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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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Scientific Event Alert Network Bulletin - Volume 08, Number 04 (April 1983)

Managing Editor: Lindsay McClelland

Aira (Japan)

Explosion rate, seismicity decline; lapilli ejected

Arenal (Costa Rica)

Lava flows active on the NW flank

Asamayama (Japan)

Summit crater explosive eruption

Atmospheric Effects (1980-1989) (Unknown)

Stratospheric aerosols reduce solar radiation; high latitude aerosols sampled

Chichon, El (Mexico)

Crater lake recedes rapidly

Colima (Mexico)

Vapor emission from fumarole field; SO2 flux estimated

Concepcion (Nicaragua)

Strong ash eruption; no damage

Etna (Italy)

Lava effusion continues; central crater explosions; deformation, temperature and self-potential data

Ioto (Japan)

Earthquake swarm, two weak steam explosions

Irazu (Costa Rica)

Fumarolic activity on the NW flank

Kilauea (United States)

Lava effusion stops; low level harmonic tremor, local incandescence, and extension continue

Kusatsu-Shiranesan (Japan)

Small phreatic explosion; harmonic tremor

Langila (Papua New Guinea)

Six explosions, highest cloud to 8 km

Macdonald (Undersea Features)

Eighth known eruptive episode detected

Manam (Papua New Guinea)

Vapor emissions, detonations, glow, ashfalls

Masaya (Nicaragua)

Gas column and incandescence from lava lake

Michoacan-Guanajuato (Mexico)

Fumaroles emit acid gases

Momotombo (Nicaragua)

Fumarole temperatures continue to increase

Negro, Cerro (Nicaragua)

Gas column; fumarole hotter than in mid-1982

Niigata-Yakeyama (Japan)

Fresh ash on snow

Poas (Costa Rica)

Fumarole and crater lake temperatures increase

Ruapehu (New Zealand)

Crater lake green; low pH of river water

San Cristobal (Nicaragua)

Slow fumarole temperature increase; gas column

St. Helens (United States)

Intrusive and extrusive dome growth continue

Telica (Nicaragua)

Increased seismicity and fumarolic activity in February

Ulawun (Papua New Guinea)

Increased seismicity, including volcanic tremor

White Island (New Zealand)

Deflation ends



Aira (Japan) — April 1983 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Explosion rate, seismicity decline; lapilli ejected

The number of recorded explosions from the summit crater of Minami-dake declined to [36] in March and 22 in April. Observers saw lapilli ejected by about 1/4 of the explosions in March and 1/3 in April, but no damage was reported. The monthly number of recorded seismic events, including tremors, was 1,358 in March and 768 in April. On 2 March, rain-triggered debris flows in S and E flank valleys temporarily blocked a road.

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

Information Contacts: JMA, Tokyo.


Arenal (Costa Rica) — April 1983 Citation iconCite this Report

Arenal

Costa Rica

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

All times are local (unless otherwise noted)


Lava flows active on the NW flank

The lava flow that began to move down the NW flank in mid-November continued to advance very slowly. By 5 April, its front was at 700 m elevation, but it was being overridden by a new faster-moving flow (the 41st since 1968) which had reached 1,200 m elevation. Gas emission remained constant from the active crater.

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

Information Contacts: J. Barquero H., J. de Dios Segura, Univ. Nacional, Heredia.


Asamayama (Japan) — April 1983 Citation iconCite this Report

Asamayama

Japan

36.406°N, 138.523°E; summit elev. 2568 m

All times are local (unless otherwise noted)


Summit crater explosive eruption

JMA scientists have sent details of the explosive, summit crater eruption on 8 April. Local seismic activity had increased in mid-March, but returned to background level in late March. In early April, high-frequency B-type earthquakes and volcanic tremor were observed more frequently than usual (figure 7).

Figure (see Caption) Figure 7. Daily number of recorded volcanic tremor events (top) and B-type earthquakes (bottom) at Asama, January-April 1983. Courtesy of JMA.

The eruption began at 0159. The air shock (amplitude, 0.2 millibars) and eruption earthquake (amplitude, 125 µm) were recorded at the Karuizawa Weather [Station. JMA] personnel heard the thunder-like sound that accompanied the explosion, and observed the ejection of the incandescent tephra column. During the next 11 minutes, four more eruption earthquakes were recorded; seismic activity then declined rapidly. Only two volcanic earthquakes were recorded between the initial explosion and 0600, when most activity had ceased.

By 0450, when the summit was first visible from the [Weather Station], a 600-m-high, gray plume was being blown WSW from the summit. As the wind reversed during the eruption, ash was carried ENE (figure 8). Near Ko-Asama, a lava dome about 3 km E of the summit, 2.7 kg of tephra per m2 accumulated, including lapilli as large as 1 cm in diameter. By 0600 activity was limited to a 300 m-high vapor plume. No further explosions had been recorded by sunset. A forest fire started by the incandescent tephra on the S flank of Asama was extinguished by 0430.

Figure (see Caption) Figure 8. Area of ashfall from Asama, 8 April 1983. Courtesy of JMA.

After the eruption, seismic activity declined to below background levels. Only a few seismic events per day were recorded.

Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.

Information Contacts: JMA, Tokyo.


Atmospheric Effects (1980-1989) (Unknown) — April 1983 Citation iconCite this Report

Atmospheric Effects (1980-1989)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Stratospheric aerosols reduce solar radiation; high latitude aerosols sampled

Atmospheric scientists continued to monitor the stratospheric cloud ejected by El Chichón's March-April 1982 explosions. Poor weather plagued attempts to gather lidar data in Hawaii and Japan, but a few measurements were obtained. In Hawaii, declines were recorded in April for both peak and integrated backscatter, indicating decreases in the aerosol concentration within the densest layers and the cloud as a whole. In Japan, however, limited data showed a recovery of peak backscattering ratios to March levels, after a decline in early April.

