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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

Aira (Japan) Ash plumes continue at the Minamidake crater from July through December 2018

Ibu (Indonesia) Thermal anomalies and ash explosions from the crater continue during May-November 2018

Masaya (Nicaragua) Lava lake activity continued from May through October 2018; lava lake lower than recent months

Sarychev Peak (Russia) Thermal anomalies, surface activity, and ash explosions during October-November 2017 and September-October 2018

Suwanosejima (Japan) Multiple explosive events with incandescence and ash plumes during November 2018

Etna (Italy) Lava flows emerge from NSEC in late August and late November 2018; Strombolian activity continues from multiple vents

Dukono (Indonesia) Regular ash explosions continuing as of September 2018

Ulawun (Papua New Guinea) Ash plumes on 8 June, 21 September, and 5 October 2018

Langila (Papua New Guinea) Several weak ash plumes during June, September, and October 2018

Sangeang Api (Indonesia) Ongoing crater activity and thermal anomalies during September 2017-October 2018

Sheveluch (Russia) Thermal anomalies along with minor gas and steam emissions continue through October 2018

Gamalama (Indonesia) Weak explosion on 4 October 2018



Aira (Japan) — January 2019 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Ash plumes continue at the Minamidake crater from July through December 2018

Sakurajima is one of the most active volcanoes in Japan and is situated in the Aira caldera in southern Kyushu. It regularly produces ash plumes and scatters blocks onto the flanks during explosions. This report covers July through December 2018 and describes activity at the Minamidake crater, which has continued with the activity typically observed at Sakurajima volcano. In late 2017 the eruptive activity has migrated from being centered at the Showa crater, to being focused at the Minamidake crater. This change has continued into the later half of 2018. The following activity summarizes information issued by the Japan Meteorological Agency (JMA), the Japan Volcanic Ash Advisory Center (VAAC), and satellite data.

Activity from July through December 2018 was focused at the summit Minamidake crater with 8 to 64 ash emission events per month, with 50-60% being explosive in nature during four of the six months reported (table 20, figure 67). The maximum explosions per day was 64 on 31 August (figure 68). No pyroclastic flows were recorded during this time. Recent activity at the Showa crater has been declining and no activity was observed during the reporting period. Sakurajima has remained on Alert Level 3 on a 5-level scale during this time, reflecting the regular ash plumes and volcanic blocks that erupt out onto the slopes of the volcano during explosive events.

Table 20. Monthly summary of eruptive events recorded at Sakurajima's Minamidake crater in Aira caldera, July-December 2018. The number of events that were explosive in nature are in parentheses. No events were recorded at the Showa crater during this time. Data courtesy of JMA (July to December 2018 monthly reports).

Month Ash emissions (explosive) Max. plume height above the crater Max. ejecta distance from crater
Jul 2018 29 (16) 4.6 km 1.7 km
Aug 2018 64 (37) 2.8 km 1.3 km
Sep 2018 44 (22) 2.3 km 1.1 km
Oct 2018 8 (0) 1.6 km --
Nov 2018 14 (2) 4 km 1.7 km
Dec 2018 56 (34) 3 km 1.3 km
Figure (see Caption) Figure 67. Satellite images showing ash plumes from Sakurajima's Minamidake summit crater (Aira caldera) in August, September, and November 2018. Natural color satellite images (bands 4, 3, 2) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 68. Explosions per day at Sakurajima's Minamidake summit crater (Aira caldera) for July through December 2018. Data courtesy of JMA.

Activity through July consisted of 29 ash emission events (16 of which were explosive) producing ash plumes up to a maximum height of 4.6 km above the crater and ballistic ejecta (blocks) out to 1.7 km from the crater, but ash plumes were more commonly 1.2 to 2.5 km high. The largest explosive event occurred on 16 July, producing an ash plume up to 4.6 km from the vent and ejecting ballistic rocks out to 1.3-1.7 km from the crater (figure 69). On 17 July, sulfur dioxide emissions were measured at 1,300 tons per day, and on 26 July emissions were measured to be 2,100 tons per day.

Figure (see Caption) Figure 69. Ash plumes erupting from the Sakurajima Minamidake crater (Aira caldera) on 16 July 2018 at 1538 (upper) and 1500 (lower) local time. The ash plumes reached 4.6 km above the crater rim and ejected rocks out to 1.3-1.7 km from the crater. Higashikorimoto webcam images courtesy of JMA (July 2018 monthly report).

During August the Minamidake crater produced 64 ash emission events (37 explosive in nature) with a maximum ash plume height of 2.8 km above the crater, and a maximum ballistic ejecta distance of 1.3 km from the crater on 31 August (figure 70). Ash plumes were more commonly up to 1 to 2.1 km above the crater. Sulfur dioxide emissions were very high on 2 August, measured as high as 3,200 tons per day, and was measured at 1,500 tons per day on 27 August.

Figure (see Caption) Figure 70. Activity at Sakurajima volcano (Aira Caldera) in August 2018. Top: A gas-and-ash plume that reached 2.8 km above the crater at 1409 on 29 August. Bottom: Scattered incandescent blocks out to 1-1.3 km from the crater on the flanks of Sakurajima after an explosion on 31 August. Higashikorimoto and Kaigata webcam images courtesy of JMA (August 2018 monthly report).

Throughout September 44 ash emission events occurred, with 22 of those being explosive in nature. The Maximum ash plume height reached 2.3 km above the crater, and the maximum ejecta landed out to 1.1 km from the crater. An explosive event on 9 September ejected material out to 700 m away from the crater and on 22 September an event scattered blocks out to 1.1 km from the crater (figure 71).

Figure (see Caption) Figure 71. Incandescent blocks on the flanks of Sakurajima volcano (Aira caldera) after an explosion on 22 September 2018 at 2025. The event scattered blocks out to 1.1 km from the Minamidake crater. Kaigata webcam image courtesy of JMA (September 2018 monthly report).

October and November were relatively quiet with regards to the number of ash emission events with only 22 events over the two months. The maximum ash plume heights reached 1.6 and 4 km, respectively. An observation flight on 22 October showed the currently inactive Showa crater restricted to minor fumarolic degassing, and steam-and-gas and dilute ash plume activity in the Minamidake crater (figure 72). An eruption on 14 November at 0043 local time produced an ash plume to over 4 km above the crater and scattered incandescent blocks out to over 1 km from the crater (figure 73). This was the first ash plume to exceed a height of 4 km since 16 July 2018. Two events occurred during 16-19 November that produced ash plumes up to 1.6 km. Sulfur dioxide measurements were 3,400 tons on 4 October, 400 tons on 17 October, 1,000 tons on 23 October, 1,100 tons on 6 November, and 1,400 tons on 20 November.

Figure (see Caption) Figure 72. Minor fumarolic degassing has occurred in Sakurajima's Showa crater (Aira caldera) and the vent has been blocked by ash and rock. The active Minamidake crater is producing a blue-white plume to 400 m above the crater and a dilute brown plume that remained within the crater. Images taken by the Japan Maritime Self-Defense Force 1st Air Group P-3C on 22 October 2018, courtesy of JMA (October 2018 monthly report).
Figure (see Caption) Figure 73. Eruption of Sakurajima (Aira caldera) on 14 November at 0043 local time ejecting incandescent blocks more than 1 km from the crater and an ash plume up to 4 km above the crater. Photos courtesy of The Asahi Shimbun.

Small ash plumes continued through December with 56 ash emission events, 34 of which were explosive in nature. The maximum ash plume height above the crater reached 3 km, and the maximum distance that ejecta traveled from the vent was 1.3 km, both during an event on 24 December (figure 74). An explosive event produced an ash plume that reached a height of 2.5 km above the crater and scattered ejecta out to 1.1 km from the crater.

Figure (see Caption) Figure 74. An explosive event at 1127 on 24 December 2018 at Sakurajima's Minamidake crater (Aira caldera). The ash plume reached 3 km above the crater rim. Higashikorimoto webcam image courtesy of JMA (December 2018 monthly report).

Intermittent incandescence was observed at the summit at nighttime throughout the entire reporting period. Areas of elevated thermal energy within the Minamidake crater were visible in cloud-free Sentinel-2 satellite images (figure 75) and elevated temperatures were detected in MIROVA on a few days.

Figure (see Caption) Figure 75. Sentinel-2 thermal satellite images showing the summit area of Sakurajima volcano, Aira caldera, in October 2018. The areas of elevated thermal activity (bright orange-red) are visible within the Minamidake crater. No thermal anomalies are visible within the Showa crater. Thermal (Urban) satellite images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); 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); 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/); The Asahi Shimbun (URL: http://www.asahi.com/ajw/articles/AJ201811140035.html accessed on 12 March 2018).


