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Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information is preliminary at time of publication and subject to change.


Recently Published Bulletin Reports

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

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

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

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

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

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

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

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

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

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

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

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



Aira (Japan) — July 2019 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


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

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

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

Table 21. Monthly summary of eruptive events recorded at Sakurajima's Minamidake crater in Aira caldera, January-June 2019. The number of events that were explosive in nature are in parentheses. No events were recorded at the Showa crater during this time. Data courtesy of JMA (January to June 2019 monthly reports).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Mike Day, Minnesota, Twitter (URL: https://twitter.com/MikeDaySMM, photo at https://twitter.com/MikeDaySMM/status/1083489400451989505/photo/1); Kratü, Twitter (URL: https://twitter.com/TalesOfKratue, photo at https://twitter.com/TalesOfKratue/status/1101469595414589441/photo/1); Tim Board, Japan, Twitter (URL: https://twitter.com/Hawkworld_, photo at https://twitter.com/Hawkworld_/status/1107789108754038789); Aone Wakatsuke, Twitter (URL: https://twitter.com/AoneWakatsuki, photo at https://twitter.com/AoneWakatsuki/status/1138420031258210305/photo/3).


Agung (Indonesia) — June 2019 Citation iconCite this Report

Agung

Indonesia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); The Jakarta Post, Mount Agung eruption disrupts Australian flights, (URL: https://www.thejakartapost.com/news/2019/05/25/mount-agung-eruption-disrupts-australian-flights.html); PunapiBali (URL: http://punapibali.com/, Twitter: https://twitter.com/punapibali, image at https://twitter.com/punapibali/status/1098869352588288000/photo/1); Jamie S. Sincioco, Phillipines (URL: Twitter: https://twitter.com/jaimessincioco. Image at https://twitter.com/jaimessincioco/status/1113765842557104130/photo/1); Pantau.com (URL: https://www.pantau.com/berita/erupsi-gunung-agung-sebagian-wilayah-bali-terpapar-hujan-abu?utm_source=dlvr.it&utm_medium=twitter); Volcanoverse (URL: https://www.youtube.com/channel/UCi3T_esus8Sr9I-3W5teVQQ); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN ).


Kerinci (Indonesia) — June 2019 Citation iconCite this Report

Kerinci

Indonesia

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

All times are local (unless otherwise noted)


Intermittent explosions with ash plumes, February-May 2019.

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

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

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

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

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

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

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

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Nuansa Jambi, Informasi Utama Jambi: (URL: https://nuansajambi.com/2019/03/20/gunung-kerinci-semburkan-asap-tebal/); Kerinci Time (URL: https://kerincitime.co.id/gunung-kerinci-semburkan-abu-vulkanik.html); Uzone.id (URL: https://news.uzone.id/gunung-kerinci-erupsi-5-desa-tertutup-abu-tebal).


Suwanosejima (Japan) — July 2019 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Small ash plumes continued during January through June 2019

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

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

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

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

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

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

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

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

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


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

Great Sitkin

United States

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

All times are local (unless otherwise noted)


Small steam explosions in early June 2019

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

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

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

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

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

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


Ibu (Indonesia) — July 2019 Citation iconCite this Report

Ibu

Indonesia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


Ebeko (Russia) — July 2019 Citation iconCite this Report

Ebeko

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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


Klyuchevskoy (Russia) — July 2019 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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


Yasur (Vanuatu) — June 2019 Citation iconCite this Report

Yasur

Vanuatu

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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


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

Bagana

Papua New Guinea

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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


Ambae (Vanuatu) — June 2019 Citation iconCite this Report

Ambae

Vanuatu

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

All times are local (unless otherwise noted)


Declining thermal activity and no explosions during February-May 2019

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

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

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

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

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


Sangay (Ecuador) — July 2019 Citation iconCite this Report

Sangay

Ecuador

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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Bulletin of the Global Volcanism Network - Volume 28, Number 02 (February 2003)

Managing Editor: Edward Venzke

Barren Island (India)

Fumarolic activity noted during fieldwork in February

Deception Island (Antarctica)

Fumarole temperatures stable during 2000-2002; sulfur dioxide detected

Etna (Italy)

Petrographic and geochemical comparison of 2001 and 2002 lavas

Fournaise, Piton de la (France)

Infrared data from November-December 2002 eruption

Galeras (Colombia)

Phreatic explosion in June 2002; increased long-period seismicity in late 2002

Klyuchevskoy (Russia)

Seismicity above background levels; explosion and thermal anomaly

Lengai, Ol Doinyo (Tanzania)

Continuing lava flows and vent activity in late December 2002

Monowai (New Zealand)

Volcanic earthquake swarm during 1-24 November eruption

Montagu Island (United Kingdom)

Satellite data provide first evidence of Holocene eruptive activity

Nyiragongo (DR Congo)

Aftershocks, lava lake, SO2 fumes, acidic rains, and highly fluorinated water

Popocatepetl (Mexico)

Cycles of dome growth and destruction; continuing explosive activity

Reventador (Ecuador)

Ashfall in January, mudflows in February-March; additional data from November

Ruapehu (New Zealand)

Volcanic tremor episodes and Crater Lake temperature variations

Saunders (United Kingdom)

Lava lake detected in satellite imagery during 1995-2002

Sheveluch (Russia)

Continued lava dome growth, short-lived explosions, and seismicity

Soufriere Hills (United Kingdom)

Continued dome growth, rockfalls, and pyroclastic flows

White Island (New Zealand)

Increased SO2 emissions since December, mud ejections in February



Barren Island (India) — February 2003 Citation iconCite this Report

Barren Island

India

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

All times are local (unless otherwise noted)


Fumarolic activity noted during fieldwork in February

A team of scientists from India and Italy carried out detailed geological, volcanological, geochemical, and geothermal investigations on Barren Island (figures 4 and 5) during 3-6 February 2003. The scientific team, led by Dornadula Chandrasekharam, included Piero Manetti, Orlando Vaselli, Bruno Capaccioni, and Mohammad Ayaz Alam. The Indian Coast Guard vessel CGS Lakshmi Bai carried the team from Port Blair on 3 February 2003; the journey takes ~5-6 hours depending on sea conditions. Because of the great depths around the island, it is not possible to anchor, so the team was ferried to the island in a small rubber boat. After the ship returned on the morning of 6 February, a trip around the island was made to see the steep seaward face of the prehistoric caldera wall.

Figure (see Caption) Figure 4. Barren Island as seen from the vessel CGS Lakshmi Bai on 3 February 2003. Courtesy of D. Chandrasekharam and others.
Figure (see Caption) Figure 5. Preliminary sketch map of Barren Island. Courtesy of D. Chandrasekharam and others.

The volcano consists of a caldera, which opens towards the W, with a central polygenetic vent enclosing at least five nested tuff cones. Two spatter cones are located on the W and SE flanks of the central cone (figure 6).

Figure (see Caption) Figure 6. A spatter cone on the SW flank of the central cinder cone at Barren Island around 3 February 2003. Courtesy of D. Chandrasekharam and others.

An eruption in 1991 ended more than 200 years of quiescence. Another eruption in 1994-95 left two spatter cones on its SE and W flanks. From these vents two aa lava flows poured out, both reaching the sea, during two distinct eruptive phases separated by ashfall. The lava flow created a delta into the sea (figure 7). There has been no documented eruptive activity since 1995, but Indian Coast Guards informed the team of renewed activity (strong gas and possible lava emission) in January 2000. The volcano currently exhibits continuing fumarolic activity. Steaming ground was visible at numerous places on the island.

Figure (see Caption) Figure 7. Lava from the 1994-95 eruptions on Barren Island formed a tongue that reached the sea. Courtesy of D. Chandrasekharam and others.

On 5 February the team climbed the summit of the central cinder cone that showed strongly fumarolic (but not presently active) areas with layers of sulfur deposits (figure 8). The ascent to the crater was relatively difficult since the material on the very steep slope was loose (figure 9). Neither magma nor gas emissions were observed within the craters of the different cones. From the middle to the upper part of the W cone, the ground temperature was relatively high (>40°C), and steaming ground was visible at different sites. Fumarolic activity, with temperatures up to 101°C, was mainly concentrated along the upper crater wall of the SW cone. Blue fumes (indicative of SO2) and the aroma of acidic gases such as HCl were not recorded.

Figure (see Caption) Figure 8. Fumarolic deposit on top of the central cinder cone at Barren Island on 5 February 2003. Courtesy of D. Chandrasekharam and others.
Figure (see Caption) Figure 9. Central cinder cone showing steep slopes at Barren Island on 5 February 2003. Courtesy of D. Chandrasekharam and others.

The pre-caldera deposits were characterized by more than five lava flows (prehistoric?) separated by scoria-fall beds and minor ash, tuff, and cinder deposits. The lava flows varied in thickness from 2 to 3 m, whereas the pyroclastic layers vary in thickness from 1 to 4 m. These lava flows could be clearly seen towards the N part of the main caldera. Towards the SE part of the inner caldera a 5-m-wide, NNE-SSW trending dike was observed. This feeder dike was fine-to-medium grained and contains buff-colored olivine, green pyroxene, and plagioclase phenocrysts. The N and NW part of the caldera has been mantled by a ~50-m-thick sequence of breccias and tuff representing syn/post-caldera phreatic and hydromagmatic activity, whereas the products of a small littoral cone occured mainly towards the W side. The lava flows of the main caldera were highly porphyritic with phenocrysts of green pyroxene (~3 cm) and plagioclase feldspars. Several steam vents could be seen within the 1994-95 lava flows. Some of these vents exhibited a lack of steam emanations at the time of the visit.

The outer and part of the inner caldera contains thick vegetation, which escaped the fury of the recent eruptions. Feral goats and rats dominate the island. Two fresh-water springs were discovered towards the SE part of the caldera. This is possibly the fresh water source for the goats living in this island. Chemical analysis indicates that the water from the springs is potable.

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

Information Contacts: Dornadula Chandrasekharam, Department of Earth Sciences, Indian Institute of Technology, Bombay 400076, India (URL: http://www.geos.iitb.ac.in/index.php/dc); Piero Manetti, Italian National Science Council (CNR), Institute of Geosciences and Earth Resources (CNR-IGG), Viale Moruzzi, 1, 56124 Pisa, Italy; Orlando Vaselli, Department of Earth Sciences, University of Florence, Via G. La Pira, 4 - 50121 Florence, Italy; Bruno Capaccioni, Institute of Volcanology and Geochemistry, University of Urbino, Loc. La Crocicchia, 61029 Urbino, Italy; Mohammad Ayaz Alam, Research Scholar, Department of Earth Sciences, Indian Institute of Technology, Bombay 400076, India.


Deception Island (Antarctica) — February 2003 Citation iconCite this Report

Deception Island

Antarctica

63.001°S, 60.652°W; summit elev. 602 m

All times are local (unless otherwise noted)


Fumarole temperatures stable during 2000-2002; sulfur dioxide detected

The Deception Volcano Observatory has monitored the volcano every austral summer since 1993. Investigations of fumarole geochemistry, thermal anomalies, and volcanic activity were made during the summer survey of 2000 and 2002 by the Argentina Research Group. Compared to measurements made during the latest surveys, temperatures of fumaroles and hot soils remained stable at 99-101°C in Fumarole Bay, 97°C on Caliente Hill, 65°C in Whalers Bay, 41°C in Telefon Bay, and 70°C in Pendulum Cove (figure 18).

Figure (see Caption) Figure 18. Map of Deception Island showing the area of geothermal anomalies during austral summer 2002. Courtesy of A.T.Caselli, M. dos Santos Afonso, and M. Agusto.

Following a possible magma intrusion during the summer of 1999 (BGVN 24:05), the composition of gases from fumarolic vents at Fumarole Bay changed compared to previous surveys. The chemical composition of the fumarolic gases was mainly H2O (70-95 vol. %), CO2 (5-30%), H2S (0.1-0.3%), and SO2 (0.01-0.08%). For the first time, SO2 was detected. Elemental sulfur and iron sulfide coatings on lapilli were found around the vent outlets and at a few centimeters of depth, respectively. Elemental sulfur and iron sulfide occurrences were intermittent during the 2000 and 2002 summer surveys.

Geologic Background. Ring-shaped Deception Island, one of Antarctica's most well known volcanoes, contains a 7-km-wide caldera flooded by the sea. Deception Island is located at the SW end of the Shetland Islands, NE of Graham Land Peninsula, and was constructed along the axis of the Bransfield Rift spreading center. A narrow passageway named Neptunes Bellows provides entrance to a natural harbor that was utilized as an Antarctic whaling station. Numerous vents located along ring fractures circling the low, 14-km-wide island have been active during historical time. Maars line the shores of 190-m-deep Port Foster, the caldera bay. Among the largest of these maars is 1-km-wide Whalers Bay, at the entrance to the harbor. Eruptions from Deception Island during the past 8700 years have been dated from ash layers in lake sediments on the Antarctic Peninsula and neighboring islands.

Information Contacts: A.T.Caselli, M. dos Santos Afonso, and M. Agusto, Universidad de Buenos Aires, Instituto Antártico Argentino, Ciudad Universitaria, Pabellón 2, C1428EHA Buenos Aires, Argentina.