Pyrheliometer data from Japan and Colorado show substantial reductions in direct solar radiation after the March-April 1982 injection of stratospheric aerosols. Japanese stations between 26.3°N and 43.3°N showed significant increases in turbidity and decreases in transmissivity since last autumn. These effects seemed to occur earlier at the southernmost station. Direct solar radiation first began to show a slight decline at Boulder, Colorado in July 1982 (about 2%) and was about 6% below the 1978 value in September (figure 2). The major decrease in direct solar radiation occurred in late October (around the 27th), with November and December 1982 having average values 13% and 20% less than the 1978 means. However, January-April 1983 data show increasing direct solar radiation, indicating a slow diminuition in cloud density over Boulder. Total radiation data (direct plus diffuse on a horizontal surface) show a much smaller effect. Changes to these data first became apparent in November with a decrease of slightly more than the 2% measurement/analytical noise, and the December 1982 values were about 3% below the December 1978 mean. Edwin Flowers noted that reductions in direct solar radiation caused by previous volcanic aerosol clouds were usually of short duration, interspersed with periods of normal transmission. However, once the effects of the El Chichón aerosols began to be observed, solar radiation values remained depressed, without periods of normal transmission, indicating the cloud's strong lateral uniformity.

Figure with caption Figure 2. Comparison of direct solar radiation (in watt-hours/m2) at Boulder, Colorado (40°N, 105.2°W) before and after the arrival of El Chichón aerosols. The dense cloud of H2SO4 droplets scatters sunlight, measureably reducing the amount that reaches the Earth's surface. Ratios (1982-83 divided by 1978-79 values) show little change before the appearance of a dense aerosol cloud over Colorado in late October 1982. A slight increase in direct solar radiation January-April 1983 suggests a slow diminution in aerosol density. The right-hand column shows the number of hours of measurement each month, 1982-83 and 1978-79 (left and right of slash, respectively). Courtesy of Edwin Flowers.

A cooperative NASA-NOAA effort, using real-time TOMS data from the Nimbus-7 polar orbiting satellite, identified episodes of tropospheric-stratospheric "folding" that brought stratospheric air to within 3 km of sea level in the arctic. During one of these events, on 23 March, a NOAA P3 Orion aircraft sampled stratospheric aerosols along the coast of Greenland on a flight between Thule (77.5°N, 69.3°W) and Söndre Strömfjord (67°N, 50.6°W). In 6 hours of sampling, mainly at about 4.5 km altitude, aerosols were collected with 9 different filter systems. Concentrations of 0.1 and 1.0 µm particles exceeded 2000/cm3 with occasional peak values to 5,000/cm3. These particles were predominantly droplets, probably of H2SO4. Larger (1-5 µm) fragmented particles were present in concentrations about 1/1000 of the smaller ones and were predominantly composed of Si, lesser amounts of Fe, and traces of Al. In scanning electron micrographs, these particles appeared similar to El Chichón ash collected on the ground shortly after the March-April 1982 explosions. Although the sampling system was designed to operate at 4.5 km altitude or lower, some aerosols were also collected at about 7.5 km, also in stratospheric air. Along with the droplets and fragmented particles, some NaCl was recovered, although in concentrations only 1/1,000-1/10,000 of the droplets. Salt had also been collected at 4.5 km, but Russell Schnell noted that at the lower altitude the source of the NaCl could have been sea water, extremely unlikely at 7.5 km. NaCl crystals were collected by NASA aircraft from the El Chichón cloud in April and May 1982. In tropospheric air, aerosol concentrations were 100/cm3 or less and included very few particles that looked volcanic.

H. H. Lamb reported increased evidence of stratospheric aerosols over Norwich, England. Since early March normal blue skies have been absent; clear sky colors range from milky blue at considerable distance from the sun to strongly increasing whiteness within 30°-50° of arc from the sun. Sky seen in gaps between clouds within 15°-30° of the sun has invariably been virtually white. During many evenings, particularly in March but continuing as of mid-April, the dominant sky color after sunset has been sepia brown to bronze. From Jeddah, Saudi Arabia, Edward Brooks occasionally observed bands of volcanic aerosols from late March through late April, although brilliant dawn and twilight colors were less frequent than in previous months. In addition to colors observed shortly before sunrise and shortly after sunset, caused by illumination of aerosols in the lower stratosphere, material higher in the stratosphere sometimes resulted in colors long before sunrise and after sunset. On 23 March, SSW-NNE bands of aerosols were visible to 7° altitude in the WSW sky around sunset, and faint SSE-NNW aerosol bands below 5° in the ENE were illuminated during a 2-stage dawn the next day. Many sunrises and sunsets in late March were pale to nearly colorless. A brilliant sunset 4 April was followed by a 2-stage dawn on the 5th. Although dawn colors were nearly absent 7 April, faint brown, narrow, closely-spaced N-S bands of volcanic aerosols were seen at 15° altitude in the E; a colorful dusk that evening was also accompanied by brown N-S-trending aerosols. More aerosol bands were visible the next morning. A dense haze, probably stratospheric, was visible early 9 April as were gray N-S bands of haze that evening, accompanying chalky-appearing dawn and dusk colors that extended to 30-35° altitude. Pale dawns and twilights were observed when cloud conditions permitted 10-15 April, but brilliant colors reappeared at sunset 16 April and bands of aerosols were present at 3° altitude late on the 18th and early on the 19th. Neither bright colors nor aerosol bands were observed from sunset 19 April through the 21st.

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

Information Contacts: R. Schnell, NOAA/GMCC; E. Flowers, NOAA; T. Yamauchi, JMA, Japan; T. Fujita, Meteorological Research Inst., Japan; M. Hirono, Kyushu Univ., Japan; T. DeFoor, MLO; E. Brooks, Saudi Arabia; H. Lamb, Univ. of East Anglia, England.


