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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) Explosions with ejecta and ash plumes continue weekly during January-June 2019

Agung (Indonesia) Continued explosions with ash plumes and incandescent ejecta, February-May 2019

Kerinci (Indonesia) Intermittent explosions with ash plumes, February-May 2019.

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

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

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

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

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

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

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

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

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



Aira (Japan) — July 2019 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Explosions with ejecta and ash plumes continue weekly during January-June 2019

Sakurajima rises from Kagoshima Bay, which fills the Aira Caldera near the southern tip of Japan's Kyushu Island. Frequent explosive and occasional effusive activity has been ongoing for centuries. The Minamidake summit cone has been the location of persistent activity since 1955; the Showa crater on its E flank has also been intermittently active since 2006. Numerous explosions and ash-bearing emissions have been occurring each month at either Minamidake or Showa crater since the latest eruptive episode began in late March 2017. This report covers ongoing activity from January through June 2019; the Japan Meteorological Agency (JMA) provides regular reports on activity, and the Tokyo VAAC (Volcanic Ash Advisory Center) issues tens of reports each month about the frequent ash plumes.

From January to June 2019, ash plumes and explosions were usually reported multiple times each week. The quietest month was June with only five eruptive events; the most active was March with 29 (table 21). Ash plumes rose from a few hundred meters to 3,500 m above the summit during the period. Large blocks of incandescent ejecta traveled as far as 1,700 m from the Minamidake crater during explosions in February and April. All the activity originated in the Minamidake crater; the adjacent Showa crater only had a mild thermal anomaly and fumarole throughout the period. Satellite imagery identified thermal anomalies inside the Minamidake crater several times each month.

Table 21. Monthly summary of eruptive events recorded at Sakurajima's Minamidake crater in Aira caldera, January-June 2019. 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 (January to June 2019 monthly reports).

Month Ash emissions (explosive) Max. plume height above crater Max. ejecta distance from crater
Jan 2019 8 (6) 2.1 km 1.1 km
Feb 2019 15 (11) 2.3 km 1.7 km
Mar 2019 29 (12) 3.5 km 1.3 km
Apr 2019 10 (5) 2.2 km 1.7 km
May 2019 15 (9) 2.9 km 1.3 km
Jun 2019 5 (2) 2.2 km 1.3 km

There were eight eruptive events reported by JMA during January 2019 at the Minamidake summit crater of Sakurajima. They occurred on 3, 6, 7, 9, 17, and 19 January (figure 76). Ash plume heights ranged from 600 to 2,100 m above the summit. The largest explosion, on 9 January, generated an ash plume that rose 2,100 m above the summit crater and drifted E. In addition, incandescent ejecta was sent 800-1,100 m from the summit. Incandescence was visible at the summit on most clear nights. During an overflight on 18 January no significant changes were noted at the crater (figure 77). Infrared thermal imaging done on 29 January indicated a weak thermal anomaly in the vicinity of the Showa crater on the SE side of Minamidake crater. The Kagoshima Regional Meteorological Observatory (KRMO) (11 km WSW) recorded ashfall there during four days of the month. Satellite imagery indicated thermal anomalies inside Minamidake on 7 and 27 January (figure 77).

Figure (see Caption) Figure 76. Incandescent ejecta and ash emissions characterized activity from Sakurajima volcano at Aira during January 2019. Left: A webcam image showed incandescent ejecta on the flanks on 9 January 2019, courtesy of JMA (Explanation of volcanic activity in Sakurajima, January 2019). Right: An ash plume rose hundreds of meters above the summit, likely also on 9 January, posted on 10 January 2019, courtesy of Mike Day.
Figure (see Caption) Figure 77. The summit of Sakurajima consists of the larger Minamidake crater and the smaller Showa crater on the E flank. Left: The Minamidake crater at the summit of Sakurajima volcano at Aira on 18 January 2019 seen in an overflight courtesy of JMA (Explanation of volcanic activity in Sakurajima, March 2019). Right: Two areas of thermal anomaly were visible in Sentinel-2 satellite imagery on 27 January 2019. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

Activity increased during February 2019, with 15 eruptive events reported on days 1, 3, 7, 8, 10, 13, 14, 17, 22, 24, and 27. Ash plume heights ranged from 600-2,300 m above the summit, and ejecta was reported 300 to 1,700 m from the crater in various events (figure 78). KRMO reported two days of ashfall during February. Satellite imagery identified thermal anomalies at the crater on 6 and 26 February, and ash plumes on 21 and 26 February (figure 79).

Figure (see Caption) Figure 78. An explosion from Sakurajima at Aira on 7 February 2019 sent ejecta up to 1,700 m from the Minamidake summit crater. Courtesy of JMA (Explanation of volcanic activity in Sakurajima, February 2019).
Figure (see Caption) Figure 79. Thermal anomalies and ash emissions were captured in Sentinel-2 satellite imagery on 6, 21, and 26 February 2019 originating from Sakurajima volcano at Aira. Top: Thermal anomalies within the summit crater were visible underneath steam and ash plumes on 6 and 26 February (closeup of bottom right photo). Bottom: Ash emissions on 21 and 26 February drifted SE from the volcano. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

The number of eruptive events continued to increase during March 2019; there were 29 events reported on numerous days (figures 80 and 81). An explosion on 14 March produced an ash plume that rose 3,500 m above the summit and drifted E. It also produced ejecta that landed 800-1,100 m from the crater. During an overflight on 26 March a fumarole was the only activity in Showa crater. KRMO reported 14 days of ashfall during the month. Satellite imagery identified an ash plume on 13 March and a thermal anomaly on 18 March (figure 82).

Figure (see Caption) Figure 80. A large ash emission from Sakurajima volcano at Aira was photographed by a tourist on the W flank and posted on 1 March 2019. Courtesy of Kratü.
Figure (see Caption) Figure 81. An ash plume from Sakurajima volcano at Aira on 18 March 2019 produced enough ashfall to disrupt the trains in the nearby city of Kagoshima according to the photographer. Image taken from about 20 km away. Courtesy of Tim Board.
Figure (see Caption) Figure 82. An ash plume drifted SE from the summit of Sakurajima volcano at Aira on 13 March (left) and a thermal anomaly was visible inside the Minamidake crater on 18 March 2019 (right). "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

A decline in activity to only ten eruptive events on days 7, 13, 17, 22, and 25 was reported by JMA for April 2019. An explosion on 7 April sent ejecta up to 1,700 m from the crater. Another explosion on 13 April produced an ash plume that rose 2,200 m above the summit. Most of the eruptive events at Sakurajima last for less than 30 minutes; on 22 April two events lasted for almost an hour each producing ash plumes that rose 1,400 m above the summit. Ashfall at KRMO was reported during seven days in April. Two distinct thermal anomalies were visible inside the Minamidake crater on both 12 and 27 April (figure 83).

Figure (see Caption) Figure 83. Two thermal anomalies were present inside Minamidake crater at the summit of Sakurajima volcano at Aira on 12 (left) and 27 (right) April 2019. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

There were 15 eruptive events during May 2019. An event that lasted for two hours on 12 May produced an ash plume that rose 2,900 m from the summit and drifted NE (figure 84). The Meteorological Observatory reported 14 days with ashfall during the month. Two thermal anomalies were present in satellite imagery in the Minamidake crater on both 17 and 22 May.

Figure (see Caption) Figure 84. An ash plume rose 2,900 m above the summit of Sakurajima at Aira on 12 May 2019 (left); incandescent ejecta went 1,300 m from the summit crater on 13 May. Courtesy of JMA (Explanation of volcanic activity in Sakurajima, May 2019).

During June 2019 five eruptive events were reported, on 11, 13, and 24 June; the event on 11 June lasted for almost two hours, sent ash 2,200 m above the summit, and produced ejecta that landed up to 1,100 m from the crater (figure 85). Five days of ashfall were reported by KRMO.

Figure (see Caption) Figure 85. A large ash plume on 11 June 2019 rose 2,200 m above the summit of Sakurajima volcano at Aira. Courtesy of Aone Wakatsuki.

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); Mike Day, Minnesota, Twitter (URL: https://twitter.com/MikeDaySMM, photo at https://twitter.com/MikeDaySMM/status/1083489400451989505/photo/1); Kratü, Twitter (URL: https://twitter.com/TalesOfKratue, photo at https://twitter.com/TalesOfKratue/status/1101469595414589441/photo/1); Tim Board, Japan, Twitter (URL: https://twitter.com/Hawkworld_, photo at https://twitter.com/Hawkworld_/status/1107789108754038789); Aone Wakatsuke, Twitter (URL: https://twitter.com/AoneWakatsuki, photo at https://twitter.com/AoneWakatsuki/status/1138420031258210305/photo/3).


Agung (Indonesia) — June 2019 Citation iconCite this Report

Agung

Indonesia

8.343°S, 115.508°E; summit elev. 2997 m

All times are local (unless otherwise noted)


Continued explosions with ash plumes and incandescent ejecta, February-May 2019

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung on Bali remained quiet until a new eruption began in November 2017 (BGVN 43:01). Lava emerged into the summit crater at the end of November and intermittent ash plumes rose as high as 3 km above the summit through the end of the year. Activity continued throughout 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the slow effusion of the lava within the summit crater (BGVN 43:08, 44:02). Information about the ongoing eruptive episode comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the ongoing eruption from February through May 2019.

Intermittent but increasingly frequent and intense explosions with ash emissions and incandescent ejecta characterized activity at Agung during February through May 2019. During February, explosions were reported three times; events on seven days in March were documented with ash plumes and ashfall in surrounding villages. Five significant events occurred during April; two involved incandescent ejecta that traveled several kilometers from the summit, and ashfall tens of kilometers from the volcano. Most of the five significant events reported in May involved incandescent ejecta and ashfall in adjacent villages; air traffic was disrupted during the 24 May event. Ash plumes in May reached altitudes over 7 km multiple times. Thermal activity increased steadily during the period, according to both the MIROVA project (figure 44) and MODVOLC thermal alert data. MAGMA Indonesia reported at the end of May 2019 that the volume of lava within the summit crater remained at about 25 million m3; satellite information indicated continued thermal activity within the crater. Alert Level III (of four levels) remained in effect throughout the period with a 4 km exclusion radius around the volcano.

Figure (see Caption) Figure 44. Thermal activity at Agung from 4 September 2018 through May 2019 was variable. The increasing frequency and intensity of thermal events was apparent from February-May. Courtesy of MIROVA.

Steam plumes rose 30-300 m high daily during February 2019. The Agung Volcano Observatory (AVO) and PVMBG issued a VONA on 7 February (UTC) reporting an ash plume, although it was not visible due to meteoric cloud cover. Incandescence, however, was observed at the summit from webcams in both Rendang and Karangasem City (16 km SE). The seismic event associated with the explosion lasted for 97 seconds. A similar event on 13 February was also obscured by clouds but produced a seismic event that lasted for 3 minutes and 40 seconds, and ashfall was reported in the village of Bugbug, about 20 km SE. On 22 February a gray ash plume rose 700 m from the summit during a seismic event that lasted for 6 minutes and 20 seconds (figure 45). The Darwin VAAC reported the plume visible in satellite imagery moving W at 4.3 km altitude. It dissipated after a few hours, but a hotspot remained visible about 10 hours later.

Figure (see Caption) Figure 45. An ash plume rose from the summit of Agung on 22 February 2019, viewed from the Besakih temple, 7 km SW of the summit. Courtesy of PunapiBali.

Persistent steam plumes rose 50-500 m from the summit during March 2019. An explosion on 4 March was recorded for just under three minutes and produced ashfall in Besakih (7 km SW); no ash plume was observed due to fog. A short-lived ash plume rose to 3.7 km altitude and drifted SE on 8 March (UTC) 2019. The seismic event lasted for just under 4 minutes. Ash emissions were reported on 15 and 17 March to 4.3 and 3.7 km altitude, respectively, drifting W (figure 46). Ashfall from the 15 March event spread NNW and was reported in the villages of Kubu (6 km N), Tianyar (14 km NNW), Ban, Kadundung, and Sukadana. MAGMA Indonesia noted that two explosions on the morning of 17 March (local time) produced gray plumes; the first sent a plume to 500 m above the summit drifting E and lasted for about 40 seconds, while the second plume a few hours later rose 600 m above the crater and lasted for 1 minute and 16 seconds. On 18 March an ash plume rose 1 km and drifted W and NW. An event on 20 March was measured only seismically by PVMBG because fog prevented observations. An eruption on 28 March produced an ash plume 2 km high that drifted W and NW. The seismic signal for this event lasted for about two and a half minutes. The Darwin VAAC reported the ash plume at 5.5 km altitude, dissipating quickly to the NW. No ash was visible four hours later, but a thermal anomaly remained at the summit (figure 47). Ashfall was reported in nearby villages.

Figure (see Caption) Figure 46. Ash plumes from Agung on 15 (left) and 17 (right) March 2019 resulted in ashfall in communities 10-20 km from the volcano. Courtesy of PVMBG and MAGMA Indonesia (Information on G. Agung Eruption, 15 March 2019 and Gunung Agung Eruption Press Release March 17, 2019).
Figure (see Caption) Figure 47. A thermal anomaly was visible through thick cloud cover at the summit of Agung on 29 March 2019 less than 24 hours after a gray ash plume was reported 2,000 m above the summit. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

The first explosion of April 2019 occurred on the 3rd (UTC); PVMBG reported the dense gray ash plume 2 km above the summit drifting W. A few hours later the Darwin VAAC raised the altitude to 6.1 km based on infrared temperatures in satellite imagery. The seismic signal lasted for three and a half minutes and the explosion was heard at the PGA Post in Rendang (12 km SW). Incandescent material fell within a radius of 2-3 km, mainly on the S flank (figure 48). Ashfall was reported in the villages of Telungbuana, Badeg, Besakih, Pempatan, Teges, and Puregai on the W and S flanks (figure 49). An explosion on 11 April also produced a dense gray ash plume that rose 2 km above the summit and drifted W. A hotspot remained about six hours later after the ash dissipated.

Figure (see Caption) Figure 48. Incandescent ejecta appeared on the flanks of Agung after an eruption on 4 April 2019 (local time) as viewed from the observation post in Rendang (8 km SW). Courtesy of Jamie Sincioco.
Figure (see Caption) Figure 49. Ashfall in a nearby town dusted mustard plants on 4 April 2019 from an explosion at Agung the previous day. Courtesy of Pantau.com (Photo: Antara / Nyoman Hendra).

PVMBG reported an eruption visible in the webcam early on 21 April (local time) that rose to 5.5 km altitude and drifted SW. The ash spread W and S and ash fell around Besakih (7 km SW), Rendang (8 km SW), Klungkung (25 km S), Gianyar (20 km WSW), Bangli (17 km WNW), Tabanan (50 km WSW), and at the Ngurah Rai-Denpasar Airport (60 km SW). About 15 hours later a new explosion produced a dense gray ash plume that rose to 3 km above the summit and produced incandescent ejecta in all directions as far as 3 km away (figure 50). The ash spread to the S and ashfall was reported in Besakih, Rendang, Sebudi (6 km SW), and Selat (12 km SSW). Both of the explosions were heard in Rendang and Batulompeh. The incandescent ejecta from the explosions remained within the 4-km exclusion zone. A satellite image on 23 April showed multiple thermal anomalies within the summit crater (figure 51). A dense gray plume drifted E from Agung on 29 April (30 April local time) at 4.6 km altitude. It was initially reported by ground observers, but was also visible in multispectral satellite imagery for about six hours before dissipating.

