summit and contains an active lava lake within a 250-m-wide, 100-m-deep inner crater; other lava lakes are sometimes present. The glacier-covered volcano was erupting when first sighted by Captain James Ross in 1841. Continuous lava-lake activity with minor explosions, punctuated by occasional larger Strombolian explosions that eject bombs onto the crater rim, has been documented since 1972, but has probably been occurring for much of the volcano's recent history.

Information Contacts: P. Kyle, New Mexico Inst. of Mining & Tech.; J. Kienle and C. Wilson, Univ. of Alaska.


Etna (Italy) — September 1984 Citation iconCite this Report

Etna

Italy

37.748°N, 14.999°E; summit elev. 3295 m

All times are local (unless otherwise noted)


Lava flows, Strombolian activity and ash emission

Continuing strombolian activity, particularly intense at times (on the 14th and 20th) and very irregular in intensity and duration, marked the activity in September. Beginning 27 September, this activity was nearly replaced by expulsions of reddish ash at irregular intervals, rarely accompanied by the ejection of incandescent material (bombs and incandescent lava fragments). Lava flows, rarely thick (20 September), usually emerged from effusive vents on the S rim of the Southeast Crater at 3,050 m elevation, and were directed mainly SE, E, S, and ENE. A lava flow advanced S to about 100 m from the rifugio Torre del Filosofo. The flows moved across the lava field, rarely advancing below 2,700 m elevation, within the Valle del Bove.

"Strombolian activity occurred at the bottom of Bocca Nuova. The activity was particularly violent at times with ejection of incandescent lava fragments above the level of the crater rim (24 and 27 September). Generally, only gas emissions were observed. The Chasm usually remained obstructed. Rarely (11 and 24 September), incandescent gas under pressure was observed emerging from a small vent. From the Northeast Crater, isolated expulsions of reddish ash continued, but activity was usually limited to quiet gas and vapor emissions."

Michael Matson reported that a weather satellite image on 14 September at 0740 showed a plume at 4.5 km elevation or higher extending SE from Etna. Ejection of the plume was estimated to have begun 1-2 hours earlier. No plume was evident on an image at 0946.

The following report by Christopher Kilburn, is based on observations 25 August-1 October.

"Since the eruption began in late April, a cone has developed inside the upper E rim of the Southeast Crater, roughly coincident with the position of the most northerly vent active in 1979 (figure 15). On 1 October the cone was ~120 x 100 m at its base (the longer axis oriented roughly NNW) and some 30-40 m high. Until 20 September, the strombolian activity consisted of intermittent violent explosions, with peak frequencies of 14/minute and bomb trajectories ranging from subvertical to directed. Lower-angle ejections were mainly to the E and S, but occasionally to the N and W. Bombs of the order of 0.04 m3 had maximum ranges of ~300-400 m. After 20 September, the violence of the explosions markedly decreased. Weak ejections every few minutes or hours were interspersed with periods of inferred internal collapse that generated small convection columns of pale brown ash and dust. This change in explosive behaviour followed a brief period of rapid lava discharge to the E on 20 September as well as a period of heavy precipitation. Enlargement of the vent at the top of the new cone, which occurred sometime between 13 and 24 September, may have been associated with the 20 September lava discharge.

Figure (see Caption) Figure 15. Morphology of Southeast Crater before the 1984 eruption (left); contours are approximate, in meters above sea level. Morphology of Southeast Crater 11 September 1084 (center) and 1 October 1984 (right); dashed line indicates the approximate extent of ponded lava, arrows the direction of lava discharge. After Murray, J. B., 1982, Sommit del Mt. Etna, Settembre 1981, 1:5000 scale map, Ordnance Survey, Southampton, U.K. Courtesy of Christopher Kilburn.