Ibu (Indonesia) — December 2018 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


Thermal anomalies and ash explosions from the crater continue during May-November 2018

Continuing activity at Ibu has consisted of numerous thermal anomalies and, except apparently for the period from September 2017 through early March 2018, intermittent ash explosions (BGVN 43:05). This activity continued through November 2018. The Alert Level has remained at 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side.

Ash plumes were seen frequently during May-November 2018 (table 4). Plume heights above the crater were generally 400-80 m. However, ash plumes on 28 and 29 July rose 5.5 and 4.8 km, respectively. Seismicity associated with ash plumes were characterized by explosion and avalanche signals.

Table 4. Ash explosions reported at Ibu, May-November 2018. Data courtesy of PVMBG and Darwin VAAC.

Date Time Ash plume (height above crater rim) Plume Drift
05 May 2018 0622 600 m N, NE
06 Jun 2018 1206 500 m N
12 Jun 2018 1750 600 m N
14-19 Jun 2018 -- 200-600 m N
21 Jun 2018 0857 600 m N
22-26 Jun 2018 -- 850 m WNW, W
27 Jun 2018 -- 500 m W
06 Jul 2018 -- 800 m N
10-15 Jul 2018 -- 200-800 m --
28 Jul 2018 1852 5.5 km SE
29 Jul 2018 1612 4.8 km N, SE
13 Aug 2018 0259 600 m --
20 Aug 2018 1742 1.2 km --
24 Aug 2018 0838 800 m S
28, 30 Sep 2018 -- 500 m N, NE
06 Oct 2018 -- 500 m WSW
19 Oct 2018 1223 400 m N
26 Nov 2018 -- 500 m SE

The number of thermal anomalies during this time, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, ranged from 2 days/month (July) to 9 days/month (September); some events were two pixels. Days with anomalies and ash explosions were not well correlated. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected numerous hotspots every month of the reporting period, almost all of which were within 5 km of the volcano and of low-to-moderate power. Infrared satellite imagery showed that the volcano had at least two, and sometimes three, active dome or vent locations (figure 14).

Figure (see Caption) Figure 14. Sentinel-2 satellite images of Ibu on 19 August 2018. Top image (infrared, bands 12, 11, 8A) shows a large central hotspot and a smaller thermal area immediately to the west. Bottom image (natural color, bands 8, 4, 3) shows both an ash plume (gray) and steam plume (white), along with fresh and older lava in the crater. Courtesy of Sentinel Hub Playground.

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/); 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).


Masaya (Nicaragua) — November 2018 Citation iconCite this Report

Masaya

Nicaragua

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

All times are local (unless otherwise noted)


Lava lake activity continued from May through October 2018; lava lake lower than recent months

Masaya is one of the most active volcanoes in Nicaragua and one of the few volcanoes on Earth to contain an active lava lake. The edifice has a caldera that contains the Masaya (also known as San Fernando), Nindirí, San Pedro, San Juan, and Santiago (currently active) craters. In recent years, activity has largely consisted of lava lake activity along with dilute plumes of gas with little ash. In 2012 an explosive event ejected ash and blocks. This report summarizes activity during May through October 2018 and is based on Instituto Nicaragüense de Estudios Territoriales (INETER) reports and satellite data.

Reports issued from May through July 2018 noted that Masaya remained relatively calm. Sentinel-2 thermal satellite images show consistently high temperatures in the Santiago crater with the active lava lake present (figure 65).

Figure (see Caption) Figure 65. Sentinel-2 thermal satellite images showing the detected heat signature from the active lava lake at Masaya during May-July 2018. The lava lake is visible (bright yellow-orange) and a gas-and-steam plume is visible traveling towards the W to SW. Thermal (urban) satellite images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Reports from August through October 2018 indicated relatively low levels of activity. On 28 September the lava lake within the Santiago crater was observed with a lower surface than previous months. Fumarole temperatures up to 340°C were recorded (figure 66). Sentinel-2 thermal images show the large amount of heat consistently emanating from the active lava lake (figure 67). Sulfur dioxide was measured on 28 and 30 August with an average of 1,462 tons per day, a higher value than the average of 858 tons per day detected in February. Sulfur dioxide levels ranged from 967 to 1,708 tons per day on 11 September.

Figure (see Caption) Figure 66. FLIR (forward-looking infrared) and visible images of the Santiago crater at Masaya showing fumarole temperatures. The scale in the center shows the range of temperatures in the FLIR images. Courtesy of INETER (September 2018 report).
Figure (see Caption) Figure 67. Sentinel-2 thermal satellite images showing the heat signature from the active lava lake at Masaya during August-October 2018. The lava lake is visible (bright yellow-orange) and a gas-and-steam plume is visible traveling towards the SW. Thermal (urban) satellite images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Overall, activity from May through October 2018 was relatively quiet with continued lava lake activity. The thermal energy detected by the MIROVA algorithm showed fluctuations but were consistent (figure 68). The MODVOLC algorithm for near-real-time thermal monitoring of global hotspots detected 4-8 anomalies per month for this period, which is lower than previous years (figure 69).

Figure (see Caption) Figure 68. Middle infrared MODIS thermal anomalies at Masaya for April through October 2018. The data show relatively constant thermal activity related to the persistent lava lake. Courtesy of MIROVA.
Figure (see Caption) Figure 69. Thermal alerts for Masaya in May through October 2018. Courtesy of HIGP - MODVOLC Thermal Alerts System.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://webserver2.ineter.gob.ni/vol/dep-vol.html); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); 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/).


Sarychev Peak (Russia) — November 2018 Citation iconCite this Report

Sarychev Peak

Russia

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

All times are local (unless otherwise noted)


Thermal anomalies, surface activity, and ash explosions during October-November 2017 and September-October 2018

Located on Matua Island in the central Kurile Islands, Russia, Sarychev Peak (figures 19 and 20) had a significant eruption in June-July 2009 (BGVN 34:06, 35:09). Prior to this, a 1946 eruption resulted in the crater with a diameter and depth of approximately 250 m, with steep, sometimes overhanging crater walls. The N crater wall may have collapsed after a 1960 eruption, based on eyewitness accounts. A 1976 eruption included strong emissions and lava flows which resulted in a crater diameter of approximately 200 m and a floor 50-70 m below the rim. The eruption on 11-16 June 2009 encompassed more than ten large explosions, resulting in pyroclastic flows and ash plumes. The area of island covered by the June 2009 pyroclastic flows was more than 8 km2 (BGVN 34:06). Monitoring reports come from the Kamchatkan Volcanic Eruption Response Team (KVERT) and the Sakhalin Island Volcanic Eruption Response Team (SVERT).

Figure (see Caption) Figure 19. Photo looking into the crater of Sarychev Peak from the crater rim on 27 June 2017. Courtesy of V. Gurianov, Institute of Volcanology and Seismology FEB, RAS, KVERT.
Figure (see Caption) Figure 20. Sentinel-2 satellite image (natural color, bands 4, 3, 2) of Sarychev Peak on 8 September 2017. Courtesy of Sentinel Hub Playground.

Thermal anomalies were noted by the NOAA Cooperative Institute for Meteorological Satellite Studies over a period of five hours on 14 October 2017 in satellite data from Terra MODIS, S-NPP VIIRS, and Himawari-8; a plume of unknown composition accompanied the anomaly. A smaller thermal anomaly was present on 12 October, but not seen the following day during favorable viewing conditions. Another thermal anomaly was reported by SVERT on 21 October; views on other days that week of 17-23 October were obscured by clouds. On 7 November gas emissions and an elongated area of snow melt and potential thermal signature was visible on the N flank of the volcano (figure 21). On 8 and 13 November steam emissions were reported by SVERT and cloud cover prevented additional observations.

Figure (see Caption) Figure 21. Sentinel-2 satellite images of Sarychev Peak on 7 November 2017. Top image (natural color, bands 4, 3, 2) shows a white plume rising from the summit crater and a dark area extending about 1.25 km NW on the snow-covered slopes. Bottom image (atmospheric penetration, bands 12, 11, 8A) shows hot areas (in orange) of volcano material near the summit within the dark area seen in visible imagery. Courtesy of Sentinel Hub Playground.

The volcano was usually cloud-covered after mid-November 2017 through mid-February 2018. A small white plume seen in Sentinel-2 imagery on 20 February 2018 was not accompanied by a noticeable thermal anomaly, and the island appeared completely snow-covered. No activity of any kind was seen on the next cloud-free images taken on 4 and 11 May 2018, when the summit crater was filled with snow.