Etna (Italy) — February 2003 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Petrographic and geochemical comparison of 2001 and 2002 lavas

On 27 October 2002 Mount Etna opened on both its northern and southern sides (BGVN 27:10-27:12), erupting lava from vents about 2,500-1,800 m elevation on the NNE flank and 2,800-2,700 m on the S flank. The N vents emitted two flows that stopped after a few days, the longer of which stretched ~5 km. The S vents erupted lighter intermittent lava flows, but showed much stronger and sustained explosive activity that developed two large cinder cones at 2,750 and 2,850 m elevation.

The northern lavas are similar to the tephra erupted from Northeast Crater during the summer of 2002 and, more generally, to the trachybasalts that characterized Etna's activity during the past centuries (Tanguy and others 1997, and references therein). They are typically porphyritic (30-40% phenocryts), containing numerous millimeter-sized crystals of plagioclase (An 86-65/Or 0.4-2.1), clinopyroxene (En 42.3-37/Fs 11.7-15.5), and fewer ones of olivine (Fo 76-71) and titanomagnetite (Usp 35-43). The silica content is about 47-48% with a "normal" MgO content of about 5% and "low" CaO/Al2O3.

The southern lavas are significantly higher in MgO (~6.5%) and CaO/Al2O3 with fewer phenocrysts that comprise barely 10% of the rock. Olivine crystals are decidedly more magnesian (Fo 82-76), although other minerals are much like those described above, with plagioclase An 80.8-63.8/Or 0.8-1.3, clinopyroxene En 42-34/Fs 12-15.7, and titanomagnetite Usp 37-42.7. It must be pointed out, however, that plagioclase and titanomagnetite are here almost entirely confined within the groundmass, a characteristic that is uncommon in Etnean lavas and characterizes some of the most basaltic samples.

A particularity of the southern 2002 lavas is the presence of destabilized amphibole crystals, together with quartz-bearing inclusions (sandstones) surrounded by a reaction rim of pyroxene and embedded in a rhyolitic matrix. These characteristics are quite similar to those already found in the 2001 lavas emitted at 2,100 m elevation on this same flank (BGVN 26:10). The 2002 amphibole is present in rarer and smaller "megacrysts" that do not exceed 2 cm in length and display a reaction rim composed of rhonite, anorthitic plagioclase, and olivine within a silicic and potassic glass. Its chemical composition is similar to that of the 2001 amphibole.

Orthopyroxene was found in a southern flow emitted at the very beginning of the eruption (27 October). The average of 16 microprobe analyses is as follows (Centre de microanalyse Camparis, University of Paris 6): SiO2, 53.18; TiO2, 0.23; Al2O3, 0.79; Cr2O3, 0.04; FeO, 19.43; MnO, 0.80; MgO, 23.52; CaO, 1.72; Na2O, 0.05; Total, 99.75. The composition is thus hypersthene close to bronzite, typical of basalts or basaltic andesites. Hypersthene here occurs as crystals 0.5-0.7 mm in length, always surrounded by clinopyroxene. The two minerals are not in equilibrium as indicated by their different Mg values (0.69 for Opx, 0.71 to 0.78 for Cpx). This is the first time that such large crystals of orthopyroxene have been observed in lavas of the last tens of thousand years. Orthopyroxene is very rare at Etna, being previously found on only two or three occasions in pre-Etnean basalts about 200,000 years old.

Olivine separates from both N and S lavas (~100 crystals each) were microprobed, showing a single distribution for the N flank of Fo 69-70 for 65% of the crystals. The S lavas have a twofold behavior with Fo 78-81 for 37% of the crystals and Fo 73-75 for 45% of them. These results are similar to what was found between the upper southern 2001 lavas (including the NE flank below Pizzi Deneri) and those emitted at lower elevation (S 2,600 m and S 2,100 m). It is worth noting that the 2,600 m S vent of the 2001 eruption is close (~1 km) to the 2,700 m S vent of the 2002 eruption.

Based on these preliminary results, the low porphyritic index added to the whole rock chemical composition and that of the olivine crystals, a common origin is suggested for the southern 2002 lavas and those emitted low on the S flank during the 2001 eruption.

Reference. Tanguy, J.C., Condomines, M., and Kieffer, G., 1997, Evolution of the Mount Etna magma: Constraints on the present feeding system and eruptive mechanism: Journal of Volcanology and Geothermal Research, v. 75, p. 221-250.

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: Roberto Clocchiatti, CNRS-CEN Saclay, Lab. Pierre Süe, 91191 Gif sur Yvette, France; Jean-Claude Tanguy, Univ. Paris 6 & Institut de Physique du Globe de Paris, Observatoire de St. Maur, 94107 St. Maur des Fossés, France.


Piton de la Fournaise (France) — February 2003 Citation iconCite this Report

Piton de la Fournaise

France

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

All times are local (unless otherwise noted)


Infrared data from November-December 2002 eruption

Following the 16 November-3 December 2002 eruption (BGVN 27:11), the Observatoire volcanologique du Piton de la Fournaise reported on 19 December that very strong seismicity had continued at a rate of more than 1,000 earthquakes per day. The earthquakes were located a few hundred meters below Dolomieu crater.

MODIS tracking of effusive activity during 2000-2002. The November-December 2002 eruption was detected by the Hawai'i Institute of Geophysics and Planetology MODIS thermal alert system (http://modis.higp.hawaii.edu/). The eruption was apparent as a major hot spot in the SW sector of Reunion (figure 66). The first image on which activity was flagged was that of 1030 (0630 UTC) on 16 November 2002. At that point the flagged anomaly was six 1-km pixels (E-W) by 2-3 pixels (N-S). The hot spot attained roughly the same locations and dimensions on all subsequent images, where hot pixels were flagged on 16 images during November 16-3 December 2002. The exception was an image acquired at 2255 (1855 UTC) on 30 November (figure 66), on which the hot spot attained its largest dimensions of ~12 x 5 pixels. The increase in hot spot dimensions towards the end of November is also apparent in the radiance trace (figure 67). However, without examination of the raw images HIGP scientists cannot determine from the hot spot data alone whether this recovery was due to an increase in activity or an improvement in cloud conditions. This was the 6th eruption of Piton de la Fournaise tracked by the MODIS thermal alert (Flynn et al., 2002; Wright et al., 2002) since its inception during April 2000 (figure 68).

Figure (see Caption) Figure 66. Hot-spot pixels flagged at Piton de la Fournaise by the MODIS thermal alert at 0630 UTC on 16 November 2002 (top) and 1855 UTC on 30 November 2002 (bottom). Courtesy of the HIGP Thermal Alerts Team.
Figure (see Caption) Figure 67. Piton de la Fournaise hot spot radiance detected by MODIS during 15 November-5 December 2002. Courtesy of the HIGP Thermal Alerts Team.
Figure (see Caption) Figure 68. Piton de la Fournaise hot spot radiance detected by MODIS during April 2000-December 2002. Courtesy of the HIGP Thermal Alerts Team.

References. Wright, R., Flynn, L.P., Garbeil, H., Harris, A.J.L., and Pilger, E., 2002, Automated volcanic eruption detection using MODIS: Remote Sensing of Environment, v. 82, p. 135-155.

Flynn, L.P., Wright, R., Garbeil, H., Harris, A.J.L., and Pilger, E, 2002, A global thermal alert using MODIS: initial results from 2000-2001: Advances in Environmental Monitoring and Modeling (http://www.kcl.ac.uk/kis/ schools/hums/geog/advemm.html), v. 1, no. 3, p. 5-36.

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

Information Contacts: Observatoire volcanologique du Piton de la Fournaise, 14 RN3, le 27Km, 97418 La Plaine des Cafres, La Réunion, France; Andy Harris, Luke Flynn, Harold Garbeil, Eric Pilger, Matt Patrick, and Robert Wright, HIGP Thermal Alerts Team, Hawai'i Institute of Geophysics and Planetology (HIGP) / School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Galeras (Colombia) — February 2003 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Phreatic explosion in June 2002; increased long-period seismicity in late 2002

A slight increase in the number of volcano-tectonic (VT) and long-period (LP) events occurred during April through September 2002, although the energy levels diminished. Between October and December 2002, scientists noted a small decrease in VT seismicity and a considerable increase in seismic activity related to fluid-movement. An increase in LP signals, difficult to classify due to their non-typical signatures, coincided with strong rainfall over Pasto and the volcano. The geothermal system at Galeras, with fumarolic zones having temperatures between 100 and 370°C, easily interacts with rainwater, producing exothermic reactions with seismic and near-surface manifestations.

During April-June, there were 191 VT events with a seismic energy release of 1.08 x 1016 erg. Both the number of events and the total energy increased during July-September, when 209 VT events with a seismic energy release of 5.64 x 1015 erg were recorded. In comparison, there were 197 VT events with an energy release of 2.86 x 1015 erg during October-December. The vast majority of the events occurred close to the active crater and in the volcanic edifice. Other earthquakes occurred at depths of 0.2-16 km beneath the summit throughout the second half of 2002.

Volcano-tectonic earthquakes were felt in Pasto on 8 April (2 km deep, ML 3.6), 17 April (2 km deep, ML 4.2), 28 April (12 km deep, ML 3.2), 24 May (8 km deep, ML 2.3), 21 June (9 km deep, ML 3.0), 22 July (5 km deep, ML 2.7), and 1 November (5 km depth, ML 3.2, 3.8 km from the crater). The 17 April event was followed by 12 aftershocks from the main crater area; the strongest was ML 2.6. In Consacá, two events were felt on 12 August within 4 minutes of each other (5 km deep, ML 2.9 and 3.4). The strongest 12 August earthquake was located ~6 km SW of the crater. A strong event on 20 December (4 km deep, ML 3.6) was felt in the town of Yacuanquer and was centered ~5 km SW of the active crater.

During April-June, 111 LP events and 82 spasmodic tremor episodes were registered with a total energy release of 2.89 x 1014 erg. Some spasmodic tremor episodes were harmonic, with dominant frequencies of 2.5-2.7 Hz. Seismic events related to fluid movements during July through September had low frequencies between 2 and 3 Hz and high frequencies of 10.5, 12.1, 13.7, and 14.1 Hz. These frequencies appeared all over the local reporting stations. In total, there were 161 registered LP events and 17 spasmodic tremor episodes with a total energy release of 1.1 x 1014 erg. In addition, some spasmodic tremor episodes were of the harmonic type with dominant frequencies of 2.5 and 3.0 Hz. During October-December the frequencies exhibited spikes between 10 and 16 Hz. Sometimes these events showed one or more precursor signals with very short amplitude and appeared in doubles or triplets. The frequencies kept on time over many stations indicating a processes more directly related to the source rather than the path or station site. Overall, there were 1,541 LP events and 209 spasmodic tremor episodes in October-December with a total energy release of 2.65 x 1015 erg.

Reactivation of El Pinta Crater. Slight gas emissions were observed at the end of May from the El Pinta crater (E of the main crater), inactive since 1991. On 5 June 2002 began the number of daily seismic events increased. A team visiting the summit on 7 June noted an increase in the quantity and pressure of gas emissions at different points of the main crater and in El Pinta. However, temperatures did not show significant variations compared to previous months. Elevated temperatures were observed toward the SW sector of the active cone with values of 340°C at the Las Chavas fumarole field. Also on 7 June spasmodic tremor was registered at the observatory that signified a hydrothermal event. A subsequent field inspection observed a fine layer of ash and precipitate sulfur, besides great gas emission from El Pinta. The material emitted by El Pinta consisted of lapilli, ash, and clay; a high percentage of the sample was pre-existing material. Some reports of gas emissions coincide with spasmodic tremor records at the Galeras observatory site. After 11 June this activity began to decrease. The VT earthquakes that accompanied this activity were located in the main crater zone with depths to 3 km.

Geologic Background. Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Long-term extensive hydrothermal alteration has contributed to large-scale edifice collapse on at least three occasions, producing debris avalanches that swept to the west and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid-Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.

Information Contacts: Marta Calvache, Observatorio Vulcanológico y Sismológico de Pasto (OVSP), INGEOMINAS, Carrera 31, 18-07 Parque Infantil, P.O. Box 1795, Pasto, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html).


Klyuchevskoy (Russia) — February 2003 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Seismicity above background levels; explosion and thermal anomaly

Seismicity was above background levels at Kliuchevskoi during 29 November 2002 through at least 4 March 2003. Tens of earthquakes per day were recorded, mostly at depths of ~30 km (table 8), and intermittent spasmodic volcanic tremor occurred. During December through February, gas-and-steam plumes generally rose up to 2 km above the crater. The Concern Color Code fluctuated between Yellow and Orange, but by the end of the report period remained at Yellow.

Table 8. Earthquakes recorded at Kliuchevskoi during 29 November 2002-28 February 2003. Courtesy KVERT.