"Lava discharge was virtually continuous from ephemeral vents S and E of the base of the new cone. Lava flowed S, SE, and E over low points in the Southeast Crater rim. Activity typically alternated between the S and E vents at intervals of one to several days. The successive aa flows, few of which were longer than 1.5 km with frontal thicknesses rarely exceeding 5 m, created a compound flow field with an estimated area that approached 1.5 km2 by 1 October (figure 16). By 23 September, ponding inside the Southeast Crater had reached a maximum accumulated thickness of more than 45 m, raising the level of its bottom to ~3,065 m above sea level. Assuming a conservative average thickness of 5 m, and including the material within the Southeast Crater, a provisional estimate of the minimum volume of the flow field on 1 October is 8.5 x 106 m3, yielding a minimum average effusion rate of ~0.64 m3/s. Estimates of the eruption rate, made near the vent 17-28 September, were 0.5-1.0 m3/s for lava discharged toward the S. The chief uncertainties in these discharge rates are the velocity profiles across the flow surface and with depth, and the thickness of the flow; for the minimum value, parabolic velocity profiles and a flow depth of 3-4 m have been assumed, the maximum (central) surface velocity and lava channel width being estimated in the field.

Figure (see Caption) Figure 16. Provisional sketch map of 1984 lava flows as of 1 October. Courtesy of Christopher Kilburn.

"The Strombolian activity at Bocca Nuova was accompanied by the emission of large quantities of SO2-rich fumes. Until at least 24 September, magma was probably roughly 100-200 m below the W rim; observations were obscured by fumes. An apparently fresh bomb was found ~20-30 m from the NW rim 24 September, while others, up to 70 cm across, were seen being expelled toward the N and NW 28-29 September to a maximum estimated range of ~100-120 m. It is not known whether ejection of material outside the crater indicated a rise in level of magma within Bocca Nuova or an increase in explosive vigour due to changes in the physical state of the magma, notably in its vesicle content."

Geologic Background. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Information Contacts: R. Romano, IIV; C. Kilburn, Univ. of London; J. Murray, D. Decobecq, and C. Delmotte, Univ. Paris Sud; P. Briole, PIRPSEV; M. Matson, NOAA.


Home Reef (Tonga) — September 1984 Citation iconCite this Report

Home Reef

Tonga

18.992°S, 174.775°W; summit elev. -10 m

All times are local (unless otherwise noted)


Pumice from March eruption found 1,300 km to the WSW

Pumice that was probably from the March eruption of Home Reef was collected in August at Beautemps-Beaupré (northern Loyalty Islands, 20.4°S, 166.2°E) and on 3 September at Yate (southern New Caledonia, 22.15°S, 167.00°E), both roughly 1,300 km WSW of Home Reef. Fishermen reported that pumice arrived at Yate by 19 August or 1-2 days earlier during a few days of rough seas. The largest pumice fragment found was 9 cm long but the pumice averaged 1-2 cm in diameter. Small shells up to 1 cm long were frequently attached to the pumice. As of mid-September, no pumice had arrived in the Solomon Islands, roughly 2,600 km NW of Home Reef.

Geologic Background. Home Reef, a submarine volcano midway between Metis Shoal and Late Island in the central Tonga islands, was first reported active in the mid-19th century, when an ephemeral island formed. An eruption in 1984 produced a 12-km-high eruption plume, copious amounts of floating pumice, and an ephemeral island 500 x 1500 m wide, with cliffs 30-50 m high that enclosed a water-filled crater. Another island-forming eruption in 2006 produced widespread dacitic pumice rafts that reached as far as Australia.

Information Contacts: P. Maillet, J. Eissen, and M. Monzier, ORSTOM, New Caledonia; D. Tuni, Ministry of Lands, Energy, and Natural Resources, Solomon Islands.


Karangetang (Indonesia) — September 1984 Citation iconCite this Report

Karangetang

Indonesia

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

All times are local (unless otherwise noted)


Seismicity and minor tephra emission since January; ash column and nuées ardentes in September

An explosive eruption on 5 September was preceded by seismicity and nine months of minor tephra ejection. Rumblings were heard on 4 January, followed by an explosion that ejected ash. From February through April, rumbling preceded episodes of ash emission. On 31 May at 0724, an ash column rose to 1.5 km above the summit. During the night of 7-8 June, glowing lava fragments were ejected from the main crater. On 20 July, ash emission was accompanied by rumbling. The number of local seismic events increased through the first half of 1984 (table 1). Volcanic tremors were recorded 24 August, although no surface activity was seen. Ash emission occurred 3 September at 0447, producing an eruption column that rose 600 m. Glowing lava fragments were occasionally ejected. Rumbling accompanied the activity.