Figure (see Caption) Figure 50. An explosion at Agung on 21 April 2019 sent incandescent eject 3,000 m from the summit. Courtesy of MAGMA Indonesia (Gunung Agung Eruption Press Release April 21, 2019).
Figure (see Caption) Figure 51. Multiple thermal anomalies were still present within the summit crater of Agung on 23 April 2019 after two substantial explosions produced ash and incandescent ejecta around the summit two days earlier. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG reported an eruption on 3 May 2019 that was recorded on a seismogram with a signal that lasted for about a minute. Satellite imagery reported by the Darwin VAAC showed a growing hotspot and possible ash near the summit at 4.3 km altitude moving NE. A few days later, on 6 May, a gray ash plume rose to 5.2 km altitude and drifted slowly W before dissipating; it was accompanied by a seismic signal that lasted for about two minutes. Explosions on 12 and 18 May produced significant amounts of incandescent ejecta (figure 52). The seismic signal for the 12 May event lasted for about two minutes; no plume was observed due to fog, but incandescent ejecta was visible on the flanks and the explosion was heard at Rendang. The Darwin VAAC reported an ash plume from the explosion on 17 May (18 May local time) at 6.1 km altitude in satellite imagery moving E. They revised the altitude a short while later to 7.6 km based on IR temperature and movement; the plume drifted N, NE, and E in light and variable winds. A few hours after that it was moving NE at 7.6 km altitude and SE at 5.5 km altitude; this lasted for about 12 hours until it dissipated. Ashfall was reported in villages downwind including Cutcut, Tongtongan, Bonyoh (20 km WNW), and Temakung.

Figure (see Caption) Figure 52. Explosions on 12 (left) and 18 (right) May (local time) 2019 produced substantial ejecta on the flanks of Agung visible from a distance of 10 km or more in PVMBG webcams. The ash plume from the 18 May event resulted in ashfall in numerous communities downwind. Courtesy of PVMBG (Information Eruption G. Agung, May 13, 2019, Information Eruption G. Agung, May 18, 2019).

The initial explosion on 18 May was captured by a webcam at a nearby resort and sent incandescent ejecta hundreds of meters down the NE flank within 20 seconds (figure 53). Satellite imagery on 3, 8, 13, and 18 May indicated multiple thermal anomalies growing stronger at the summit. All of the images were captured within 24 hours of an explosive event reported by PVMBG (figure 54).

Figure (see Caption) Figure 53. The 18 May 2019 explosion at Agung produced an ash plume that rose to over 7 km altitude and large bombs of incandescent material that traveled hundreds of meters down the NE flank within the first 20 seconds of the explosion. Images taken from a private webcam located 12 km NE. Courtesy of Volcanoverse, used with permission.
Figure (see Caption) Figure 54. Satellite images from 3, 8, 13, and 18 May 2019 at Agung showed persistent and increasing thermal anomalies within the summit crater. All images were captured within 24 hours of explosions reported by PVMBG. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG issued a VONA on 24 May 2019 reporting a new ash emission. They indicated that incandescent fragments were ejected 2.5-3 km in all directions from the summit, and the seismic signal lasted for four and a half minutes (figure 55). A dense gray ash plume was observed from Tulamben on the NE flank rising 2 km above the summit. Satellite imagery indicated that the plume drifted SW and ashfall was reported in the villages of Besakih, Pempatan, Menanga, Sebudi, Muncan, Amerta Bhuana, Nongan, Rendang, and at the Ngurah Rai Airport in Denpassar. Additionally, ashfall was reported in the districts of Tembuku, Bangli, and Susut (20 km SW). The Darwin VAAC reported an ash plume visible in satellite imagery at 4.6 km altitude along with a thermal anomaly and incandescent lava visible in webcam imagery. The remains of the ash plume were about 170 km S of the airport in Denpasar (60 km SW) and had nearly dissipated 18 hours after the event. According to a news article several flights to and from Australia were cancelled or diverted, though the International Gusti Ngurah Rai (IGNR) airport was not closed. On 31 May another large explosion produced the largest ash plume of the report period, rising more than 2 km above the summit (figure 56). The Darwin VAAC reported its altitude as 8.2 km drifting ESE visible in satellite data. It split into two plumes, one drifted E at 8.2 km and the other ESE at 6.1 km altitude, dissipating after about 20 hours.

Figure (see Caption) Figure 55. A large explosion at Agung on 24 May 2019 produced incandescent ejecta that covered all the flanks and dispersed ash to many communities to the SW. Courtesy of PVMBG (Gunung Agung Eruption Press Release 24 May 2019 20:38 WIB, Kasbani, Ir., M.Sc.).
Figure (see Caption) Figure 56. An explosion at Agung on 31 May 2019 sent an ash plume to 8.2 km altitude, the highest for the report period. Courtesy of Sutopo Purwo Nugroho, BNPB.

Geologic Background. Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.

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/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); 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); The Jakarta Post, Mount Agung eruption disrupts Australian flights, (URL: https://www.thejakartapost.com/news/2019/05/25/mount-agung-eruption-disrupts-australian-flights.html); PunapiBali (URL: http://punapibali.com/, Twitter: https://twitter.com/punapibali, image at https://twitter.com/punapibali/status/1098869352588288000/photo/1); Jamie S. Sincioco, Phillipines (URL: Twitter: https://twitter.com/jaimessincioco. Image at https://twitter.com/jaimessincioco/status/1113765842557104130/photo/1); Pantau.com (URL: https://www.pantau.com/berita/erupsi-gunung-agung-sebagian-wilayah-bali-terpapar-hujan-abu?utm_source=dlvr.it&utm_medium=twitter); Volcanoverse (URL: https://www.youtube.com/channel/UCi3T_esus8Sr9I-3W5teVQQ); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN ).


Kerinci (Indonesia) — June 2019 Citation iconCite this Report

Kerinci

Indonesia

1.697°S, 101.264°E; summit elev. 3800 m

All times are local (unless otherwise noted)


Intermittent explosions with ash plumes, February-May 2019.

Frequently active, Indonesia's Mount Kerinci on Sumatra has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838. Intermittent explosions with ash plumes, usually multiple times per month, have characterized activity since April 2018. Similar activity continued during February-May 2019, the period covered in this report with information provided primarily by the Indonesian volcano monitoring agency, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), MAGMA Indonesia, notices from the Darwin Volcano Ash Advisory Center (Darwin VAAC), and satellite data. PVMBG has maintained an Alert Level II (of 4) at Kerinci for several years.

On 13 February 2019 the Kerinci Volcano Observatory (KVO), part of PVMBG, noted a brownish-white ash emission that was drifting NE about 400 m above the summit. The seismicity during the event was dominated by continuous volcanic tremor. A brown ash emission was reported on 7 March 2019 that rose to 3.9 km altitude and drifted NE. Ash also drifted 1,300 m down the SE flank. Another ash plume the next morning drifted W at 4.5 km altitude, according to KVO. On 10, 11, and 13 March KVO reported brown ash plumes drifting NE from the summit at about 4.0-4.3 km altitude. The Darwin VAAC observed continuous ash emissions in satellite imagery on 15 March drifting W at 4.3 m altitude that dissipated after about 3 hours (figure 10). A gray ash emission was reported on 19 March about 600 m above the summit drifting NE; local news media noted that residents of Kayo Aro reported emissions on both 18 and 19 March (figure 11). An ash emission appeared in satellite imagery on 25 March (figure 10). On 30 March the observatory reported two ash plumes; a brown emission at 0351 UTC and a gray emission at 0746 UTC that both drifted NE at about 4.4 km altitude and dissipated within a few hours. PVMBG reported another gray ash plume the following day at a similar altitude.

Figure (see Caption) Figure 10. Sentinel-2 satellite imagery of Kerinci from 15 (left) and 25 (right) March 2019 showed evidence of ash plumes rising from the summit. Kerinci's summit crater is about 500 m wide. "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 11. Dense ash plumes from Kerinci were reported by local news media on 18 and 19 March 2019. Courtesy of Nusana Jambi.

Activity continued during April with a brown ash emission reported on 3 April by several different agencies; the Darwin VAAC and PVMBG daily reports noted that the plume was about 500 m above the summit (4.3 km altitude) drifting NE. KVO observed two brown ash emissions on 13 April (UTC) that rose to 4.2 km altitude and drifted NE. Satellite imagery showed minor ash emissions from the summit on 14 April; steam plumes 100-500 m above the summit characterized activity for the remainder of April (figure 12).

Figure (see Caption) Figure 12. A dilute ash emission rose from the summit of Kerinci on 14 April 2019 (left); only steam emissions were present on a clear 29 April in Sentinel-2 imagery (right). "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.

Ashfall on the NE and S flanks within 7 km of the volcano was reported on 2 May 2019. According to a news article, at least five villages were affected late on 2 May, including Tanjung Bungo, Sangir, Sangir Tengah, Sungai Rumpun, and Bendung Air (figures 13 and 14). The smell of sulfur was apparent in the villages. Brown ash emissions were observed on 3 and 4 May that rose to 4.6 and 4.1 km altitude and drifted SE. The Darwin VAAC reported an emission on 5 May, based on a pilot report, that rose to 6.7 km altitude and drifted NE for about an hour before dissipating. A brown ash emission on 10 May rose 700 m above the summit and drifted SE. Satellite imagery captured ash emissions from the summit on 14 and 24 May (figure 15). For the remainder of the month, 300-700-m-high dense steam plumes were noted daily until PVMBG reported white and brown plumes on 26 and 27 May rising 500-1,000 m above the summit. Although thermal anomalies were not reported during the period, persistent weak SO2 emissions were identified in TROPOMI instrument satellite data multiple times per month (figure 16).

Figure (see Caption) Figure 13. Ashfall was reported from five villages on the flanks of Kerinci on 2 May 2019. Courtesy of Uzone.
Figure (see Caption) Figure 14. An ash plume at Kerinci rose hundreds of meters on 2 May 2019; ashfall was reported in several nearby villages. Courtesy of Kerinci Time.
Figure (see Caption) Figure 15. Ash emissions from Kerinci were captured in Sentinel-2 satellite imagery on 14 (left) and 24 (right) May 2019. The summit crater is about 500 m wide. "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 16. Weak SO2 anomalies from Kerinci emissions were captured by the TROPOMI instrument on the Sentinel-5P satellite multiple times each month from February to May 2019. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

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/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Nuansa Jambi, Informasi Utama Jambi: (URL: https://nuansajambi.com/2019/03/20/gunung-kerinci-semburkan-asap-tebal/); Kerinci Time (URL: https://kerincitime.co.id/gunung-kerinci-semburkan-abu-vulkanik.html); Uzone.id (URL: https://news.uzone.id/gunung-kerinci-erupsi-5-desa-tertutup-abu-tebal).


Suwanosejima (Japan) — July 2019 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Small ash plumes continued during January through June 2019

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

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

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

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

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

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

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

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

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


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

Great Sitkin

United States

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

All times are local (unless otherwise noted)


Small steam explosions in early June 2019

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

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

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

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

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

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


Ibu (Indonesia) — July 2019 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


Ebeko (Russia) — July 2019 Citation iconCite this Report

Ebeko

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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


Klyuchevskoy (Russia) — July 2019 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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


Yasur (Vanuatu) — June 2019 Citation iconCite this Report

Yasur

Vanuatu

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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


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

Bagana

Papua New Guinea

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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


Ambae (Vanuatu) — June 2019 Citation iconCite this Report

Ambae

Vanuatu

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

All times are local (unless otherwise noted)


Declining thermal activity and no explosions during February-May 2019

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

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

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

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

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


Sangay (Ecuador) — July 2019 Citation iconCite this Report

Sangay

Ecuador

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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Bulletin of the Global Volcanism Network - Volume 42, Number 09 (September 2017)

Managing Editor: Edward Venzke

Barren Island (India)

Decreased and intermittent thermal anomalies after mid-March 2017

Bogoslof (United States)

Ash-bearing explosions begin in December 2016; lava dome emerges in June 2017

Bristol Island (United Kingdom)

First eruption since 1956; lava flows and ash plumes, April-July 2016

Etna (Italy)

Lava flows during May 2016 followed by new fracture zones and major subsidence at the summit craters

Fogo (Cape Verde)

November 2014-February 2015 eruption destroys two villages, lava displaces over 1000 people

Krakatau (Indonesia)

Eruption during 17-19 February 2017 sends large lava flow down the SE flank

Langila (Papua New Guinea)

Eruption continues, intensifying from mid-December 2016 through July 2017

Masaya (Nicaragua)

Persistent lava lake and gas plume activity, with intermittent ash emission, through mid-July 2017

Popocatepetl (Mexico)

Ongoing steam, gas, ash emissions, and lava dome growth and destruction, July 2016-July 2017

Sangeang Api (Indonesia)

Weak Strombolian activity and occasional weak ash plumes, 15 July-12 August 2017



Barren Island (India) — September 2017 Citation iconCite this Report

Barren Island

India

12.278°N, 93.858°E; summit elev. 354 m

All times are local (unless otherwise noted)


Decreased and intermittent thermal anomalies after mid-March 2017

Following sporadic activity during the second half of 2016, a new period of strong thermal anomalies suggestive of lava flows began in mid-January 2017 (BVGN: 42:03). Scientists on a nearby research vessel observed ash emissions and lava fountains that fed lava flows during 23-26 January. Subsequent possible activity, as shown by MODIS thermal anomalies detected by MIROVA (figure 26), continued at similar levels until mid-March, after the anomalies became more intermittent and decreased in power through at least 2 September. Thermal alerts in MODVOLC were recorded during 15 January-8 March 2017.

Figure (see Caption) Figure 26. Thermal anomaly MIROVA log radiative power data from Barren Island during early September 2016-1 September 2017. Regular, low-moderate activity is evident beginning in late January through April 2017, but it thereafter wanes. Courtesy of MIROVA.

Geological Survey of India cruise in May 2015. Some observations and photos of activity on 14 and 31 May 2015 have been provided by Sachin Tripathi, a geologist at the Geological Survey of India, who was close to the volcano during the SR-013 cruise of the RV Samudra Ratnakar. On 14 May the plumes were described as light gray "mushroom shaped" clouds. Tripathi further noted that the activity occurred in discrete pulses; he observed two such events during an 8-minute period that sent ash plumes 300-400 m high (figure 27). Eruptive pulses on 31 May lasted about 20-25 seconds, with an interval of 4-5 minutes. The plumes on that day were light gray to gray, and rose to around 50-100 m. The NE portion of the island was covered with ash (figure 28).