Date Earthquakes per day
29 Nov-04 Dec 2002 Up to 33
06 Dec-13 Dec 2002 12-24
13 Dec-20 Dec 2002 6-12
19 Dec-25 Dec 2002 6-9
26 Dec-03 Jan 2003 3-11
06 Jan-09 Jan 2003 10-23
10 Jan-12 Jan 2003 12-28
13 Jan-15 Jan 2003 33-35
31 Jan-07 Feb 2003 16-39
07 Feb-14 Feb 2003 17-30
13 Feb-19 Feb 2003 14-81
21 Feb-28 Feb 2003 10-14

Visual observations and video recordings from the town of Klyuchi revealed that a plume from an explosion on 24 December 2002 rose 4 km above the crater and drifted WSW. On 5 January 2003 a faint thermal anomaly, and probable mud flow down the SSE slope were visible on satellite imagery. According to KVERT, the thermal anomaly and mud flow indicated that a lava flow may have begun to travel down the SSE slope. A probable mudflow, seen on the SE slope on 7 January, may have emerged after a short explosion to the SE or E, or after powerful fumarolic activity in the crater. During the week of 26 February-4 March, gas-and-steam plumes rose to low levels and possible ash deposits on the volcano's SE summit were visible on satellite imagery.

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), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Ol Doinyo Lengai (Tanzania) — February 2003 Citation iconCite this Report

Ol Doinyo Lengai

Tanzania

2.764°S, 35.914°E; summit elev. 2962 m

All times are local (unless otherwise noted)


Continuing lava flows and vent activity in late December 2002

Claude Grandpey visited Ol Doinyo Lengai on 29-30 December 2002 during a trip organized by the French agency Aventure et Volcans. The group arrived on the crater rim late in the morning and noted a very active lava lake in the T49 vent that began to overflow a few minutes later. The resulting lava flow was ~10-15 m wide and reached a length of ~50 m before stopping when the overflow ended after a few minutes. The temperature inside the solid flow, measured some 2 hours after it had stopped, was 462°C.

The T49 lake, roughly circular and ~5 m in diameter, was extremely active and noisily ejecting blobs of fluid lava (figure 77). This type of activity lasted all day, without additional lava flows. After several hours of careful observations, Grandpey climbed the cone and stood a few meters from the lava lake. He noted that the lake was being fed in an oblique way from a vent on its SW side; the lava would flow to the E inner side before being projected back to the W and splashing out. The pressure of the lava as it splashed against the E side could be felt, and the whole cone was vibrating. In the evening the activity decreased at the lake, and a small vent opened a few meters to the E, emitting occasional vertical squirts of lava. All the time they stayed in the crater, cone T40 kept roaring, but no lava emissions were seen.

Figure (see Caption) Figure 77. Photograph of activity at Ol Doinyo Lengai vent T49, 29 December 2002. Courtesy of Claude Grandpey.

After a night of heavy rain, the group visited the crater one more time. No lava flow had occurred during the night. Another lake was still bubbling at T49, at the exact spot were lava was squirting vertically the day before. It was violently throwing blobs of lava on its outer slopes.

Geologic Background. The symmetrical Ol Doinyo Lengai is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent stratovolcano, known to the Maasai as "The Mountain of God," rises abruptly above the broad plain south of Lake Natron in the Gregory Rift Valley. The cone-building stage ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatitic and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra ejections and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater and occasionally down the upper flanks. The depth and morphology of the northern crater have changed dramatically during the course of historical eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater. Long-term lava effusion in the summit crater beginning in 1983 had by the turn of the century mostly filled the northern crater; by late 1998 lava had begun overflowing the crater rim.

Information Contacts: Claude Grandpey, L'Association Volcanologique Européenne (LAVE), 7, rue de la Guadeloupe, 75018, Paris, France.


Monowai (New Zealand) — February 2003 Citation iconCite this Report

Monowai

New Zealand

25.887°S, 177.188°W; summit elev. -132 m

All times are local (unless otherwise noted)


Volcanic earthquake swarm during 1-24 November eruption

Numerous eruptions of Monowai Seamount (also known as Orion Seamount), an active volcano located in the Kermadec Island arc, were detected by the Polynesian Seismic Research (Reseau Sismique Polynesien, RSP) seismic network in Tahiti (figure 8). Strong T-phase waves were recorded at all of the stations in the RSP network (figure 9). The last reports of Monowai eruption activities were in January 1998 (BGVN 23:01), June 1999 (BGVN 24:06), and May 2002 (BGVN 27:05).

Figure (see Caption) Figure 8. Map of the South Pacific Ocean showing the location of some RSP (Reseau Sismique Polynesien) seismic network stations (circles indicate area of island group with labeled stations) and Monowai Seamount (star). All seismic stations are inland; there are no hydrophones in the network. Stations shown include VAH and PMOR (Tuamotu archipelago), PAE, PPT, TVO, and TIAR (Society Islands), TBI (Austral Islands), and RKT (Gambier archipelago). Courtesy of Laboratoire de Geophysique, Tahiti.
Figure (see Caption) Figure 9. Example of strong T-phase waves detected by the RSP from Monowai, 18 November 2002 (times are UTC). All the seismic stations in the network recorded the wave generated during eruption of the volcano. Note the good signal coherency between most stations. The record at the PMOR station, located in the north of Rangiroa, was masked for the T waves. Courtesy of Laboratoire de Geophysique, Tahiti.

Geophysical network. The Polynesian Seismic Network is composed of short-period seismic stations on Rangiroa atoll in the Tuamotu archipelago (stations VAH and PMOR), on Tahiti in the Society Islands (stations PAE, PPT, TVO, and TIAR), on Tubuai in the Austral Islands (station TBI), and on Rikitea in the Gambier archipelago (station RKT). There are also three long-period seismic stations in Tahiti, Tubuai, and Rikitea. In addition, Comprehensive Test Ban Treaty (CTBT) instruments located in Tahiti include a mini-array of micro-barographs, a primary seismic station (station PS18 at Papeete), and a radionuclide station.

Earthquake swarm. A volcanic earthquake swarm started on 1 November 2002 at 1200 UTC with strong explosive T-phase waves recorded by the RSP network (figure 10). The swarm stopped temporarily between 8 and 17 November; a second, very intense swarm started on 17 November (figure 11) and ended on 24 November. From inversion of T-phase wave arrival times, it was deduced that the swarm was located around Monowai Seamount. Because of the small aperture of the RSP network, the location is poorly constrained in longitude, but well constrained in latitude (figure 12). The source of the T-phase waves is most probably at Monowai.

Figure (see Caption) Figure 10. Daily history of the Monowai swarm. The maximum number of daily events was on 21 November, but the higher amplitude T-phase waves were detected during 17-19 November. Courtesy of Laboratoire de Geophysique, Tahiti.
Figure (see Caption) Figure 11. Daily history of amplitude (in nanometers) of Monowai swarm T-phase waves recorded at TVO station on Tahiti. The maximum intensity was between 17 and 19 November. These amplitudes should correlate to ground vibrations generated by the volcanic eruptions. Courtesy of Laboratoire de Geophysique, Tahiti.
Figure (see Caption) Figure 12. Map showing the best source locations of the swarms using the entire seismic network. The star is Monowai Seamount, and the dots are possible source epicenters. The effect of linearity observed on the epicenters is due essentially to the aperture size of the network, but note that the latitude is well constrained. Courtesy of Laboratoire de Geophysique, Tahiti.

Regarding T-Phase waves. A short-period wave group from a seismic source that has propagated in part through the ocean is called T-phase or T(ertiary)-wave (Linehan, 1940; Tolstoy and Ewing, 1950; Walker and Hammond, 1998). The wave group propagates with low attenuation as hydro-acoustic (compressional) waves in the ocean, constrained within a low sound speed wave guide (the sound fixing and ranging - SOFAR - channel) formed by the sound speed structure in the ocean. The T-phase signal may be picked up by hydrophones in the ocean or by land seismometers. Upon incidence with the continental shelf/slope, the wave group is transformed into ordinary seismic waves that arrive considerably later than seismic wave groups from the same source that propagated entirely through the solid earth.

References. Brothers, R.N., Heming, R.F., Hawke, M.M., and Davey, F.J., 1980, Tholeiitic basalt from the Monowai seamount, Tonga-Kermadec ridge (Note): New Zealand Journal of Geology and Geophysics, v. 23, p. 537-539.

Davey, F.J., 1980, The Monowai Seamount: an active submarine volcanic centre of the Tonga-Kermadec Ridge (Note): New Zealand Journal of Geology and Geophysics, v. 23, p. 533-536.

Linehan, D, 1940, Earthquakes in the West Indian region: Transactions, American Geophysical Union, Pt. II, p. 229-232.

Tolstoy, I., and Ewing, M., 1950, The T phase of shallow-focus earthquakes: Bulletin of the Seismological Society of America, v. 40, p. 25-51.

Walker, D.A., and Hammond, S.R., 1998, Historical Gorda Ridge T-phase swarms; relationships to ridge structure and the tectonic and volcanic state of the ridge during 1964-1966: Deep-Sea Research Part II, v. 45, n. 12, p. 2531-2545.

Geologic Background. Monowai, also known as Orion seamount, rises to within 100 m of the sea surface about halfway between the Kermadec and Tonga island groups. The volcano lies at the southern end of the Tonga Ridge and is slightly offset from the Kermadec volcanoes. Small parasitic cones occur on the N and W flanks of the basaltic submarine volcano, which rises from a depth of about 1500 m and was named for one of the New Zealand Navy bathymetric survey ships that documented its morphology. A large 8.5 x 11 km wide submarine caldera with a depth of more than 1500 m lies to the NNE. Numerous eruptions from Monowai have been detected from submarine acoustic signals since it was first recognized as a volcano in 1977. A shoal that had been reported in 1944 may have been a pumice raft or water disturbance due to degassing. Surface observations have included water discoloration, vigorous gas bubbling, and areas of upwelling water, sometimes accompanied by rumbling noises.

Information Contacts: Dominique Reymond and Olivier Hyvernaud, Laboratoire de Geophysique, CEA/DASE/LDG, Tahiti, PO Box 640, Papeete, French Polynesia.


Montagu Island (United Kingdom) — February 2003 Citation iconCite this Report

Montagu Island

United Kingdom

58.445°S, 26.374°W; summit elev. 1370 m

All times are local (unless otherwise noted)


Satellite data provide first evidence of Holocene eruptive activity

Although previous eruptions have been recorded elsewhere in the South Sandwich Islands (Coombs and Landis, 1966), ongoing volcanic activity has only recently been detected and studied. These islands (figure 1) are all volcanic in origin, but sufficiently distant from population centers and shipping lanes that eruptions, if and when they do occur, currently go unnoticed. Visual observations of the islands probably do not occur on more than a few days each year (LeMasurier and Thomson, 1990). Satellite data have recently provided observations of volcanic activity in the group, and offer the only practical means to regularly characterize activity in these islands. These observations are especially significant because there has previously been no evidence of Holocene activity on Montagu Island (LeMasurier and Thomson, 1990).

Figure (see Caption) Figure 1. The South Sandwich Island archipelago, located in the Scotia Sea. The South Sandwich Trench lies approximately 100 km E, paralleling the trend of the islands, where the South American Plate subducts westward beneath the Scotia Plate. Courtesy Hawaii Institute of Geophysics and Planetology and British Antarctic Survey.

Using Advanced Very High Resolution Radiometer (AVHRR) data, Lachlan-Cope and others (2001) observed apparent plumes and unreported single anomalous pixels intermittently on images of Montagu Island during March 1995 to February 1998. However, field investigations in January 1997 revealed that Montagu Island, as viewed from Saunders Island, was apparently inactive, with the summit region entirely covered in snow and ice. Hand-held photographs of the island obtained in September 1992 also showed the summit to be wholly inactive.

Significant volcanic activity may have begun on Montagu Island in late 2001 based upon analysis of thermal satellite imagery (1 km pixel size) from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. Using the automated MODIS Thermal Alert system (Wright and others, 2002), image pixels containing volcanic activity were detected and analyzed to characterize the eruption. From its location, the erupting center may be associated with a small hill on the NW edge of the ice-filled summit caldera, ~6 km from Mount Belinda (figure 2).

Figure (see Caption) Figure 2. Map of Montagu Island with circles showing the location of all anomalous MODIS pixels detected since October 2001. Stippled areas show rock outcrop, the remainder is snow or ice covered. Relief is shown by form lines that should not be interpreted as fixed-interval contours. Map adapted from Holdgate and Baker (1979); courtesy Hawaii Institute of Geophysics and Planetology and British Antarctic Survey.

The first thermal alert on Montagu occurred on 20 October 2001 with a single anomalous pixel on the N side of the island. Subsequent anomalies generally involved 1-2 pixels, with the exception of several images in August and September 2002 that peaked at four pixels in size (figures 3 and 4). Visual inspection of the images revealed that the anomalies were all located between the summit of Mount Belinda and the N shore, changing in position either due to satellite viewing geometry or actual migration of hot material. We can generally discount other possible explanations for the anomalies, the most likely being solar reflectance influencing the short-wave bands, due to the presence of clear anomalies in nighttime imagery and the concomitance of apparent low-level ash plumes in several of the images. The persistence of the anomaly, and the lack of large ash plumes, suggests that activity here may involve a lava lake.