Table 1. Number of local earthquakes/month recorded at Karangetang. Courtesy of VSI.

Date Tectonic Earthquakes Volcanic Earthquakes
Jan 1984 62 18
May 1984 82 57
Jun 1984 200 139
Jul 1984 456 85

On 5 September at 0905, an ash column rose 4 km from the main crater. Nuées ardentes flowed 2 km S and 1 km W, with estimated volumes of 1.5 and 0.5 x 106 m3. One week later, ash emission was continuing and weak rumbling was heard. Ten volcanic and five tectonic earthquakes were recorded daily through 16 September. About 4,500 people were temporarily evacuated from the S and W sides of the danger zone but were allowed to work in their fields during the day. No casualties were reported.

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

Information Contacts: A. Sudradjat, VSI.


Kilauea (United States) — September 1984 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Episode 25; highest fountains of 1983-84 eruption; tephra

EPISODE 25

"After a 30 day repose period, the 25th episode of the 1983-84 E rift zone eruption began at about 1604 on 19 September and ended at about 0532 the next day. Brief intervals of Strombolian activity and a small pahoehoe flow across the N spillway occurred over a 10-day period preceding episode 25. The largest flow exited through the N spillway and advanced on a broad front up to 3.3 km from Pu'u O (figure 30). A small, short-lived, fissure eruption occurred ENE of Pu'u O early in the episode, producing a thin pahoehoe flow about 800 m long just N of the National Park boundary. The total volume of lava produced was approximately 11.1 x 106 m3. An unusually thick tephra mantle, estimated to have a volume of about 1 x 106 m3, fell early in this episode, accompanying the highest (460 m) fountains yet observed in the 1983-84 eruption.

Figure (see Caption) Figure 30. Lava flows erupted from Kilauea between 3 January 1983 and 20 November 1984 on the E rift zone. Flows from episodes 25-27 are shown separately. Courtesy of HVO.

"The summit of Pu'u O increased in height by 12 m during episode 25 and, within 11 days, had collapsed about 5 m, to stand 875 m above sea level and 155 m above the pre-1983 surface. The recent basalt, like that of earlier episodes, is nearly aphyric with widely scattered small (< 1 mm) phenocrysts of olivine.

Deformation. "During the 30-day repose period prior to episode 25, the E-W tilt recorded in the Uwekahuna vault increased by 17 µrad. Summit subsidence began around 1400 on 19 September. The net deflationary tilt change recorded during episode 25 was 15 µrad. Tiltmeters near the eruption site and at a site 6.5 km uprift recorded no significant tilt change during September. By the end of the month, slow reinflation of the summit was indicated by a recovery of 6 µrad.

Seismicity. "Prior to the onset of episode 25, tiny earthquakes, registered only at the Pu'u Kamoamoa station (about 500 m uprift from Pu'u O), started to increase after about 1500 on 19 September. At 1530, the level of harmonic tremor began to increase as well. Tremor increased rapidly at 1540, and was marked by a sharper increase at 1604. At 1613 the tremor alarm at HVO was triggered. At 1615, tremor amplitude peaked and remained at a high level until 0532 on 20 September. A rapid decrease in tremor was accompanied by intermittent high-amplitude bursts. For about 6 hours following the drop in tremor, there were many tiny high-frequency shocks recorded near Pu'u O.

"From about 2000 on 19 September to 0800 on 21 September, a swarm of very small long-period earthquakes combined with intermediate-amplitude harmonic tremor, apparently related to the post-deflation adjustments of the summit storage system, was recorded in the North Pit station at the summit.

"At the end of September, the level of tremor at Pu'u O was constant and very low in amplitude. The number of microearthquakes was low in the summit region and moderate in the E rift zone."

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: G. Ulrich, A. Okamura, and R. Koyanagi, HVO.


Long Valley (United States) — September 1984 Citation iconCite this Report

Long Valley

United States

37.7°N, 118.87°W; summit elev. 3390 m

All times are local (unless otherwise noted)


Seismicity at relatively low level and inflation

The following is from a USGS report.