KVERT noted in a September report that there had been a thermal anomaly periodically observed after 7 May 2018. Fumarolic plumes were visible on 5 and 18 June 2018 (figure 22). Thermal anomalies were present on 8 and 11-12 September. Moderate explosions were reported during 11-15 September 2018, with ash emissions rising 3-4 km. On 14 September ash plumes drifted as far as 120 km NNE and the Aviation Color Code was raised to Orange. Explosions on 17 September generated ash plumes that rose as high as 4.5 km and drifted 21 km NE. Additional ash plumes identified in satellite images drifted 265 km E during 17-18 September. The eruption continued through 21 September, and a thermal anomaly was again visible on 22 September.

Figure (see Caption) Figure 22. Fumarolic activity at Sarychev Peak on 18 June 2018. Courtesy of FEC SRC Planeta, Institute of Volcanology and Seismology FEB RAS, KVERT.

Based on Tokyo VAAC data and satellite images, KVERT reported that at 1330 on 10 October 2018 an ash plume reached 1.7-2 km altitude and drifted 95 km E. SVERT reported that on 15 October an ash plume rose to 2.1 km altitude and drifted 65-70 km E. KVERT reported that a thermal anomaly was also identified in satellite images on 15 October. No further activity was seen through the end of October.

Thermal anomalies identified in MODIS data by the MIROVA system during October 2016-October 2018 occurred intermittently during the summer months each year (figure 23). However, most of those events were low-power and located several kilometers from the crater, so the heat source is unclear.

Figure (see Caption) Figure 23. Thermal anomalies detected by the MIROVA system using MODIS data at Sarychev Peak for the year ending 18 October 2017 (top) and ending 24 October 2018 (bottom), plotted as log radiative power. Most of the events shown were located several kilometers from the summit crater. Courtesy of MIROVA.

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: Sakhalin Volcanic Eruptions Response Team (SVERT), Institute of Marine Geology and Geophysics (IMG&G) Far East Division Russian Academy of Sciences (FED RAS), 1B Science St., Yuzhno-Sakhalinsk, 693022, Russia (URL: http://www.imgg.ru/); 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/); NOAA, Cooperative Institute for Meteorological Satellite Studies (CIMSS), Space Science and Engineering Center (SSEC), University of Wisconsin-Madison, 1225 W. Dayton St. Madison, WI 53706, (URL: http://cimss.ssec.wisc.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).


Suwanosejima (Japan) — January 2019 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Multiple explosive events with incandescence and ash plumes during November 2018

Suwanosejima, an andesitic stratovolcano in Japan's northern Ryukyu Islands, was intermittently active for much of the 20th century, producing ash plumes, Strombolian explosions, and ash deposits. Continuous activity since October 2004 has produced intermittent explosions, generating ash plumes in most months that rise hundreds of meters above the summit to altitudes between 1 and 3 km. Ongoing activity for the second half of 2018 is covered in this report with information provided by the Japan Meteorological Agency (JMA) and the Tokyo Volcanic Ash Advisory Center (VAAC).

Activity during July-December 2018 was intermittent with explosions reported twice in September and 21 times during November. Incandescent activity was observed a few times each month, increasing significantly during November. Thermal data support a similar pattern of activity; the MIROVA thermal anomaly graph indicated intermittent activity through the period that was most frequent during October and November (figure 33). MODVOLC thermal alerts were issued once in September (9), three times in October (7, 21), and four times on 14 and 15 November.

Figure (see Caption) Figure 33. MIROVA thermal data for Suwanosejima from 7 February through December 2018 indicated intermittent activity at the summit that increased to more significant activity during October and November before declining by the end of the year. Courtesy of MIROVA.

There were no explosions at Suwanosejima during July or August 2018; steam plumes rose 900-1,000 m above the crater rim and incandescence was intermittently observed on clear nights. During September incandescence was also observed at night; in addition, explosions were reported on 12 and 13 September, with ash plumes rising 1,100 m above the crater rim. October was again quiet with no explosions, only steam plumes rising 800 m, and occasional incandescence at night, although thermal activity increased (figure 33).

More intense activity resumed during November 2018 with 21 explosions reported. On 9 and 14 November tephra was ejected up to 700 m from the Mitake crater. The Tokyo VAAC reported an ash plume visible in satellite imagery at 2.4 km altitude moving E on 14 November. The next day, a plume was reported at 2.7 km altitude drifting NW but it was not visible in satellite imagery. JMA reported gray ash plumes that rose up to 2,000 m above the crater rim on 16 and 23 November (figure 34). The ash plume on 23 November was visible in satellite imagery drifting N at 2.7 km altitude. On 30 November the Tokyo VAAC reported an ash plume visible in satellite data drifting SE at 2.4 km altitude. Incandescence was often observed at night from the webcams throughout the month. Ashfall was confirmed in the village 4 km SSW on 14, 17, and 23 November, and sounds were reported on 20 November.

Figure (see Caption) Figure 34. Ash plumes rose 2,000 m above the crater rim at Suwanosejima on 23 November 2018 as seen with the 'campsite' webcam. Courtesy of JMA (Volcanic activity commentary (November, 2018) of Suwanose Island).

During December 2018, no explosive eruptions were reported, but an ash plume rose 1,800 m above the summit on 26 December. Incandescence was observed on clear nights in the webcam. Throughout 2018, a total of 42 explosive events were reported; 21 of them occurred during November (figure 35).

Figure (see Caption) Figure 35. Eruptive activity at Suwanosejima during 2018. Black bars represent heights of steam, gas, or ash plumes in meters above crater rim (left axis), gray volcanoes along the top represent explosions, usually accompanied by ash plumes, red volcanoes represent large explosions with ash plumes, orange diamonds indicate incandescence observed in webcams. Courtesy of JMA (Volcanic activity of Suwanose Island in 2018).

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/).


Etna (Italy) — December 2018 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 emerge from NSEC in late August and late November 2018; Strombolian activity continues from multiple vents

Italy's Mount Etna on the island of Sicily has had historically recorded eruptions for the past 3,500 years and has been erupting continuously since September 2013 through at least November 2018. Lava flows, explosive eruptions with ash plumes, and Strombolian lava fountains commonly occur from its summit areas that include the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC) (formed in 1978), and the New Southeast Crater (NSEC) (formed in 2011). A new crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC and has become the highest part of the SEC-NSEC complex. Activity during late 2017 and early 2018 consisted mostly of sporadic Strombolian activity with infrequent minor ash emissions from multiple vents at various summit craters. Lava flow activity resumed in late August 2018 and again in late November and is covered in this report with information provided primarily by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

After several months of low-level activity in early 2018, increases in Strombolian activity at several vents began in mid-July (BGVN 43:08). This was followed by new lava flows emerging from the saddle cone and the E vent of the NSEC complex in late August. Discontinuous low-intensity Strombolian activity and intermittent ash emissions were reported from multiple vents at various summit craters during September through November. In late November, renewed Strombolian activity and a new, small flow emerged from a small scoria cone inside the E vent of the NSEC crater and persisted through the end of the month. The MIROVA thermal anomaly correspond to ground observations of increased thermal activity at Etna beginning in mid-July, peaking in late August, and increasing again at the end of November 2018 (figure 222).

Figure (see Caption) Figure 222. MIROVA thermal anomaly graph for Etna from April through early December 2018 shows the increases in thermal activity from lava flows and increased Strombolian activity in late August and late November. Courtesy of MIROVA.

Low-energy Strombolian activity resumed at both of the Bocca Nuova BN-1 vents as well as the vents in the Northeast Crater (NEC) during the second week of July 2018 and continued throughout the month. The activity from BN-1 was nearly continuous, but not always visible; occasionally, lava fragments rose 100 m and could be seen outside of the crater rim. Intermittent ash emissions accompanied the Strombolian activity. Activity at NEC was characterized by strong and prolonged explosions (up to several tens of seconds), sometimes with reddish-brown ash emissions (figure 223). Three vents on the floor of NEC continued to widen due to collapse of the inner walls. A seismic swarm on 18-19 July was located between 4 and 9 km depth.

Figure (see Caption) Figure 223. Ash emissions from the Northeast Crater of Etna on a) 27 July and b) 28 July 2018 rose a few tens of meters and quickly dispersed. Left image by INGV personnel, right image by volcanology guide Francesco Ciancitto. Courtesy of INGV (Rep. 31/2018, ETNA, Bollettino Settimanale, 23/07/2018 - 29/07/2018, data emissione 31/07/2018).

During a field inspection on 30 July INGV personnel noted activity at the three vents at the bottom of Northeast Crater; the farthest west produced ash emissions, the center produced steam, and the vent under the NE crater wall produced Strombolian activity that sent ejecta as high as the crater rim. Frequent ash emissions from NEC were observed on 3, 4, and 5 August. During the first week of August 2018 Strombolian activity also continued at BN-1 (figure 224). The webcam at Montagnola (EMOH) recorded incandescence at night from Bocca Nuova.