Figure (see Caption) Figure 3. Selected MODIS images showing thermal anomalies on Montagu Island. Band 20 (3.7 µm) is shown here. The thermal anomalies appear to be located between the summit of Mount Belinda and the N shore. Images are not georeferenced for purposes of radiance integrity, therefore coastlines are approximate. Courtesy Hawaii Institute of Geophysics and Planetology and British Antarctic Survey.
Figure (see Caption) Figure 4. Summed radiance of anomalous pixels in each image. Band 21 (3.9 µm) was used for these plots. Points show the result for each image, and the line is a three point running mean of values. Courtesy Hawaii Institute of Geophysics and Planetology and British Antarctic Survey.

References. Coombs, D.S., and Landis, C.A., 1966, Pumice from the South Sandwich eruption of March 1962 reaches New Zealand: Nature, v. 209, p. 289-290.

Holdgate, M.W., and Baker, P.E., 1979, The South Sandwich Islands, I, General description: British Antarctic Survey Science Report, v. 91, 76 p.

Lachlan-Cope, T., Smellie, J.L., and Ladkin, R., 2001, Discovery of a recurrent lava lake on Saunders Island (South Sandwich Islands) using AVHRR imagery: Journal of Volcanology and Geothermal Research, v. 112, p. 105-116.

LeMasurier, W.E., and Thomson, J.W. (eds), 1990, Volcanoes of the Antarctic Plate and Southern Oceans: American Geophysical Union, Washington, D.C., AGU Monograph, Antarctic Research Series, v. 48.

Wright, R., Flynn, L.P., Garbeil, H., Harris, A.J.L., and Pilger, E, 2002, Automated volcanic eruption detection using MODIS: Remote Sensing of Environment, v. 82, p. 135-155.

Geologic Background. The largest of the South Sandwich Islands, Montagu consists of a massive shield volcano cut by a 6-km-wide ice-filled summit caldera. The summit of the 10 x 12 km wide island rises about 3000 m from the sea floor between Bristol and Saunders Islands. Around 90% of the island is ice-covered; glaciers extending to the sea typically form vertical ice cliffs. The name Mount Belinda has been applied both to the high point at the southern end of the summit caldera and to the young central cone. Mount Oceanite, an isolated 900-m-high peak with a 270-m-wide summit crater, lies at the SE tip of the island and was the source of lava flows exposed at Mathias Point and Allen Point. There was no record of Holocene or historical eruptive activity until MODIS satellite data, beginning in late 2001, revealed thermal anomalies consistent with lava lake activity that has been persistent since then. Apparent plumes and single anomalous pixels were observed intermittently on AVHRR images during the period March 1995 to February 1998, possibly indicating earlier unconfirmed and more sporadic volcanic activity.

Information Contacts: Matt Patrick, Luke Flynn, Harold Garbeil, Andy Harris, Eric Pilger, Glyn Williams-Jones, and Rob Wright, HIGP Thermal Alerts Team, Hawai'i Institute of Geophysics and Planetology (HIGP) / School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); John Smellie, British Antarctic Survey, Natural Environment Research Council, High Cross, Madingly Road, Cambridge CB3 0ET, United Kingdom (URL: https://www.bas.ac.uk/).


Nyiragongo (DR Congo) — February 2003 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Aftershocks, lava lake, SO2 fumes, acidic rains, and highly fluorinated water

Nyiragongo was last reported on through late October 2002 (BGVN 27:10). This report covers through 21 December, an interval in which the hazard status remained high, with the population asked to exercise vigilance (code Yellow). Included here are reports from the Goma Volcano Observatory (GVO), and from Dario Tedesco and Simon Carn on geochemistry and atmospheric SO2. Several episodes of strong SO2 outgassing and unfavorable wind directions caused elevated concentrations of the gas to enter cities and acid rain to damage vegetation and water supplies. High fluorine was found in some rainwater samples. The 24 October 2002 earthquake's aftershocks and the state of the volcano led to significant stress on the regional inhabitants, including those in Goma.

During the October-December reporting interval, the GVO reports noted that their roughly weekly Nyiragongo observational climbs disclosed considerable changes on the crater's floor, a spot ~700 m down inside the summit crater. Comparisons between photos taken on 24 November and 9 December 2002 revealed the merging of two adjacent molten-surfaced lakes and the birth of another similar, though smaller, lava lake at a point well over 100 m away from the merged ones. The deep crater is often filled with fumes too dense to clearly see the crater floor, and in the above-mentioned cases photographers had just 5 to 10 seconds of moderate visibility to capture their photos. This helps explain why the status and behavior of the lava lakes is often ambiguous (see BGVN 26:03). Adequate visibility during a climb on 18 December revealed that the sole lava lake seen then stood ~45 m in diameter, its surface restless and agitated.

In accord with one or more dynamic and molten-surfaced lava lakes on 20 December, SO2 gas blew into Goma, causing residents to panic. Scoria falls were noted in late October, and in one particular case by residents of the SW-flank settlement of Rusayo at around 1100 on 15 November. It was noted in October that vegetation surrounding the crater's perimeter, particularly on the W flank, had sustained acid burns from abundant degassing. During October-21 December vapors over the crater frequently glimmered red at night. The 15 November visit disclosed the escape of high-temperature gases and the existence of fissures cutting across the residual platform of 17 January 2002 deposits. Fumaroles along fissures discharged gases. SW-flank fissures were also seen.

GVO summarized the volcano observations for the interval 15-28 December 2002, noting a permanent strong gas plume at 4,200-6,000 m altitudes. They again confirmed a permanent small lava lake, about 50 m in diameter with a central active lava fountain sending molten material to ~40 m heights. Minor amounts of Pelé's-hair ash fell in both Rusayo and Kibati villages. Residents of those villages and Kibumba reported seeing incandescence in the crater.

Residents of Kibati and Kibumba were greatly concerned the night of 27-28 November due to visible glimmer that appeared be coming toward them from Nyiragongo. The glimmer was benign activity in the crater rather than lava flows descending the flanks. This behavior was associated with lava-lake degassing.

Other observatory projects in late October to late December included the installation and maintenance of lake-level sensors on Lake Kivu, installation of thermal sensors at selected spots, and improved seismic telemetry.

Deformation surveys on 31 October, 2 November, and 13 November 2002 measured the distance between cross-fracture survey points (nails) along the scarps of Monigi, Lemera, and Shaheru. The results indicated that offsets remained comparatively stable, with little change compared to previous measurements (table 6). New cross-fracture measurements were also initiated at the Mapendo station. Data collected in late December continued to lack evidence of new deformation.

Table 6. Nyiragongo deformation measured along scarps on 2 and 13 November. These reportedly showed strong consistency with preceding measurements. New measurements were initiated at newly established survey points on 13 November. These were in the Mapendo neighborhood (a site towards Gift Bosco) on a revived fracture there. Courtesy of OVG.

Date Monigi Lemera Virunga Shaheru Mapendo
02 Nov 2002 8.31 m 7.55 m 93.4 cm 14.72 m --
13 Nov 2002 8.31 m 7.55 m 93.4 cm -- 15.4 cm

Geochemistry. SO2 fluxes increased during October and November 2002, rising from below detection limits to a few thousands metric tons per day (t/d), then to up to ~20,000 t/d. Dario Tedesco suggested that the increase might be due to a more efficient conduit geometry allowing gases access to the surface. The process may have accompanied upward movement of magma or its arrival at the surface.

During the last half of November through 2 December the TOMS SO2 estimates were under reliable detection limits due low concentrations. After that, on 7 and 11 December, respectively, TOMS data measured considerable SO2, ~12,000 and ~11,000 metric tons per day (t/d) (table 7).

Table 7. SO2 fluxes at Nyiragongo based on the TOMS instrument. Courtesy of Simon Carn.

Date Daily SO2 flux (t/d)
16 Nov-02 Dec 2002 Not significant
03 Dec 2002 Less than 5,000 (weak signal)
04 Dec 2002 Data gap - no data over Nyiragongo
05 Dec 2002 ~6,000
06 Dec 2002 Data gap - no data over Nyiragongo
07 Dec 2002 ~12,000
08 Dec 2002 Data gap - no data over Nyiragongo
09 Dec 2002 Less than 5,000 (weak signal)
10 Dec 2002 Data gap - no data over Nyiragongo
11 Dec 2002 Less than 5,000 (very weak signal)
12 Dec 2002 Data gap - no data over Nyiragongo
13 Dec 2002 ~11,000

Thus the degassing had not risen to peak October-November levels, but increased since early December, either in terms of plume altitude, SO2 concentration, or both. Simon Carn noted that "We are also sometimes seeing discrete SO2 clouds to the W of the volcano, rather than SO2 plumes emerging from the volcano, perhaps suggesting discontinuous degassing."

Tedesco also pointed out that the higher SO2 fluxes accompanied acid rain falling on Goma and surroundings, with some rain samples also containing up to 15 parts per million (ppm) fluorine ion. (For comparison, the U.S. Centers for Disease Control and Prevention recommended a standard in drinking water at 0.7-1.2 ppm, a level that provides a means of preventing tooth decay without compromising public safety.) In December 2002, Goma residents complained about the acid rain, which besides affecting drinking water, put area crops in danger. Accordingly, scientists began collecting rainwater samples with the intent of carrying out regular analyses.

SO2 blew towards the S on 4 and 5 November exposing people on the upper S flanks. Researchers measured gas concentrations in Goma on 20 November at 20 selected points. They found CO2 concentrations of 0-4%, and much lower concentrations of CH4, H2S, and CO. On 4-5 December the wind carried SO2 gas into S-flank settlements. During the December, analysis of fumaroles at Sake, Mupambiro, Bulengo, and Himbi revealed similar concentrations to those seen in earlier visits (including the elevated values at Sake/Birere, which in October 2002 measured 35.1% CO2, and Mupambiro, which on 7 December measured 63.1% CO2). It was expected that the current rainy season favored enhanced CO2 flow from the ground.

Nyiragongo summit geochemical surveys in mid-November found temperature elevations of 1°C (except one summit site with a 5.7°C rise). CO2 concentrations had then risen to 3%. In a fissure called Shaheru, CO2 concentrations stood at 53%. Methane was found at all sites in dilute concentrations, ~0.1 %. H2S was below the limit of detection at all the visited sites.

The human side of January 2002 volcanism and the 24 October earthquake. Aftershocks to the unusually large earthquake of 24 October 2002 continued to be felt in the epicentral area through December. For example, Goma residents felt an M 4 tectonic earthquake with a 13 km focal depth on 13 December.

Field excursions in the reporting period revealed that the 24 October 2002 earthquake and aftershocks damaged towns in the Kitembo and Minova areas (including the towns Lwiro and Nyabibwe). The visits suggested that no lives were lost but about ten houses sustained cracks. Residents there still remained in need of humanitarian assistance, including safe housing, food, and medicine.

The December aftershocks were not reported to have caused significant damage; however, an earlier Reuters news article, published on 24 January 2002, described how about six days after the volcanism ceased in Goma, residents there had "flocked to receive aid" at distribution points, many having then gone about a week without food supplies. The news article went on to say, "the UN aims to distribute about 260 tonnes of food, which it says is enough to feed 70,000 people for a week. Each family-of an assumed seven people on average-will receive 26 kg of highly nutritious supplies including maize meal, beans, vegetable oil, and corn soya blend." The aid groups also distributed clean drinking water. The intensity of the volcanic and earthquake disasters had clearly left residents weakened and with reduced food security.

Previous Bulletin reports have included relatively few photographs of the scene in Goma due to the January 2002 eruption when lava flows overran the city. Figures 23-26, all sent to us by Wafula Mifundi, are intended to help make up for this deficiency. In many cases within Goma intense fires accompanied the lava flows. Several of the photos provided by Wafula captured these fires, including a devastating fire at a fuel depot, which accompanied an explosion that was widely discussed in the news. The photos presented here omit those of the larger fires and instead illustrate other important aspects of the crisis and its aftermath.

Figure (see Caption) Figure 23. During Nyiragongo's January 2002 eruption lavas transected Goma, a city of about a half-million people. The summit of Nyiragongo lies ~ 20 km to the N. In the foreground, middle-ground, and central background lie destroyed buildings and gardens, and what has now become a field of rubble atop the rapidly cooled, thin lava flows of the January eruption. Note that the rubble contains abundant light-colored building material, such as concrete chunks dispersed from downed buildings. Unburned wood and some leaves may represent unburned portions of trees that came into contact with cooler lava surfaces at temperatures below their kindling point. Leaves and other fallen and wind-blown plant debris may have accumulated later. Date of photo is undisclosed. Courtesy of Wafula.
Figure (see Caption) Figure 24. Nyiragongo lavas inundated these structures on 17 January 2002. A family took refuge in the lower portion of the building in the center. Trapped there by lava flows, one or more people died, including an infant. Provided courtesy of Wafula.
Figure (see Caption) Figure 25. This photo shows some of the remarkably thin and mobile lava flows pouring through a narrow chute (behind the car and in line with the left-most opening in the low structure's wall). Below that, the lava spreads and descends across a lawn. Provided courtesy of Wafula.
Figure (see Caption) Figure 26. Nyiragongo's January 2002 lavas slowly advancing across a road at an intersection. This area of Goma is called Signers rotary point. The sign advertises the Ishango Guest House. Note the lava-immersed but still-standing tree, which at this stage, may have only had substantial burns near the base of its trunk. Provided courtesy of Wafula.