El Chichon (Mexico) — April 1983 Citation iconCite this Report

El Chichon

Mexico

17.36°N, 93.228°W; summit elev. 1150 m

All times are local (unless otherwise noted)


Crater lake recedes rapidly

UNAM geologists visited El Chichón 20-24 April. Fumarolic activity continued but there was no evidence of any recent ash ejection. Variations observed in the size of the fumarole plumes were thought to be caused by changes in temperature and humidity. Portable seismometers on the crater rim 21-23 April detected only two small events in 26 hours. The shore of the crater lake had receded 38 m (horizontally) since November 1982 (when the lake was roughly 500 m long, 300 m wide, and a maximum of 50 m deep), and about 30 m of the shrinkage had taken place since the previous measurements in January. Less than a week after geologists left the volcano major additional shrinkage of the lake was reported, and as of early May the lake occupied less than half the area it had covered 24 April. Pilots overflying the volcano were asked to report further changes in the lake, but no reports had been received as of 11 May. Data from a telemetering seismometer 16 km SSE of the volcano showed no change in seismicity through 4 May.

Geologic Background. El Chichón is a small, but powerful trachyandesitic tuff cone and lava dome complex that occupies an isolated part of the Chiapas region in SE México far from other Holocene volcanoes. Prior to 1982, this relatively unknown volcano was heavily forested and of no greater height than adjacent nonvolcanic peaks. The largest dome, the former summit of the volcano, was constructed within a 1.6 x 2 km summit crater created about 220,000 years ago. Two other large craters are located on the SW and SE flanks; a lava dome fills the SW crater, and an older dome is located on the NW flank. More than ten large explosive eruptions have occurred since the mid-Holocene. The powerful 1982 explosive eruptions of high-sulfur, anhydrite-bearing magma destroyed the summit lava dome and were accompanied by pyroclastic flows and surges that devastated an area extending about 8 km around the volcano. The eruptions created a new 1-km-wide, 300-m-deep crater that now contains an acidic crater lake.

Information Contacts: S. de la Cruz-Reyna, UNAM, México.


Colima (Mexico) — April 1983 Citation iconCite this Report

Colima

Mexico

19.514°N, 103.62°W; summit elev. 3850 m

All times are local (unless otherwise noted)


Vapor emission from fumarole field; SO2 flux estimated

"Colima was emitting a moderate-sized white plume when observed 25-28 April. Most of the plume came from the fumarole field on the NW side of the summit lava field. Temperatures were as high as 565°C in some instances. Preliminary estimates of SO2 flux suggest a rate of up to 100 t/d."

Geologic Background. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Information Contacts: R. Stoiber, L. Benton, C. Connor, D. Douglass, D. Shumway, and J. Swarts, Dartmouth College.


Concepcion (Nicaragua) — April 1983 Citation iconCite this Report

Concepcion

Nicaragua

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

All times are local (unless otherwise noted)


Strong ash eruption; no damage

At the beginning of March, earthquakes were recorded and unusually strong gas columns were observed. A strong ash eruption began on 15 March and continued until the 24th, but caused no damage. Earthquakes accompanied the activity, but there were very few compared to the usual seismicity at the volcano. The ash eruptions were smaller than those of 1977 (2:4).

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

Information Contacts: D. Fajardo B., INETER.


Etna (Italy) — April 1983 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Lava effusion continues; central crater explosions; deformation, temperature and self-potential data

The eruption was continuing as of 6 May. J. C. Tanguy noted that temperature station cables in the S part of the summit zone broke on 27 March between 0530 and 0946, probably because of the opening of the eruption fracture. Fissures extended S from 2,700 m (where two explosion vents formed on 31 March) to 2,450 m, then turned SSW along the trend of the 1910 eruption. Small hornitos and spatter cones formed between 2,450 and 2,350 m. The main effusive vent was at 2,280 m altitude. On 31 March, the temperature of lava at this vent was 1,067°C at 60 cm depth, and the same value was measured in the main flow 30-40 m downslope on 4 April. F. Mousnier-Lompre and G. Scarpinati recorded a lava temperature of 1,078°C on 1 May. J.B. Murray and A. Pullen reported that lava flow surface velocities measured 17-30 April were in the 1.17-3.41 m/s range. Using surface velocities, Murray and Pullen calculated an average effusion rate of 22 m3/s if flow thickness was 3 m and 44 m3/s if the thickness was 5 m.

Romolo Romano reported that lava flowed S and SW, forming a wide, complex field as much as 1 km across and 40 m thick. On the E side of the field, the fronts of the longest flows were about 6 km from the vent and reached 1,150 m altitude before stopping. On 23 April, the principal flow shifted to the W side of the field, and advanced to about 6.5 km from the vent, stopping at 1,100 m altitude only 30 m from a road. On 4 May the primary flow was again moving down the E side of the lava field and had reached 1,450 m altitude as of early 6 May. Lava flowed from the vent at about 2 m/s, a rate of about 10 m3/s, and had a temperature of about 1,030°C [but note 1,067° and 1,078° above]. The rate of advance of the flow fronts was quite variable and dependent on the gradient; estimated velocities ranged from a very few meters per hour to ~60 m/hour. The area covered by the lava was about 4 km2 on 6 May and the volume of lava emitted was ~40 x 106 m3.

Earlier in the eruption, small hornitos and spatter cones had formed above the main effusive vent and small quantities of lava fragments were ejected. Vapor emission continued from this portion of the eruption fissure but no lava fragment ejection has been noted since 10 April. Two explosion vents [not one as originally reported] at 2,700 m altitude ejected ash during the morning of 1 April [not 28 March as originally reported; Tanguy and Patané (1984), Frazzetta and Romano (1984)], but only vapor emission has been observed at this vent since then.