"Following decay of the January 1983 earthquake swarm activity to background levels in the spring of 1983 (SEAN 07:02, 08:01, 08:02, and 08:03), seismic activity has persisted at a relatively low level. Within the caldera, this background level typically involves several earthquakes (magnitude greater than or equal to 1) per day and an occasional locally felt M 3 event. A M 4.2 earthquake on 28 April 1984 and a M 3.8 event in a swarm that began 16 July 1984 are the largest events to occur in the caldera since the January 1983 swarm. Deformation data show evidence for only modest inflation of the resurgent dome following the January 1983 swarm. Frequently repeated trilateration measurements, however, show continued extensional deformation within the caldera at rates of several microstrain units per year.

"With the reduced rates of seismic activity and ground deformation in the caldera during the last year, the possibility of an imminent eruption appears more remote than during the previous 2 years. In a letter dated 11 July 1984, the Director of the USGS advised California officials that a volcanic eruption does not pose an immediate threat to public safety in the Long Valley region and that the Long Valley region does not satisfy the imminent threat criteria for an official Hazard Warning for volcanic activity.

"The Long Valley region had been under a Notice of Potential Volcanic Hazard since May 1982. Prior to September 1983, this was the lowest of three levels used by the USGS to express the relative urgency of a potential geologic hazard when formally notifying the public and responsible officials. In September 1983, the 3-level terminology was changed to a single-level system termed a Hazard Warning. The USGS is continuing its intensive seismic, geophysical, and geodetic monitoring of Long Valley Caldera that was initiated in mid-1982."

Geologic Background. The large 17 x 32 km Long Valley caldera east of the central Sierra Nevada Range formed as a result of the voluminous Bishop Tuff eruption about 760,000 years ago. Resurgent doming in the central part of the caldera occurred shortly afterwards, followed by rhyolitic eruptions from the caldera moat and the eruption of rhyodacite from outer ring fracture vents, ending about 50,000 years ago. During early resurgent doming the caldera was filled with a large lake that left strandlines on the caldera walls and the resurgent dome island; the lake eventually drained through the Owens River Gorge. The caldera remains thermally active, with many hot springs and fumaroles, and has had significant deformation, seismicity, and other unrest in recent years. The late-Pleistocene to Holocene Inyo Craters cut the NW topographic rim of the caldera, and along with Mammoth Mountain on the SW topographic rim, are west of the structural caldera and are chemically and tectonically distinct from the Long Valley magmatic system.

Information Contacts: D. Hill, USGS, Menlo Park, CA.


Manam (Papua New Guinea) — September 1984 Citation iconCite this Report

Manam

Papua New Guinea

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

All times are local (unless otherwise noted)


Ash-laden emissions, incandescence

"Following the brief intense eruption of 25 August, activity was steady at a weak-moderate level in September. Both summit craters continued to release ash-laden emissions. Incandescent activity was observed at Southern crater at the beginning and middle of the month, and Main crater incandescence was seen for a few days at mid-month. Seismic amplitudes declined slightly to levels about three times normal. Slight radial inflation of the volcano took place early in the month."

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, RVO.


Mayon (Philippines) — September 1984 Citation iconCite this Report

Mayon

Philippines

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

All times are local (unless otherwise noted)


Explosive activity reintensifies; 73,000 evacuated

Quoted material is from PHIVOLCS.

"Eruptive activity started 9 September at 1923. Initial activity was dominantly Strombolian, with incandescent spattering at the summit and production of small lava flows. A mound of solidified lava inside the crater blocked the 1968 notch at the SW rim, so the small lava flows and initial pyroclastic flows (see below) moved predominantly NW.