Seismicity. The late October-early November 2002 earthquakes that were interpreted as magmatic, were relatively deep, at 10-25 km. Most of these earthquakes occurred in an elliptical area, although some struck ten's of kilometers W of Goma beneath the Bay of Sake in Lake Kivu, an area where previous earthquakes have sometimes occurred.

During the first half of November seismicity dropped significantly. It was noted that the operational seismic network then consisted of seven stations (table 8); an eighth station was not functioning. During November tectonic seismicity returned to normal; however, magmatic seismicity continued. In the week ending on the 9th, magmatic seismicity centered on the N side of Nyamuragira, a zone adjacent its recent eruption. In contrast, during this same interval earthquakes were rare at Nyiragongo, although gas escaping the crater remained visible from Goma, certifying ongoing intra-crater activity. During the week ending on the 16th, some earthquakes were centered about Nyiragongo. During the latter half of December most of the region's high-frequency and volcano- tectonic earthquakes were associated with an epicentral zone stretching from the 24 October major earthquake near Kalehe to W of Nyamuragira. Some HF events also occurred in the Nyiragongo vicinity too.

Table 8. Nyiragongo and Nyamuragira earthquakes and tremor recorded at Katale and Rusayo stations during November-December 2002. The Katale station sits on the E flank of Nyamuragira; the Rusayo station, on the SW flank of Nyiragongo. The dates on the left are for weekly intervals, except the last entry, which is for a 2-week interval (a fortnight). In the last entry, the elevated high-frequency earthquake count at Katale station was due to a swarm to N of Nyamuragira on 27-28 December. Courtesy of GVO.

 

End of week (or fortnight) Type A High-Freq Type C Low-Freq Total Tremor - described or minutes with amplitude >= 1 mm
Rusayo seismic station
09 Nov 2002 86 178 264 5838
16 Nov 2002 78 185 263 3956
23 Nov 2002 79 207 286 1435
30 Nov 2002 33 160 193 2508
07 Dec 2002 42 137 179 --
14 Dec 2002 57 124 181 --
(28 Dec 2002) (88) (270) (358) ("Several hours per day")
 
Katale seismic station
09 Nov 2002 137 231 368 3998
16 Nov 2002 114 328 442 7713
23 Nov 2002 118 356 474 Feeble (1 mm)
30 Nov 2002 92 239 331 2248
07 Dec 2002 107 348 455 --
14 Dec 2002 120 169 289 --
(28 Dec 2002) (253) (513) (766) ("Several hours per day") Type A swarm to N of Nyamuragira

The seismic reference stations Katale and Rusayo both registered sub-continuous volcanic tremor during much of the reporting interval (table 8). Rusayo station's tremor was attributed primarily to Nyiragongo, and except for one week in November, it registered the larger share of tremor.

During the week ending 23 November seismicity stayed about the same and tremor dropped considerably, particularly at neighboring volcano Nyamuragira where it was described as feeble (table 8). Banded tremor registered 29 November at the stations of Kunene, Rusayo, Bulengo, Kibumba, and Katale (during 0630-0745 UTC), with the highest amplitude at Katale station, implying Nyamuragira as their source, plausibly a reactivation associated with the 24 October earthquake. Many epicenters also concentrated in the vicinity of that neighboring volcano. On the other hand, epicenters for long-period earthquakes appeared to come from Nyiragongo. The epicenters were determined to a margin of error of ± 2 km.

Geologic Background. One of Africa's most notable volcanoes, Nyiragongo contained a lava lake in its deep summit crater that was active for half a century before draining catastrophically through its outer flanks in 1977. The steep slopes of a stratovolcano contrast to the low profile of its neighboring shield volcano, Nyamuragira. Benches in the steep-walled, 1.2-km-wide summit crater mark levels of former lava lakes, which have been observed since the late-19th century. Two older stratovolcanoes, Baruta and Shaheru, are partially overlapped by Nyiragongo on the north and south. About 100 parasitic cones are located primarily along radial fissures south of Shaheru, east of the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by voluminous lava flows that extend long distances down the flanks, which is characterized by the eruption of foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities, as did lava flows that inundated portions of the major city of Goma in January 2002.

Information Contacts: Kasereka Mahinda, Kavotha Kalendi Sadaka, Celestin Kasereka, Jean-Pierre Bajope, Mathieu Yalire, Arnaud Lemarchand, Jean-Christophe Komorowski, and Paolo Papale, Goma Volcano Observatory (GVO), Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; Dario Tedesco, Environmental Sciences Department, Via Vivaldi 43, 81100 Caserta, Italy; Jacques Durieux, Groupe d'Etude des Volcans Actifs (GEVA), 6, Rue des Razes 69320 Feyzin, France; Simon Carn, TOMS Volcanic Emissions Group, Joint Center for Earth Systems Technology (NASA/UMBC), University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 USA (URL: https://so2.gsfc.nasa.gov/); Reuters News Service; BBC News (URL: http://news.bbc.co.uk/).


Popocatepetl (Mexico) — February 2003 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Cycles of dome growth and destruction; continuing explosive activity

From November 2002 through mid-February 2003, volcanic activity at Popocatépetl was similar to that during July-October 2002 (BGVN 27:10). Activity consisted principally of small-to-moderate eruptions of steam, gas, and minor amounts of ash, and occasional explosions that ejected incandescent fragments for short distances. Larger explosions on 6 November, 18 and 23 December 2003, 9 January, and during 4-10 February 2003 produced ash plumes that reached approximate heights of 4, 2, 2, 3, and 2 km above the crater, respectively. Volcano-tectonic (VT) earthquakes (M 2.0-3.2) occurred frequently, most located to the SE, N, and E at depths up to 7.5 km beneath the crater. Episodes of harmonic and low-amplitude tremor were registered almost daily, typically for a few hours.

Until November, the daily emissions reported by the Centro Nacional de Prevencion de Desastres (CENAPRED) typically numbered from as few as 5 to as many as 20. In late November, this number increased markedly with 78 detected on 24 November and 40 the following day. Subsequently the daily number of these small-to-moderate emissions occasionally exceeded 30 through mid-February 2003.

New episodes of low-frequency tremor, beginning on 19 November, signaled the growth of a new lava dome within the crater. Aerial photographs obtained by the Mexican Ministry of Communications and Transportation on 2 December confirmed the presence of a fresh lava dome with a base diameter of 180 m, and a height of ~52 m. CENAPRED reported that the explosive activity reported on 18 and 23 December was related to the destruction of the lava dome. Photographs of the lava dome taken on 9 January revealed that the dome's inner crater had subsided. The volume of dome material ejected during the December explosions was calculated to be ~500,000 m3.

CENAPRED stated that explosive activity beginning in mid-January was related to the growth of a new lava dome in the crater. On 22 January a significant increase in volcanic microseismicity was recorded. According to the Washington Volcano Ash Advisory Center, on 25 January an ash emission reached ~10.7 km altitude. The explosion on 4 February ejected incandescent volcanic material that fell as far as ~2 km down the volcano's flanks. Similar emissions continued and were related to partial destruction of the lava dome. According to CENAPRED, as long as there are remains of a lava dome in the crater, a significant chance of further explosive activity remains, including ash emissions and incandescent ejections around the crater. The Alert Level remained at Yellow (second on a scale of three colors) and CENAPRED recommended that people avoid entering the restricted zone that extends 12 km from the crater. However, the road between Santiago Xalitzintla (Puebla) and San Pedro Nexapa (Mexico State), including Paso de Cortés, remained open for controlled traffic.

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

Information Contacts: Alicia Martinez Bringas, Angel Gómez Vázquez, Roberto Quass Weppen, Enrique Guevara Ortiz, Gilberto Castelan, Gerardo Jímenez and Javier Ortiz, Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México D.F. 04360, Mexico (URL: https://www.gob.mx/cenapred/); Servando De la Cruz-Reyna, Instituto de Geofísica, UNAM. Cd. Universitaria. Circuito Institutos. Coyoácan. México, D.F. 04510 (URL: http://www.geofisica.unam.mx/); Washington Volcano Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Associated Press.


Reventador (Ecuador) — February 2003 Citation iconCite this Report

Reventador

Ecuador

0.077°S, 77.656°W; summit elev. 3562 m

All times are local (unless otherwise noted)


Ashfall in January, mudflows in February-March; additional data from November

On 3 November 2002, an unexpected eruption occurred at Reventador (BGVN 27:11). The following report provides an update on recent activity and additional information about the November eruption, including discussion of a site visit after the eruption and satellite data.

Recent activity. Seismicity was low during mid-December 2002. On 10 January, Instituto Geofísico (IG) reported that several lahars occurred that day in the Marquer and Reventador rivers. Ashfall was reported in the N sector of Quito, ~90 km to the WSW. In the afternoon a bluish gas column was observed exiting the crater. IG personnel stated that lava was slowly advancing and that 80-90% of the 3 November 2002 pyroclastic-flow deposits were covered by lahars.

During late February, rain generated mudflows that ended near the Montana River and disrupted traffic on a highway. White steam exited the volcano. Seismicity remained low, and was characterized by bands of harmonic tremor and volcano-tectonic (VT) earthquakes.

Intense rains during the first few days of March caused mudflows and again disrupted traffic. A gas column reached 300-500 m above the summit. Low-level seismicity was characterized by bands of harmonic tremor and a few isolated earthquakes. The seismic station in Copete registered high-frequency signals associated with lahars.

Site visit during 17-19 November 2002. The following report of an investigation of the 3 November 2002 explosion (BGVN 27:11) was submitted by Claus Siebe (Instituto Geofísico (IG), UNAM). Siebe, Jesús Manuel Macías, and Aurelio Fernández were able to fly to Quito on 17 November. On 18 November they interviewed Ing. Marcelo Riaño (general manager of the Trans-Equatorian Oil-Pipeline) as well as Patricia Mothes, Minard Hall, and Hugo Yepes (IG).

On 19 November they arrived in El Chaco (~34 km from Reventador) and traveled to the confluences of the Ríos Marker and Montana with the Río Coca (both are located 8 km from the crater). A small apron of fresh lahar deposits ~300 m wide covered the area adjacent to the Río Marker where the road had been before the 3 November eruption. Several dozens of workers with heavy machinery were trying to make a temporary passage over the gravel and boulder surface for the waiting trucks. For a few minutes they could see for the first and only time a ~1-km-high brownish ash column rising from the crater before incoming clouds hindered further visual contact.

"At the time of our visit, the Río Marker was diminished to such an extent that we could jump from boulder to boulder from one side to the other of the stream without getting wet. The vegetation around the confluence of the rivers was completely destroyed, and surviving trees were scorched and defoliated. The base layer of the fresh deposits consisted of up to 2.5-m-thick, partly matrix-supported, partly clast-supported pyroclastic-flow deposit with abundant wood and charcoal fragments (abundant scoriaceous boulder- and gravel-sized clasts were subrounded while dense clasts were angular). This was overlain by a sequence of several sandy-gravelly lahar units with abundant charcoal supporting larger boulders as well as clasts from the underlying pyroclastic-flow deposit.

About 400 m from the Río Marker, after passing a narrow zone of unaffected vegetation, we were able to reach the Río Montana, where a similar situation was encountered (figure 7). Here, at places the lahar deposits were still steaming with a sulfurous smell. The bridge over the river was destroyed, but the oil pipeline was still basically intact (figure 8). Since the area did not seem safe (the last lahar had been emplaced less than 24 hours prior) the team returned to El Chaco, where they interviewed several people and obtained photographs of the pyroclastic flow and its deposits taken on 3 November 2002 (figures 9-11).

Figure (see Caption) Figure 7. Fresh lahar deposits at Reventador near the confluence of Río Montana with Río Coca on 19 November 2002. According to workers trying to repair the road the still-warm and steaming surface of the lahar deposit shown in the photo was produced during the afternoon of 18 November after heavy rain. This was the 10th lahar event since 3 November. Courtesy of Claus Siebe.
Figure (see Caption) Figure 8. Photo looking downstream near the confluence of Río Montana with Río Coca on the ESE flank of Reventador. In the foreground are the fresh lahar deposits. In the middle ground is the destroyed concrete bridge over the Río Montana as well as the oil-pipeline immediately behind. The bulldozer is trying to built a temporary passage for hundreds of trucks waiting on both sides of the road. In the background is the Río Coca with distal-debris avalanche deposit (19,000 Y BP) forming the vegetated hills behind the river. Photo taken on 19 November shortly after 1300 by Claus Siebe. Courtesy of Claus Siebe.
Figure (see Caption) Figure 9. Pyroclastic flow descending Reventador's SE slopes during the morning of 3 November 2002. Photo was taken from the E (Transoceanic road in the foreground). This anonymous photo was purchased at a small hotel in El Chaco. Courtesy of Claus Siebe.
Figure (see Caption) Figure 10. Fresh pyroclastic-flow deposits from Reventador, produced on 3 November 2002, ponding against the bridge over the Río Montana. This anonymous photo was purchased at a small hotel in El Chaco. Courtesy of Claus Siebe.
Figure (see Caption) Figure 11. Distal pyroclastic-flow deposits from Reventador and scorched vegetation along the Transandean oil-pipeline near the confluence of the Río Montana with the Río Coca. This anonymous photo was purchased at a small hotel in El Chaco. Courtesy of Claus Siebe.