Figure (see Caption) Figure 27. Two images from a video that illustrate the pulsating eruption at Barren Island on 14 May 2015. The top image shows the remains of an older plume above the island and a new plume just rising from the summit. The bottom image shows the ash plume rising to about 300-400 m above the island. Courtesy of Sachin Tripathi, Geological Survey of India.
Figure (see Caption) Figure 28. Photograph of an ash plume rising from the active vent at Barren Island on 31 May 2015. Ashfall can be seen covering the NE portion of the island. Courtesy of Sachin Tripathi, Geological Survey of India.

Geologic Background. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Information Contacts: Sachin Tripathi, Geological Survey of India; MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


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

Bogoslof

United States

53.93°N, 168.03°W; summit elev. 150 m

All times are local (unless otherwise noted)


Ash-bearing explosions begin in December 2016; lava dome emerges in June 2017

Bogoslof lies 40 km N of the main Aleutian arc, over 1,350 km SW of Anchorage, Alaska (figure 2). Its intermittent eruptive history, first recorded in the late 18th century, has created and destroyed several distinct islands that are responsible for a unique and changing landscape at the summit of this submarine volcano, and produced multiple explosive ash-bearing plumes. The last subaerial eruption, in July 1992, created a lava dome on the N side of the island, adjacent to an eroded dome created in 1927 (BGVN 17:07, figure 1). A new eruption began on 20 December 2016, and was ongoing through July 2017. Information comes from the Alaska Volcano Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC).

Figure (see Caption) Figure 2. Index map showing the location of Bogoslof. Adapted from Beget et al. (2005). Courtesy of AVO.

AVO notes that there is no ground-based monitoring equipment on Bogoslof, so monitoring is accomplished using satellite images, information from the Worldwide Lightning Location Network pertaining to volcanic-cloud lightning, and data from seismic and infrasound (airwave sensor) instruments. The infrasound instruments are located on neighboring Umnak (100 km SW) and Unalaska Islands (85 km SE) and further away at Sand Point (500 km E) on Popof Island, and on the Alaska mainland in Dillingham (825 km NE). AVO also receives reports from observers on ships and airplanes.

The first eruption at Bogoslof since 1992 began during mid-December 2016, when an ash plume was seen on 20 December. Numerous explosions were recorded via seismic, infrasound, lightning, satellite, and visual observations until 19 February 2017, and the morphology of the island changed significantly during that time. Ashfall was reported in Unalaska on 31 January. A large explosion on 7 March produced a substantial ash plume, and was followed by four days with earthquake swarms that lasted for hours. An explosion on 16 May produced an ash plume that rose to over 10 km altitude. A larger explosion on 28 May created tephra jets, pyroclastic fall and flow material around the island, and a possible 13.7-km-high ash plume. A substantial submarine sediment plume was observed in early June, followed by confirmation of a lava dome above the ocean surface during 5-6 June. A series of explosions during 10 June destroyed the lava dome. Explosions producing ash plumes that rose to altitudes above 10 km occurred on 23 June and 2 July; several additional smaller explosions were recorded through mid-July.

Activity during December 2016-February 2017. According to AVO, Bogoslof showed signs of unrest beginning on 12 December 2016 in seismic, infrasound (air-wave), and satellite data. Ash emissions may have occurred on 16 and 19 December on the basis of recorded lightning strikes, seismic data, and sulfur dioxide clouds detected by satellite instruments, though there were no direct visual observations from satellite or ground observers. On 20 December, a powerful, short-lived explosion at about 1535 AKST (0035 UTC 21 December) sent ash to over 10.3 km altitude which then drifted S (figure 3).

Figure (see Caption) Figure 3. Bogoslof's eruption plume was captured on 20 December shortly after 1530 AKST from an aircraft at 36,000 feet (10.9 km). The aircraft was about 20 miles N of Bogoslof Island flying W. Photo by Paul Tuvman, courtesy of AVO.

An explosion on 21 December at 1610 AKST was detected in satellite images and seismic data from neighboring islands. This eruption lasted about 30 minutes and sent ash as high as 10.7 km which then drifted N. Satellite images from the next day showed that a small new island had formed just offshore of the NE end of the main island. The previous shore and much of the NE side of Bogoslof Island adjacent to the new island was mostly removed and, according to AVO, was likely the site of the new, underwater vent; deposition of material was visible on the W side of the island (figure 4).

Figure (see Caption) Figure 4. Analysis of shoreline change and vent location from the 20-21 December 2016 eruption of Bogoslof. The base image is from 19 March 2015 and the analysis was conducted using data from 22 December 2016, a day after the large explosive eruption on 21 December. Note that the location of the vent for the eruption was underwater or near the shoreline on the NE part of Bogoslof Island. Deposits have enlarged portions of the island and were interpreted by AVO to be comprised of coarse-grained volcanic ash and blocks of lava. The areas marked with "+" are material that was added during the eruption. The area marked with "-" represents material removed during the eruption. Courtesy of AVO.

During the morning of 23 December 2016, observers aboard a Coast Guard vessel reported ash emission, lightning, and the ejection of incandescent lava and fragmental material. Ash emission and lava ejection subsided after about an hour. The ash cloud was carried N over the Bering Sea and did not penetrate above the regional cloud tops at 9.1 km altitude. Similar, repeated, short-duration explosions continued every few days through 19 February 2017 before the first break in activity (table 1).

Table 1. Observations of activity at Bogoslof, December 2016-July 2017, as reported by AVO and the Anchorage VAAC. Date is local AKST or AKDT (starting 10 June). Plume altitude in kilometers. Drift is direction and distance in kilometers.

Date Time (local) Observation and notes Plume Altitude (km) Drift Detection Method
12 Dec 2016 -- "Unrest" -- -- Seismic, infrasound, satellite
16 Dec 2016 -- Possible ash emissions -- -- Lightning, seismic, SO2
19 Dec 2016 -- Possible ash emissions -- -- Lightning, seismic, SO2
20 Dec 2016 1530 Explosive eruption with ash plume 10.3 S Pilot, satellite
21 Dec 2016 1610 30-minute-long explosion with ash plume 10.7 N Satellite, seismic
23 Dec 2016 0930 Explosion with ash, lightning, incandescent lava, and debris, 60 minute duration Below 9.1 N Coast Guard observers from nearby vessel
25 Dec 2016 evening Tremor, possible minor, low-level ash emission, lightning -- -- Seismic, lightning
26 Dec 2016 1405 Ash Plume 9.1 WSW Lightning, seismic, satellite
28 Dec 2016 1755 Tremor, 50 minutes, Cloud cover obscured -- -- Seismic
29 Dec 2016 1900, 2345 Continuous tremor at 1900, 30-minute-long ash producing event at 2345 6.1 NE Seismic station on Umnak, infrasound, satellite
30 Dec 2016 2230 Explosive event, 45 minutes, Cloud cover obscured -- -- Seismic, infrasound, lightning
31 Dec 2016 0500 Low-level eruptive activity, continuous; cloud cover obscured; windy conditions affect local seismic stations -- -- Dillingham infrasound
02 Jan 2017 1353 Minor explosions, 10 minutes of increased seismicity, cloud cover obscured -- -- Seismic, infrasound
03 Jan 2017 2118 Seismic activity, 5 minutes, ash plume 10.0 N Seismic, infrasound, lightning, satellite
05 Jan 2017 1324 Increased seismicity, ash plume, detached 10.7 NNW Seismic, lightning, satellite, pilot
08 Jan 2017 2233, 2256 Two strong seismic pulses, two volcanic clouds 10.7 NW Seismic, infrasound, satellite
12 Jan 2017 1123, 1230 Two short-lived explosions, plumes 5.5, 4.4 -- Seismic, pilot
14 Jan 2017 2126, 2216 Six explosions, beginning 2216, no ash plumes observed -- -- Seismic, lightning
17 Jan 2017 0400, 0740 Increasing tremor signal, Steam with minor ash 4.6 -- Seismic, satellite
18 Jan 2017 1320 Explosion, dark ash cloud, strong thermal anomaly around vent 9.4 NE Seismic, pilot, lightning, infrasound, satellite, SO2, MODVOLC
20 Jan 2017 1317 Explosion, ice-rich ash plume, lava at vent 11.0 SE Seismic, lightning, pilot, satellite imagery of lava, infrasound
22 Jan 2017 1409 Explosion, ash plume 9.1 -- Lightning, satellite
24 Jan 2017 0453 Explosion, ice-rich cloud with likely ash 7.6-10.7 E Seismic, lightning
26 Jan 2017 0650, 0706 Exposion, ice-rich cloud with likely ash; ash drifted in multiple directions 9.8, 6.1 SE, NE Seismic, lightning
27 Jan 2017 0824 Explosion, ice-rich cloud with likely ash 7.6 -- Seismic, lightning
30 Jan 2017 2020 Eruption cloud, more than 10 short explosions, Trace ashfall in Dutch Harbor (98 km E) and strong SO2 odor 7.6 125 km SE Seismic, infrasound, lightning, satellite
03 Feb 2017 0457, 0533 Increased seismicity, small explosions, no ash detected -- -- Seismic, infrasound
03 Feb 2017 1641 Seismic event, small plume 7.6 40 km N Infrasound, satellite, pilot
5, 7, 8 Feb 2017 -- Weakly elevated surface temp -- -- Satellite
13 Feb 2017 0724 Increased seismicity, no ash emissions above 3 km -- -- Seismic, satellite
17 Feb 2017 0955, 1546 Explosive event, ash plume 11.6, 7.6 N Seismic, satellite, pilot, infrasound, lightning
18 Feb 2017 0450 Explosion, ash emissions 7.6 SW Seismic, infrasound, lightning, satellite
19 Feb 2017 1708-1745 Series of short explosive pulses, plume 7.6 160 km SE Seismic, infrasound, satellite
07-08 Mar 2017 2236 3 hour explosive event, large ash plume, over 1,000 lightning strokes 10.7 E Seismic, lightning, infrasound
09-10 Mar 2017 1750 Earthquake swarm, 20 hours -- -- Seismic
10-11 Mar 2017 1900 Earthquake swarm, 10 hours -- -- Seismic
12 Mar 2017 0500 Earthquake swarm -- -- Seismic
13 Mar 2017 1131 Seismic event, small ash cloud, weakly elevated surface temps 5.5 90 km SSW Seismic, satellite
16 May 2017 2232 Increased seismicity, ash plume, 73 minutes 10.4 SW Seismic, infrasound, lightning, satellite, pilot
28 May 2017 1416 Explosion, ash plume, 50 minutes, plume visible for 4 days 10.7-13.7 W, NE Seismic, satellite, pilot
31 May 2017 1842 Several hour-long seismic swarm followed by short duration explosion, volcanic cloud 7.3 WNW Seismic, infrasound, satellite
05 Jun 2017 0750 Explosion, small volcanic cloud -- -- Seismic, pilot
06 Jun 2017 0600 Brief explosive event, possible plume, lava dome emerges 1.8 -- Seismic, infrasound, satellite
10 Jun 2017 0318 Explosive eruption, ash-rich cloud 10.4 NW Seismic, infrasound, lightning, satellite
12 Jun 2017 1747 Series of explosive events, ash plumes 7.6 SE Seismic, infrasound
13 Jun 2017 0817 Six-minute long explosion, no plume observed -- -- Seismic, infrasound
23 Jun 2017 1649 Five explosions, ash plume 11.0 400-490 km E Seismic, infrasound
26 Jun 2017 1645 14-minute explosion, ash plume 7.6 -- Seismic
27 Jun 2017 0317 14-minute explosion, ash plume 9.1 NW Seismic, lightning
30 Jun 2017 0124 Explosion, 20 minutes, small cloud -- 16 km N Seismic
02 Jul 2017 1248 16-minute explosion, ash plume 11 E Seismic, infrasound
04 Jul 2017 1651 13-minute explosive event, eruption cloud 8.5 SE Seismic
04 Jul 2017 1907 11-minute-long explosion, small cloud 9.8 SE Seismic
08 Jul 2017 1015 Two eruption pulses, ash plume 9.1 N Seismic, satellite
09 Jul 2017 2347 Two eruptions, 5-minutes and 7-minutes long, small ash cloud 6.1 SE Seismic, satellite
10 Jul 2017 1000, 1706 Two explosions, no confirmed ash -- -- Seismic, infrasound

AVO reported that photos taken by a pilot on 10 January showed Bogoslof covered with dark gray ash, and a roughly 300-m-diameter submarine explosion crater on the E side of the island. The dark (ash-rich) plume from an explosion on 18 January (figure 5) was identified in satellite images and observed by a pilot; the event produced lightning strikes and infrasound signals detected by sensors in Sand Point and Dillingham. Analysis of a satellite image suggested the presence of very hot material (possibly lava) at the surface immediately surrounding the vent, which was the first such observation since the beginning of the eruption. The first MODVOLC thermal alerts were issued on 18 January.

Figure (see Caption) Figure 5. A large explosion at Bogoslof on 18 January 2017 produced a dark ash cloud that rose to 9.4 km and drifted NE. Captured by MODIS on NASA's Terra satellite. Courtesy of NASA Earth Observatory.

AVO analysis of satellite images from 16 and 18 January 2017 (before the eruption that day) showed that the vent area, which formed on the NE end of the island in shallow water, had been filling in with eruptive material and building out of the water. On 20 January, satellite images showed an ice-rich plume and lava present at the vent. Prevailing winds carried the plume to the SE over the SW end of Unalaska Island, but no ash fall was reported. A high spatial resolution satellite image collected on 24 January showed AVO that the explosive eruptions continued to change the morphology of the island and the coastline (see figure 7). The eruptive vent, however, remained below sea level in the N portion of a figure-eight-shaped bay, as indicated by the presence of upwelling volcanic gases. There was no sign of lava at the surface.

A series of more than 10 short-duration explosions beginning on 30 January (AKST) and detected in seismic, infrasound, and lightning data, resulted in an ash plume that rose to 7.6 km altitude and drifted 125 km SE. Trace amounts of ashfall and a strong SO2 odor were reported in Dutch Harbor on Unalaska Island (98 km E) (figure 6). Satellite images acquired on 31 January showed additional significant changes to the morphology of the island (figure 7). AVO stated that freshly erupted volcanic rock and ash had formed a barrier that separated the vent from the sea.

Figure (see Caption) Figure 6. Trace ashfall in Unalaska, Alaska, on 31 January 2017 from Bogoslof. Courtesy of AVO.
Figure (see Caption) Figure 7. Changes in the morphology of Bogoslof Island resulting from the ongoing 2016-17 eruption. The 30-31 January 2017 eruptive activity generated roughly 0.4 square kilometers of new land. As of 31 January 2017 the island area was 1.02 square kilometers, roughly three times the size of the pre-eruption island. Nearly all of this new material consisted of unconsolidated pyroclastic fall and flow (surge) deposits that are highly susceptible to wave erosion. Courtesy of AVO.

On 19 February 2017, a series of short-lived explosive pulses resulted in a plume that drifted 160 km SE over Unalaska Island. AVO geologists on the island described the cloud has having a white upper portion and a slightly darker lower portion. A satellite image from 23 February showed that the vent location at Bogoslof remained underwater. After the 19 February events, the volcano was quiet for two weeks.