Figure (see Caption) Figure 224. Activity during the first half of August 2018 at Etna was concentrated at BN-1, the Northeast Crater (NEC), and the E vent of the New Southeast Crater (NSEC), shown in red. Courtesy of INGV (Rep. 33/2018, ETNA, Weekly Bulletin, 08/06/2018 - 12/08/2018, issue date 08/14/2018).

After several months of calm, explosive activity also resumed at the E vent of the of the New Southeast Crater, high on the E flank, in early August. An explosion in the early morning of 1 August 2018 generated a gray-brown ash plume that rose several hundred meters above the summit (figure 225). Smaller emissions occurred throughout the day, and the EMOH camera recorded sporadic Strombolian explosions at night, which continued through the first week of August.

Figure (see Caption) Figure 225. After several months of calm, a resurgence of explosive activity was observed at the E vent (formed 25 November 2015) on the high E flank of the New Southeast Crater. The activity started with an explosion at 0408 UTC (= local time -2 hours), and generated a gray-brown ash plume that rose several hundred meters above the top of the volcano (a, b). In the following hours other smaller ash emissions occurred, and in the evening, the EMOH camera recorded sporadic Strombolian explosions (c). This activity continued, with fluctuations in the frequency and magnitude of the explosions, for the rest of the month (d, e, f). Courtesy of INGV (Rep. 32/2018, ETNA, Bollettino Settimanale, 30/07/2018 - 05/08/2018, data emissione 07/08/2018).

Similar activity at BN-1, NEC, and the reactivated vent at NSEC continued through the second and third weeks of August. On 16 August 2018 a new vent opened in the BN-2 area on the E side of the Voragine (inactive since December 2015) and exhibited both degassing and Strombolian activity (figure 226). During that week Strombolian activity also continued at the NEC, but activity became more sporadic at the E vent of NSEC. During the last week of August, Strombolian activity and intense degassing continued in the western sector of Bocca Nuova (BN-1). Occasionally, lapilli fragments a few centimeters in diameter were ejected onto the S rim of the crater. Strombolian activity also continued from multiple vents at the bottom of NEC. The frequency and intensity of explosions was variable and increased significantly during 22 August, ejecting coarse pyroclastic material outside the crater rim.

Figure (see Caption) Figure 226. The crater floor of Bocca Nuova at Etna on 16 and 17 August 2018 with thermal (a) and visible (b) images. The incandescent areas are highlighted with colors ranging from yellow to red and white in the thermal image. BN-1 (reactivated in November 2016) is in the foreground, and vent BN-2, which re-opened on 16 August in the south-eastern sector of the Bocca Nuova, is in the back (upper right). Thermal image by Francesco Ciancitto, photograph by Marco Neri. Courtesy of INGV (L'Etna non va in vacanza: aumenta di intensità l'attività eruttiva sommitale, 23 Agosto 2018, INGV Blog).

Beginning on 23 August 2018 about 1800 UTC, activity resumed at the saddle cone located between the old cone of the Southeast Crater (SEC) and the new cone (NSEC). Strombolian activity, initially modest, quickly became more intense, producing almost continuous explosions with the launch of coarse ejecta up to a height of 100-150 m. At 1830 UTC, while Strombolian explosions of modest intensity were also taking place at the E vent of NSEC, a small lava flow emerged from the E vent and traveled a few hundred meters E towards the Valle del Bove. Shortly after 1830 UTC another lava overflow was also observed moving N from the saddle cone (figures 227 and 228).

Figure (see Caption) Figure 227. Strombolian ejecta rose 100 m from the cono della sella (saddle cone) at the New Southeast Crater of Etna and lava flowed from both the E vent (left) and N from the saddle cone (right), shortly before midnight on 23 August 2018. Photo by Boris Behncke, courtesy of INGV blog 25 August 2018 (L'Etna fa gli straordinari: attività eruttiva al Nuovo Cratere di Sud-Est).
Figure (see Caption) Figure 228. Map of the summit crater area (DEM 2014, Aerogeophysics Laboratory - Rome Section 2, modified). BN = Bocca Nuova; VOR = Voragine; NEC = Northeast Crater; SEC = Southeast Crater; NSEC = New Southeast Crater. The yellow dots indicate the position of the degassing vents and those in red are the vents with Strombolian activity. The map also shows the flows produced by the saddle cone and the E vent of NSEC through 27 August 2018. Courtesy of INGV (Rep. N° 35/2018, ETNA, Bollettino Settimanale, 20/08/2018 - 26/08/2018, data emissione 28/08/2018).

Strombolian explosions of moderate intensity continued throughout the night from the saddle cone. The following morning (24 August) a small lava overflow emerged from the vent and stopped after traveling a few tens of meters towards the S flank of the NSEC cone (figure 228, small orange flow within saddle, and figure 229b). The Strombolian activity was accompanied by an abundant and continuous emission of ash, whichformed a small plume that rose a few hundred meters from the vent (figure 229c). The Strombolian activity at the saddle cone decreased gradually on 25 August.

Figure (see Caption) Figure 229. Eruptive activity at Etna during 23-24 August 2018. a) 23 August shortly before midnight; Strombolian activity from the saddle cone and lava flows from the E vent of the NSEC (white arrow) and from the cone of the saddle northwards (red arrow). Photo by B. Behncke taken from Fornazzo. b) 24 August, Strombolian activity and small lava overflow southward taken by the thermal camera of La Montagnola. c) 24 August, ash emitted during the Strombolian activity from the cone of the saddle, taken by the visible camera of La Montagnola. Courtesy of INGV (Rep. 35/2018, ETNA, Bollettino Settimanale, 20/08/2018 - 26/08/2018, data emissione 28/08/2018).

Strombolian activity was continuing on 27 August 2018 at NSEC, and the flow to the N into the Valle del Leone began cooling after lava stopped feeding it that evening. The same day, a new lava overflow emerged from the E vent of NSEC (figure 230) and flowed E towards the Valle del Bove for about 24 hours (figure 231).

Figure (see Caption) Figure 230. Map of the summit crater area of Etna (DEM 2014, Aerogeophysics Laboratory - Rome Section 2, modified). BN = Bocca Nuova; VOR = Voragine; NEC = Northeast Crater; SEC = Southeast Crater; NSEC = New Southeast Crater. The yellow dots are degassing vents and those in red have Strombolian activity. The map also shows the flows produced by NSEC during the last two weeks of August 2018. The yellow flow was cooling by 27 August when the new red flow emerged from the E vent of NSEC and lasted for about 24 hours. Courtesy of INGV (Rep. 36/2018, ETNA, Bollettino Settimanale, 27/08/2018 - 02/09/2018, data emissione 04/09/2018).
Figure (see Caption) Figure 231. A thermal image taken by Pizzi Deneri on 27 August 2018 at Etna shows the two flows on the flanks of NSEC. View is from the N. The flow labelled in red flows E from the E vent, and the other flow travels N from the Cono della sella (saddle cone) into the Valle del Leone and then moves east. Courtesy of INGV (Rep. 36/2018, ETNA, Bollettino Settimanale, 27/08/2018 - 02/09/2018, data emissione 04/09/2018).

Discontinuous Strombolian activity continued from NSEC after the effusive activity ended in late August. Several loud explosions from NSEC were reported by people living near the E flank of Etna during the first week of September. Strombolian activity, modest ash emissions, and significant gas emissions were also produced by BN-1; BN-2 exhibited only continuous degassing activity. Explosive activity declined during the second week of September. Discontinuous low-intensity Strombolian activity and intermittent ash emissions from Bocca Nuova, New Southeast Crater, and Northeast Crater characterized activity for the remainder of September. During the last week of the month, NEC produced frequent gray-brown ash emissions from a vent located in the western part of the crater floor, and included jets of ash, blocks, and volcanic bombs (figure 232).

Figure (see Caption) Figure 232. Ash emissions from Etna's Northeast Crater in late September 2018. The four top images are explosions from a vent at the bottom of NEC on 24 September 2018; the bottom image is one of the many ash emissions observed on 30 September. Courtesy of INGV (Rep. N° 40/2018, ETNA, Bollettino Settimanale, 24/09/2018 - 30/09/2018, data emissione 02/10/2018).

Discontinuous low-intensity Strombolian activity and intermittent ash emissions from the Bocca Nuova, the New Southeast Crater, and Northeast Crater characterized activity during all of October 2018. Two vents remained active at the bottom of Bocca Nuova (BN-1). During a visit on 16 October, INGV-OE geologists noted that the northernmost vent produced nearly continuous Strombolian activity with frequent explosions; occasionally fragments exceeded the crater rim in height but still fell within the crater. The southernmost vent, on the crater floor about 130 m from the edge, was characterized by explosive activity that produced mainly spattering which covered both the crater floor and walls (figure 233). On 25 October the webcam at Bronte recorded an ash emission from Bocca Nuova that resulted from three closely-spaced explosions. The ash was red and dispersed rapidly to the S causing ashfall near Torre del Filosofo and Rifugio Sapienza.