At about 2200 we drove to the summit of a hill (2,959 m elevation) N of Sta. Rosa, 27.5 km from the summit of Reventador. Although the night was clear and we had a good view, the summit was covered by clouds and no incandescence from an advancing lava flow could be seen.

From conversations with personnel from PETROECUADOR, road workers, peasants, etc., the team obtained the following information. Workers from TECHINT, an Argentinian company building a second pipeline parallel to the existing one, were at their campsite near the Río Montana when the eruption started in the early hours of 3 November (it was still dark). The eruption came without prior warning, but they were able to evacuate before strong explosions around 0900 sent pyroclastic flows along the Ríos Montana and Marker. These flows destroyed the road and parts of the new pipeline still under construction. The old pipeline was displaced several meters horizontally but never broke. At places the pyroclastic-flow deposits came to rest in direct contact with the tube. Temperature measurements at points of contact yielded values of 80°C. In subsequent days several lahars came down the Ríos Montana and Marker after heavy rains, further damaging the road (but not the pipeline). The pipeline has continued its operation; it delivers more than 400,000 barrels of oil per day to the Pacific coast.

Inhabitants of the small village of El Reventador, located ~12 km downstream from the confluence of the Ríos Montana and Coca voluntarily evacuated their homes when they heard the explosions around 0900.

One of the scoriaceous juvenile rock samples collected near the confluence of Río Marker with Río Coca was analyzed by X-ray fluorescence and thin sections were made of the same sample. The results revealed that the rock is an andesite (SiO2= 58.1%) similar in composition to those erupted in 1976 (55-58% SiO2).

Satellite data. Simon Carn (NASA/UMBC) reported that TOMS observations of the Reventador eruption clouds during 3-4 November suggest modest SO2 burdens and spatial separation of the emitted SO2 and ash. Carn, with input from Andy Harris, also constructed a timeline of notable events during 3-6 November along with potentially useful satellite images and overpasses (table 2).

Table 2. Preliminary timeline of the November 2002 eruption of Reventador, compiled using satellite imagery and information from IG and the Washington VAAC. Courtesy of Simon Carn and Andy Harris.

Date Time (UTC) Satellite Event
3 Nov 2002 0700 -- Seismic events recorded
3 Nov 2002 0945 GOES-8 Clear - no hot spot
3 Nov 2002 1000 -- Eruption begins; 3 km ash column, incandescent ejecta
3 Nov 2002 1015, 1045, 1115 GOES-8 Clear - no hot spot
3 Nov 2002 1245, 1315, 1345 GOES-8 Ash
3 Nov 2002 1400 -- Main eruption phase; pyroclastic flows reported
3 Nov 2002 1415 GOES-8 Ash, ring-shaped cloud?
3 Nov 2002 1445 GOES-8 Ash
3 Nov 2002 1510 MODIS Terra Ash
3 Nov 2002 1515 GOES-8 Ash
3 Nov 2002 1530 GOME SO2
3 Nov 2002 1543 EP TOMS SO2, ash
3 Nov 2002 1545, 1615, 1645 GOES-8 Ash
3 Nov 2002 1707 NOAA-16 AVHRR Ash
3 Nov 2002 1715 GOES-8 Ash
3 Nov 2002 1722 SeaWiFS Ash
3 Nov 2002 1745 GOES-8 Ash
3 Nov 2002 1810 -- Ash begins to fall in Quito
3 Nov 2002 1815, 1845, 1915, 1945 GOES-8 Ash
3 Nov 2002 2000 -- Ash covers large area of Ecuador, reaching coast
3 Nov 2002 2015 GOES-8 Ash, gravity waves?
3 Nov 2002 2045, 2115, 2145, 2215 GOES-8 Ash, gravity waves
4 Nov 2002 0345, 0415, 0445, 0515, 0545, 0615 GOES-8 Cloud-covered
4 Nov 2002 0625 MODIS Aqua Ash, SO2
4 Nov 2002 0645 GOES-8 Cloud clearing- possible hot spot
4 Nov 2002 0710 NOAA-16 AVHRR Ash
4 Nov 2002 0715, 0745 GOES-8 Hot spot
4 Nov 2002 0815, 0845 GOES-8 Strong hot spot and plume
4 Nov 2002 0915 GOES-8 Strong hot spot and minor plume
4 Nov 2002 0945, 1015 GOES-8 Strong hot and detached minor plume
4 Nov 2002 1045 GOES-8 Hot spot
4 Nov 2002 1115 GOES-8 Ash, strong hot spot and main plume
4 Nov 2002 1145, 1215, 1245, 1315, 1345, 1415 GOES-8 Ash, main plume extends W
4 Nov 2002 1445 GOES-8 Ash, main plume (N arm) reaches coast
4 Nov 2002 1515 GOES-8 Ash
4 Nov 2002 1530 GOME SO2
4 Nov 2002 1555 MODIS Terra SO2
4 Nov 2002 1632 EP TOMS SO2, ash
4 Nov 2002 1715 GOES-8 Plume still attached to hot spot
4 Nov 2002 1835 NOAA-16 AVHRR Ash
4 Nov 2002 1845 MODIS Aqua SO2
5 Nov 2002 1645, 1715, 1745 GOES-8 Low-level ash
5 Nov 2002 1815, 1845, 1915 GOES-8 Low-level ash
6 Nov 2002 1530 GOME SO2
6 Nov 2002 1544, 1634, 1545, 1634, 1546 EP TOMS SO2

The TOMS overpass at 1543 UTC on 3 November captured the early phase of the eruption. An ash signal was localized over the volcano and a more extensive SO2 cloud containing ~12 kilotons SO2 was spreading E and W.

At 1632 UTC on 4 November, TOMS detected several distinct cloud masses. A cloud containing no detectable ash and ~11 kilotons SO2 was situated E of Ecuador on the Perú/Colombia border, a maximum distance of ~600 km from Reventador beyond which a data gap intervened. A second cloud containing ~42 kilotons SO2 and a weak ash signal was observed over the Pacific Ocean around 700 km from the volcano. The highest ash concentrations were detected in a cloud straddling the coast of Ecuador ~260 km W of the volcano that covered ~70,000 km2. This cloud contained little SO2. It is assumed that these clouds (total ~53 kilotons SO2) were erupted on 3 November.

A plume was also detected extending ~200 km W of Reventador, containing ~10 kilotons SO2. Based on high temporal resolution GOES imagery this plume first appeared sometime between 1045 UTC and 1115 UTC on 4 November. Nearby Guagua Pichincha was also reported active at this time by the Washington VAAC, and may have contributed some SO2; the highest SO2 concentrations in the Reventador plume were measured in the TOMS pixel covering Guagua Pichincha.

On 5 November neither SO2 nor ash were detected by TOMS, although a ~700-km-wide data gap occurred off the coast of Ecuador. The TOMS orbit was better placed on 6 November but no SO2 or ash were apparent. However, renewed SO2 emissions were detected on 7 November.

Geologic Background. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Information Contacts: P. Ramon, M. Hall, P. Mothes, and H. Yepes, Instituto Geofísico (IG), Escuela Politécnica Nacional, Quito (URL: http://www.igepn.edu.ec/); Simon A. Carn, Joint Center for Earth Systems Technology (NASA/UMBC), University of Maryland-Baltimore County, 1000 Hilltop Circle, Baltimore, MD (URL: https://jcet.umbc.edu/); Andy Harris, HIGP/SOEST, University of Hawaii at Manoa, HI 96822 USA (URL: http://goes.higp.hawaii.edu/); Claus Siebe and Gabriel Valdez Moreno, Instituto de Geofísica, UNAM, Mexico, D.F.; Jesús Manuel Macías, CIESAS-Mexico, Juarez 87, Tlalpan, DF. CP14000; Aurelio Fernández Fuentes, Centro Universitario de Prevencion de Desastres, Universidad de Puebla, Mexico; Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).


Ruapehu (New Zealand) — February 2003 Citation iconCite this Report

Ruapehu

New Zealand

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

All times are local (unless otherwise noted)


Volcanic tremor episodes and Crater Lake temperature variations

Between 6 and 16 September 2002 the Institute of Geological & Nuclear Sciences (IGNS) reported that there were four short-lived episodes of volcanic tremor at Ruapehu. The duration of these episodes ranged from 8 to more than 40 hours. Episodes with similar characteristics were recorded previously in 2002 on 21 February (~12 hours duration), 17 May (~24 hours), 29 May (~18 hours), 17 June (~24 hours), and 15 July (~8 hours). The September events were unusual because there were four tremor episodes in a ten-day period. Another IGNS report on 8 October noted that there had been five short-lived episodes of moderate-strong volcanic tremor since 6 September, with durations of 8 hours to more than 2 days (figure 25). Tremor levels were generally higher than normal background levels starting on 22 September.

Figure (see Caption) Figure 25. Plot of volcanic tremor amplitudes at Ruapehu, 10 September-8 October 2002. Courtesy of IGNS.

The temperature of Crater Lake during two visits between 16 September and 8 October remained around 19°C, similar to the 19.4°C value measured on 30 August. Intermittent weak seismic tremor continued during November, along with a small number of volcanic earthquakes early in the month. Water temperature of Crater Lake measured during 22-29 November was 24°C, an increase of 5°C from the previous month. Weak tremor continued as of 13 December, accompanied by a small number of minor volcanic earthquakes. Volcanic tremor and earthquakes continued through 19 December, and the water temperature of Crater Lake was reported to be 35°C.

The water temperature measured at Crater Lake at the end of January was 32°C, down 8°C from two weeks earlier (40°C). Minor volcanic tremor continued through February, then steadily declined during 21-28 February to low background levels. On 5 March the temperature measured at Crater Lake had decreased another 2°C to 30°C. The lake was a uniform light gray color with some surface sulfur slicks. Seismic tremor remained at normal levels as of 21 March, but there were periods of moderate tremor on the nights of 14 and 15 March. The temperature of Crater Lake rose to 35°C on 15 March; there were sulfur slicks on the lake surface.

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: Institute of Geological & Nuclear Sciences (IGNS), Private Bag 2000, Wairakei, New Zealand (URL: http://www.gns.cri.nz/).


Saunders (United Kingdom) — February 2003 Citation iconCite this Report

Saunders

United Kingdom

57.8°S, 26.483°W; summit elev. 843 m

All times are local (unless otherwise noted)


Lava lake detected in satellite imagery during 1995-2002

Although previous eruptions have been recorded in the South Sandwich Islands (Coombs and Landis, 1966), ongoing volcanic activity has only recently been detected and studied. These islands (figure 1) are all volcanic in origin, but sufficiently distant from population centers and shipping lanes that eruptions, if and when they do occur, currently go unnoticed. Visual observations of the islands probably do not occur on more than a few days each year (LeMasurier and Thomson, 1990). Satellite data have recently provided observations of volcanic activity in the group, and offer the only practical means to regularly characterize activity in these islands.

Figure (see Caption) Figure 1. The South Sandwich Island archipelago, located in the Scotia Sea. The South Sandwich Trench lies approximately 100 km E, paralleling the trend of the islands, where the South American Plate subducts westward beneath the Scotia Plate. Courtesy Hawaii Institute of Geophysics and Planetology and British Antarctic Survey.

Using Advanced Very High Resolution Radiometer (AVHRR) data, Lachlan-Cope and others (2001) discovered and analyzed an active lava lake on the summit of Saunders Island (figure 2) that was continuously present for intervals of several months between March 1995 and February 1998; plumes originating from the island were observed on 77 images during April 1995-February 1998. J.L. Smellie noted that during helicopter overflights on 23 January 1997 (Lachlan-Cope and others, 2001) "dense and abundant white steam was emitted from the crater in large conspicuous puffs at intervals of a few seconds alternating with episodes of less voluminous, more transparent vapour." Smellie also observed that the plume commonly extended ~8-10 km downwind.

Figure (see Caption) Figure 2. Map of Saunders Island, adapted from Holdgate and Baker (1979). Lighter shaded stippled areas show rock outcrop, the remainder is snow or ice covered. Relief is shown by form lines that should not be interpreted as fixed-interval contours. Courtesy Hawaii Institute of Geophysics and Planetology and British Antarctic Survey.

The MODIS Thermal Alert system also detected repeated thermal anomalies throughout 2000-2002 in the summit area (figure 3), indicating that activity at the lava lake has continued. Anomalous pixels (1 km pixel size) were detected intermittently and were all 1-2 pixels in size, consistent with the relatively small confines of the crater. The timing of anomalous images in this study likely has more to do with the viewing limitations imposed by weather (persistent cloud cover masks any emitted surface radiance in the majority of images) than it has to do with fluctuations in activity levels, so this plot of radiance (figure 4) should not be used as a proxy for lava lake vigor.