Activity during March 2017. A 3-hour-long explosive event occurred overnight during 7-8 March 2017 and produced numerous strokes of volcanic lightning, high levels of seismicity and infrasound, and an ash cloud up to 10.7 km altitude that moved E over Unalaska Island. The seismicity was among the highest levels observed for the eruption sequence that began in mid-December 2016, and the more than 1,000 detected lightning strokes were by far the highest number observed to date. The eruptive activity again changed the shape of the island and temporarily dried out the vent area. Satellite images from 8 March showed that the W coast of the island appeared to have grown significantly due to the eruption of new volcanic ash and blocks. A new vent was also identified on the NW side of the island, and the lava dome emplaced during the 1992 eruption was partially destroyed (figure 8).

Figure (see Caption) Figure 8. A Worldview-2 satellite image of Bogoslof Island on 11 March 2017 showing features and changes resulting from the 7-8 March 2017 activity. A new vent developed on the NW shore of the island adjacent to the lava dome that formed during the 1992 eruption. Most of the deposits on the surface appear fine-grained and were likely emplaced by pyroclastic base surges. The surface of these deposits exhibit ripples, dunes, and ballistic impact craters. The scalloped appearing shoreline of the intra-island lake is probably the result of groundwater related erosion (sapping) of the pyroclastic deposits as water refills the lake. Most or all of the water in the lake was likely expelled by the eruption column exiting the primary or other vents. The area of Bogoslof Island in this image is about 0.98 square kilometers. Image data provided under Digital Globe NextView License. Courtesy of AVO.

Two earthquake swarms were detected during 9-11 March; the first began at 1750 on 9 March and ended at 1400 on 10 March, and the second was detected from 1900 on 10 March to 0500 on 11 March. Mildly elevated surface temperatures were identified in satellite data during 10-11 March. A third swarm began at 0500 on 12 March. A 12-minute-long explosive event, beginning at 1131 on 13 March, produced a small ash cloud that rose to an altitude of 5.5 km and drifted SSW. AVO noted that after the event, the level of seismic activity declined and the repeating earthquakes of the previous several days had stopped. Weakly elevated surface temperatures were observed in two satellite images from 13 March. A photograph taken by a pilot showed a low-level, billowy steam plume rising from the general area of the intra-island lake. Except for weakly elevated surface temperatures in satellite data, no significant activity was reported during the rest of March. The only activity detected during April 2017 was a brief increase in seismicity on 15 April. Aerial reconnaissance by the US Coast Guard on 8 May showed the dramatic changes of the island's shape (figure 9).

Figure (see Caption) Figure 9. Bogoslof Island viewed from the NW on 8 May 2017. Fire Island (a remnant of lava from an 1883 eruption) is in the right foreground, and the new steaming lake that includes the submarine vent is behind the two dome remnants in the mid-ground. The 1992 lava is the remnant on the left and the 1926-28 lava is on the right. Bogoslof Island aerial reconnaissance courtesy of U.S. Coast Guard Air Station Kodiak and U.S.C.G. Cutter Mellon. Photo by Max Kaufman, courtesy of AVO.

Activity during May-July 2017. Following a pause in explosive activity that lasted a little over two months, Bogoslof erupted explosively at 2232 (AKDT) on 16 May. The eruption, which lasted about 70 minutes, was detected by seismic and infrasound sensors on neighboring islands and the resulting ash-cloud-generated volcanic lightning that was detected by the Worldwide Lightning Location Network. A pilot report and satellite images showed that the plume rose as high as 10.4 km, and then drifted SW. Trace ashfall was reported in the community of Nikolski on Umnak Island (125 km SW). A drifting sulfur dioxide cloud from the eruption was detected for several days using satellite-based sensors. The eruption altered the northern coastline of the island, with the crater lake breached by a 550-m-wide gap along the N shore. Part of the NE shore had been extended 300 m due to new tephra deposits.

Another large explosion began at 1416 on 28 May 2017. Pilot and satellite observations indicated that ash plumes rose at least 10.7 km and possibly as high as 13.7 km altitude (figure 10). An observer on Unalaska Island reported seeing a large white-gray mushroom cloud form over Bogoslof, with ashfall to the W. The event lasted 50 minutes. On 29 May the ash cloud continued to drift NE, and on 2 June, an SO2 plume from the event was still visible in satellite data drifting over the Hudson Bay region.

Figure (see Caption) Figure 10. Enlarged portions of 28 May 2017 satellite image of Bogoslof Island. Inset image on lower left shows pyroclastic fall and flow material emplaced over water. Some of the material appears to have been disturbed, possibly by the force of the eruption column. It is unclear if this material represents new land or material floating on the water. Tephra jets are common features of many shallow submarine eruptions. The inset image in the upper right shows a weak base surge propagating from the base of the eruption column across the tuff ring. Image data provided under the Digital Globe NextView License. Courtesy of AVO.

On 5 June, a vessel in the area reported vigorous steaming and a white plume rising at least a kilometer above sea level. Also, a substantial submarine sediment plume was seen in satellite imagery drifting N from the lagoon area (figure 11). A brief explosive event at 0600 on 6 June likely produced a low-level (less than 3 km) emission. A possible plume at 1.8 km that quickly dissipated was identified in a satellite image following the detection of the activity in seismic and infrasound data.

Figure (see Caption) Figure 11. Landsat-8 image of Bogoslof from 5 June 2017 at 2200 UTC (1400 AKDT). This composite image of visible and thermal infrared data shows a sediment plume in the ocean that extends from the vent region in the horseshoe-shaped lagoon. Warm water outflow is highlighted in color extending northward from the lagoon where it mixes with colder ocean water. A hot vent just S of the lagoon can be seen in orange, and several small puffs of white steam are visible coming from this region. Courtesy of NASA Earth Observatory.

AVO reported that a new lava dome breached the surface of the ocean on or around 6 June 2017; it was the first observation of lava at the surface since the start of the eruption in mid-December 2016 (figure 12). The dome was an estimated 110 m in diameter on 7 June, and then grew to 160 m in diameter by 9 June. Four short-duration explosions were detected in seismic and/or infrasound data between 5 and 7 June, and generated volcanic clouds that in many cases were too small to be observed in satellite data. AVO reported that robust steaming was identified in satellite data and by observers aboard a U.S. Fish and Wildlife Service ship in the region following the emergence of the lava dome likely due to, or enhanced by, the effusion of lava into the ocean.

Figure (see Caption) Figure 12. Comparison of satellite radar images from 31 May and 8 June 2017 of Bogoslof showing the newly emplaced lava dome. The diameter of the short-lived dome was about 110 m. N is to the top. Courtesy of AVO.

A series of six explosions was detected on 10 June, starting with a 2-hour explosive event that emitted an ash-rich cloud to 10.4 km altitude that was detected in seismic, infrasound, lightning, and satellite data. This event destroyed the 160-m-diameter lava dome that was first observed on 5 June (figure 13). On 12 June, a series of four small explosions lasting 10-30 minutes each emitted volcanic clouds that rose to a maximum height of 7.6 km, and dissipated within about 30 minutes. On 13 June, a six-minute-long explosion occurred, although no ash cloud was observed in satellite imagery likely because it's altitude was below detection limits.

Figure (see Caption) Figure 13. Worldview satellite image of Bogoslof taken at 2313 UTC on 12 June 2017. Note that N is to the lower left of the image. The circular embayments were formed by a series of more than 40 explosions that began in mid-December 2016. These explosions have greatly reshaped the island as material was removed and redeposited as air fall. Vigorous steaming was observed S of the most active vent areas in the lagoon. Lava extrusion produced a circular dome that first rose above the water on 5 June and grew to a diameter of ~160 m before being destroyed by an explosion early in the day on 10 June. Large blocks of the destroyed dome can be seen littering the surface of the island near the lagoon. Courtesy of AVO.

Weakly elevated surface temperatures detected in satellite imagery on 10 and 11 June suggested to AVO that a new lava dome was extruding beneath the ocean surface. Satellite imagery showed persistent degassing from the island in between explosions. In addition, residents of Unalaska/Dutch Harbor reported smelling sulfur on 12 June, and winds were consistent with a source at Bogoslof. AVO reported that elevated surface temperatures and a small steam emission were identified in satellite images during 13-14 and 16 June. A 13-km-long steam plume was visible on 18 June.

A series of nine explosions were detected in seismic and/or infrasound data during the night of 23 June, the largest of which produced a volcanic cloud reaching an altitude of 11 km that drifted well over 400 km E (figure 14). Additional explosions on 26 and 27 June sent volcanic clouds to 7.6 and 9.1 km altitude, respectively. Winds carried most of these plumes N and NE; AVO received no reports of ashfall from local communities. Bogoslof erupted again on 29 June and produced a small plume, and several times during the first two weeks of July explosions produced larger plumes that rose to 8.5-11 km altitude. Two explosions that occurred on 10 July without producing observed ash were the last for the rest of the month. Weakly elevated surface temperatures were observed in clear satellite images on 12 and 16 July. No further activity was reported for the rest of July 2017.

Figure (see Caption) Figure 14. Ash plume rising above Bogoslof, 1814 AKDT, 23 June 2017. The view is from Mutton Cove on SW Unalaska Island about 67 km SE of the volcano. AVO estimated the volcanic cloud reached about 11 km above sea level. Photo by Masami Sugiyama courtesy of Allison Everett and AVO.

A modest thermal signal was detected by the MIROVA system between February and July 2017 consistent with the activity that suggested lava dome growth during that time (figure 15).

Figure (see Caption) Figure 15. MIROVA Log Radiative Power graph of thermal energy at Bogoslof for the year ending on 17 August 2017. A low-level thermal anomaly was first detected in early March, and was intermittent through early July. Courtesy of MIROVA.

References: Beget, J.E., Larsen, J.F., Neal, C.A., Nye, C.J., and Schaefer, J.R., 2005, Preliminary volcano-hazard assessment for Okmok Volcano, Umnak Island, Alaska: Alaska Division of Geological & Geophysical Surveys Report of Investigation 2004-3, 32 p., 1 sheet, scale 1:150,000.

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

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.dggs.alaska.gov/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845(URL: http://vaac.arh.noaa.gov/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/).


Bristol Island (United Kingdom) — September 2017 Citation iconCite this Report

Bristol Island

United Kingdom

59.017°S, 26.533°W; summit elev. 1100 m

All times are local (unless otherwise noted)


First eruption since 1956; lava flows and ash plumes, April-July 2016

Bristol Island, near the southern end of the seven South Sandwich Islands in the isolated Southern Atlantic Ocean, lies 800 km SE of South Georgia Island at latitude 59° S. Historic eruptions occurred on Bristol Island in 1823, the 1930s, and the 1950s. A new eruption was reported from Mount Sourabaya, a cone near the center of the island, beginning at the end of April 2016. It produced ash plumes and strong thermal anomalies most likely generated by lava flows until the end of July 2016. Information about Bristol Island comes from NASA Earth Observatory and other satellite imagery data, and the Buenos Aires Volcanic Ash Advisory Center (VAAC).

Evidence for a new eruption at Bristol Island first appeared in Landsat 8 imagery on 24 April 2016 as a large steam plume and a thermal anomaly at the summit (figure 1). Another image on 1 May showed the still-active plume and an elongation of the thermal anomaly to the W, suggesting that lava may have breached the crater rim. Two MODVOLC thermal alerts also appeared on 24 April; their frequency and intensity increased significantly in subsequent days.

Figure (see Caption) Figure 1. The Operational Land Imager (OLI) on the Landsat 8 satellite acquired these two false-color images on 24 April (upper) and 1 May (lower) 2016 of an eruption at Mount Sourabaya, a stratovolcano on Bristol Island. The images were built from a combination of shortwave-infrared, near-infrared, and red light (Landsat bands 6-5-4) that helps detect the heat signature of an eruption. Both images show what could be lava (red-orange), while white plumes of steam trail away from the crater. In the lower (1 May) image, the thermal anomaly extends farther to the W, suggesting a lava flow. The band combination makes the ice cover of the island appear bright blue-green. Courtesy of NASA Earth Observatory.

The number of daily MODVOLC thermal alerts increased during May 2016 to as many as 35 on 26 May. On many days, more than 10 thermal alerts were issued. The distribution of the alert pixels suggested that an E-W linear feature such as one or more lava flows was responsible for many of the thermal anomalies (figure 2).

Figure (see Caption) Figure 2. MODVOLC thermal alerts for Bristol Island during selected dates in late April and May 2016. Top left: Nine thermal alerts issued during 25-30 April form two linear features trending WNW and WSW. Top right: 59 alerts issued during 11-15 May suggest intensification of heat flow. Lower left: 35 alerts on 26 May are scattered over a wide area. Lower right: 20 alerts issued on 29 May are concentrated in an E-W trending distribution, suggesting one or more flows of some kind as the heat source. Courtesy of HIGP MODVOLC Thermal Alerts System.

A Moderate Resolution Imaging Spectroradiometer (MODIS) satellite image of Bristol Island acquired on 28 May 2016 showed an ash plume from Mt. Sourabaya drifting NE (figure 3). The Buenos Aires VAAC issued the first reports of gas and possible ash plumes on 29 May 2016, noting that they drifted as far as 185 km N, NNE, and SE at an altitude of approximately 1.5 km.

Figure (see Caption) Figure 3. On 28 May 2016, the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Terra satellite acquired this natural-color image of an ash plume streaming NE from Bristol Island. The plume casts a shadow on the sea ice below. Most of the white in the image is likely ice, rather than clouds. Courtesy of NASA Earth Observatory.

The Buenos Aires VAAC issued multiple daily ash advisories during 29 May-7 June 2016. They noted that weather clouds mostly prevented satellite observations of Mount Sourabaya during 1-6 June, though a thermal anomaly was detected during 1-2 and 5-7 June. Satellite images from Suomi NPP/VIIRS often showed possible ash plumes mixed with clouds, but revealed distinct plumes on 2 and 4 June (figure 4) drifting E, and on 7 June towards the NE. On 16 June, a diffuse plume of volcanic ash was reported by the Buenos Aires VAAC moving SE at about 1.5 km altitude. MODVOLC thermal alerts continued even more strongly in June than during May. On almost every day, more than ten alerts were recorded, and they continued with a broad E-W distribution similar to that seen during May.

Figure (see Caption) Figure 4. An ash plume can be seen drifting E on 4 June 2016 from Bristol Island in this Suomi NPP/VIIRS image (Corrected Reflectance – True Color). Courtesy of NASA Worldview.

On 16 and 18 July, ash seen in Suomi NPP/VIIRS imagers appeared to be drifting NE, and on 19 July a faint thin ash plume was identified drifting 100 km NE; the persistent thermal anomaly continued to be visible. No further VAAC reports were issued after 21 July. Numerous MODVOLC thermal alerts continued during most days of July, until they stopped abruptly after the 17 alerts issued on 26 July (figure 5). The MIROVA thermal anomaly system captured a strong signal from Bristol Island between late April and late July 2016 (figure 6).