Throughout the eruption, ash was ejected at varying intensity from Bocca Nuova. More vigorous ash ejection 2-5 May sent plumes to 2 km above the crater and caused ashfalls on the mainland (Calabria coast) at least 60 km from the volcano. On 4 May, a polar orbiting satellite image showed the beginning of an ash emission episode at 0453. By the next image at 0606, a narrow plume extended nearly 1,000 km SE from Etna at an altitude of about 7.5 km. Venting was continuing at 0945 but the plume was smaller; at 1603, it was 100-150 km long. Another image, at 0705 on 6 May, showed a plume ~100 km long. From the Chasm, weak emission of gas that sometimes contained reddish ash has been observed during the eruption. In the Northeast and Southeast craters, eruptive activity was limited to weak fumarolic emissions, but new concentrations of large fractures were seen in these craters as well as small internal collapses.

Murray and Pullen reported that vertical ground deformation during 1981-82 was characterized by summit deflation and S flank inflation. Reoccupation of a precise leveling network 20-22 April 1983 showed large changes on the upper S flank (near Piccolo Rifugio) since September 1982: 42 cm of uplift W of the eruption fissure, 12 cm of uplift E of the fissure, and a drop of 126 cm on the fissure itself. Large and complex movements had occurred elsewhere, including deflation of 76 cm above the eruption fissure at about 2,900 m altitude (near Torre del Filosofo). Horizontal measurements across the fissure showed an E-W extension of 1.3 to 2 m since August 1981, with contraction of 17 cm and 6 cm at 500 m and 1 km W of the fissure. A network of 25 dry-tilt stations occupied 24-29 April 1983 showed no general inflation or deflation of the edifice since 1982.

Ground temperature measurements at 6 m depth on the S flank at 1,900 m altitude showed a strong increase in November 1982 (figure 10). In the summit zone, ground self-potential increased at roughly the same time and again in mid-January. A very steep rise occurred in early April, after the start of the eruption (figure 11). Immediately before the eruption a geophone in the S summit zone registered strong seismic activity, up to 134 events/hour during the morning of 27 March.

Figure (see Caption) Figure 10. Ground temperatures measured July 1982-March 1983 at 6 m depth, Silvestri station (closed circles) and Calcarazzi station (open circles), Etna's south rift zone, 1,900 m altitude.
Figure (see Caption) Figure 11. Ground self-potential (top), and temperature (bottom), at 120 cm depth, recorded at Vulcarolo station, south summit zone, 2,965 m altitude. Note that the very steep rise in self-potential occurred in early April, after the start of the eruption. Telemeasurements by ARGOS system.

Further References. Frazzetta, G., and Romano, R., 1984, The 1983 Etna eruption: event chronology and morphological evolution of the lava flow: BV, v. 47, p. 1079-1096.

Tanguy, J., and Patané, G., 1984, Activity of Mount Etna, 1977-1983: volcanic phenomena and accompanying seismic tremor: BV, v. 47, p. 965-976. (both in Barberi and Villari, eds., 1984, cited after 8:07)

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

Information Contacts: R. Romano, L. Villari, S. Gresta, and O. Consoli, IIV; J. Tanguy and J. Murray, PIRPSEV; A. Pullen, Imperial College; M. Matson, NOAA; C. Archambault and J. Stoschek, CNET, France; S. Scalia and G. Scarpinati, Acireale; J.Bartaire J. and N. Bartaire, St. Maur des Fossés; R. Cristofolini, M. Cosentino, G. Lombardo, G. Patanè, A. Viglianisi, and P. Villari, Ist. di Scienze della Terra, Catania; P. Mousnier-Lompré, Servizio Sismico Regionale.


Ioto (Japan) — April 1983 Citation iconCite this Report

Ioto

Japan

24.751°N, 141.289°E; summit elev. 169 m

All times are local (unless otherwise noted)


Earthquake swarm, two weak steam explosions

The National Research Center for Disaster Prevention reported that two weak steam explosions from Asodai Crater 28-29 November 1982 were associated with an earthquake swarm 25-30 November. Among the 1,492 recorded seismic events were 13 felt shocks. Before the swarm, the maximum number of recorded seismic events for a 5-day period had been 104. The earthquakes cracked roads in some places.

Geologic Background. Ioto (changed from Iwo-jima in 2007) in the central Volcano Islands portion of the Izu-Marianas arc lies within a 9-km-wide submarine caldera. Ioto, Iwo-jima, and Iojima are among many transliterations of the name. The volcano is also known as Ogasawara-Iojima to distinguish it from several other "Sulfur Island" volcanoes in Japan. The triangular, low-elevation, 8-km-long island narrows toward its SW tip and has produced trachyandesitic and trachytic rocks that are more alkalic than those of other Izu-Marianas arc volcanoes. The island has undergone dramatic uplift for at least the past 700 years accompanying resurgent doming of the caldera. A shoreline landed upon by Captain Cook's surveying crew in 1779 is now 40 m above sea level. The Motoyama plateau on the NE half of the island consists of submarine tuffs overlain by coral deposits and forms the island's high point. Many fumaroles are oriented along a NE-SW zone cutting through Motoyama. Numerous historical phreatic eruptions, many from vents on the west and NW sides of the island, have accompanied the remarkable uplift.

Information Contacts: JMA.


Irazu (Costa Rica) — April 1983 Citation iconCite this Report

Irazu

Costa Rica

9.979°N, 83.852°W; summit elev. 3432 m

All times are local (unless otherwise noted)


Fumarolic activity on the NW flank

Fumarolic activity continued on the NW flank, where temperatures oscillated between 74 and 81°C. The main crater and Diego de la Haya crater remained inactive.