Figure (see Caption) Figure 3. Selected MODIS images showing thermal anomalies on Saunders Island. Band 20 (3.7 µm) is shown here. Anomalous pixels on Saunders Island correspond to the lava lake in the summit crater of Mt. Michael volcano. Images are not georeferenced for purposes of radiance integrity, therefore coastlines are approximate. Courtesy Hawaii Institute of Geophysics and Planetology and British Antarctic Survey.
Figure (see Caption) Figure 4. Summed radiance of anomalous pixels in each image. Band 21 (3.9 µm) was used for these plots. Points show the result for each image, and the line is a three point running mean of values. Courtesy Hawaii Institute of Geophysics and Planetology and British Antarctic Survey.

References. Coombs, D.S., and Landis, C.A., 1966, Pumice from the South Sandwich eruption of March 1962 reaches New Zealand: Nature, v. 209, p. 289-290.

Holdgate, M.W., and Baker, P.E., 1979, The South Sandwich Islands, I, General description: British Antarctic Survey Science Report, v. 91, 76 p.

Lachlan-Cope, T., Smellie, J.L., and Ladkin, R., 2001, Discovery of a recurrent lava lake on Saunders Island (South Sandwich Islands) using AVHRR imagery: Journal of Volcanology and Geothermal Research, v. 112, p. 105-116.

LeMasurier, W.E., and Thomson, J.W. (eds), 1990, Volcanoes of the Antarctic Plate and Southern Oceans: American Geophysical Union, Washington, D.C., AGU Monograph, Antarctic Research Series, v. 48.

Wright, R., Flynn, L.P., Garbeil, H., Harris, A.J.L., and Pilger, E, 2002, Automated volcanic eruption detection using MODIS: Remote Sensing of Environment, v. 82, p. 135-155.

Geologic Background. Saunders Island is a volcanic structure consisting of a large central edifice intersected by two seamount chains, as shown by bathymetric mapping (Leat et al., 2013). The young constructional Mount Michael stratovolcano dominates the glacier-covered island, while two submarine plateaus, Harpers Bank and Saunders Bank, extend north. The symmetrical Michael has a 500-m-wide summit crater and a remnant of a somma rim to the SE. Tephra layers visible in ice cliffs surrounding the island are evidence of recent eruptions. Ash clouds were reported from the summit crater in 1819, and an effusive eruption was inferred to have occurred from a N-flank fissure around the end of the 19th century and beginning of the 20th century. A low ice-free lava platform, Blackstone Plain, is located on the north coast, surrounding a group of former sea stacks. A cluster of parasitic cones on the SE flank, the Ashen Hills, appear to have been modified since 1820 (LeMasurier and Thomson, 1990). Vapor emission is frequently reported from the summit crater. Recent AVHRR and MODIS satellite imagery has revealed evidence for lava lake activity in the summit crater.

Information Contacts: Matt Patrick, Luke Flynn, Harold Garbeil, Andy Harris, Eric Pilger, Glyn Williams-Jones, and Rob Wright, HIGP Thermal Alerts Team, Hawai'i Institute of Geophysics and Planetology (HIGP) / School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); John Smellie, British Antarctic Survey, Natural Environment Research Council, High Cross, Madingly Road, Cambridge CB3 0ET, United Kingdom (URL: https://www.bas.ac.uk/).


Sheveluch (Russia) — February 2003 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Continued lava dome growth, short-lived explosions, and seismicity

During mid-September 2002 through February 2003 at Shiveluch, a lava dome continued to grow in the active crater. Short-lived explosions generally sent gas-steam plumes tens of meters to ~3 km above the dome. Seismicity remained above background levels. Earthquakes with magnitudes of ~2-2.7, as well as many smaller ones, occurred at depths of 0-6 km (table 5). Thermal anomalies were visible on satellite imagery (table 6). Intermittent spasmodic tremor with amplitudes of 0.3-1.3 x 106 mps occurred throughout the report period.

Table 5. Earthquakes, explosions, and plumes at Shiveluch during 26 September 2002 through February 2003. Courtesy KVERT.

Date Earthquakes Magnitude Explosions Plume height above dome
26 Sep-04 Oct 2002 11 2-2.7 38 1-2.5 km
04 Oct-11 Oct 2002 7 2-2.4 16 1-2 km
11 Oct-18 Oct 2002 4 2-2.2 13 1-2.5 km
18 Oct-25 Oct 2002 -- -- 10 1.0 km
25 Oct-01 Nov 2002 -- -- 8 2 km
01 Nov-08 Nov 2002 -- -- 7 2-3 km
11 Nov 2002 6 2.0-2.4 -- --
11 Nov-14 Nov 2002 5 2.0-2.4 7 2-3 km
14 Nov-20 Nov 2002 6 2.0 19 2-3 km
22 Nov-29 Nov 2002 2 1.9 8 1-2 km
29 Nov-06 Dec 2002 -- -- 9 1-2 km
06 Dec-13 Dec 2002 3 1.7-2.3 8 1-2 km
13 Dec-20 Dec 2002 1 1.8 7 1-2 km
20 Dec-27 Dec 2002 -- -- 6 2-3 km
27 Dec-03 Jan 2003 -- -- 25 2 km
03 Jan-10 Jan 2003 -- -- 11 1.5 km
10 Jan-17 Jan 2003 -- -- 12 2 km
17 Jan-24 Jan 2003 -- -- 11 2 km
31 Jan-07 Feb 2003 6 1.6-2.5 -- 1.5 km
07 Feb-14 Feb 2003 -- -- 10 1.0 km
14 Feb-21 Feb 2003 -- -- 17 1.5 km
21 Feb-28 Feb 2003 1 2.1 14 3.0 km

Table 6. Plumes at Shiveluch visible on satellite imagery during October 2002 through February 2003. Courtesy KVERT.

Date Number of pixels Max band-3 temp. (°C) Background (°C) Comment
02 Oct 2002 2-3 40.46-45.48 ~-10 to -3 A 15 km faint plume extended to the SE
27 and 30 Sep, 01-03 Oct 2002 2-4 -- -- On 2 October, an 80-km plume extending to the SE was observed in a NOAA16 image
05 Oct-07 Oct 2002 2-8 36.81-49.35 ?-14-0 On 6 October, a 111-km plume extended to the SE
09 Oct-10 Oct 2002 2-8 -- -- --
11 Oct-13 Oct 2002 2 15-49 -19 to -6 --
12 Oct-14 Oct 2002 2-3 -- -- --
21-22, 24-25 Oct 2002 1-8 33-49 -20 to -1 On 22 October a faint plume extended 125 km to the SE
21 Oct-24 Oct 2002 1-5 -- -- NOAA12, NOAA16, and MODIS imagery
27 Oct-30 Oct 2002 2-6 17-36 -22 to -6 AVHRR
27 Oct-30 Oct 2002 2-6 -- -- NOAA12, NOAA16, MODIS
08 Nov-09 Nov 2002 2-4 34-49 -20 to -4 AVHRR; On 8 November a faint ~11-km-long plume extended to the SE, visible on band-3
08 Nov and 09 Nov 2002 4, 9 -- -- MODIS
08 Nov-11 Nov 2002 2-4 -- -- NOAA12 and NOAA16
11 and 13 Nov 2002 4-5 40-49 -18 to -10 AVHRR
11-13 Nov 2002 2-5 -- -- NOAA12 and NOAA16
13 Nov 2002 4 -- -- MODIS from Sakhalin
16-19, 22 Nov 2002 2-6 2-49 -26 to -20 AVHRR and MODIS; On 17-18 November, 20-km and 70-km-long gas-steam plumes extended to the WNW and SSE, respectively
23, 25-27 Nov 2002 1-5 1-49 -27 to -20 AVHRR and MODIS; on 27 November a 150-km-long gas-steam plume extended to the NE
29 Nov-05 Dec 2002 2-5 -1 to 49 -31 to -20 AVHRR and MODIS; on 29 November, a possible steam-gas plume extended 80 km to the SSE
01 and 05 Dec 2002 -- -- -- Gas-and-steam plumes extended 40 km and 45 km to the ENE and NNW
09 Dec-12 Dec 2002 2-6 3-39 -29 to -20 AVHRR and MODIS
13-17 and 19-20 Dec 2002 1-6 -15 to 49 -34 to -25 AVHRR and MODIS
19-20 and 23-25 Dec 2002 1-6 10-40 -27 to -23 --
27, 29, 31 Dec and 01-02 Jan 2003 2-4 -7 to 34 -38 to -30 On 1 January, a 10+ km plume extending ESE was visible on MODIS imagery
03 Jan-10 Jan 2003 1-6 -8 to 47.5 -30 to -13 --
10-13 and 15 Jan 2003 1-7 12-47.5 -33 to -20 --
17-22 and 24 Jan 2003 1-4 -2 to 19 -27 to -20 --
25-29 Jan 2003 2-7 -2 to 46 -25 to -15 --
01-06 Feb 2003 2-6 3-49 -24 to -9 Gas-steam plumes extended ~40 km to the W and NNE from the dome on 1 and 3 Feb, respectively
07-13 Feb 2003 1-7 -12 to 49 -30 to -12 Gas-steam plume extended ~35 km NNW from the dome on 9 Feb
14-20 Feb 2003 1-6 26-49 -33 to 5 On 15 Feb a wide gas-steam plume extended > 25 km E; on 16 Feb a narrow plume extended 110 km N; during 16-17 Feb ash and pyroclastic deposits were noted from the S to E slopes; a gas-steam plume extended 30 km W on 19 Feb; a gas-steam plume extended up to 96 km SSW on 20 Feb
21-28 Feb 2003 2-6 21-49 -30 to -8 Gas-steam plumes extended up to 50 km to the SSW, SE, and NE during 24-27 Feb

Incandescence was observed at the lava dome on 6 October. On 11 November, seismic data indicated possible hot avalanches sending clouds up to 5.5 km above the dome.

During late November and early December, gas-and-steam plumes extended >10 km to the E and W. On 19 December, short-lived explosions at 1238 and 1514 sent gas-ash plumes to ~5.5 km and 5.0 km altitude, respectively. In the first case, pyroclastic flows moved to the SE; in the second, to the S, inside the Baidarnaya river. The runout of both pyroclastic flows was 3 km.

On 28 December 2002, a small amount of light-gray ash was observed on the surface of snow. During early January 2003, plumes extended >5-10 km to the W and NW. During late February, plumes extended 10-40 km to the SW, S, and SE. Ash was noted in plumes on 24 October, 1, 11, 15, 19, and 20 November, 1, 19, and 24 December, 4 and 25 January, and 15, 17, 25, and 26 February. The Concern Color Code remained at Yellow.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Soufriere Hills (United Kingdom) — February 2003 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Continued dome growth, rockfalls, and pyroclastic flows

During mid-September 2002 through February 2003 at Soufrière Hills, the dome continued to grow, producing numerous rockfalls and small-to-moderate pyroclastic flows. Most of the activity was concentrated on the NE and N flanks, producing numerous pyroclastic flows in White's Ghaut, the Tar River Valley, and Tuitt's Ghaut. Pyroclastic flows and rockfalls also traveled down the W and NW flanks. Ashfall affected surrounding areas, accumulating in thicknesses up to 9 mm. The Washington VAAC issued notices to the aviation community almost daily. Seismicity was dominated by rockfalls (table 42).

Table 42. Seismicity at Soufrière Hills during 13 September 2002-28 February 2003. *During some weeks, the number of seismic events was under-represented because of problems with the seismic stations. Courtesy MVO.

Date Rockfall Hybrid Long-period Long-period / Rockfall Volcano-tectonic
13 Sep-20 Sep 2002 689 67 162 41 1
20 Sep-27 Sep 2002 680 36 260 55 0
27 Sep-04 Oct 2002 811 15 223 51 2
04 Oct-11 Oct 2002* 468 3 77 42 0
11 Oct-18 Oct 2002* 650 2 98 80 1
18 Oct-25 Oct 2002 536 6 120 27 1
25 Oct-01 Nov 2002 670 9 148 72 0
01 Nov-08 Nov 2002 694 3 60 38 0
08 Nov-15 Nov 2002* 409 0 29 8 1
15 Nov-22 Nov 2002 592 2 88 37 1
22 Nov-29 Nov 2002 586 0 44 32 0
29 Nov-06 Dec 2002 354 0 33 43 0
06 Dec-13 Dec 2002 427 6 47 30 0
13 Dec-20 Dec 2002 742 2 50 50 0
20 Dec-27 Dec 2002 760 5 45 30 0
27 Dec-03 Jan 2003 863 3 86 41 1
03 Jan-10 Jan 2003 789 0 120 54 0
10 Jan-17 Jan 2003 606 7 67 42 2
17 Jan-24 Jan 2003 566 0 58 24 1
24 Jan-31 Jan 2003 745 2 177 62 1
31 Jan-07 Feb 2003 882 6 148 114 0
07 Feb-14 Feb 2003 840 3 117 78 1
14 Feb-21 Feb 2003 905 8 87 80 1
21 Feb-28 Feb 2003 1078 1 92 85 0

Activity during September 2002. Lava-dome growth was directed to the NE during 13-20 September, with frequent rockfalls and small pyroclastic flows sending material to a sector extending from the central Tar River Valley on the E flank to the NE flanks above Tuitt's Ghaut. Some material tumbled through a notch onto the N flank. A major change in direction of extrusion followed a hybrid earthquake swarm between 0703 and 1515 on 19 September. Growth of the previously active NE lobe stagnated during 21-22 September. A near-vertical spine was extruded in the central area around the 21st, possibly indicating a switch in growth direction. On 26 September a swarm of 36 hybrid events occurred between 0330 and 1112. The same day observations revealed a large new dome lobe that had extruded towards the W in the area previously known as Gages Wall. Material spalling off of this lobe produced rockfalls and small pyroclastic flows down Gages Valley that reached up to 1 km.