Figure (see Caption) Figure 5. MODVOLC thermal alerts during July 2016 suggest multiple origin points for the substantial thermal anomalies. Top left: the distribution of the 23 alerts issued on 3 July suggests multiple origin points. Top right: two distinct sources are apparent from the 15 alerts issued on 7 July. Lower left: the 30 alerts issued on 13 July are spread over a large E-W area and reflect multiple source points. Lower right: the 17 Alerts on 26 July show NE-SW trending elongate zones of thermal anomalies. Courtesy of HIGP MODVOLC Thermal Alerts System.
Figure (see Caption) Figure 6. A strong thermal anomaly signal is apparent at Bristol Island during April-July 2016 in the MIROVA thermal anomaly data. Both blue and black lines signify eruptive activity. Courtesy of MIROVA.

Two satellite images, from 21 August and 22 September 2016, confirm the presence of new lava fields around the summit of Mount Sourabaya that were created during the April-July 2016 eruption (figure 7).

Figure (see Caption) Figure 7. Satellite imagery of Mount Sourabaya on Bristol Island on 21 August and 22 September 2016 after the eruptive episode of April-July shows evidence of lava flows onto ice and snow surrounding the summit. The upper image is from the Landsat Viewer/EOS Data Analytics annotated by the South Sandwich Islands blog; the lower image is a Landsat 8 image annotated by Cultur Volcan.

Geologic Background. The 9 x 10 km Bristol Island near the southern end of the South Sandwich arc lies across Fortser's Passage from the Southern Thule Islands and forms one of the largest islands of the chain. Largely glacier-covered, it contains a horseshoe-shaped ridge at the interior extending northward from the highest peak, 1100-m-high Mount Darnley. A steep-sided flank cone or lava dome, Havfruen Peak, is located on the east side, and a young crater and fissure are on the west flank. Three large sea stacks lying off Turmoil Point at the western tip of the island may be remnants of an older now-eroded volcanic center. Both summit and flank vents have been active during historical time. The latest eruption, during 1956, originated from the west-flank crater, and deposited cinder over the icecap. The extensive icecap and the difficulty of landing make it the least explored of the South Sandwich Islands.

Information Contacts: NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php?lang=es); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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/); South Sandwich Islands Volcano Monitoring Blog (URL: http://southsandwichmonitoring.blogspot.com/); Cultur Volcan, Journal d'un volcanophile (URL: https://laculturevolcan.blogspot.com/).


Etna (Italy) — September 2017 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 during May 2016 followed by new fracture zones and major subsidence at the summit craters

Italy's Mount Etna on the island of Sicily has had historically recorded eruptions for the past 3,500 years. Lava flows, explosive eruptions with ash plumes, and lava fountains commonly occur from its major summit crater areas, the North East Crater (NEC), the Voragine-Bocca Nuova complex (VOR-BN), the South East Crater (SEC) (formed in 1978), and the New South East Crater (NSEC) (formed in 2011). The Etna Observatory, which provides weekly reports and special updates on activity, is run by the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV). This report uses information from INGV to provide a detailed summary of events between April 2016 and January 2017.

Summary of April 2016-January 2017 activity. A new eruptive episode at Etna began on 15 May 2016 and included activity around all four major summit cones; Strombolian activity began at NSEC on 15-16 May, from a pit on the E flank of the cone. The following night, thermal webcams suggested Strombolian activity at NEC. This ceased on 18 May when Strombolian activity started at VOR that also produced a large ash plume. Lava then overflowed the W rim of BN and headed W multiple times during the next few days. A different flow emerged from a fracture on the SE side of VOR near SEC on 21 May. Activity from all of the active vents had ended by 26 May. New fracture zones trending N-S and NE-SW, and extensive subsidence within VOR were observed at the summit craters at the end of May after the episode ceased.

Intermittent weak ash emissions during late May and July and intense degassing from several craters were the primary activity until explosive activity at VOR began on 7 August and opened a new vent along the inner wall of the NE rim. Strong subsidence followed at VOR and BN during August and September, creating a single large crater that included both areas. Dense ash emissions from the vent on the upper E flank of NSEC in mid-October and a few modest ash emissions from VOR and NSEC were observed. There was also persistent incandescence from the new vent at VOR and its continued subsidence through early January 2017. After the spike in activity during May 2016, heat flow diminished, but was persistent throughout the period (figure 174).

Figure (see Caption) Figure 174. MIROVA log radiative power thermal anomaly graph of activity at Etna from late May 2016 through early January 2017. A major effusive eruptive event with lava flows and Strombolian activity caused a spike in heat flow during late May 2016, but heat flow was persistent throughout the period. Courtesy of MIROVA.

Activity during March-April 2016. After the major lava fountains and ash plumes of the first week of December 2015 (BGVN 42:05), eruptive activity was lower through March 2016. Sporadic ash emissions and minor incandescence were reported a few times each month. The largest event was an explosion on 23 February 2016; it produced an ash plume that drifted NE and caused ashfall in communities as far as 40 km away.

Continuous degassing accompanied dense ash emissions from the North East Crater (NEC) and the New South East Crater (NSEC) during 31 March-1 April 2016. Winds sent material to the SW, and then changed direction to the N the following day, dispersing pyroclastic material around the crater area. Ash emissions continued to be weak but persistent for the rest of April from NEC and NSEC, while only minor degassing was observed from the Voragine-Bocca Nuova complex (VOR-BN). A new pit crater was observed near the center of BN from the gradual collapse of the crater between 19 February and 15 April 2016.

Activity during May 2016. Although visibility was limited due to weather in early May 2016, discontinuous explosive activity with minor ash emissions was observed over several days from NEC and NSEC near the top of Valle del Bove (a large valley SE of the summit crater area). Weak incandescence from NSEC was detected by the high-resolution webcam at Monte Cagliato for the first time in several months during the night of 16 May, and marked the beginning of a new eruptive episode that lasted until 25 May 2016, involving activity at all four summit crater areas (figure 175).

Figure (see Caption) Figure 175. The four summit craters at Etna shown in a DEM from 2014 created and modified by INGV's Aerogeophysical Laboratory. The black hatched lines outline the rims of the craters. BN = Bocca Nuova, VOR = Voragine; they are delimited by a single crater rim after the explosive activity of December 2015; NEC = North East Crater; SEC = South East Crater with cone of the New South East Crater (NSEC) on its SE flank. Activity from the 17-25 May 2016 episode is shown in red and yellow and discussed in the text. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 16/05/2016-22/05/2016, Reporte No. 21/2016).

Explosive activity first observed during the night of 15-16 May 2016 at NSEC came from a pit on the E flank of the cone. The following night, webcams also showed a thermal anomaly at NEC, interpreted by INGV as probable Strombolian activity. At first light on 17 May, intense degassing was observed from NEC which lasted throughout the day and included minor ash emissions. Strong explosions from NEC were heard about 10 km from the crater. Strombolian activity rising tens of meters above the rim was first observed around 2000 UTC. During the night of 17-18 May, intermittent flashes, likely from explosive activity, originated from the pit on the E flank of NSEC.

Continued explosions at NEC during the morning of 18 May produced an ash cloud that drifted ESE. This activity ceased around 1050 UTC, when Strombolian activity began at VOR that rapidly evolved into a lava fountain. The activity also created an ash plume that rose to an altitude of 7 km and drifted due E. The lava fountain continued until about 1430 UTC. Shortly after the Strombolian activity began at VOR (around 1100 UTC), lava overflowed the W rim of BN and headed W towards Monte Nunziata. It traveled for about 2 km and stopped at an elevation of around 2,100 m based on observations from the Bronte thermal webcam. Also at 1100 UTC, a small explosive vent opened at the base of the N side of NEC (Bocca 1 in red, figure 175) that spattered for a few minutes. Around 1530 UTC, an improvement in weather conditions permitted observation of a new lava flow in the Valle del Bove. The flow, fed by a vent at the base of the E side of NEC (Bocca 2 in red, figure 175), headed E towards Monte Simone, and stopped at an elevation of approximately 2,400 m.

By the morning of 19 May, although adverse weather conditions prevented observations, a sudden increase in the amplitude of tremor and loud explosions heard in communities E and S of the volcano suggested another explosive episode at VOR. A dense eruptive cloud drifted E. A new lava flow emerged from the W rim of BN, and headed W on top of the flow from the previous day. It divided into several arms, the longest of which flowed about 1,800 m, near Monte Nunziata, without reaching the nearby highway. Strombolian activity was again observed at VOR beginning around 1900 UTC on 20 May when weather conditions improved.

Beginning around 0140 UTC on 21 May 2016, a rapid escalation of the amplitude of volcanic tremor occurred together with increased explosions from VOR. Around 0200 a small lava flow was observed from a fracture at the base of the SE side of the cone of VOR near the base of SEC (the yellow flow marked on figure 175). The intense explosive activity at VOR generated a plume that drifted S. Tremor amplitude decreased suddenly around 0600. Lava was observed overflowing the W rim of BN around 0700, covering the flows of the previous days. Strombolian activity was again observed from VOR during the night of 21-22 May. Sporadic ash emissions from the pit on the E flank of NSEC during the early morning of 22 May quickly dissipated. That afternoon, renewed Strombolian activity began at NEC which intensified and then ended during the following night (figure 176).

Figure (see Caption) Figure 176. Volcanic activity at Etna during 20-22 May 2016. a) intense explosive activity of 21 May at VOR, taken from the thermal webcam at Monte Cagliato; b) the lava flow from the fracture on the SE side of VOR during the explosive activity of 21 May, photo by Alessandro Lo Piccolo; c) intense degassing on 20 May from the fracture that fed the lava flow shown in (b) the following day, taken from the Piano delle Concazze; d) the overflow from the western edge of BN during 21 May, taken from Bronte's thermal webcam; e) Strombolian activity at VOR taken by the high definition camera of Monte Cagliato at 1845 UTC on 22 May; f) ash emission from the pit on the E flank of the NSEC, taken with the camera at Monte Cagliato on 22 May at 0630 UTC. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 16/05/2016-22/05/2016, Reporte No. 21/2016).

A new round of weak Strombolian activity began at VOR around 1900 on 23 May 2016. Activity continued until 1750 on 24 May when explosive activity increased sharply. Vigorous Strombolian activity peaked during the night of 24-25 May. Incandescent material rose a few hundred meters into the air, and mostly fell back into the crater. It was not accompanied by a lava flow or ash plume. Activity began decreasing during the afternoon of 25 May, and ceased sometime during the following night. Both ground-based and aerial observations by INGV personnel on 26 and 27 May confirmed the end of the eruptive episode and documented its effects (figure 177).

Figure (see Caption) Figure 177. The summit area of Etna seen from the north on 27 May 2016 after the eruptive episode of 15-25 May. At the North East Crater (NEC), the black dashed line shows the position of its rim prior to the eruptive phase that started on 15 May. Large areas of the crater rim collapsed on both the N and S sides. The S side of the collapsed NEC rim intersects a fracture zone that forms a graben (yellow arrows) that trends N-S and cuts across the E rim of the VOR. A second graben trends SE from the VOR. Fumarolic activity is visible in both structures. Degassing is also visible from a vent at the bottom of VOR (red arrow within VOR). The NW-SE trending graben that extends between VOR and SEC appears to terminate at the eruptive vent created on 21 May (red arrow between NSEC and SEC). However, slope failure on the N flank of the SEC cone (white arrows) suggests to INGV geologists that the structural zone continues SE towards NSEC. Inset photo is an image of NEC captured with the thermal camera by Sonia Calvari, showing the NEC crater bottom filled with the detritus from the collapse of the southern crater wall. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 23/05/2016-29/05/2016, No. 22/2016).

A N-S trending fracture zone about 400 m wide and 1,300 m long was observed extending S beginning at the northern side of NEC, crossing the E rim of the Central Crater (the combined VOR-BN complex), where it changes direction and extends SE toward the SEC (figure 178). A vent at the base of the saddle between SEC and VOR fed weak effusive activity on 21 May. Tens of meters of collapse within the graben contributed to the destruction of the S rim of NEC, significantly changing its shape and filling it with debris.

Figure (see Caption) Figure 178. The summit area of Etna seen from the SE on 27 May 2016. The yellow arrows highlight a new NW-SE trending fracture system that produced a near-symmetrical graben on the E side of the Central Crater (the combined VOR-BN complex). It then veers to the N and joins with another graben (the black arrow) that breaches the rim of the NEC. The dotted black line highlights the portion of collapsed NEC rim during the recent eruptive period. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 23/05/2016-29/05/2016, No. 22/2016).

Major subsidence at VOR after the end of the Strombolian activity of 23-26 May 2016 created numerous sub-circular concentric fractures within the crater with a vent degassing at the base (figure 179). The BN area was filled with the eruptive material that had overflowed the W rim (figure 180).

Figure (see Caption) Figure 179. Detail of the Central Crater (CC), comprising the VOR and BN craters at Etna. View is from the NW on 27 May 2016. The concentric subcircular fractures with a degassing vent located at the bottom of the crater (red arrow) formed during collapse immediately after the end of the Strombolian activity at VOR from 23 to 26 May 2016. The yellow arrows (above) show the position of the graben responsible for the collapse of part of the NEC. The white arrows (bottom) highlight the western portion of the N-S oriented fracture zone, which affects NEC, VOR, and BN. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 23/05/2016-29/05/2016, No. 22/2016).
Figure (see Caption) Figure 180. View of the summit of Etna from the WSW on 27 May 2016. In the foreground is the Central Crater, consisting of VOR and BN. The two white arrows point to the overflow area of the lava flows from the W edge of BN during 18-21 May. The yellow arrows highlight the main fractures bordering the E side of the crater area, extending from NEC to SEC. The dotted black line highlights the portion of collapsed NEC during the recent eruptive period. The three red arrows highlight the locations of the recent eruptive vents: north of NEC (far left), within the VOR, and at the base of the saddle between the Central Crater and the SEC. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 23/05/2016-29/05/2016, No. 22/2016).

Activity during June 2016-January 2017.A weak ash emission from VOR on the morning of 31 May 2016 was the only additional eruptive activity during May. INGV volcanologists making ground observations on 3 June noted about 10 m of subsidence of the lava surface filling BN and continued collapse at the center of VOR. Intense degassing of mostly water vapor occurred from the fracture on the SE side of VOR. Strong degassing continued from all the new fracture zones at the summit during June and July. Ground-based thermal imagery recorded on 16 June indicated temperatures as high as 300°C around the fractures within the Central Crater. A helicopter overflight on 14 July showed few changes in the graben system first documented at the end of May, except for continued collapse near the S rim of NEC. Minor ash emissions resumed at NSEC; they were observed during 10-14, 19-21, and 26-28 July. Explosions were heard from the W side of BN during a visit by INGV scientists on 28 July.

Intense and persistent degassing continued during August 2016 from NEC and from the fractures between NEC and VOR (figure 181). Incandescence was observed within the fractures on 4 August. NSEC produced minor ash emissions again during 4-5 August. Low intensity explosive activity began at VOR on 7 August, but no material was ejected beyond the crater rim. An incandescent vent was observed within the collapsed inner wall of VOR on 10 August (figure 182). Explosive activity and incandescence was intermittent from this vent during 7-22 August. The apparent temperature at the vent as measured by thermal camera was greater than 580°C on 22 August. Weak and episodic ash emissions also occurred from a vent on the upper E side of NSEC on 27 and 29 August. Incandescent degassing continued at the 7 August VOR vent throughout September, along with persistent fumarolic emissions from the fracture zones.