Geologic Background. Irazú, one of Costa Rica's most active volcanoes, rises immediately E of the capital city of San José. The massive volcano covers an area of 500 km2 and is vegetated to within a few hundred meters of its broad flat-topped summit crater complex. At least 10 satellitic cones are located on its S flank. No lava flows have been identified since the eruption of the massive Cervantes lava flows from S-flank vents about 14,000 years ago, and all known Holocene eruptions have been explosive. The focus of eruptions at the summit crater complex has migrated to the W towards the historically active crater, which contains a small lake of variable size and color. Although eruptions may have occurred around the time of the Spanish conquest, the first well-documented historical eruption occurred in 1723, and frequent explosive eruptions have occurred since. Ashfall from the last major eruption during 1963-65 caused significant disruption to San José and surrounding areas.

Information Contacts: J. Barquero H. and J. de Dios Segura, Univ. Nacional, Heredia.


Kilauea (United States) — April 1983 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Lava effusion stops; low level harmonic tremor, local incandescence, and extension continue

"The third major episode of the E rift eruption ended at 0247 on 9 April. The initial activity was at a vent that erupted 28-30 March, producing an aa flow that extended nearly 5 km SE along the Hawaii Volcanoes National Park boundary. A vent about 2 km to the ENE in the same location as the source of the lava flow that entered the Royal Gardens subdivision during episode 2 erupted steadily from 29 March-9 April. Marked by two fountains that were the sources of flows that exited N and S, the vent was the locus of all April lava production. These fountains, and in particular the steadily active and more prominent N fountain that was commonly 100 m high and at times estimated to be 300 m high, were the source of tephra for construction of an 80-m-high cinder cone.

"From 29 March to the end of the eruption, a flow composed of aa locally more that 12 m thick advanced slowly about 3 km NE to the vicinity of Kalalua. Another flow moved SE between earlier flows of 7 January and 27 February-4 March. Lava production at the S fountain changed from sporadic to steady on 4 April and at least 3 lava flows were fed in succession during the remainder of episode 3. These flows were approximately 3.0, 1.5, and 7.2 km long. The advance of each of the first two apparently stopped when the lava stream feeding it was diverted to form the next. The fronts of these aa flows advanced at average rates of approximately 100 m/hour and at times faster than 200 m/hour through gently sloping rain forests. The last and longest of the 3 flows began its advance on 6 April. It entered Royal Gardens subdivision on 8 April and destroyed 6 structures before the eruption stopped early on 9 April. Near the end of the eruption the flow front reached a velocity of 6 m/minute as the narrow and elongate terminus, centered on a subdivision street, advanced down a steep slope. Decemberelerating advance of the flow front continued through at least 11 April.

"January-April lava covered about 15 km2, approximately double the 7 km2 that had been covered by the end of episode 2 on 4 March (figure 17). As a preliminary estimate, a minimum of 50 x 106 m3 of lava had been extruded since eruptive activity began on 3 January. The most recent basalt is megascopically identical to the earlier lava. It is slightly porphyritic with scattered small phenocrysts of plagioclase and olivine. This, as well as continued relatively low lava temperatures (1,112-1,129°C) and unchanged composition of eruptive gases, implied that stored E rift magma had remained as the source for all January-April 1983 lava.

"The summit (Uwekahuna) water tube tiltmeter recorded nearly 30 µrad of decreasing tilt related to subsidence during the third episode of the eruption (figure 18). Since the beginning of intrusive/eruptive activity on 2 January, the cumulative tilt decrease was nearly 200 µrad, suggesting a net volume loss in the summit area of at least 80 x 106 m3. Harmonic tremor decreased significantly when lava fountaining stopped. As of 10 May, tremor continued at a very low level in the general area of the recently active vents.

"Although hot gases of magmatic origin were becoming progressively less concentrated and more oxidized, they continued to be emitted from the recently active part of the fissure system. Local but decreasing incandescence also continued. These observations combined with the observations of persistent low tremor and minor extension across the fissure system (10 mm of extension had occurred by 29 April on a survey line established 8 days earlier) suggested that the feeder system was still active and renewal of eruptive activity was possible."

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

Information Contacts: E. Wolfe, A. Okamura, R. Koyanagi, and S. Brantley, HVO; UPI.


Kusatsu-Shiranesan (Japan) — April 1983 Citation iconCite this Report

Kusatsu-Shiranesan

Japan

36.618°N, 138.528°E; summit elev. 2165 m

All times are local (unless otherwise noted)


Small phreatic explosion; harmonic tremor

. . . Local seismicity had declined after the December activity, but increased in early January (see table 1), when 91 volcanic earthquakes and 44 tremor events were recorded. After mid-January no tremor events were recorded, but the number of volcanic earthquakes was greater than background level in early March.

At 0459 on 9 March the seismograph at Maebashi District Meteorological Observatory recorded a swarm of volcanic earthquakes that lasted only a few minutes. JMA scientists noted that these earthquakes were similar in wave form to those recorded during previous eruptions. . . . In April, activity was limited to occasional white vapor ejections. On 10 April, one vapor plume rose to 60 m above Yugama Crater. Volcanic tremor, possibly accompanied by vapor ejections, was observed 9-12 and 19-20 April.

Geologic Background. The Kusatsu-Shiranesan complex, located immediately north of Asama volcano, consists of a series of overlapping pyroclastic cones and three crater lakes. The andesitic-to-dacitic volcano was formed in three eruptive stages beginning in the early to mid-Pleistocene. The Pleistocene Oshi pyroclastic flow produced extensive welded tuffs and non-welded pumice that covers much of the E, S, and SW flanks. The latest eruptive stage began about 14,000 years ago. Historical eruptions have consisted of phreatic explosions from the acidic crater lakes or their margins. Fumaroles and hot springs that dot the flanks have strongly acidified many rivers draining from the volcano. The crater was the site of active sulfur mining for many years during the 19th and 20th centuries.

Information Contacts: JMA, Tokyo.