"A fairly strong eruption 10 September at 2300 marked the start of Vulcanian activity. Ash-laden steam clouds rose 5 km above the summit and a pyroclastic flow moved down to the NW, reaching 700 m elevation. Stronger explosions 11 September reopened the notch at the SW rim, so more of the later lava and pyroclastic flows moved SW than NW. The eruption continued to intensify, peaking 13 September. Cauliflower-shaped, ash-laden steam clouds accompanied by rumbling sounds reached a maximum height of 15 km before drifting SW, W, and NW. Continuous volcanic tremors with increasing amplitude were recorded, punctuated by explosion earthquakes. Two lava flows emerged through the SW breach. One reached 500 m elevation, adjacent to and W of the 1978 flow. The other, a little farther W, advanced to 1,400 m elevation (figure 2). The new lava is porphyritic augite-hypersthene andesite.

Figure (see Caption) Figure 2. Map of Mayon showing the extent of the 1984 lava flows, after Corpuz (1985).

"Activity gradually declined 14-21 September. A mild eruption 22 September at 0502 was accompanied by a volcanic earthquake felt at intensity II on the MRF scale at the Mayon Resthouse Observatory. A relatively quiet period followed. A very strong explosion 23 September at 0433 ejected voluminous ash-laden steam clouds that reached 10 km in height. Incandescent tephra rose 2 km above the summit and spread in all directions, covering the summit area with red-hot tephra to about 1,500 m elevation. A large notch was formed in the SE rim of the crater and a smaller one in the E rim. Subsequent pyroclastic flows were directed predominantly SE and E, although some moved in other directions along gullies. Ash fell within about 50 km SW, W, and NW of the summit. Areas E and NE of the volcano received most of the fine airfall tephra generated by pyroclastic flows. The eruption continued to intensify until the 24th. Voluminous ash emission, sometimes sustained for 5 minutes, occurred at intervals of 2-15 minutes, accompanied by strong detonations and at times by electrical discharges. Maximum height of the eruption clouds was 15 km. On 24 September at 1614, a nuée ardente [almost] reached the nearest village. A large volume of pyroclastic flow material was deposited on the SE flank. The eruption started to decline 25 September. By 5 October activity was limited to weak steaming and faint to moderate crater glow, accompanied by volcanic tremors and discrete earthquakes."

Press sources reported reintensification of the eruption 6 October. Ash-laden steam clouds rose as much as 1.7 km above the summit and lava flowed 1 km from the crater.

"Mudflows generated by rain destroyed three sections of the Legaspi-Santo Domingo highway roughly 8 km SE of the volcano. Larger mudflows on the 27th overran the same portion of highway. Two bridges were destroyed along the Malilipot-Santo Domingo highway, roughly 8 km E of Mayon."

As of 30 September, press sources reported that 6,500 hectares of farmland had been covered by mudflows.

"Implementation of the Mayon preparedness plan was fairly smooth. On 10 September, the area within 6 km of the summit was declared off-limits and all residents were recommended for evacuation. On 12 September, the danger zone was extended to 8 km from the summit on the S and SW flanks. About 26,000 people were evacuated during the first phase of the eruption. On 23 September, the danger zone was expanded again, to 10 km from the summit on the SE side and 8 km from the summit around the rest of the volcano. All residents of that area were recommended for evacuation and the number of evacuees swelled to more than 73,000 at 50 centers. No casualties were attributed directly to the eruption or mudflows."

Reference. Corpuz, E., 1985, Chronology of the September-October 1984 eruption of Mayon volcano, Philippines in Punongbayan, R.S. (ed.), 1985, Special issue on the 1984 eruption of Mayon: Philippine Journal of Volcanology, v. 2, p. 36-51 (9 papers, 205 p.).

Further Reference. Umbal, J., 1987, Recent lahars of Mayon volcano in Geologic hazards and disaster preparedness systems: National Science and Technology Authority, p. 56-76.

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

Information Contacts: PHIVOLCS, Quezon City; DPA; AP.


Rabaul (Papua New Guinea) — September 1984 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, ground deformation rates decline

"Declining seismicity and rates of ground deformation were evident in September. The total number of caldera earthquakes for the month was 4048 and the seismic energy released amounted to about [8 x 1014] ergs (compared to 5,285 earthquakes and about [2.4 x 1016] ergs in August).

"Seismicity was concentrated in the N part of the caldera seismic zone. Measured vertical uplift continued to be greatest along the SE coast of Matupit Island. However, the maximum uplift in September was only 14 mm (compared to 35 mm in August). Tilt and horizontal distance measurements continued to indicate slow steady inflation and expansion in the 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, RVO.