Figure (see Caption) Figure 181. Intense degassing within NEC and along the fractures between NEC and VOR at Etna on 3 August 2016. This view to the N shows the rim of NEC at the top and the new graben that breaches the rim. Photo by B. Behncke, courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 01/08/2016 - 07/08/2016, No. 32/2016).
Figure (see Caption) Figure 182. A new vent opened on 7 August 2016 from the collapse of the inner wall of VOR near its NE rim at Etna. Photo by B. Behncke on 10 August 2016, courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 08/08/2016-14/08/2016, No. 33/2016).

A series of low-frequency seismic events were recorded at the summit on 10 October, some accompanied by explosive sounds. The strongest seismic event produced ash and hot gas that was recorded by two thermal cameras during the early afternoon. The ash rose from the W part of BN about 100 m above the rim and drifted rapidly E. During an inspection on 12 October, INGV scientists noted that subsidence of about 50 m had occurred within the BN, centered near the W crater wall, and was ongoing. They observed the sudden dropping of material along concentric fractures accompanied by reddish ash and modest steam emissions. One of these events exposed an incandescent area within the fresh lava (figure 183).

Figure (see Caption) Figure 183. The bottom of the BN crater at Etna on 12 October 2016 during a collapse within the peak subsidence zone, showing incandescent material under the fresh lava. Photo by B. Behncke, courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 10/10/2016-16/10/2016, No. 42/2016).

Dense ash emissions were produced on 17 October from the 25 November 2015 vent on the upper E flank of the NSEC (figure 184). A diffuse brown ash plume was observed the next day during a field inspection of the area. Intermittent diffuse brown ash emissions were again observed on 6 November. Persistent fumaroles from the vent at VOR and bottom subsidence at BN continued during November where two distinct areas of subsidence (BN-1 and BN-2) were visible (figure 185).

Figure (see Caption) Figure 184. A Digital Elevation Map of the summit crater area at Etna (DEM 2014, Aerogeophysics Laboratory - Section 2 modified) showing the active degassing areas during August-December 2016. The yellow dot shows the position of the vent opened on 7 August 2016 in the upper part of the E wall of the VOR; the red dot indicates the location of the vent opened in November 2015 on the upper E flank of the NSEC, from which minor ash emitted during October and November 2016. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 31/10/2016-06/11/2016, No. 45/2016).
Figure (see Caption) Figure 185. An aerial view from the W of the summit crater area of Etna on 13 November 2016 annotated with areas of activity. The Central Crater (CC), highlighted by the dashed yellow line. Inside, the VOR and BN have coalesced; two depressions (BN-1 and BN-2) were undergoing constant, slow subsidence (especially BN-1) with enough heat released to prevent snow buildup. The subsidence of BN-1 and BN-2 began on 10 October 2016. Near the E edge of the VOR, gas emissions continued from the 7 August 2016 vent 'Bocca attiva dal 7 Agosto 2016'. Photo by Piero Berti, courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 07/11/2016-13/11/2016, No. 46/2016).

Intermittent, low-intensity incandescence at the VOR vent appeared during the night of 28-29 November 2016. Sporadic, minor ash emissions occurred from the saddle area between SEC and NSEC during 15 December. Incandescence that evening from the VOR vent was also recorded on the webcams. A light coating of ash and a few lithic blocks appeared the next morning in the fresh snow on the flank of the SEC. Modest ash emissions from the same area continued intermittently through the end of December. On 31 December, a diffuse ash plume was also noted from the vent on the upper E flank of NSEC. Sporadic incandescence continued from the VOR vent during early January 2017.

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/).


Fogo (Cape Verde) — September 2017 Citation iconCite this Report

Fogo

Cape Verde

14.95°N, 24.35°W; summit elev. 2829 m

All times are local (unless otherwise noted)


November 2014-February 2015 eruption destroys two villages, lava displaces over 1000 people

The 25-km-wide island of Fogo in the Cape Verde Islands, 750 km W of Dakar, Senegal, is a single massive stratovolcano with a 9-km-wide summit caldera (Cha Caldera) that is breached to the east. A steep-sided central cone, Pico, rises more than a kilometer above the caldera floor, and is capped by a 500-m-wide, 150-m-deep summit crater; it was apparently almost continuously active from the time of Portuguese settlement in 1500 CE until around 1760. Several lava flows that erupted during the eighteenth and nineteenth centuries reached the eastern coast below the breached caldera rim (BGVN 20:03, figure 1). Lava flows in 1951 and 1995 were contained within the W half of the Cha Caldera, as were the flows from the November 2014-February 2015 eruption (figure 16) described below. Information for this report comes from the Toulouse Volcanic Ash Advisory Center (VAAC), the Observatório Vulcanológico de Cabo Verde (OVCV), and satellite and news data from several sources.

Figure (see Caption) Figure 16. The Advanced Land Imager (ALI) on the Earth-Observing 1 (EO-1) satellite captured this image on 24 December 2014 of the eruption at Fogo that began on 23 November 2014. The top image offers a broad view of the island's most distinctive feature: Cha Caldera. The nine-kilometer wide caldera has a western wall that towers a kilometer above the crater floor. The eastern half of the crater wall is gone, erased by an ancient collapse. The lower image shows a more detailed view of the caldera. The volcanic plume streams from a fissure at the SW base of Pico de Fogo, the island's highest point. Both of the villages destroyed by the eruption, Portela and Bangaeira, were located within the caldera. In late November, lava poured into Portela; by 8 December it had entered Bangaeira. The volcanic plume obscures the remains of the two villages, but the white roofs of a few structures are visible on the upper left side of the image. In addition to the north flow that affected the villages, the 2014 eruption also produced flows that moved S and W. Courtesy of NASA Earth Observatory.

The April-May 1995 eruption produced lava flows from a vent at the SW base of the Pico cone (BGVN 20:05, figure 3) that flowed SW and NW from the vent. They cut off the main access road to the larger villages of Portela and Bangaeira along the NW side of the caldera, but the approximately 1,300 residents from the various communities within the caldera were all safely evacuated, and the villages were spared. Effusive activity produced Strombolian fountains, pyroclastic material, ash plumes, and both pahoehoe and aa lava flows. The lava flows destroyed the small settlement of Boca de Fonte (population 56) near the caldera wall about 2 km W of the eruption center, and reached to within 300 m of Portela village. By the time it was over at the end of May 1995, new lava flows covered about 6.3 km2 of land, and ranged from one to over twenty meters thick.

The most recent eruption at Fogo began with lava flows emerging from a similar fissure vent at the base of Pico on 23 November 2014 (figure 17), and continued through 8 February 2015 according to OVCV; the flows covered about 4 km2 of land. The villages of Portela and Bangaeira, located 4-5 km NW of Pico with a combined population of about 1,000 residents, were not spared during the 2014-15 eruption as they had been in 1995; both villages were largely destroyed (figure 18), although their inhabitants were safely rescued. The eruption began from a fissure near the 1995 vent, but it soon emerged from multiple vents along the fissure with Strombolian activity (figure 19), explosions, lava fountains, and ash emissions.

Figure (see Caption) Figure 17. Lava and gas emerge from a fissure at Fogo on 24 November 2014, one day after the eruption began in this satellite image used by Google Earth. The fissure is located at the SW base of Pico, the cone within the Cha Caldera. Image copyright by DigitalGlobe, courtesy of Google Earth.
Figure (see Caption) Figure 18. The villages of Portela and Bangaeira were destroyed by the lava flows at Fogo during late November 2014-February 2015. This image of a home in Portela trapped in a lava flow was taken between 30 November and 3 December 2014. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 19. Strombolian activity at dawn on 30 November 2014 from multiple fissure vents at Fogo. Copyright by Martin Rietze, used with permission.

The lava flows consisted of three primary lobes that traveled NNW, S, and W (BGVN 39:11, figure 8). During the earliest days of the eruption in late November, lava flowed to the NNW destroying much of Portela (figure 20 and 21) and to the S from the main fissure. The flow to the S ceased after 30 November.

Figure (see Caption) Figure 20. Lava advances NNW on the community of Portela at Fogo sometime during 30 November-3 December 2014. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 21. A lava flow consumes a house in the village of Portela at Fogo on 30 November 2014. Copyright by Martin Rietze, used with permission.

The main flows continued NNW into the first week of December; they destroyed the remaining structures in Portela and caused extensive damage in Bangaeira and at the Parque Natural de Fogo headquarters (figures 22 and 23). A third lobe flowed to the W of the fissure during the second half of December, reaching the base of the 1-km-high caldera rim where it damaged farms and infrastructure in the small village of Ilhéu de Losna (see figure 16). The lava had ceased advancing by early January.

Figure (see Caption) Figure 22. Lava flow on 1 December 2014 at Fogo emerges from a fissure vent. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 23. Advancing lava flow with blocky (aa) texture at Fogo during 30 November-3 December 2014. Photo copyright by Martin Rietze, used with permission.

The MODVOLC thermal alert system issued eight thermal alerts from the lava flows (figure 24) on 23 November 2014. Tens of alerts were reported almost daily through 19 December, with a peak of 46 alerts on 30 November. For the rest of December, as many as 10 alerts a day were recorded. By January 2015, they became more intermittent, with no more than three alerts issued in any day, and they occurred on only 11 days of the month. The final two thermal alerts were recorded on 7 February 2015.

Figure (see Caption) Figure 24. A cascade of lava flows from a fissure vent at Fogo during 30 November-3 December 2014. Photo copyright by Martin Rietze, used with permission.

Ash emissions from the fissure vents were intermittent throughout the eruption (figures 25). The first major plume on 24 November 2014 was reported by the Toulouse VAAC as consisting largely of SO2, with very little ash. It rose to 9.1 km altitude, drifted 220 km NW, and caused minor ashfall on the flanks of the volcano. After the initial plume of mostly SO2, ash emissions from the vent were generally below 3.9 km altitude and limited to the immediate area of the island (figure 26).

Figure (see Caption) Figure 25. Residents flee with their belongings as ash emissions and lava flows emerge from multiple vents on the SW flank of Pico cone at Fogo during the last week of November 2014. Photo by Joao Relvas/Lusa, courtesy of The Observador, published on 30 November 2014.
Figure (see Caption) Figure 26. Ash explosion and incandescent material erupted from a fissure vent during 30 November-3 December 2014. Photo copyright by Martin Rietze, used with permission.

Ash was reported rising to 2 km above the summit (4.8 km altitude) on 2 December (figure 27), and ashfall was reported near San Felipe (17 km SW). Ash and SO2 emissions decreased in mid-December; the next plume was reported on 21 December rising 800 m above the summit. Additional plumes during 30 December-2 January rose 400-900 m above the cone and occasionally sent tephra up to 40 m away. Several explosions of gas-and-ash plumes during 8-12 January produced plumes that rose up to 2 km above the summit and drifted E or SE. The largest plume, on 12 January, was very dense and dark-gray, it rose 2 km and drifted E; tephra was also ejected 50 m above the crater and was observed by people in San Felipe and other parts of the island.

Figure (see Caption) Figure 27. Ash emission on 2 December 2014 from the fissure vent at Fogo. The plume was reported at 2 km above the summit of Pico. Photograph copyright by Martin Rietze, used with permission.

Satellite data on SO2 flux from Fogo corroborated the VAAC reports of the high SO2 content in the emissions, especially during the first two weeks of the eruption when Dobson Unit (DU) values greater than 2 were recorded several times, and the plume areas covered several hundred thousand square kilometers (figure 28).

Figure (see Caption) Figure 28. Sulfur dioxide plumes measured with the Aura Instrument on the OMI satellite show substantial amounts of SO2 released from Fogo during the eruption of November 2014-February 2015. Top Left: The SO2 plume captured on 24 November covered over 325,000 km2 and registered over 40 Dobson Units (DU), a measure of the molecular density of SO2 in the atmosphere; Top Right: the plume on 26 November covered almost 700,000 km2 and drifted N and E; Lower Left: on 1 December the 590,000 km2 plume drifted in multiple directions from the vent; Lower Right: on 3 December the large plume drifted NE and registered at almost 20 DU. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. The island of Fogo consists of a single massive stratovolcano that is the most prominent of the Cape Verde Islands. The roughly circular 25-km-wide island is truncated by a large 9-km-wide caldera that is breached to the east and has a headwall 1 km high. The caldera is located asymmetrically NE of the center of the island and was formed as a result of massive lateral collapse of the ancestral Monte Armarelo edifice. A very youthful steep-sided central cone, Pico, rises more than 1 km above the caldera floor to about 100 m above the caldera rim, forming the 2829 m high point of the island. Pico, which is capped by a 500-m-wide, 150-m-deep summit crater, was apparently in almost continuous activity from the time of Portuguese settlement in 1500 CE until around 1760. Later historical lava flows, some from vents on the caldera floor, reached the eastern coast below the breached caldera.

Information Contacts: Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/vaac/); Observatório Vulcanológico de Cabo Verde (OVCV), Departamento de Ciência e Tecnologia, Universidade de Cabo Verde (Uni-CV), Campus de Palmarejo, Praia, Cape Verde (URL: https://www.facebook.com/pages/Observatorio-Vulcanologico-de-Cabo-Verde-OVCV/175875102444250); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Google Earth (URL: https://www.google.com/earth/); The Observador (URL: http://observador.pt/2014/11/30/erupcoes-vulcanicas-da-ilha-fogo-evoluem-para-estado-critico/); Martin Rietze, Photographer (URL: http://www.mrietze.com/web13/Fogo_f14.htm).


Krakatau (Indonesia) — September 2017 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 813 m

All times are local (unless otherwise noted)


Eruption during 17-19 February 2017 sends large lava flow down the SE flank

The most recent reported eruptive activity from the Anak Krakatau cone was a pilot report of an ash plume on 31 March 2014 (BGVN 40:08). Monitoring reports by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) from January 2014 through July 2015 only noted seismicity and fumarolic emissions.

The only indication of possible eruptive activity in the second half of 2015 through 2016 reported by PVMBG was a Volcano Observatory Notice for Aviation (VONA) on 20 June. The seismograph at the Anak Krakatau Volcano Observatory detected an eruption at 0551 local time (2251 UTC), but the eruption was not observed visually because of cloudy weather. There had been a swarm of volcanic earthquakes about one day earlier, and seismicity had significantly increased 3 hours before the eruption. After the eruption, seismicity gradually decreased. Although thermal anomalies were frequently recorded in 2016 (figure 36, bottom), they may have been a result of strong hot fumaroles at the summit dome; no PVMBG or tourist reports indicated active lava flows or ash plumes.

Figure (see Caption) Figure 36. Thermal anomalies at Krakatau identified by the MIROVA system using MODIS data for the year ending 19 February 2017. The record indicates regular thermal signatures, which may be a result of strong fumarolic activity in the summit crater. Courtesy of MIROVA.