Langila (Papua New Guinea) — April 1983 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)


Six explosions, highest cloud to 8 km

"A generally low level of activity prevailed during April. However, Crater 2 produced some discrete Vulcanian explosions (table 1). The explosion on the 18th was witnessed from an aircraft about 70 km away. The eruption cloud rose steadily for about 15 minutes, then began spreading at its top to become mushroom-shaped. Weak emissions of grey ash clouds were also reported on 8, 14, 20, 21, and 29 April. Crater 3 was quiet for most of the month, releasing weak white vapour, although grey emissions were reported on 21 and 26 April. On the 30th a Vulcanian explosion sent ash and vapour to a height of about 3 km. Seismic activity was generally at a low level, with occasional explosion earthquakes."

Table 1. Heights of Vulcanian explosion columns above Crater 2 at Langila, April 1983.

Date Column Height (km)
09 Apr 1983 0.3
10 Apr 1983 0.3
15 Apr 1983 3.0
18 Apr 1983 8.0
26 Apr 1983 5.0

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: C. McKee, RVO.


Macdonald (Undersea Features) — April 1983 Citation iconCite this Report

Macdonald

Undersea Features

28.98°S, 140.25°W; summit elev. -39 m

All times are local (unless otherwise noted)


Eighth known eruptive episode detected

On 14 March, four RSP stations recorded acoustic waves (T-phase) from activity interpreted as a shallow submarine eruption at Macdonald Seamount. The signals were received at Moorea, Vaihoa on Rangiroa, Tubuai, and Rikitea in the Gambier Islands. Strong explosive signals began at 0914, and were followed by continuous noise of varying intensity. The activity began in the same manner as the seven previous eruptions, and was probably comparable in strength and development to that of February 1981. However, high background noise levels caused by the passage of Cyclone Reva over Polynesia made interpretation difficult.

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

Information Contacts: J. Talandier, Lab. de Géophysique, Tahiti.


Manam (Papua New Guinea) — April 1983 Citation iconCite this Report

Manam

Papua New Guinea

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

All times are local (unless otherwise noted)


Vapor emissions, detonations, glow, ashfalls

"A slight intensification of the ongoing mild eruptive activity was evident in April. Increased seismicity and continuous, voluminous blue vapour emissions occurred at both summit craters from mid-month. Both craters continued to emit pale grey or brown ash clouds that reached maximum heights of about 1000 m above the summit. Emissions from Southern crater were accompanied by sharp detonations, booming, and rumbling of varying intensities, at intervals of 5-25 minutes. Similar sound effects from Main crater were occasionally heard.

"Southern crater glow was seen on most nights in the month, although a hiatus occurred 14-16 April. Ejections of incandescent lava that reached maximum heights of about 250 m above the crater were seen on about 30% of nights. Weak or fluctuating Main crater glow was observed 5-8 and 14-19 April. Ashfalls were recorded in coastal areas, about 5 km from the summit, on about 35% of days.

"No significant tilt changes were recorded in April, but seismicity showed a mild intensification. Seismic amplitudes increased near the beginning of the month and remained double normal size. Daily earthquake totals varied from 2500 at the beginning and end of the month to a peak of 3500 on 23 April."

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

Information Contacts: C. McKee, RVO.


Masaya (Nicaragua) — April 1983 Citation iconCite this Report

Masaya

Nicaragua

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

All times are local (unless otherwise noted)


Gas column and incandescence from lava lake

A strong gas column was observed. Through 9 March, incandescence was noted.

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

Information Contacts: D. Fajardo B., INETER.


Michoacan-Guanajuato (Mexico) — April 1983 Citation iconCite this Report

Michoacan-Guanajuato

Mexico

19.85°N, 101.75°W; summit elev. 3860 m

All times are local (unless otherwise noted)


Fumaroles emit acid gases

"Fumaroles at several localities were emitting small amounts of acid gases but there was no visible plume at the summit or elsewhere when visited 28 April-1 May. Temperatures were mostly less than 150°C but some were much hotter, over 400°C."

Geologic Background. The widespread Michoacán-Guanajuato volcanic field contains over 1400 vents, including the historically active cinder cones of Parícutin and Jorullo, covering a 200 x 250 km wide area of Michoacán and Guanajuato states in west-central México. Cinder cones are the predominant volcanic form, but small shield volcanoes, lava domes, maars and tuff rings (many in the Valle de Santiago area), and coneless lava flows are also present. The shield volcanoes are mostly Pleistocene in age, and have morphologies similar to small Icelandic-type shield volcanoes, although the Michoacán-Guanajuato shields have higher slope angles and smaller basal diameters. Jorullo, which was constructed in the 18th century, and Parícutin, which grew above a former cornfield during 1943-52, are the two best known of the roughly 1000 small volcanic centers scattered throughout the volcanic field.

Information Contacts: R. Stoiber, L. Benton, C. Connor, D. Douglass, D. Shumway, and J. Swartz, Dartmouth College.


Momotombo (Nicaragua) — April 1983 Citation iconCite this Report

Momotombo

Nicaragua

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

All times are local (unless otherwise noted)


Fumarole temperatures continue to increase

Fumarolic activity increased over that of 1981, especially in the S part of the crater. Temperatures continued to increase, reaching 855°C in March . . . . Seismographs recorded magmatic movement but no discrete earthquakes.

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

Information Contacts: D. Fajardo B., INETER.


Cerro Negro (Nicaragua) — April 1983 Citation iconCite this Report

Cerro Negro

Nicaragua

12.506°N, 86.702°W; summit elev. 728 m

All times are local (unless otherwise noted)


Gas column; fumarole hotter than in mid-1982

A small column of gases was observed in March, but there was no seismic activity. A fumarole temperature of 337°C was measured, 17° higher than in mid-1982.

Geologic Background. Nicaragua's youngest volcano, Cerro Negro, was created following an eruption that began in April 1850 about 2 km NW of the summit of Las Pilas volcano. It is the largest, southernmost, and most recent of a group of four youthful cinder cones constructed along a NNW-SSE-trending line in the central Marrabios Range. Strombolian-to-subplinian eruptions at intervals of a few years to several decades have constructed a roughly 250-m-high basaltic cone and an associated lava field constrained by topography to extend primarily NE and SW. Cone and crater morphology have varied significantly during its short eruptive history. Although it lies in a relatively unpopulated area, occasional heavy ashfalls have damaged crops and buildings.