St. Helens (United States) — September 1984 Citation iconCite this Report

St. Helens

United States

46.2°N, 122.18°W; summit elev. 2549 m

All times are local (unless otherwise noted)


New lobe in collapse zone on composite dome

The new lobe, which began to emerge during the night of 9-10 September and had stopped growing by the 14th, partially filled an elongate E-W-trending collapse zone, about 350 m long by 250 m wide, on the dome's upper W side. The collapse, in what had been the highest part of the dome, destroyed much of the March 1984 lobe and engulfed the notch produced by explosions in May (SEAN 09:05). The SE wall of the collapse zone was defined by the zone of fissuring observed in early September. The volume of collapse was about 1.3 x 106 m3.

The new lobe was about 250 m long by 220 m wide, with an average thickness of 35 m. The USGS calculated its volume at about 2 x 106 m3. It was almost entirely confined within the collapse zone, although it protruded considerably above the rim of the collapse zone. Sublimate deposits were more extensive than on previous lobes, and a large area at the top of the new lobe was a dirty yellow color.

At least 3.4 x 106 m3 of internal expansion of the dome took place during the period of accelerating deformation prior to extrusion of the new lobe. Between the afternoon of 9 September and the next morning, targets on the NW side of the dome moved outward as much as 52 m. Displacement rates dropped sharply on the 10th, and by 11 September outward movement was occurring at only centimeters per day. Deformation remained very slow through early October.

After increasing sharply to 786 t/d on 10 September shortly after the new lobe was first observed, rates of SO2 emission declined to less than 300 t/d on the 12th, less than 200 t/d the next afternoon, and just under 100 t/d by the 15th. A period of higher SO2 emission rates occurred in late September, with measurements on the 23rd, 26th, and 28th yielding values of 190, 135, and 148 t/d, but SO2 values had dropped to less than 50 t/d on 2 October.

Seismicity gradually declined 11-12 September, from about 20 events per hour on the 11th to about 5 per hour late on the 12th, after very vigorous activity the previous two days (SEAN 09:08). Most earthquakes had stopped by 13 September, but surface events, primarily caused by rockfalls, were frequent that day and remained frequent for the next week. The number of surface events declined by the last week in September and seismic activity remained low through early October.

Geologic Background. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago and has been the most active volcano in the Cascade Range during the Holocene. Prior to 2200 years ago, tephra, lava domes, and pyroclastic flows were erupted, forming the older St. Helens edifice, but few lava flows extended beyond the base of the volcano. The modern edifice was constructed during the last 2200 years, when the volcano produced basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the north flank, and were witnessed by early settlers.

Information Contacts: D. Swanson, C. Mullins, USGS CVO, Vancouver, WA; C. Jonientz-Trisler, University of Washington.


Ulawun (Papua New Guinea) — September 1984 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Mild strombolian eruption

"After several weeks of intensified seismicity and occasional small phreatic explosions, a mild Strombolian eruption began on 4 September and ended on 11 September.

"Previous Ulawun eruptions developed rapidly (within hours) to full-scale eruptions, including lava effusion and paroxysmal explosive activity culminating in the formation of pyroclastic flows. However, the 1984 eruption developed slowly from the first appearance of summit glow on 4 September, and no effusion or paroxysmal activity took place. The eruption reached a peak 6-9 September when mild, rhythmic, almost ash-free, Strombolian explosions took place every few seconds.

"During an aerial inspection on 7 September, a pool of fluid lava was observed in the bottom of the summit crater, about 50-100 m below the rim; explosions took place from a small circular central vent. Most ejecta were contained by the crater walls, but occasional larger explosions showered the upper flanks of the volcano with incandescent tephra. Visible shock waves were generated by the stronger explosions. A white eruption plume several tens of kilometers long was formed at the peak of the eruption. Seismic amplitudes were 30-40 times normal on 7 and 8 September, and the seismicity was characterized by irregular tremor produced by the frequent explosions.