The PVMBG reported that seismicity was dominated by shallow volcanic earthquakes in February 2017. In a Volcano Observatory Notice for Aviation (VONA), the aviation color code was reported to be raised to Orange. Emission earthquakes increased beginning on 17 February and gradually formed continuous tremor. At 1535 on 17 February 2017 at 1535 infrared MODIS data recorded by MODVOLC measured a 2-pixel thermal alert from the Aqua satellite, and on 18 February 2017 at 0650 a 2-pixel thermal alert was measured from the Terra satellite. Satellite thermal anomalies identified by the MIROVA system showed a strong sequence of anomalies around this same time (figure 36, top). Harmonic tremor began to be recorded at 1810 on 19 February. Almost an hour later, at 1904, Strombolian explosions ejected incandescent material 200 m high.

O.L. Andersen, a professional photographer, visited Anak Krakatau 25-26 February 2017. The eruption earlier in the month had resulted in a new lava flow on the SE flank (figure 37) where the September 2012 lava flow was located. He observed that "The new layer of lava-flow is black, compared to the red color of the 2012 lava flow. The lava flow has cooled down since the material was deposited. Fresh volcanic blocks were also seen distributed on the SE, S, E flank of Krakatau." No eruptions of ash were observed by Andersen, but gas emissions were present. Further, Andersen noted "After having studied aerial views of the crater area (figure 38), it seems that the source vent of the new lava-flow, is the same vent (main, central vent) that was involved in the 2012 eruption. On the top of the vent, it now seems to be a lava-dome...."

Figure (see Caption) Figure 37. The new lava flow on Anak Krakatau of February 2017 shows up as black material on top of the more reddish colored lava from the September 2012 event. The flow came from the new vent at the summit. Copyrighted image courtesy of O.L. Andersen (used with permission).
Figure (see Caption) Figure 38. Aerial view of the summit of Anak Krakatau taken looking E on 25 February 2017. The new lava shows as a black flow from the summit toward the upper right into the ocean. The northern vent is on the crater rim left of the center of the photograph. Copyrighted image courtesy of O.L. Andersen (used with permission).

A comparison of photos from October 2015 and February 2017 composed by Andersen showed the morphological changes during that time, including the new dome and lava flows (figure 39). Incandescence was obvious at night (figure 40) and from aerial observations of the lava dome Andersen noted that the area with incandescence was small, and that "the lava dome did not appear to be overly active." Andersen observed further that the "main crater and summit area today seem to be of a more complex and dynamic character than it was before the eruption of September 2012. From footage of 2010/2011 the main crater was seen to be broad and fairly deep. Now the main crater is filled with material, with two lava flows originating from this vent running down on the SW and E flanks. On the northern side of the summit an eruption vent is also clearly observed...."

Figure (see Caption) Figure 39. A comparison of the Anak Krakatau summit area of 26 February 2017 and 11 October 2015 taken looking west. Note the new dome in the center of the 2017 photo and the new lava that came from the vent and flowed down the SE slope of the volcano. Copyrighted image courtesy of O.L. Andersen (used with permission).
Figure (see Caption) Figure 40. Incandescence from Anak Krakatau on the evening of 25 February 2017. Copyrighted image courtesy of O.L. Andersen (used with permission).

Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

Information Contacts: Øystein Lund Andersen (URL: http://www.oysteinlundandersen.com/krakatau-volcano/visit-to-anak-krakatau-volcano-february-2017/); 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/); 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/).


Langila (Papua New Guinea) — September 2017 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)


Eruption continues, intensifying from mid-December 2016 through July 2017

Eruptive activity at Langila was intermittent during 2016, with ash plumes seen during April-May and November-December (BGVN 42:01); thermal anomalies were somewhat more commonly detected, but were also intermittent. No reports were available from the Rabaul Volcano Observatory during January-July 2017, but volcanic ash warnings were issued by the Darwin Volcanic Ash Advisory Centre (VAAC). Thermal anomaly data acquired by satellite-based MODIS instruments showed a strong increase in activity beginning in mid-December 2016 that was ongoing as of early August 2017.

Ash plumes were reported frequently during the first half of 2017 except during March and early April. The plumes rose to altitudes between 1.8 and 3 km (table 4). The aviation color code has remained at Orange (third highest of a four-step universal volcanic ash alert level system for aviation) throughout 2016 and through July 2017.

Table 4. Ash plumes from Langila reported during January-June 2017. Observations are based on analyses of satellite imagery and wind data; dates are based on local time. Courtesy of the Darwin VAAC.

Date Max. Plume Altitude (km) Drift
02 Jan 2017 2.1 NE
05 Jan 2017 2.4 45 km W
12-13, 15 Jan 2017 2.1 ESE and SE
25-27 Jan 2017 1.8-3 NW and N
17-18 Feb 2017 1.8 SE
24 Feb 2017 2.4 N
23-25 Apr 2017 2.1 55 km S and SE
26 Apr 2017 2.1 E and NE
02 May 2017 2.1 E and NE
10-14 May 2017 1.8-2.4 N, NW, and S
19 May 2017 4.6 ~170 km WSW
19-20 May 2017 1.8 N and NNW
23 May 2017 2.1, 3 NW, SW
24-27 May 2017 2.1-3 75-85 km W and NW
01 Jun 2017 1.8 N and NW
07 Jun 2017 2.1 45 km NW
12 Jun 2017 1.8 WNW
20 Jun 2017 2.1 NW
21 Jun 2017 2.1 95 km NW

Thermal alerts, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were identified often during December 2016 through June 2017. The MIROVA volcano hotspot detection system, also based on analysis of MODIS data, detected occasional anomalies from August 2016 through late December 2016 (BGVN 42:01), followed by more continuous anomalies through late July 2017 (figure 6). The most intense anomalies over this time period occurred from mid-April to early May 2017.

Figure (see Caption) Figure 6. Plot of MIROVA thermal anomaly MODIS data for the year ending on 8 August 2017. Courtesy of MIROVA.

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/); 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/).


Masaya (Nicaragua) — September 2017 Citation iconCite this Report

Masaya

Nicaragua

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

All times are local (unless otherwise noted)


Persistent lava lake and gas plume activity, with intermittent ash emission, through mid-July 2017

Masaya volcano near the Pacific Ocean in Nicaragua (figure 52) is one of the most active volcanos in that country. The period from October 2015 through August 2016 saw the re-emergence of the lava lake, increased seismic frequency and amplitude, intermittent explosive activity, and continued strong thermal anomalies from satellite and ground based sources as a result of the newly active lava lake. (BGVN 41:08). Thermal satellite data analyzed by MIROVA measured moderate volcanic radiative power beginning January 2016 and continuing regularly through August 2016. The Instituto Nicareguense de Estudios Territoriales (INETER), Sistema Nacional para la Prevencion, Mitigacion y Atencion de Desastres (SINAPRED), and the Washington Volcanic Ash Advisory Center (VAAC) monitor the volcano's activity and provide regular reports.

Figure (see Caption) Figure 52. Maps and aerial photo of the Masaya complex. (a) Regional location map showing of Masaya. (b) Map showing the Las Sierras Caldera enclosing the Masaya caldera, which in turn encloses the recent vents (black dots); distances to major towns (circles) and cities are given. (c) Map of active crater area showing structural features, such as eruptive fissures (dashed lines), pit crater edges (filled triangles),and explosion crater edges (open triangles); lava flows and lakes (shaded) and tephra cover (blank) are also shown including dates of eruption (e.g. L1772 is the 1772 flow and F1906 is the fissure that erupted gas in 1906). (d) Aerial photo of the same area as the map in (c). From Rymer and others (1998).

Ash and steam emissions have been reported by the Washington VAAC from satellite data from August 2016 through mid-July 2017, the latest on 13 May 2017 when both satellite images showed and a pilot observed a W-drifting ash emission from Masaya. Plumes with possible ash content were noted on 15 August, 28 August, and 3 November 2016. Plumes identified on 5 and 21 January 2017 were stated to have minor ash content. Monthly reports from INETER consistently noted ongoing gas emissions, lava lake activity, and variable seismicity.

Since August 2016, thermal anomalies recorded by MIROVA seemed nearly constant in power level and regularity until about May 2017, at which time both seemed to decrease slightly (figure 53). Since mid-May 2017, MODIS thermal satellite data processed by MODVOLC measured thermal alerts have decreased from nearly daily in July 2016 to 4-6/month through July 2017.

Figure (see Caption) Figure 53. Thermal anomaly data identified by the MIROVA system at Masaya for the year ending 11 July 2017. Courtesy of MIROVA.

INETER reported that from 1 to 5 May 2017 fieldwork was conducted with scientists from the University of McGill (Canada) and the Volcanological and Seismological Observatory of Costa Rica (OVSICORI). Measurements of sulfur dioxide (SO2) in the plume emitted by the Santiago crater were carried out using the DOAS Mobile technique, and samples of hydrogen sulfide (H2S), hydrogen bromide (HBr) and bromine chloride (BrCl) were collected to be analyzed by ion chromatography at McGill (figures 54 and 55).

Figure (see Caption) Figure 54. Scientists from the University of McGill and OVSICORI installed different equipment for gas measurements near the Santiago crater at Masaya during 1-5 May 2017. Courtesy of INETER (Boletín mensual Sismos y Volcanes de Nicaragua. Mayo, 2017).
Figure (see Caption) Figure 55. Drones were used by University of McGill and OVSICORI scientists to measure sulfur dioxide (SO2) gases at the altitude of the gas plume at Masaya during 1-5 May 2017. Courtesy of INETER (Boletín mensual Sismos y Volcanes de Nicaragua. Mayo, 2017).

During the INETER field monitoring that took place on 22 May 2017, strong convection of the lake was observed, as were landslides on almost all of the walls. Fumaroles were seen that are possibly not new, but were active due to recent rainfall. The landslides on the W wall of the crater have been occurring since the end of February (figure 56). They are believed by INETER to be caused by undercutting of the walls by lava lake convection (figure 57).

Figure (see Caption) Figure 56. Collapse on the W wall of Santiago crater at Masaya reported by Park rangers on 15 May 2017. Courtesy of INETER (Boletín mensual Sismos y Volcanes de Nicaragua. Mayo, 2017).
Figure (see Caption) Figure 57. Lava lake in Santiago crater of Masaya in May 2017. Courtesy of INETER (Boletín mensual Sismos y Volcanes de Nicaragua. Mayo, 2017).

References. Rymer, H., van Wyk de Vries, B., Stix, J., and Williams-Jones, G., 1998, Pit crater structure and processes governing persistent activity at Masaya Volcano, Nicaragua. Bull. Volcanol., v. 59, pp. 345-355.

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); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Sistema Nacional para la Prevencion, Mitigacion y Atencion de Desastres, (SINAPRED), Edificio SINAPRED, Rotonda Comandante Hugo Chávez 50 metros al Norte, frente a la Avenida Bolívar, Managua, Nicaragua (URL: http://www.sinapred.gob.ni/).


Popocatepetl (Mexico) — September 2017 Citation iconCite this Report

Popocatepetl

Mexico

19.023°N, 98.622°W; summit elev. 5393 m

All times are local (unless otherwise noted)


Ongoing steam, gas, ash emissions, and lava dome growth and destruction, July 2016-July 2017

Frequent historical eruptions have occurred since pre-Columbian time at México's Popocatépetl. More recently, activity picked up in the mid-1990s after about 50 years of quiescence. The current eruption, which has been ongoing since January 2005, has included frequent ash plumes rising generally 1-4 km above the 5.4-km-elevation summit, and numerous episodes of lava-dome growth and destruction within the 500-m-wide summit caldera. Multiple emissions of steam and gas occur daily, many contain small amounts of ash. Larger, more explosive events that generate ashfall in neighboring communities usually occur every month or two. Information about Popocatépetl comes from daily reports provided by México's Centro Nacional de Prevención de Desastres (CENAPRED). Many ash emissions are also reported by the Washington Volcanic Ash Advisory Center (VAAC). Satellite visible and thermal imagery and SO2 data also provide important observations. Activity through June 2016 was typical of the ongoing eruption with near-constant emissions of water vapor, gas, and ash, and at least two episodes of dome growth and destruction (BGVN 42:07). This report covers similar activity through July 2017.

Activity at Popocatépetl during July 2016-July 2017 was typical of the ongoing eruption since 2005. Near constant steam-and-gas emissions often contained minor amounts of ash. Explosions with ash plumes occurred several times a week during most months. Incandescence at the summit was usually visible on clear nights; nighttime explosions revealed incandescent blocks travelling 100 m or more down the flanks. Large ash explosions on 25 and 26 November 2016 sent ash plumes to 11.5 and 10.9 km altitude, respectively. Ashfall was reported from communities within about 35 km on five different occasions. Thermal activity slowly increased during 2016 to high levels indicative of dome growth during December 2016 and January 2017; they diminished early in 2017 and then fluctuated through July 2017. Sulfur dioxide plumes were persistent in satellite data with plume densities generally exceeding two Dobson Units (DU) several times each month.

Activity during July-September 2016. Intermittent activity continued during July 2016. Tens of daily emissions of gas and steam were reported during the first and last weeks of the month; explosions with ash plumes also generally occurred daily during those weeks, and incandescence was visible on clear nights. The Washington VAAC reported ash emissions observed on 3 July at 7.9 km altitude drifting W, 2.5 km above the summit. Explosions on 4 July produced ash plumes that rose to 8.5 km altitude, just over 3 km above the crater and drifted WSW. Ashfall was reported in Atlatlahucan (30 km WSW) and Tepetlixpa (20 km W). Continuous ash emissions rising to just under 6 km altitude were seen in satellite imagery on 10 July extending almost 40 km W from the summit. Multiple daily explosions occurred during 24-26 July (figure 84). A small cloud of volcanic ash was centered about 35 km W of the summit early on 25 July at 5.8 km altitude. Later in the day, another plume was observed at 7 km altitude drifting WNW and then WSW before dissipating. Satellite imagery confirmed an ash emission on 30 July that rose to 6.7 km altitude and drifted W-WSW. MODVOLC thermal alerts were issued on 3, 10 (2) and 27 July. Small SO2 plumes were recorded daily by the Aura instrument on the OMI satellite. Most measured around two Dobson Units (DU) with an area of about 100,000 km2.

Figure (see Caption) Figure 84. An ash plume at Popocatépetl drifts W from the summit on 25 July 2016 as captured by the ALTZOMONI CENAPRED webcam located about 10 km N of the volcano. Courtesy of CENAPRED.

Tens of daily emissions were common during August 2016, some of which contained minor amounts of ash. Six landslides were detected by the seismic network on 11 August (figure 85). The two largest had volumes of 440 and 220 m3. The Washington VAAC reported an ash plume moving NW at 7.3 km altitude just after midnight on 1 August, extending about 35 km from the summit. A short while later, continuous emissions were reported extending up to 75 km W at 6.1 km altitude. By 0910 UTC, they extended 220 km WNW at 7.3 km altitude. The edge of the plume farthest from the summit had reached close to 500 km W by 1945 UTC when it was last observed. The webcam captured an emission on 11 August but it was not visible in satellite imagery due to weather clouds. An explosion on 12 August generated an ash plume that rose 2.5 km above the 5.4-km-high summit crater and drifted WNW, causing ashfall in Ozumba (18 km W) and Atlautla (16 km W). An explosion at 0034 on 13 August ejected incandescent material onto the flanks. An ash emission was seen in satellite imagery at 8.2 km altitude about 35 km W of the summit later in the morning. Another ash emission was observed with the webcam midday on 15 August that produced an ash plume that rose to 8.5 km altitude and drifted WSW. An ash plume on 21 August drifted W at 6.1 km altitude, and one on 28 August was observed in satellite imagery moving NNW below 7.3 km altitude. Two explosions on 27 August at 1505 and 1537, and one at 0559 on 28 August sent incandescent fragments down the flanks.