Figure (see Caption) Figure 233. Inside the Bocca Nuova BN-1 crater at Etna on 16 October 2018, two vents were active. The northernmost vent (yellow arrow) had Strombolian activity; the southernmost vent, visible on the right, produced mostly "spattering". Photo by M. Coltelli, courtesy of INGV (Rep. N° 43/2018, ETNA, Bollettino Settimanale, 15/10/2018 - 21/10/2018, data emissione 23/10/2018).

Strombolian activity at NSEC gradually intensified during the first week of November 2018 and was sometimes accompanied by ash emissions that rapidly dispersed, falling mainly near the vent and in the Valle del Bove to the E. Audible explosions from the activity were heard in Zafferana Etnea on the E flank. Several clear views of the summit and details of the active vents were well exposed during an overflight on a clear 9 November day (figure 234).

Figure (see Caption) Figure 234. An aerial view of the Etna summit craters taken on a clear 9 November 2018 day with the assistance of the 2nd Coast Guard Core of Catania. View is to the NW. BN = Bocca Nuova; VOR = Voragine; NEC = Northeast Crater; SEC = Southeast Crater; NSEC = New Southeast Crater. Courtesy of INGV (Rep. N° 46/2018, ETNA, Bollettino Settimanale, 05/11/2018 - 11/11/2018, data emissione 13/11/2018).

Three vents were visible at BN-1 during the 9 November 2018 overflight (figure 235); continuous Strombolian activity occurred at vent 1, whose fallout of pyroclastic debris remained within the crater; discontinuous Strombolian activity was observed at vent 2 associated with weak, pulsing ash emissions; only degassing activities were observed at vent 3. At BN-2, intense degassing accompanied discontinuous Strombolian activity that was associated with weak pulsating ash emissions, and several high temperature gas emission points. Scientists also observed a collapse on a portion of the northern inner wall of BN-1 from the explosion on 25 October.

Figure (see Caption) Figure 235. Aerial view of Bocca Nuova (BN) and Voragine (VOR) at Etna on 9 November 2018 taken with helicopter support of the 2nd Coast Guard Core of Catania. The yellow hatched line indicates the wall of the area that collapsed on 25 October 2018. Inset a) thermal image of Bocca Nuova showing the structure of the three eruptive vents within BN-1 and the eruptive vent within the BN-2. Courtesy of INGV (Rep. N° 46/2018, ETNA, Bollettino Settimanale, 05/11/2018 - 11/11/2018, data emissione 13/11/2018).

Modest outgassing continued at Voragine (VOR) from the 7 August 2016 vent near the rim during November. At NEC, continuous and intense Strombolian activity from the crater floor caused pyroclastic ejecta to land outside the crater rim (figure 236). At the NSEC complex, high-temperature anomalies were visible at the NW crater edge, and the E vent of NSEC had a small scoria cone that produced discontinuous Strombolian explosions and minor ash emissions (figure 237).

Figure (see Caption) Figure 236. Aerial view of Voragine (VOR) and the Northeast Crater (NEC) at Etna taken on 9 November 2018 with helicopter support of the 2nd Coast Guard Core of Catania. The 7 August 2016 vent at VOR had a vigorous steam emission (yellow arrow). Inset a) thermal image showed the Strombolian activity in the bottom of NEC. Courtesy of INGV (Rep. N° 46/2018, ETNA, Bollettino Settimanale, 05/11/2018 - 11/11/2018, data emissione 13/11/2018).
Figure (see Caption) Figure 237. Thermal activity was evident in several places at the SEC-NSEC complex at Etna during the 9 November 2018 overflight with the helicopter of the 2nd Coast Guard Core of Catania (inset a, upper image). The small scoria cone (conetto di scorie) was visible inside the E vent (Bocca orientale) of the New Southeast Crater, seen from the East on 9 November (lower image). Upper image from INGV weekly (Rep. N° 46/2018, ETNA, Bollettino Settimanale, 05/11/2018 - 11/11/2018, data emissione 13/11/2018), lower image by Stefano Branca (INGV-Osservatorio Etneo) from INGV blog (Piccoli coni crescono: aggiornamento sullo stato di attività dell'Etna al 7 dicembre 2018).

A seismic swarm with over 40 events affected the W flank of Etna on 20 November 2018; the hypocenters were located between 15 and 27 km depth. A small lava flow also emerged on 20 November from the scoria cone inside the E vent at NSEC. The flow lasted for a few hours and remained inside the E vent. A new flow from the same scoria cone at the NSEC east vent appeared on 26 November accompanied by continued Strombolian activity. The flow remained high on the E flank at an elevation of about 3,200 m. Flow activity continued into the first days of December with frequent incandescent blocks moving down the NSEC E flank (figure 238). Elsewhere at Etna, Strombolian activity continued accompanied by sporadic and modest ash emissions from Bocca Nuova, the New Southeast Crater and the Northeast Crater through the end of November (figure 239).

Figure (see Caption) Figure 238. Strombolian activity and emission of a small lava flow from the E vent of the New Southeast Crater was seen from the E at dawn on 29 November 2018. The lava flow was very short, but the detachment and rolling of numerous incandescent blocks from the front and sides of the flow created the impression that the flow reached the base of the New Southeast Crater cone. The scoria cone inside the E vent grew considerably compared to its size observed on 9 November (figure 237). Photo by Giò Giusa. Courtesy of INGV, INGV Blog (Piccoli coni crescono: aggiornamento sullo stato di attività dell'Etna al 7 dicembre 2018).
Figure (see Caption) Figure 239. Incandescence from Strombolian activity was visible inside the NSEC (right) and BN (left) craters at Etna on 22 November 2018 as viewed from Tremestieri Etneo. Photo by B. Behncke, courtesy of INGV (Rep. N° 48/2018, ETNA, Bollettino Settimanale, 19/11/2018 - 25/11/2018, data emissione 27/11/2018).

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: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/ ); 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/).


Dukono (Indonesia) — December 2018 Citation iconCite this Report

Dukono

Indonesia

1.693°N, 127.894°E; summit elev. 1229 m

All times are local (unless otherwise noted)


Regular ash explosions continuing as of September 2018

The long-term eruption at Dukono has been characterized by frequent ash explosions through at least March 2018 (BGVN 43:04). The current report shows that this pattern continued through at least September 2018. The data below were provided by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Center for Volcanology and Geological Hazard Mitigation (CVGHM), and the Darwin Volcanic Ash Advisory Centre (VAAC).

Between April and September 2018 there were about five reports per month about ash plumes. Altitudes generally ranged from 1.4-2.1 km, although 3 km was reported during 2-8 May and 3.4 km was reported during 25-31 July (table 18).

Table 18. Monthly summary of reported ash plumes from Dukono for April-September 2018. The direction of drift for the ash plume through each month was highly variable. Data courtesy of the Darwin VAAC and PVMBG.

Month Plume Altitude (km) Notable Plume Drift
Apr 2018 1.5-2.1 --
May 2018 1.5-3 Ash plumes drifted as far as 225 km NW on 28 May
Jun 2018 1.4-2.1 --
Jul 2018 1.8-3.4 --
Aug 2018 1.8-2.4 --
Sep 2018 1.8-2.1 --

No thermal anomalies at Dukono, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were detected during the reporting period. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected a low-power hotspot in early April (about 2.5 km from the volcano) and a possible low-power hotspot in late August 2018 (about 5 km from the volcano).

Geologic Background. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

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/); 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/).


Ulawun (Papua New Guinea) — November 2018 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)


Ash plumes on 8 June, 21 September, and 5 October 2018

Typical activity at Ulawun consists of sporadic explosions with weak ash plumes. During 2017, sporadic explosions occurred between late June through early November with ash plumes rising no more than 3 km in altitude (BGVN 42:12). This report describes activity between January and September 2018.

According to the Darwin Volcanic Ash Advisory Centre (VAAC), a NOTAM (Notice to Airmen) stated that on 8 June 2018 an ash plume rose to an altitude of 2.1 km and drifted W. The Darwin VAAC also reported that a pilot observed an ash plume on 21 September 2018 rising to an altitude of 3.7 km and drifting W. Ash was not confirmed in satellite images, though weather clouds obscured views.

On 5 October 2018 the Darwin VAAC identified a steam-and-ash emission in satellite images rising to an altitude of 4.6 km and drifting WSW. It was also reported by ground observers. The Rabaul Volcano Observatory reported that during 1-12 October white, and sometimes light gray, emissions rose from the summit crater; seismicity was low.