Information Contacts: D. Fajardo B., INETER.


Niigata-Yakeyama (Japan) — April 1983 Citation iconCite this Report

Niigata-Yakeyama

Japan

36.921°N, 138.036°E; summit elev. 2400 m

All times are local (unless otherwise noted)


Fresh ash on snow

On the morning of 15 April, a local resident noticed gray-tinted snow on the N flank and a plume near the summit area. On 18 April, a joint observation team from the firehouse, the district forestry office, and the city office of [Itoigawa] (20 km NE of the volcano), visited the summit area and found that ash had fallen on the snow over the N flank. Analysis of an ash sample at Niigata University showed that the ash was not freshly magmatic, but was composed of fragmented old rock that contained mainly plagioclase, amphibole, and pyroxene phenocrysts. No seismic activity was recorded, but no JMA seismograph is installed within 30 km of the volcano.

The volcano is a 400-m-high lava dome that rests on 2,000-m-high mountains underlain by sedimentary rock. During its last eruption, a phreatic explosion from fissures in the N and W flanks [near the summit] on 28 July 1974, three climbers were killed by ejecta, ash fell as far as 100 km to the NE damaging about 220 km2 of farmland, and two mudflows descended the N flank.

Geologic Background. Niigata-Yakeyama, one of several Japanese volcanoes named Yakeyama ("Burning Mountain"), is a very young andesitic-to-dacitic lava dome in Niigata prefecture in central Honshu, near the Japan Sea. The small volcano rises to 2400 m and was constructed on a base of Tertiary mountains 2000 m high beginning about 3100 years ago. Three major magmatic eruptions took place in historical time, producing pyroclastic flows and surges and lava flows that traveled mainly down the Hayakawa river valley to the north and NW. The first of these eruptions took place about 1000 years ago (in 887 and possibly 989 CE) and produced the Hayakawa pyroclastic flow, which traveled about 20 km to reach the Japan Sea, and the massive Mae-yama lava flow, which traveled about 6.5 km down the Hayakawa river valley. The summit lava dome was emplaced during the 1361 eruption, and the last magmatic eruption took place in 1773 CE. Eruptive activity since 1773 has consisted of relatively minor phreatic explosions from several radial fissures and explosion craters that cut the summit and flanks of the dome.

Information Contacts: JMA, Tokyo.


Poas (Costa Rica) — April 1983 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Fumarole and crater lake temperatures increase

Fumarolic activity continued from the eroded cone formed during the 1953-55 eruption. Fumarole and crater lake temperatures generally increased through the 5-month period (see table 3). The water level in the lake has dropped 5 m during the current dry season. The lake's pH was 0.2.

Geologic Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: J. Barquero H. and J. de Dios Segura, Univ. Nacional, Heredia.


Ruapehu (New Zealand) — April 1983 Citation iconCite this Report

Ruapehu

New Zealand

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

All times are local (unless otherwise noted)


Crater lake green; low pH of river water

When W.W. Chadwick visited the volcano on 18 April, the lake was mostly green, with extensive floating yellow and gray sulfur slicks. Minor upwelling, marked by a light gray patch, was occurring over the N vents; none was observed over the central vent. There was no evidence of recent eruptions or surging. Lake temperature measured at the outlet was 20°C, 3° lower than on the previous visit, 17 March. . . .

On 25 March the New Zealand Railways Communications Section, Taumaranui, reported an abnormally low pH for the Whangaehu River, which drains Crater Lake. Records showed a pH of 3.5 on 3 March, 4.0 on 11 March, 3.5 on 18 March, but 1.5 on 25 March. Chadwick interpreted the data as showing that Crater Lake was overflowing continuously during March and that a substantial increase in flow occurred toward the end of the month.

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

Information Contacts: W. Chadwick, NZGS, Wairakei.


San Cristobal (Nicaragua) — April 1983 Citation iconCite this Report

San Cristobal

Nicaragua

12.702°N, 87.004°W; summit elev. 1745 m

All times are local (unless otherwise noted)


Slow fumarole temperature increase; gas column

Temperatures continued to increase slowly, to 620°C on 2 February. A strong gas column was blown W. New N-S-trending fissures were observed. During February, 13-14 seismic events were recorded per day, but could only be detected by very sensitive instruments.

Geologic Background. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Information Contacts: D. Fajardo B., INETER.


St. Helens (United States) — April 1983 Citation iconCite this Report

St. Helens

United States

46.2°N, 122.18°W; summit elev. 2549 m

All times are local (unless otherwise noted)


Intrusive and extrusive dome growth continue

Since early February, growth of the composite lava dome has been essentially continuous. Accelerating outward movement of the dome had preceded previous extrusion episodes, but stopped as lava reached the surface. However, substantial endogenous growth has continued throughout the current episode. Poor weather continued to hamper observations.

About 1 April, a broad stubby spine began to emerge at roughly 1 m/day from the center of the February lobe, reaching 30 m in N-S dimension, 20 m E-W, and about 25 m in height. Growth of this spine stopped about 15 April, and extrusion of another spine started about 70 m to the SE. The latter spine remained active until about 27 April, when at 60 m height it was the highest point on the dome and roughly the same size as the now-toppled February spine (SEAN 08:02). Between visits to the crater 29 April and 4 May a new lobe began to grow high on the NE flank of the February lobe. This lava had a typical "spreading center" source and scoriaceous carapace. Extrusion continued as of 11 May, but the growth rate was slow and the lobe remained several times smaller than previous ones.