Figure (see Caption) Figure 85. A landslide on 11 August 2016 at Popocatépetl was captured by the Tlamacas CENAPRED Webcam located about 5 km N of the summit. Courtesy of CENAPRED.

MODVOLC thermal alerts were issued on 1 (4), 3, 4, 11 (2), 13, and 29 August 2016. SO2 plumes were also captured daily by the Aura Instrument on the OMI satellite, with similar values to those recorded during July. During an overflight of Popocatépetl on 30 August 2016 CENAPRED scientists confirmed that explosions during 27-28 August had destroyed lava dome 69 (first identified on 1 August). The crater which had hosted the dome was 300 m in diameter and 30 m deep (figure 86).

Figure (see Caption) Figure 86. An overflight of Popocatépetl on 30 August 2016 confirmed that explosions during 27-28 August had destroyed lava dome 69 (first identified on 1 August). The crater which had hosted the dome was 300 m in diameter and 30 m deep. Courtesy of CENAPRED.

Only one MODVOLC thermal alert was reported on 14 September 2016. SO2 emissions continued at similar levels to the previous months. Tens of daily steam-and-gas emissions were recorded and crater incandescence was visible on clear nights. An explosion on 8 September produced an ash plume that rose 1.5 km above the crater. On 11 September, an explosion generated a plume that rose 1 km, and an explosion that night ejected incandescent material onto the flanks. CENAPRED reported two volcanic ash emissions on 14 September that rose to 7.3 km. Weather clouds prevented satellite observations of the first, but the second one was observed extending 10 km W of the summit, and reached about 50 km before dissipating. Minor amounts of volcanic ash and steam on 23 September extended NW about 30 km from the summit at 5.5 km altitude. The Mexico City Meteorological Weather Office (MWO) reported volcanic ash at 7.3 km altitude on 29 September, but it was not observed in satellite imagery due to weather clouds.

Activity during October-December 2016. An increase in thermal activity was responsible for ten MODVOLC thermal alerts on 4, 7, 14, 16 (2), 20, 23, 27, 28, and 30 October 2016. Although near-constant steam-and-gas emissions continued, some with minor amounts of ash, there was only one observation of an ash plume from the Washington VAAC, on 28 October at 6.4 km altitude drifting SW. Sulfur dioxide emissions appeared to decrease in the Aura satellite data, although there were values measured over two DU at least four days of the month. Fewer ash emissions were reported during November 2016 as well, but ten MODVOLC thermal alerts were reported on 5, 14, 24, 25, 26 (2), 28, and 30 (3) November.

Ash emissions increased significantly during the last week of November. An ash plume at 5.5 km altitude was visible 55 km E of the summit on 24 November. A larger emission on 25 November was observed at 9.1 km altitude towering above the summit and drifting N (figure 87) with additional ash emissions at 7.3 km altitude drifting SE. Ashfall was reported from this event in areas downwind, including in the municipalities of Atlixco (25 km SE), Tochimilco (15 km SSE), and San Pedro Benito Juárez (12 km SE). Emissions were observed as high as 11.5 km altitude drifting NE later in the day; they continued drifting ENE at 7.9 km into the next day before dissipating 250 km from the summit. A new ash emission on 26 November rose to 10.9 km altitude. It was visible 300 km S of the summit while a second ash cloud was centered 150 km S at 5.2 km altitude. Later in the day, an ash emission was observed at 6.7 km drifting SW.

Figure (see Caption) Figure 87. An ash plume at Popocatépetl rises toward 9.1 km altitude on 25 November 2016 as viewed from CENAPRED'S Altzomoni WEBCAM, located about 10 km N of the summit. Courtesy of CENAPRED.

During 28-29 November 2016 there was another pulse of activity with 48 detected emissions. Beginning at 0559 on 28 November, water vapor, gas, and ash emissions became constant, rising as high as 1.5 km above the crater rim and drifting NE. Incandescent fragments were ejected 300-800 m from the crater, mainly onto the NE flank during the next night (figure 88). Ash fell in Atlixco, Chiautzingo (25 km NE), Domingo Arenas (22 km NE), Huejotzingo (27 km NE), Juan C. Bonilla (33 km NE), San Andrés Calpan (18 km NE), and San Martín Texmelucan (Puebla state, 35 km NNE), and in San Miguel (Tlaxcala state). Plumes from these emissions were reported on 29 November at 7.3 km altitude, and they drifted as far as 170 km NE; remnant ash was observed over the Gulf of Mexico on 30 November. Emission intensity increased again on 30 November and a new continuous plume at 6.4 km altitude extended 370 km NE before dissipating. At 1500 UTC on 30 November, a second higher plume was reported by the Washington VAAC at 9.3 km altitude centered 400 km NE of the summit. The continuous emissions became intermittent on 1 December; the last of the emissions dissipated about 200 km NE of the summit. A short puff noted on the webcam late on 1 December was the last VAAC report for 2016.

Figure (see Caption) Figure 88. Incandescent fragments were ejected 300-800 m onto the NE flank of Popocatépetl on 29 November 2016, as seen from the Tlamacas webcam located about 5 km N of the volcano. Courtesy of CENAPRED.

While ash emissions decreased during December 2016, steam-and-gas emissions continued, and thermal activity increased. MODVOLC alerts were reported 24 times on 17 different days. More substantial SO2 plumes than seen in previous months were also captured by the Aura satellite instrument on 8 and 31 December (figure 89). A new lava dome (71) first detected by CENAPRED on 29 and 30 November had almost completely filled the internal crater by 12 December (figure 90), reaching 280 m in diameter and 50 m thick. The volume of the dome was estimated to be about 3 million m3.

Figure (see Caption) Figure 89. The Aura Instrument on the OMI satellite captured substantial SO2 plumes from Popocatépetl on 8 (top) and 31 (bottom) December 2016. The plume on 8 December drifted NE for several hundred kilometers, and had a maximum DU (Dobson Unit) value of 6.02. The plume on 31 December drifted N and then NE a similar distance and recorded a DU value of 4.91. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 90. A new lava dome was photographed at the summit of Popocatépetl during an overflight on 12 December 2016. Courtesy of CENAPRED.

Activity during January-April 2017. Low-intensity steam-and-gas emissions continued during January 2017; incandescence was regularly observed at the summit. During January, only one emission was reported by the Washington VAAC, on 23 January at 7.6 km altitude drifting NW. They noted that the satellite imagery indicated the emission was mostly gas and water vapor with minor amounts of ash. Thermal activity continued to increase in January 2017 with 35 alerts reported on 26 days of the month. The increase in thermal activity was also visible in the MIROVA log radiative power information plotted from the MODIS thermal anomaly data (figure 91). SO2 plumes were also notable through 18 January, after which they decreased in both size and density in satellite data.

Figure (see Caption) Figure 91. MIROVA log radiative power data for Popocatépetl for the 12 months leading up to 4 August 2017. The increase in thermal activity beginning in late November 2016 corresponds to observations by CENAPRED of the growth of a new lava dome at the summit. Courtesy of MIROVA.

Ash emissions were reported on three days during February 2017. A plume on 7 February rose to 5.8 km altitude and drifted W, dissipating quickly. A plume on 12 February was reported at 6.1 km altitude drifting 10 km N of the summit. An ash emission was recorded on the CENAPRED webcam on 15 February (figure 92); it was seen in satellite imagery at 6.7 km altitude drifting NE, and dissipated after about six hours. Thermal activity decreased during February relative to January. MODVOLC only reported 16 thermal alerts on 11 days of the month.

Figure (see Caption) Figure 92. An ash emission from Popocatépetl on 15 February 2017 was later observed in satellite imagery at 6.7 km altitude drifting NE. Image taken by the Altzomoni webcam, located about 10 km N of the volcano. Courtesy of CENAPRED.

Continued steam-and-gas emissions during March 2017 were accompanied by a few ash-bearing explosions. The webcam captured an ash emission on 8 March that the Washington VAAC observed in satellite imagery drifting N at 5.8 km altitude. Another emission late on 11 March rose to 6.1 km and drifted E; it contained mostly gas with only small amounts of ash. Late on 28 March, an ash cloud was observed in satellite imagery centered about 50 km ENE of the summit at 5.8 km altitude. Thermal activity continued to decrease with only ten MODVOLC thermal alerts issued on six different days during March.

Thermal alerts were fewer still during April 2017; one appeared on 6 April, and then a cluster of six were reported during 24-30 April. Ash emissions were reported by the Washington VAAC on 16, 20, 24, and 25 April. Constant emissions were seen by the webcam on 16 April; they likely contained ash, and were estimated to be at 6.1 km altitude. A small puff of ash was seen in satellite imagery on 20 April drifting S to about 35 km at the same altitude. Multiple emissions of ash mixed with steam and gas were observed in satellite imagery on 24 April moving SE at 5.6 km altitude. Constant steam-and-gas emissions continued throughout the month, with incandescence visible on clear nights. Tephra from explosions on 26 and 27 April was ejected 100 m NE of the crater.

Activity during May-July 2017. Thermal activity increased somewhat during May 2017. Seventeen MODVOLC alerts were reported on 13 different days. SO2 emissions with DU values greater than two occurred eight times during the month. Low intensity explosions with water vapor, gas, and ash emissions occurred daily throughout the month. On 18 May, the Washington VAAC reported an ash plume at 7.3 km altitude drifting N, and they observed a bright hotspot in shortwave imagery. Multiple emissions were later observed, with plumes rising to 7.6 km, moving NNE 70 km from the summit. A small puff of ash was seen in satellite imagery on 21 May at 7 km altitude approximately 25 km from the summit moving N. The leading edge of a new emission was observed the next day about 45 km SSW of the summit at 6.1 km altitude. An ash emission was observed on the CENAPRED webcam on 30 May, but weather clouds obscured any satellite observations.

MODVOLC thermal alerts were reported on 6, 16, 17, 18(3) and 21 June 2017. Observers noted material being ejected 200 m from the crater on 3 June. Cloud cover obscured satellite and webcam views of a reported ash plume on 12 June. A small ash emission was reported on 13 June 16 km W of the summit at 7.0 km altitude.

A series of ash emissions were reported by the Washington VAAC almost daily during 2-11 July 2017. A social media post by CENAPRED and a webcam image showed an ash emission (figure 93) on 2 July. It was observed by the Washington VAAC in satellite imagery moving SW at 6.7 km altitude. Minor ashfall on 2 July was also noted in Ozumba (18 km W), Amecameca (19 km NW), Tlalmanalco (26 km NW), Chalco (38 km NW), Ayapango (22 km NW), Tenango del Aire (28 km NW), and San Pedro Nexapa (14 km NW). An emission on 3 July was confirmed in visible satellite imagery drifting WNW at 6.7 km altitude. On 4 July, a plume was observed in satellite imagery 25 km NE of the summit at 7.6 km altitude. An ash emission observed in the webcam early on 6 July was not visible in satellite imagery due to weather clouds, but a larger emission that evening was spotted with difficulty at 7.6 km altitude, in spite of the weather clouds. CENAPRED reported that the plume was clearly visible nearly 2 km above the summit. The next day, clouds obscured the summit from the webcam, but an ash emission was clearly visible in satellite imagery at 7.6 km altitude moving NW. The webcam recorded additional emissions on 9 and 11 July; they were obscured from satellite images by weather clouds. A plume of mostly gas and steam with a small amount of ash near the summit extended 55 km W of the summit on 31 July at 6.4 km altitude.

Figure (see Caption) Figure 93. An ash emission at Popocatépetl on 2 July 2017 as seen from the Altzomoni webcam, 10 km N of the volcano. Courtesy of CENAPRED.

MODVOLC thermal alerts were reported on 13-15, 21, 23 (2) and 28 July. Sulfur dioxide plumes with densities between one and two Dobson Units were captured by the Aura Instrument on the OMI satellite almost every day of the month.

Geologic Background. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Information Contacts: Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México D.F. 04360, México (URL: http://www.cenapred.gob.mx/), Daily Report Archive (URL: https://www.gob.mx/cenapred/archivo/articulos?order=DESC&page=1); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Sangeang Api (Indonesia) — September 2017 Citation iconCite this Report

Sangeang Api

Indonesia

8.2°S, 119.07°E; summit elev. 1912 m

All times are local (unless otherwise noted)


Weak Strombolian activity and occasional weak ash plumes, 15 July-12 August 2017

Strong explosions at Sangeang Api on 30-31 May 2014 generated ash plumes that rose as high as 15 km altitude, followed by less intense activity that produced ash plumes during the first half of June 2014 and 1 July-1 November 2015 (BGVN 41:10). No further activity was reported by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and Darwin Volcanic Ash Advisory Centre (VAAC) until June 2017.

The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected thermal anomalies in MODIS satellite data near the summit during the second week of January 2017, when four were recorded (figure 16). The number increased significantly beginning with the latter half of February. Another increase in the number and power of the anomalies took place at the beginning of June 2017 and continued into mid-August.

Figure (see Caption) Figure 16. Thermal anomalies identified by the MIROVA system (radiative power) at Sangeang Api for the year ending 11 August 2017. Note that the anomaly lines in late 2016 are not on the island. Courtesy of MIROVA.

Thermal anomalies identified using the MODVOLC algorithm were first recorded on 25 February 2017. Over the same time period as the MIROVA data, through 11 August, there were 105 thermal alerts. Cumulatively, the locations of the alert pixels define an area extending from the summit crater to about 2.5 km down the E flank (figure 17).

Figure (see Caption) Figure 17. Thermal anomalies (alert pixels) identified by the MODVOLC system at Sangeang Api for 25 February-11 August 2017. The eastern-most pixels are at the summit area. Courtesy of HIGP - MODVOLC Thermal Alerts System.

According to PVMBG, a small Strombolian eruption at 1154 on 15 July 2017 generated an ash plume that rose 100-200 m above the crater rim and drifted SW. Seismicity had increased starting in April. Based on analyses of satellite imagery, PVMBG observations, and wind data, the Darwin VAAC reported that on 16 July an ash plume rose to an altitude of 2.1 km, or 200 m above the crater rim, and drifted NW. The Darwin VAAC also reported ash plumes to altitudes of 2.4-4.3 km on 19-20 July, 29-30 July, 7-8 August, and 12 August 2017; in most cases they drifted NW.

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, Doro Api and 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/).

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

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

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

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



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

False Report of Mount Pinokis Eruption

Philippines

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


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

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

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

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

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


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

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

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

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Elgon (Uganda) — December 2005

Elgon

Uganda

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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