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

Information Contacts: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea.


Langila (Papua New Guinea) — November 2018 Citation iconCite this Report

Langila

Papua New Guinea

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

All times are local (unless otherwise noted)


Several weak ash plumes during June, September, and October 2018

After Vulcanian activity in the latter part of 2009, activity at Langila subsided, with infrequent activity until 2016, when activity increased somewhat through May 2018 (BGVN 34:11, 35:02, 42:01, and 42:09). This pattern of intermittent activity continued through October 2018. No reports were available from the Rabaul Volcano Observatory during the current reporting period (June-October 2018), but volcanic ash warnings were issued by the Darwin Volcanic Ash Advisory Centre (VAAC).

Four explosions were reported by the Darwin VAAC in June 2018, generating ash plumes that rose 2.1-3.4 km (table 6). There were no reports of an explosion in July or August 2018. Additional ash plumes were detected on 29 September and 30 October 2018

Table 6. Reports of ash plumes from Langila during 1 June-30 October 2018 based on analyses of satellite imagery and wind model data. Courtesy of the Darwin VAAC.

Date Ash plume altitude (km) Ash plume drift Observations
07 Jun 2018 3.4 SW Detached from the summit.
10 Jun 2018 2.1 -- Dissipated.
17 Jun 2018 2.4 W --
20-21 Jun 2018 2.4 W, NW --
29 Sep 2018 2.4 NE --
30 Oct 2018 2.7 SE --

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

Information Contacts: 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/).


Sangeang Api (Indonesia) — November 2018 Citation iconCite this Report

Sangeang Api

Indonesia

8.2°S, 119.07°E; summit elev. 1949 m

All times are local (unless otherwise noted)


Ongoing crater activity and thermal anomalies during September 2017-October 2018

A significant increase in the number of thermal anomalies at Sangeang Api was recorded during February and June through mid-August 2017, along with a small Strombolian eruption in mid-July that generated an ash plume (BGVN 42:09). The high number of thermal anomalies continued through at least 20 October 2018. The current report summarizes activity between 1 September 2017 and 20 October 2018. The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and Darwin Volcanic Ash Advisory Centre (VAAC).

Based on a Volcano Observatory Notice for Aviation (VONA) from PVMBG, on 9 May 2018 a gas emission was observed at 1807 that rose to an altitude of 4,150 m and drifted W. Consequently, the Aviation Color Code was raised from unassigned to Yellow. Clear thermal satellite imagery the next day showed hot material traveling about 500 m SE out of the summit crater and continuing another 500 m down the E flank (figure 18).

Figure (see Caption) Figure 18. Sentinel-2 satellite image of Sangeang Api on 10 May 2018. This "Atmospheric penetration" view (bands 12, 11, and 8A) highlights hot material extending more than a kilometer from the vent in the summit crater to the SE and onto the E flank. Courtesy of Sentinel Hub.

Based on another VONA from PVMBG, an ash emission at 1338 on 15 October 2018 rose 250 m above the summit and drifted SW, W, and NW. The VONA noted that the ash emission possibly rose higher than what a ground observer had estimated. Seismic data was dominated by signals indicating emissions as well as local tectonic earthquakes. The Aviation Color Code was raised from Yellow to Orange.

During the reporting period, MODIS satellite instruments using the MODVOLC algorithm recorded thermal anomalies between 3 and 12 days per month, many of which had multiple pixels. October 2017 had the greatest number of days with hotspots (12), while the lowest number was recorded during December 2017 through February 2018 (3-4 days per month). The vast majority of anomalies issued from the summit; a few were along the E flanks. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, recorded numerous hotspots during the previous 12 months through mid-October 2018, except for the second half of January 2018 (figure 19). Almost all recorded MIROVA anomalies were within 5 km of the volcano and of low to moderate radiative power.

Figure (see Caption) Figure 19. Thermal anomalies identified by the MIROVA system (Log Radiative Power) at Sangeang Api for the year ending 19 October 2018. Courtesy of MIROVA.

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

Information Contacts: 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/); 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).


Sheveluch (Russia) — November 2018 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Thermal anomalies along with minor gas and steam emissions continue through October 2018

Volcanic activity at Sheveluch declined during the period of May through October 2018. This decline followed a lengthy cycle of eruptive activities which began in 1999, including pyroclastic flows, explosions, and lava dome growth, as previously reported through April 2018 (BGVN 43:05). According to the Kamchatka Volcanic Eruption Response Team (KVERT), during this time a thermal anomaly was detected in satellite imagery and two gas-and-steam events were reported in July and October 2018. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

KVERT reported that satellite data showed a plume of re-suspended ash up to 62 km to the SE of the volcano on 18 July 2018. Moderate gas and steam emissions rose from the volcano on 19-26 October 2018. Thermal anomalies were frequently reported by KVERT during May through October 2018. The MIROVA system detected intermittent low-power thermal anomalies during this time.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far East Division, 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/).


Gamalama (Indonesia) — November 2018 Citation iconCite this Report

Gamalama

Indonesia

0.8°N, 127.33°E; summit elev. 1715 m

All times are local (unless otherwise noted)


Weak explosion on 4 October 2018

The most recent of the previous intermittent weak explosions on Gamalama was on 3 August 2016, which produced an ash plume and ashfall that closed a nearby airport for a day (BGVN 42:03). This report discusses eruptive activity in October 2018. The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM).

PVMBG reported that an explosion at 1152 on 4 October 2018, likely phreatic, generated an ash plume that rose about 250 m above the summit and drifted NW. Eight volcanic earthquakes were recorded about an hour before the event. Based on satellite data and information from PVMBG, the Darwin Volcanic Ash Advisory Centre (VAAC) reported that during 5-6 October ash plumes rose to an altitude of 2.1 km and drifted W and NW. The Alert Level remained at 2 (on a scale of 1-4); visitors and residents were warned not to approach the crater within a 1.5-km radius. On 10 October PVMBG reported only gas emissions (mostly water vapor), and the Aviation Color Code was lowered from Orange to Yellow.

No significant SO2 levels near the volcano were recorded by NASA's satellite-borne ozone instruments (Suomi NPP/OMPS and Aura/OMI) during early October. However, Simon Carn reported that the newer TropOMI instrument aboard the Copernicus Sentinel-5P satellite showed significant SO2 levels as high as 12 TRM/DU (levels in middle troposphere layer, as measured in Dobson Units) on 4 October 2018 (figure 7).

Figure (see Caption) Figure 7. Weak SO2 emissions from Gamalama on 4 October 2018 were detected by the Sentinel-5P TROPOMI instrument. Courtesy of Simon Carn.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 5+7, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL:http://www.bom.gov.au/info/vaac/); Simon Carn, Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA (URL: http://www.volcarno.com/, Twitter: @simoncarn).

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Scientific Event Alert Network Bulletin - Volume 10, Number 05 (May 1985)

Managing Editor: Lindsay McClelland

Concepcion (Nicaragua)

Small ash eruptions

Etna (Italy)

Lava flows toward SW and SE; strong gas and vapor emissions

Fournaise, Piton de la (France)

Eruption with premonitory seismicity

Kilauea (United States)

Summit inflation and low-level harmonic tremor continue; episode 33 of 1983-85 eruption

Masaya (Nicaragua)

Small ash eruptions

Momotombo (Nicaragua)

Continued high fumarole temperatures

Ruapehu (New Zealand)

Hydrothermal eruptions accompany seismic activity

Ruiz, Nevado del (Colombia)

Increased seismicity and abnormal fumarolic activity

Soputan (Indonesia)

Seven-hour tephra eruption; jumbo jet flies through plume

St. Helens (United States)

Strong seismicity accompanies major dome-building episode

Tecapa (El Salvador)

Earthquake swarm at historically inactive volcano



Concepcion (Nicaragua) — May 1985 Citation iconCite this Report

Concepcion

Nicaragua

11.538°N, 85.622°W; summit elev. 1700 m

All times are local (unless otherwise noted)


Small ash eruptions

A series of small ash eruptions occurred in December 1984.

Geologic Background. Volcán Concepción is one of Nicaragua's highest and most active volcanoes. The symmetrical basaltic-to-dacitic stratovolcano forms the NW half of the dumbbell-shaped island of Ometepe in Lake Nicaragua and is connected to neighboring Madera volcano by a narrow isthmus. A steep-walled summit crater is 250 m deep and has a higher western rim. N-S-trending fractures on the flanks have produced chains of spatter cones, cinder cones, lava domes, and maars located on the NW, NE, SE, and southern sides extending in some cases down to Lake Nicaragua. Concepción was constructed above a basement of lake sediments, and the modern cone grew above a largely buried caldera, a small remnant of which forms a break in slope about halfway up the N flank. Frequent explosive eruptions during the past half century have increased the height of the summit significantly above that shown on current topographic maps and have kept the upper part of the volcano unvegetated.