"Regular reports and advice were transmitted by RVO to provincial government authorities throughout, and reactions to the eruption were controlled and rational, resulting in minimal disturbance to daily life."

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

Information Contacts: C. McKee, RVO.


Unzendake (Japan) — September 1984 Citation iconCite this Report

Unzendake

Japan

32.761°N, 130.299°E; summit elev. 1483 m

All times are local (unless otherwise noted)


Earthquake swarm

Local seismic activity, which had increased since May, peaked in August when 6,370 seismic events, including 409 felt events, were recorded (figure 1). During the evening of 6 August the number of recorded earthquakes increased rapidly (table 1). Two large felt shocks and several minor felt shocks occurred within 10 minutes, causing 10 landslides and injuring two persons. Seismic activity has since declined, but remained above normal as of 26 September.

Figure (see Caption) Figure 1. Daily number of felt earthquakes at Unzen Volcano, August 1984. Courtesy of JMA.

Table 1. Earthquakes of M >= 4.0, 6 August 1984. Intensities are measured at the JMA Unzendake Weather Station, using the JMA scale (0-VII).

Time Magnitude Depth of Focus Intensity
1728 4.8 6 km IV
1730 5.7 7 km I
1735 4.0 15 km I
1738 5.0 11 km V
1841 4.1 10 km IV
1949 4.0 8 km IV

Epicenters of the swarm, determined by the JMA seismic network, were concentrated on the W coast of Shimabara Peninsula about 8 km W of Fuken-dake, the most recently active peak of the Unzen Volcano Complex (figure 2). The depth of seismic sources deepened from E to W (figure 2, inset). The characteristic hypocenter distribution coincides with previous results from the University of Kyoto and JMA. Earthquake swarms without eruption have often occurred at Unzen.

Figure (see Caption) Figure 2. Map of Shimabara Peninsula. The Unzen Volcanic Complex occupies most of the peninsula. Fuken-dake (open triangle), Maye-dake (solid triangle) and epicenters of events, 6 August, 1300-7 August, 0325 (open squares) are shown. The E-W cross-section (inset) shows a depth range from the surface to 20 km. Courtesy of JMA.

No eruptive activity has been observed since 1792, when explosions at Fuken-dake in February were followed by lava extrusion in March, and earthquakes and landslides in April and May. On 21 May an avalanche from Maye-dake (near the E coast), caused by an earthquake, created a major tsunami in Shimabara Bay that caused [15,000] fatalities and much destruction.

Further Reference. Sawada, Y., 1978, Seismic activity at Unzen-dake volcano and the unusual number of its occurrence and frequency: Papers in Meteorology & Geophysics, v. 29, p. 83-96.

Geologic Background. The massive Unzendake volcanic complex comprises much of the Shimabara Peninsula east of the city of Nagasaki. An E-W graben, 30-40 km long, extends across the peninsula. Three large stratovolcanoes with complex structures, Kinugasa on the north, Fugen-dake at the east-center, and Kusenbu on the south, form topographic highs on the broad peninsula. Fugendake and Mayuyama volcanoes in the east-central portion of the andesitic-to-dacitic volcanic complex have been active during the Holocene. The Mayuyama lava dome complex, located along the eastern coast west of Shimabara City, formed about 4000 years ago and was the source of a devastating 1792 CE debris avalanche and tsunami. Historical eruptive activity has been restricted to the summit and flanks of Fugendake. The latest activity during 1990-95 formed a lava dome at the summit, accompanied by pyroclastic flows that caused fatalities and damaged populated areas near Shimabara City.

Information Contacts: JMA, Tokyo; Kyodo News Service, Tokyo.


Villarrica (Chile) — September 1984 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Brief ash eruption; increased seismicity

"A brief eruption from Villarrica's central crater was reported during the afternoon of 11 August. After three strong explosions and underground rumbling, a dark ash column was seen rising more than 200 m above the summit. Winds blew the ash over the snow-covered SE flank. Seismometers operated by the Universidad de la Frontera at Temuco (100 km NW of the volcano) recorded an increase in seismicity during the event."

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

Information Contacts: H. Moreno R., Univ. de Chile, Santiago.

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/).