Dramatic deformation has continued on the E and particularly the NE sector of the dome since early-mid March. Because of frequent rockfalls, it was difficult to maintain targets on these areas of the dome, but rates of displacement reached 1.5 m/day, and averaged about 1 m/day over roughly 1-week periods. Between measurements 4 and 11 May, the NE margin of the dome moved 9 m outward and 2.5 m downward. Deformation on the N side of the dome was limited, but significant rate changes were observed. Through March the rate was constant at about 1.5 cm/day, but dropped to about 1 cm/day around 1 April as spine growth started. Deformation slowed further to 7-8 mm/day around the 15th as growth of one spine stopped and extrusion of another began, but returned to about 1 cm/day at the end of the month and remained at that rate as of 11 May. The W side of the dome, site of the most rapid deformation before many previous extrusion episodes, remained quite stable. No significant deformation of the edifice as a whole was detected.

Vapor and tephra emissions continued from the main vent near the source area of the February lobe but were relatively infrequent, occurring one to three times per day. Blocks up to 30 cm in diameter were ejected. Tephra could often be seen in the plumes, which sometimes rose to 1 km above the crater rim; the largest, 18 April at 1259, reached 6 km altitude. There was no apparent correlation between plume emissions and changes in extrusive activity or deformation.

SO2 emission remained at roughly 150 t/d until about 27 April, when it dropped to 60-90 t/d. A similar rate was measured 30 April and 4 May, but SO2 emission returned to 150 t/d 11 May.

Seismic activity remained elevated through April. All but nine of the 243 events with locatable foci were of low-frequency with emergent onsets, a similar pattern to that seen in March. Between 1 and 12 April, daily earthquake totals commonly ranged from four to eight, increased to eight to twelve events per day 13-24 April, then dropped slightly to an average of eight per day through the end of the month. Surface and avalanche events showed a similar pattern. Numerous gas-emission events were recorded. Many began with a series of high-amplitude events that ended within a few minutes or gradually faded into brief periods of harmonic tremor. About 20 April, sequences of tiny discrete similar events, previously seen in February (SEAN 08:02), reappeared on one seismometer, but these events could not be located and their significance remained uncertain. The start of extrusion of a new lobe of lava between visits to the crater 29 April and 4 May was not marked by an obvious change in seismicity. Geologists working in the crater 11 May heard loud but relatively small earthquakes, which had not been audible during previous extrusion episodes.

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

Information Contacts: D. Swanson, T. Casadevall, USGS CVO, Vancouver, WA; S. Malone, University of Washington.


Telica (Nicaragua) — April 1983 Citation iconCite this Report

Telica

Nicaragua

12.606°N, 86.84°W; summit elev. 1036 m

All times are local (unless otherwise noted)


Increased seismicity and fumarolic activity in February

After a tephra eruption ended 1 March 1982, seismicity returned to normal. Through November 1982 about 14 events were recorded per day. On 10 February 1983 a portable seismograph installed on the flank recorded 66 earthquakes. This increase was paralleled by stronger fumarolic activity on the S, SE, and SW part of the volcano.

Geologic Background. Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Information Contacts: D. Fajardo B., INETER.


Ulawun (Papua New Guinea) — April 1983 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Increased seismicity, including volcanic tremor

"Intriguing seismicity, possibly indicating an eruption in the near future, continued in April and included periods of volcanic tremor. Amplitudes of discrete events were generally low, although a degree of cyclicity in amplitudes was apparent, with a period of about 8-11 days. Daily earthquake totals increased from about 600 to about 1,500.

"After the 21-23 March seismic crisis, Ulawun's seismicity showed a fairly steady decay, reaching a very low level in early April. One clear A-type event was recorded on 7 April. A new seismic crisis, preceded by a lull about 2 hours long, began on 10 April at about 0310. The initial, strong continuous tremor changed to discontinuous tremor within a few hours. The entire period of tremor lasted about 6 hours. After this crisis, a steady decline was evident until 17 April. Small A-type events were recorded 11-16 April.

"On 17 April, 5 periods of tremor occurred. After about 3 hours of very low seismicity, the first began at 1645. A distinct lull also preceded the third period. Tremor was mostly continuous, with total duration of about 280 minutes. Individual periods lasted about 29-106 minutes, and were followed by about 5 hours of frequent discrete shocks and discontinuous tremor. Beginning 18 April a gradual decay in amplitude and frequency of occurrence of the shocks was recorded. Possible small A-type events were recorded 20-29 April.

"No unusual visible activity directly accompanied the seismic crisis. However, ejection of one or more smoke rings, seen to rise rapidly to about 500 m above the summit, was reported 11-18 April. Blue vapour emission was seen 14 April. Ulawun's usual white vapour emissions were moderate to strong throughout the month, but increased toward the end."

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the N coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1,000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: C. McKee, RVO.


White Island (New Zealand) — April 1983 Citation iconCite this Report

White Island

New Zealand

37.52°S, 177.18°E; summit elev. 321 m

All times are local (unless otherwise noted)


Deflation ends

When NZGS personnel visited the island on 14 April, they observed few differences in 1978 Crater. The small green ponds present during the previous visit on 22 March had enlarged and merged to cover 60-70% of the crater floor. Color ranged from orange adjacent to the fumaroles to lime green. Fumarolic activity continued on the W wall and up the NW-trending gully system. Activity at Donald Mound appeared to have declined, but no fumarole temperatures were measured. Very small changes in tilt were recorded: +8 mm about 150 m W of Donald Mound, and +9 mm about 100 m N of it. The NZGS noted that these changes indicated an end to the deflation of the Donald Mound area recorded between November 1982 and January 1983 (figure 8).

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

Information Contacts: P. Otway, NZGS, Waikarei; B. Scott, NZGS, Rotorua; G. Sorrell, DSIR, Wellington.

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

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

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (SEAN 30:12) Elgon

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



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

False Report of Mount Pinokis Eruption

Philippines

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


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

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

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

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

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


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

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

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

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Elgon (Uganda) — December 2005

Elgon

Uganda

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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