Information Contacts: D. Fajardo B., INETER.


Etna (Italy) — May 1985 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 toward SW and SE; strong gas and vapor emissions

"The eruption continued through May without significant changes from last month. The main lava channel has been transformed into a lava tube, between 2,510 and 2,320 m elevation, that has at least four windows through which it was possible to see the lava flow. The lava has maintained a constant velocity during the last few weeks. On 23 May another lava overflow occurred as a result of roof collapse along the upper portions of the lava tube (2,485 m elevation), generating small lava flows of brief duration.

"The numerous short-lived vents inside the lava field (from 2,320 to 2,150 m elevation) were variable, as usual, in number and position. The lava flows that originated from these short-lived vents have increased the size of the lava field on both the W and E sides to a maximum width of ~1.5 km.

"Beginning 10 May the lava moved mainly toward the SW (Monte Rinatura and Monte Nero). Around the beginning of June there were numerous lava flows toward the SE (1910 craters area). Lava continued to flow toward the south (Monte Castellazzi area), but these flows were not strongly fed. None of the lava flows descended below 2,000 m elevation.

"The more or less intense emission of gas and vapor from both vents of the central crater and from the Northeast Crater continue. Emissions of ash are rare and inconsistent. Gas under pressure emerged from a small opening at the southern base of the 1984 cone inside the Southeast Crater (P. Briole, personal communication). R. Clocchiatti conducted temperature measurements with a thermocouple; the temperature ranged between 1053°C and 1,088°C (CEN-SACLAY).

"M. Cosentino and G. Lombardo reported that no particular seismic activity was recorded. Instead, an increase in the average amplitude of harmonic tremor was noticed, probably connected to the degassing of the central and Northeast craters.

"The Etna guides and rescue volunteers from the Italian Alpine Club (A. Cristaudo and A. Nicotra) helped with information on the activity."

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.


Piton de la Fournaise (France) — May 1985 Citation iconCite this Report

Piton de la Fournaise

France

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

All times are local (unless otherwise noted)


Eruption with premonitory seismicity

"Since the last eruption, seismicity and deformation measured at the four summit stations had remained at very low levels (0-5 earthquakes and 1-7 µrad of tilt per month). The pattern of tilt vectors implied a progressive deflation of the area that had undergone large deformation during the last eruption.

"Beginning on 15 May, several small earthquakes (M <1) were recorded at depths of 1.5-2.5 km beneath the summit. Simultaneously, the summit dry tilt stations began to show an inflationary pattern. The number of seismic events progressively increased. Seismic activity peaked on 8 June with 13 events, and decreased to a low level on the 13th. No significant migration of the earthquakes was observed. Inflation appeared to have been almost continuous except during two episodes when deformation slowed (3 June) or reversed (8 June) corresponding to the periods of largest seismic energy release.

"This activity differed from the 1983 pre-eruptive crisis. The late 1983-early 1984 eruption was preceded by two weeks of seismic activity (48 events) with no associated deformation. The most recent activity lasted for at least four weeks. The earthquakes are located in the same area as before, but summit tilt stations show inflation of 15-40 µrads."

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

Information Contacts: J. Lenat, OVPDLF; M. Kasser, Inst. Geographique National (IGN), Paris; A. Nercessian, IPG, Paris; R. Vie le Sage, Délégation aux Risques Majeurs (DRM), Paris; P. Bachelery, Univ. de la Réunion; A. Bonneville, Univ. du Languedoc; G. Boudon, Obs. Volc. de la Mt. Pelée; M. Halbwaks, Univ. de Chambéry.


Kilauea (United States) — May 1985 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Summit inflation and low-level harmonic tremor continue; episode 33 of 1983-85 eruption

"For the first time since October 1984, Kilauea did not erupt during a calendar month. Mapping of episode 32 (21-22 April) eruptive products was completed in May and showed that 16.1 x 106 m3 of lava and 0.25 x 106 m3 of tephra (dense rock equivalent) were produced. Lava from the 1983-85 eruption covered 40 km2 of the middle E rift zone.

"Following episode 32, magma was first visible in the conduit on 9 May, at approximately 50 m depth. By the end of May, the magma column had risen to within 30 m of the Pu`u `O`o crater floor and remained mostly crusted over.

Deformation. "The summit of Kilauea continued to inflate during May. However, a period of significant summit subsidence occurred from 22 May at 1800 to 27 May at 0900. During this interval, the Uwekahuna tiltmeter recorded 2.8 µrad of summit deflation. The net inflation during May was 5.7 µrad.

Seismicity. "Harmonic tremor continued at a fluctuating low level in the middle E rift zone near Pu`u `O`o following episode 32. The number of shallow microearthquakes in the E rift zone and summit region varied from several tens to a few hundreds per day. Short-period summit earthquakes increased gradually in response to the slow rate of inflation. Frequent bursts of long-period events and harmonic tremor were recorded from intermediate to deep sources beneath Kilauea."

Addendum: Episode 33 of the middle E rift zone eruption occurred on 1213 June. Discontinuous low level fountaining and spillover from the Pu`u `O`o vent began at 0430 on the 12th. By 2306, fountaining had become vigorous and continuous. Lava flowed about 3.5 km to the SE over older lavas from Pu`u `O`o before the episode ended at [0453] on the 13th.

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

Information Contacts: C. Heliker, G. Ulrich, R. Hanatani, R. Koyanagi, and R. Okamura, HVO.


Masaya (Nicaragua) — May 1985 Citation iconCite this Report

Masaya

Nicaragua

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

All times are local (unless otherwise noted)


Small ash eruptions

In December 1983, 4,993 microearthquakes were recorded at Masaya. Early that month, a very large gas column was continuing to emerge from Santiago Crater. A series of small ash eruptions occurred in April 1984. There was a small gas explosion on 23 January 1985, and another ash eruption occurred in April 1985.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.

Information Contacts: D. Fajardo B., INETER.


Momotombo (Nicaragua) — May 1985 Citation iconCite this Report

Momotombo

Nicaragua

12.423°N, 86.539°W; summit elev. 1270 m

All times are local (unless otherwise noted)


Continued high fumarole temperatures

Summit fumarole temperatures have remained high, with small fluctuations probably related to seasonal rainfall variations. The maximum temperature in 1984 was 895°C in August; the same fumarole had a temperature of 875°C when measured in 1985.

Geologic Background. Momotombo is a young stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows extend down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms an island offshore in Lake Managua. Momotombo has a long record of Strombolian eruptions, punctuated by occasional stronger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after a 10 April 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the south flank.

Information Contacts: D. Fajardo B., INETER.


Ruapehu (New Zealand) — May 1985 Citation iconCite this Report

Ruapehu

New Zealand

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

All times are local (unless otherwise noted)


Hydrothermal eruptions accompany seismic activity

After 3 years of quiescience, small hydrothermal eruptions began on or shortly before 21 May. On 16 May, major overflow of Crater Lake into the Whangaehu River began, as shown by pH and conductivity measurements downstream (at Tangiwai). Seismic activity, characterized by increased high-frequency tremor and local earthquakes, began [in early May, with some minor tremor on the 5th and small volcanic earthquakes on the 11th]. Eruptions were first observed in Crater Lake on 21 May and were also seen on 25 May.

On 28 May NZGS personnel noted 15 small hydrothermal eruptions during a 10-hour period. All the eruptions occurred in the lake center, where resumption of weak upwelling had first been observed on 26 April. The eruptions were characterized by updoming of the central lake surface, noisy ejection of water and mud jetting to 10 m above the lake surface, and waves radiating from the lake center. Clouds limited deformation measurements across the crater but a pair of horizontal angle observations indicated no major change in crater diameter.

The lake was battleship-gray in color, with clean snow around the water margin about 1 m above lake level. The lake temperature had increased to 45°C from the 20-25°C range of recent months. Interim analyses of the lake water show a progressive dilution throughout the summer months. Chlorine and magnesium contents have increased since activity began, but the Mg/Cl ratio has not changed significantly.

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

Information Contacts: I. Nairn and B. Scott, NZGS, Rotorua; P. Otway, NZGS, Wairakei.


Nevado del Ruiz (Colombia) — May 1985 Citation iconCite this Report

Nevado del Ruiz

Colombia

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

All times are local (unless otherwise noted)


Increased seismicity and abnormal fumarolic activity

"Since late November 1984, local earthquakes have been felt near the summit. On 22 December, stronger earthquakes were detected, followed by a half hour of apparent harmonic tremor. During a visit to the crater in early January 1985, increased fumarolic activity, evidence of phreatic explosions, and the wide deposition of sulfur salts over the adjacent snowcap were noted. At times, a thin layer of ash had been ejected, which was analyzed by J. Tomblin and found to consist of alteration products and sulfur.