Notable pyroclastic flows occurred on the evening of 25 September and the morning of the 27th. Growth and rockfall activity then changed towards the N flanks, suggesting a possible stagnation of the recently extruded western lobe. Spectacular incandescence and semi-continuous rockfall activity were observed on the NE and N flanks of the dome on the night of 26-27 September.

On 27 September a 4-hour-period of heightened activity occurred in the afternoon and evening, with small semi-continuous pyroclastic flows traveling down the N flanks and eastwards into the upper portions of Tuitt's Ghaut and then into White's Bottom Ghaut. A newly extruded lobe was visible on 28 September almost directly to the NW with a broad headwall over the N, NW, and W flanks. On the evening of 29 September there was another period of heightened activity on the N flanks that lasted 1.5 hours, with pyroclastic flows just reaching the sea along White's Bottom Ghaut. It was estimated that during this event only 2-3 x 106 m3 of the N edge of the active NW lobe was shed.

The Washington VAAC reported that a low-level ash cloud from an emission at 1510 on 29 September was visible over eastern Puerto Rico on satellite imagery through the following day. On 30 September a light dusting of white ash fell in eastern Puerto Rico at Roosevelt Roads Naval Air Station.

Activity during October 2002. Observations on 1 October revealed that re-growth of the collapsed area had occurred. A brief period of heavy rain on 2 October triggered a moderate-sized mudflow down the Belham Valley. Analysis of seismic data suggested that pyroclastic-flow activity on 2 October began at 1310, and sustained dome collapse continued for 6 hours. Low-energy pyroclastic flows were observed reaching the sea on the Tar River's flanks throughout the collapse, and ash clouds were produced that drifted to the NW. Heavy ashfall occurred in the residential areas of Salem, Old Towne, and Olveston, with deposits up to 9 mm thick. Subsequent observations revealed that this collapse was confined to the E flanks, and that this was again a relatively small event (less than 5 x 106m3 of material was shed off of the E side of the dome complex).

According to the Washington VAAC, after daybreak on 3 October there were several reports of ashfall in Puerto Rico, and visible satellite imagery at 1115 confirmed that an ash cloud around 2.4 km altitude covered most of the island. At 1615 the area of very thin ash was not visible on satellite imagery. By the next day, ash from the previous day's emissions had drifted W, and around 0902 it was located over southern Puerto Rico. A thin plume of ash also extended SSW of St. Croix island.

Early in October the NW extrusion lobe of the lava dome grew to the NW, but later growth remained more centralized and there was noticeable bulking up of the lobe's summit area. Talus continued to accumulate behind the NW buttress and in the head of Tyre's Ghaut. Minor mudflow activity occurred on 9 October. The growth of the lava dome towards the NW prompted the evacuation of populated areas along the fringes of the lower part of the Belham Valley (~300 people) on 8 and 9 October, and the area was declared part of the Exclusion Zone. A relatively small pyroclastic flow traveled NNE down the flanks on 13 October.

On the afternoon of 22 October intense rainfall at midday produced large mudflows NW in the Belham Valley. At the peak of flow, the entire width of the valley floor at Belham Bridge was flooded and standing waves up to 2.5 m high were observed. By 1430, pyroclastic-flow activity began. For several hours, pyroclastic flows from the N flank of the dome were channeled NE into the upper parts of Tuitt's Ghaut, from where they crossed over into White's Bottom Ghaut. Flows also occurred on the dome's E flank in the Tar River Valley.

The volcano was observed using a remote camera and during a flight on 31 October. The active extruded lobe in the NW continued to steadily grow, bulking out on the N and W sides. Rockfalls and pyroclastic flows traveled down the E and N flanks, particularly within Tuitt's Ghaut and the Tar River Valley. A considerable amount of debris also spalled off the W flank of the active extruded lobe and accumulated in the upper parts of Fort Ghaut.

Activity during November 2002. During early November lava-dome growth on the N part of the dome was less directed, with rockfalls dispersed over the summit and flanks. The lobe shed rockfall debris predominately down Tuitt's Ghaut and Tar River Valley, although also onto the NW flank and into the top of Gage's Valley. According to the Washington VAAC, on 8 November strong pyroclastic flows produced ash-and-gas clouds to a height of ~1.5 km.

On 8 and 9 November pyroclastic flows traveled 900-1,000 m NW into Tyer's Ghaut at the headwaters of the Belham Valley. During 12-15 November, the size and energy of the pyroclastic flows increased slightly. During 15-19 November, small pyroclastic flows traveled 1-1.5 km from the dome every few hours in Tuitt's Ghaut to the NE and in the Tar River Valley to the E. On 29 November the active lobe had a broad whaleback-shaped upper surface, which was oriented towards the NNE.

During 29 November-6 December a number of small, short-lived spines formed at the base of the active lobe in the N part of the dome complex, shedding material E into White's Ghaut and the Tar River Valley. Lava blocks continued to spall off the front of the lobe, shedding material NE into Tuitt's Ghaut and onto the northern talus slope. An average of one moderate-sized pyroclastic flow occurred per day and traveled no farther than 1-1.5 km from the lava dome into Tuitt's and White's ghauts and into the Tar River Valley. During 5-6 December, rockfalls and small pyroclastic flows occurred more frequently on the northern talus slope and on the NW, at the top of Tyer's Ghaut.

Activity during December 2002. A sustained dome collapse began on 8 December at 2045, producing energetic pyroclastic flows down White's Ghaut to the sea at Spanish Point. Ash clouds rose to ~3 km altitude and drifted WNW. In Plymouth and Richmond Hill 4 mm of ash was deposited. Seismicity returned to background levels on 9 December by 0045, and several days of weak tremor occurred.

The collapse scar on the dome's NNE flank, estimated to have had a volume of 4-5 x 106 m3, was being filled rapidly with freshly extruded lava. Observations on 13 December revealed a large amount of fragmental lava extruded in a northerly direction on the summit. A large spine was also extruded on the NW side of the summit.

During late December spectacular incandescence of the dome was observed on most nights. Activity increased during 18-20 December, and on 19 December mudflows occurred in White River, Tar River Valley, and Fort Ghaut. During 20-27 December extrusion occurred on the N, and occassionally NW, sides of the summit. A large spine was pushed up at the back of the active extruded lobe during the night of 26-27 December, but was not visible by 2 January. The Washington VAAC reported that on 28 December around 1130 a 3-km-high ash cloud generated from pyroclastic flows drifted over the islands of St. Kitts and Nevis.

Activity during January-February 2003. Activity escalated to very high levels on the night of 27 December. During 27 December-10 January continuous rockfalls and numerous pyroclastic flows spalled off the active extruded lobe on the NNE side of the lava dome. Activity decreased on the night of 2 January to moderate levels on the 3rd.

During mid-January, activity generally declined to a moderate level. During 15-17 January almost all pyroclastic flows occurred in the Tar River Valley, with only minor rockfalls traveling down the dome's NE and N sides. Lava extrusion occurred NE of the lava-dome complex that was associated with rockfalls and small pyroclastic flows down Tar River Valley, White's Ghaut, Tuitt's Ghaut, and on the northern talus slopes. On 18, 20, and 24 January small pyroclastic flows traveled ~1 km down Tyer's Ghaut.

Activity increased during late January. Growth of the active extrusion lobe continued on the N side of the lava dome. The direction of growth was generally towards the NNE, although the focus of rockfall and pyroclastic-flow activity varied from day to day. A pulse of activity occurred at midday on 30 January, during which pyroclastic flows simultaneously descended several flanks of the lava dome traveling to the Tar River Valley, White's Ghaut, Tuitt's Ghaut, and W to Fort Ghaut.

During 31 January-14 February activity remained moderate. Growth of the lava dome was focused on a large, steep lobe directed to the NE. A small amount of rockfall material was directed W towards Fort Ghaut. Rockfalls and small pyroclastic flows also occurred off the N flank of the dome onto the area of Riley's Estate.

During 19-25 February pyroclastic flows and rockfalls were concentrated more on the E flank of the lava dome and in the Tar River Valley, although there were several periods of activity on the N flank, with pyroclastic flows in Tuitt's Ghaut and at the top of Farrell's Plain.

Activity increased slightly during 21-28 February. During an observation flight on 27 February lava-dome growth was concentrated towards the NE. Pyroclastic flows and rockfalls traveled down the lava dome's E and NE flanks via the Tar River Valley and Tuitt's Ghaut. There were also several periods of activity on the N flank, with pyroclastic flows at the top of Farrell's Plain.

SO2 emission rates varied throughout the report period (table 43), and were especially high following the dome-collapse event on 9 December (2,350 tons per day average).

Table 43. SO2 emission rates at Soufrière Hills during 13 September 2002 through 28 February 2003. Courtesy MVO.

Date SO2 emissions (tons/day)
13 Sep-20 Sep 2002 85-518
11 Oct-12 Oct 2002 260-520, average of 302
13 Oct 2002 430-860, average of 691
16 Oct 2002 43-173
17 Oct-18 Oct 2002 346-518
19 Oct-21 Oct 2002 85-300
23 Oct-25 Oct 2002 430-500, peak of 1000
25 Oct-27 Oct 2002 45-260
27 Oct 2002 520
27 Oct-01 Nov 2002 25-260
01 Nov 2002 240
02 Nov 2002 208
03 Nov 2002 200
04 Nov 2002 508
06 Nov-07 Nov 2002 220
08 Nov-15 Nov 2002 520-560
15 Nov 2002 160
16 Nov 2002 340
17 Nov 2002 380
18 Nov 2002 180
19 Nov 2002 173
22 Nov-29 Nov 2002 520-1040
24 Nov 2002 170-350
29 Nov-06 Dec 2002 Average 400
29 Nov-01 Dec 2002 Average 280
06 Dec-08 Dec 2002 280
09 Dec 2002 Average 2,350
10 Dec 2002 620
06 Jan 2003 130
07 Jan 2003 200
09 Jan 2003 430
10-17 Jan 2003 ~86-1209
10 Jan 2003 ~170-520, average ~260
11 Jan 2003 Emissions of ~430 were recorded until mid-morning, but then decreased to ~86 for several hours. In the afternoon they reached ~860-1210 before dropping to ~430-518
12 Jan 2003 ~345-605, average ~354
13 Jan 2003 ~430-780, average ~490
15 Jan 2003 ~430-605, average ~527
18 Jan 2003 300
19 Jan 2003 165
20 Jan 2003 700
21 Jan-24 Jan 2003 270
24 Jan 2003 480
25 Jan-28 Jan 2003 290
29 Jan 2003 560
30 Jan 2003 620
31 Jan-07 Feb 2003 90-170
14 Feb-21 Feb 2003 170-350
21 Feb-28 Feb 2003 400-460
22 Feb 2003 840
23 Feb 2003 1120

Geologic Background. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Information Contacts: Montserrat Volcano Observatory (MVO), Mongo Hill, Montserrat, West Indies (URL: http://www.mvo.ms/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Associated Press.


White Island (New Zealand) — February 2003 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)


Increased SO2 emissions since December, mud ejections in February

Minor volcanic tremor continued, and the plume of steam and gases from the vent remained unchanged through the end of November 2002, according to the Institute of Geological & Nuclear Sciences (IGNS). The output of SO2 measured on 10 December was 112 ± 36 metric tons per day (t/d); in October the value was 63 t/d. Volcanic tremor continued and was accompanied by minor booming and explosions in the second week of December. After a brief period of increased activity at the start of the next week, volcanic tremor dropped to the weaker levels of tremor observed previously. Weak steam and gas emissions continued through 19 December, along with weak volcanic tremor.

An IGNS report on 7 February 2002 noted continuing minor volcanic tremor and a weak plume of steam and gases from the active vent. Activity increased slightly during 9-16 February. On 12 February mud was being thrown some tens of meters in the air, and ground vibrations could be felt. This corresponded to a period of slightly stronger volcanic tremor. Seismograph readings returned to normal by the 13th. Minor hydrothermal activity continued as of 21 February, and the output of SO2 had increased to 269 t/d. Seismic tremor steadily declined to low background levels in the last week of the month, though a weak plume of steam and gases was still being emitted.

Seismic tremor levels at White Island remained low on 7 March, but mud was being ejected to low levels around the active vent and a steam plume remained. There were intermittent periods of weak tremor the next week, and SO2 output was reported to be 267 t/d. Seismic tremor was at a very low level during the week ending on 21 March.

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: Institute of Geological & Nuclear Sciences (IGNS), Private Bag 2000, Wairakei, New Zealand (URL: http://www.gns.cri.nz/).

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

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

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

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



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

False Report of Mount Pinokis Eruption

Philippines

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


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

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

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

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

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


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

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

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

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Elgon (Uganda) — December 2005

Elgon

Uganda

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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