"Seismic activity continued, with 17 felt earthquakes in March and 18 in April. There are no operating seismographs in the region. Abnormal fumarolic activity also continued. The one hot spring with frequent temperature monitoring, NW of the crater, had not shown any variation in temperature.

"Ruiz is a glacier-clad stratovolcano (bordering Tolima and Caldas Departments). . . . Colombian officials have begun the necessary studies."

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

Information Contacts: M. Hall, Escuela Politécnica, Ecuador; J. Tomblin, UNDRO; O. Gómez, Civil Defense Coordinator, Manizales.


Soputan (Indonesia) — May 1985 Citation iconCite this Report

Soputan

Indonesia

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

All times are local (unless otherwise noted)


Seven-hour tephra eruption; jumbo jet flies through plume

An ash eruption from Soputan's main crater occurred 19-20 May from 1815 to 0130. The eruption column rose to 4 km altitude, and ~2 cm of ash (fine to coarse) accumulated at villages (Kawangkoan, Langoan, Noongan, and Ratahan) 9-12 km from the crater. There were no casualties and no evacuations were necessary. The volcano has remained quiet since 22 May.

On 20 May at 0058, a jumbo jet en route from Hong Kong to Sydney, Australia, with 267 passengers and 16 crew members encountered the ash cloud ~80 km SSE of the volcano (approximately 0.5°N, 124.54°E). An orange glow discharged from the nose of the aircraft and orange sparks passed over the windshield. Engine inlets were illuminated by a white light. A light haze that smelled like burnt dust filled the cabin, and ash accumulated on flat surfaces. These effects continued for 7-8 minutes, while the aircraft remained on course at 0.85x the speed of sound, for a distance of roughly 120-135 km. The aircraft continued to Sydney, arriving 4 hours after exiting the ash cloud, and landed uneventfully. Because of damage caused by the ash cloud, it was necessary to replace all four of the aircraft's engines, other navigational components, and more than a dozen windows.

The TOMS instrument on the NIMBUS 7 polar orbiting satellite detected an area of SO2 enhancement SE of Soputan during its pass at local noon on 20 May. The area of enhancement extended from about 124.5°E to 126°E near the equator and from about 125°E to 127°E at 1.5°S with the maximum at about 1°S, 126°E.

Geologic Background. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano rises to 1784 m and is located SW of Riendengan-Sempu, which some workers have included with Soputan and Manimporok (3.5 km ESE) as a volcanic complex. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

Information Contacts: VSI; Boeing, Seattle, WA; A. Krueger, NASA/GSFC.


St. Helens (United States) — May 1985 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)


Strong seismicity accompanies major dome-building episode

During mid-May, seismicity and rates of displacement began to increase from background levels. After 8 months of quiescence, a new lobe was extruded onto the composite lava dome, and a major intrusive event further enlarged the dome.

On 13 May, the number of medium- to high-frequency events recorded from the crater seismic station began to increase. Measurements on 16 May indicated that displacement rates on the dome had increased slightly while seismicity continued to build gradually. Several vigorous gas emissions, the first since 24 September 1984, occurred on 17 May from a vent in the NE part of the dome's summit area. No tephra was ejected, and the largest plume rose to just above the crater rim. Seismicity and displacement rates continued to increase, and on 20 May the USGS and University of Washington issued a volcano advisory notice stating that recent changes at the volcano suggested "renewed eruptive activity will begin within the next 2 weeks, possibly within the next few days."

By the 23rd, seismicity had reached high levels. On the 24th, very low-frequency events increased in size and number, although medium- to high-frequency events decreased. Observations made during a night overflight on the 25th at 0030 indicated increased glow from cracks on the dome. Later that morning, the low-frequency earthquakes that typically immediately precede and accompany extrusions had become more numerous, and deformation patterns suggested to USGS scientists that magma had nearly reached the surface of the dome. Observations during the next week were few because of poor weather conditions.

Between 21 and 23 May, a trough-like fracture system began to develop on top of the dome. By 27 May, this graben was 30-50 m wide and had cut across the entire S portion of the dome. Sometime between the 27th and 30th, a new lobe of gas-poor lava was extruded on the SE flank of the dome, near the E end of the newly formed graben. The 80-m-wide lobe extended out of the graben about 100 m down to the crater floor (figure 28). By the 30th, the graben was 400 m long, 30 m deep, and averaged 90-100 m wide. The dome flank S of the graben had been displaced outward.

Figure (see Caption) Figure 28. Sketch of Mt. St. Helens, by Bobbie Myers, looking NW, showing the composite lava dome after formation of the graben and extrusion of the new lobe in May 1985.

Seismicity continued at very high levels; on the 29th, M 2.5-2.8 events were recorded every few minutes as deep as 1 km below the dome. During past extrusion episodes, seismicity typically decreased sharply when lava reached the surface, but on the 31st, seismicity remained vigorous. Late on 31 May or early on 1 June, a slow decrease in the number of seismic events began. By 5 June seismicity had decreased to moderate levels and had reached background levels by the 17th.

Measurements by USGS scientists on 16 June indicated that the S flank of the dome had moved outward about 70-100 m during the eruption, but that the current displacement rate had by then decreased to about a centimeter per day. A station on the crater floor S of the dome moved 46 m outward and 18 m upward between 17 May and 8 June, but had moved only a few centimeters more by the 16th. These measurements suggested to USGS scientists that about 6-8 x 106 m3 of magma were intruded into the dome during this eruption, the largest single dome-building event since 12 June 1980.

After the vigorous gas emission events of 17 May, vapor emission continued from the same vent during the eruption. However, SO2 emission rates averaged about 40 t/d during May, about the same as the average April rate of 30 ± 5 t/d. On 30 May, the rate increased from background levels to 90 ± 10 t/d, by 2 June to 160 ± 25, and by the 8th to 220 ± 10 t/d. SO2 emission decreased to 165 ± 10 t/d on June 10th and to 60 ± 10 t/d on the 12th.

Equipment to measure H2 emission was installed on top of the dome in January. After 3 months of very low measurements, ambient H2 around the top of the dome began to increase dramatically on 24 May, continued to rise over the next few days, and reached a very high value before the station was destroyed early on the 29th. Because the instrument was not yet calibrated, the measurements cannot be quantified.

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. Newhall, S. Brantley, K. McGee, J. Sutton, B. Myers, USGS CVO, Vancouver, WA; C. Jonientz-Trisler, University of Washington.


Tecapa (El Salvador) — May 1985 Citation iconCite this Report

Tecapa

El Salvador

13.494°N, 88.502°W; summit elev. 1593 m

All times are local (unless otherwise noted)


Earthquake swarm at historically inactive volcano

"An earthquake swarm occurred by surface faulting on 21 April in the Chinameca Complex, near Tecapa, a volcano with no known historic eruption. A magnitude 4.7 (mb) earthquake, the largest so far, occurred on 23 April . . . . Four days later, 27 April, during the peak activity (in terms of numbers of recorded and felt events per day), an 8 km-long graben formed on the NW flank of the volcano. The N40°W-striking graben is 0.8-1 km wide, with a vertical offset of 30 cm. Through 6 June, 170 earthquakes were felt in the area. A very preliminary analysis of the earthquake location data implies that activity began on a tectonic fault some 15 km NW of the volcanic summit, and moved nearer to the volcano at the time the graben formed. Since 3 June, 5-20 earthquakes per day were recorded by a high-gain seismograph station 50 km from the volcano, down from 300 events per day on 26, 27, and 28 April, and 21 and 23 May."

Geologic Background. Tecapa is a complex basaltic-to-andesitic stratovolcano at the NW end of a cluster of volcanoes E of the Río Lempa between San Vicente and San Miguel volcanoes. The Berlín caldera, whose rim is visible on the W side of the complex, was formed during the eruption of the Blanca-Rosa dacitic pumice in the late Pleistocene. Following caldera formation, the cones of Cerro Las Palmas, Cerro Pelón, Tecapa-Laguna de Alegria, and Cerro Alegria were constructed along a WSW-ENE line. The crater of Tecapa-Laguna de Alegria contains a deep notch on the eastern rim and is filled by Laguna de Alegria crater lake. The volcanic complex currently displays fumarolic activity, and a producing geothermal plant is located at the Berlín geothermal field.

Information Contacts: J. González, Centro de Investigaciones Geotécnicas, San Salvador; D. Harlow, USGS.

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.

View Atmospheric Effects Reports

Special Announcements

Special announcements of various kinds and obituaries.

View Special Announcements Reports

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/).