************************************************************ SI/USGS Weekly Volcanic Activity Report 30 April-6 May 2008 ************************************************************ Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Balbi, Bougainville Island (SW Pacific) | Chaitén, Southern Chile | Ubinas, Perú Ongoing Activity: | Batu Tara, Komba Island (Indonesia) | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Nevado del Huila, Colombia | Rabaul, New Britain (SW Pacific) | Sakura-jima, Kyushu (Japan) | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Tungurahua, Ecuador | Veniaminof, Alaska Peninsula The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network. Note: Many news agencies do not archive the articles they post on the Internet, and therefore the links to some sources may not be active. To obtain information about the cited articles that are no longer available on the Internet contact the source. New Activity/Unrest BALBI Bougainville Island (SW Pacific) 5.92°S, 154.98°E; summit elev. 2715 m Based on information from RVO, the Darwin VAAC reported that Balbi erupted on 7 May. Ash was not detected on satellite imagery. Geologic Summary. The large Balbi stratovolcano forms the highest point on Bougainville Island. The 2715-m-high summit of the complex andesitic volcano is part of a large number of coalesced cones and lava domes. Five well-preserved craters occupy a NW-SE-trending ridge north of the summit cone, which also contains a crater. Three large valleys with steep headwalls dissect the flanks of the volcano. The age of the most recent eruption of Balbi volcano is not known precisely. An oral tradition of a major eruption during the 19th century is now thought to be in error, but could refer to minor eruptive activity from this relatively youthful-looking volcano. Fumaroles are located within 600-m-wide Crater B and on its western flank. Source: Darwin Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m SERNAGEOMIN reported that Chaitén erupted on 2 May, following increased seismicity in the region the day before. A pulsating white to gray ash plume rose to an estimated altitude greater than 21 km (68,900 ft) a.s.l. and drifted SSE. The Alert Level was raised to Red. Based on observations of satellite imagery and pilot reports, the Buenos Aires VAAC reported an ash plume at altitudes of 13.7-16.8 km (45,000-55,000 ft) a.s.l. drifted NE. According to news articles, Chile's government declared a state of emergency on 2 May and several hundred people were evacuated from the town of Chaitén (10 km SE). The eruption was initially thought to have been from Minchinmávida, about 17 km ENE, which last erupted in 1835. According to news sources, ashfall was reported during 2-6 May both locally and up to hundreds of kilometers away, affecting water supplies and roads. Based on observations of satellite imagery and pilot reports, the Buenos Aires VAAC reported that during 3-6 May ash plume rose to altitudes of 7-10.7 km (23,000-35,000 ft) a.s.l. and drifted SE, E, W, and NE. News sources indicated that about 4,000-5,000 people were evacuated from the town of Chaitén and surrounding areas as the eruption continued. On 5 May, ONEMI (Oficina Nacional de Emergencia - Ministerio del Interior) reported that evacuations took place in Futaleufú, about 65 km ESE, where about 30 cm of ash accumulated. One elderly person died during the evacuation efforts. On 6 May, ONEMI and SERNAGEOMIN reported that the eruption became more forceful and generated a wider and darker gray ash plume to an estimated altitude of 30 km (98,400 ft) a.s.l. All remaining people in Chaitén were ordered to evacuate, as well as anyone within 50 km of the volcano. Geologic Summary. Chaitén is a small, glacier-free caldera with a Holocene lava dome located 10 km NE of the town of Chaitén on the Gulf of Corcovado. A pyroclastic-surge and pumice deposit considered to originate from the eruption that formed the elliptical 2.5 x 4 km wide summit caldera was dated at about 9400 years ago. A rhyolitic, 962-m-high obsidian lava dome occupies much of the caldera floor. Obsidian cobbles from this dome found in the Blanco River are the source of prehistorical artifacts from archaeological sites along the Pacific coast as far as 400 km away from the volcano to the north and south. The caldera is breached on the SW side by a river that drains to the bay of Chaitén, and the high point on its southern rim reaches 1122 m. Two small lakes occupy the caldera floor on the west and north sides of the lava dome. Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/index.php, Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI) http://www.onemi.cl/, Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html, Associated Press http://ap.google.com/article/ALeqM5h7IpDogRa67ijkDYkOCyj5e827aAD90DR0Q00, Agence France-Presse http://news.yahoo.com/s/afp/20080504/sc_afp/chilevolcano_080504223559 UBINAS Perú 16.355°S, 70.903°W; summit elev. 5672 m Based on SIGMET reports and observations of satellite imagery, the Buenos Aires VAAC reported that ash plumes from Ubinas rose to altitudes of 5.5-9.1 km (18,000-30,000 ft) a.s.l. and drifted NE, E, and SE during 30 April-3 May. According to news articles, an ash-and-gas plume rose to an altitude of 6.2 km (20,300 ft) a.s.l. on 2 May. Ashfall was reported in local communities and dozens of residents of Querapi, about 4.5 km SE, were evacuated. Geologic Summary. A small, 1.2-km-wide caldera that cuts the top of Ubinas, Peru's most active volcano, gives it a truncated appearance. Ubinas is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Peru. The upper slopes of the stratovolcano, composed primarily of Pleistocene andesitic lava flows, steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas extend 10 km from the volcano. Widespread Plinian pumice-fall deposits from Ubinas include some of Holocene age. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor explosive eruptions. Sources: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html, Associated Press http://ap.google.com/article/ALeqM5h7IpDogRa67ijkDYkOCyj5e827aAD90E1GEO0, NBC http://www.wkyc.com/news/news_article.aspx?storyid=88846 Ongoing Activity BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m Based on observations of satellite imagery, the Darwin VAAC reported that low-level plumes from Batu Tara rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted NW on 3 and 7 May. Geologic Summary. The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow. Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m KVERT reported that seismic activity at Karymsky was at background levels during 25 April-2 May. Possible activity was characterized by gas-and-ash plumes that rose to altitudes of 2-2.5 km (6,600-8,200 ft) a.s.l. Based on seismic interpretation, a gas-and-ash explosion may have occurred on 26 April. Observations of satellite imagery revealed that a thermal anomaly was present in the crater on 25, 27, and 28 April. Based on airport data and information from KEMSD, the Tokyo VAAC reported that an eruption plume rose to altitudes of 3.7 km (10,000-17,000 ft) a.s.l. during 6-7 May. Ash was not detected on satellite imagery. The Level of Concern Color Code remained at Orange. Geologic Summary. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago. Construction of the Karymsky stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been Vulcanian or Vulcanian-Strombolian with moderate explosive activity and occasional lava flows from the summit crater. Most seismicity preceding Karymsky eruptions has originated beneath Akademia Nauk caldera, which is located immediately S of Karymsky volcano and erupted simultaneously with Karymsky in 1996. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m Based on visual observations from HVO and National Park Service (NPS) crews and web camera views, HVO reported that during 30 April-6 May lava flowed SE through a lava tube system underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex to the Waikupanaha ocean entry. On 4 May, lava flows from breakouts on the pali reached the coastal plain. Kilauea summit earthquakes were located beneath the Halema'uma'u crater, along the S-flank faults, and along the SW and E rift zones. The eruption from the vent in Halema'uma'u Crater continued to produce white plumes with minor ash content that drifted mainly SW. During most nights incandescence was seen at the base of the plume. Seismic tremor was elevated. The sulfur dioxide emission rate was high and fluctuated between 540 and 1,250 tonnes per day during 30 April-5 May. The background rate was 150-200 tonnes per day. Geologic Summary. Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world's most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed of lava flows less than about 1,100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island. Source: US Geological Survey Hawaiian Volcano Observatory (HVO) http://hvo.wr.usgs.gov/ NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5365 m INGEOMINAS reported that no significant morphological changes to the summit of Nevado del Huila were noted during an overflight on 6 May, although the NE and NW flanks could not be directly observed. Fumarolic plumes drifted NW. The Alert Level was lowered to Yellow (on a 4-color scale where Yellow is the second lowest). Geologic Summary. Nevado del Huila, the highest active volcano in Colombia, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. Two glacier-free lava domes lie at the southern end of the Huila volcanic complex. The first historical eruption from this little known volcano took place in the 16th century. Two persistent steam columns rise from the central peak, and hot springs are also present. Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co// RABAUL New Britain (SW Pacific) 4.271°S, 152.203°E; summit elev. 688 m RVO reported that during 30 April-7 May ash plumes from multiple places inside Rabaul caldera's Tavurvur cone rose to altitudes of 1.2-2.2 km (3,900-7,200 ft) a.s.l. and drifted N, E, and SE. Intermittent roaring and rumbling noises and occasional explosions were reported. Ashfall was reported in nearby areas. Ash in Rabaul Town (3-5 km NW) suspended by wind and traffic was problematic. During 5-7 May, incandescent tephra was occasionally visible at night. Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the E, where its floor is flooded by Blanche Bay.Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city. Source: Steve Saunders and Herman Patia, Rabaul Volcano Observatory (RVO) SAKURA-JIMA Kyushu (Japan) 31.585°N, 130.657°E; summit elev. 1117 m Based on information from JMA and observations of satellite imagery, the Tokyo VAAC reported that during 6-7 May eruption plumes from Sakura-jima rose to altitudes of 2.4-3.4 km (8,000-11,000 ft) a.s.l. The plumes drifted S. Geologic Summary. Sakura-jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow was associated with the formation of the 17 x 23-km-wide Aira caldera about 22,000 years ago. The construction of Sakura-jima began about 13,000 years ago and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kita-dake summit cone ended about 4,850 years ago, after which eruptions took place at Minami-dake. 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. Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m KVERT reported that seismic activity at Shiveluch was at background levels during 25 April-2 May. Observations of satellite imagery revealed that a thermal anomaly was present in the crater during 27, 28, and 30 April, and 1 May. On 28 April, ash deposits extending about 10 km NW were observed on satellite imagery and possible gas-and-ash explosions were detected by the seismic network. The Level of Concern Color Code remained at Orange. Geologic Summary. The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group and forms one of Kamchatka's largest and most active volcanoes. The currently active Molodoy Shiveluch lava-dome complex was constructed during the Holocene within a large breached caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. During the 1990s, intermittent explosive eruptions took place from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m MVO reported that during 25 April-2 May the level of volcano-tectonic earthquakes at Soufrière Hills increased and was the highest since February 2006. Degassing from a vent above Gages Wall was audible in the St. George's Hill area to the NW. Steaming from the area above Tyre's Ghaut to the NW was visible. The Alert Level remained elevated at 4 (on a scale of 0-5). Geologic Summary. 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. English's Crater, a 1-km-wide crater breached widely to the E, was formed during an eruption about 4,000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufrière Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat 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. Source: Montserrat Volcano Observatory (MVO) http://www.mvo.ms/ TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m The IG reported that although visual observations were occasionally limited due to cloud cover during 29 April-6 May, ash-and-steam plumes from Tungurahua were spotted and generally rose to altitudes of 5.5-7 km (18,000-23,000 ft) a.s.l. Ashfall was reported in areas to the SW and W during 29 April-1 May and on 4 May. On 30 April, explosions produced steam-and-ash plumes to altitudes of 9-10 km (29,500-32,800 ft) a.s.l. Incandescence at the summit was visible and incandescent blocks rolled down the flanks. Roaring noises were audible. On 1 May, explosions were accompanied by "cannon shots" and intense incandescence at the summit. Windows vibrated in areas 6 km NE. Incandescent blocks rolled 1 km down the flanks. On 3 May, a small lahar descended the W flank. Geologic Summary. The steep-sided Tungurahua stratovolcano towers more than 3 km above its northern base. It sits ~140 km S of Quito, Ecuador's capital city, and is one of Ecuador's most active volcanoes. Historical eruptions have all originated from the summit crater. They have been accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. The last major eruption took place from 1916 to 1918, although minor activity continued until 1925. The latest eruption began in October 1999 and prompted temporary evacuation of the town of Baños on the N side of the volcano. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/ VENIAMINOF Alaska Peninsula 56.17°N, 159.38°W; summit elev. 2507 m AVO reported on 3 May that the Volcanic Alert Level for Veniaminof was lowered to Normal and the Aviation Color Code was lowered to Green due to the absence of ash emissions and elevated surface temperatures. Seismicity was still above past background levels, but the rate and intensity had declined over the previous several weeks. Geologic Summary. Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the N, is deeply notched on the W by Cone Glacier, and is covered by an ice sheet on the S. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which reaches an elevation of 2,156 m and rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface. Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/ +++++++++++++++++++++++++++++++++++++ Sally Kuhn Sennert SI/USGS Weekly Volcanic Activity Report Editor Global Volcanism Program http://www.volcano.si.edu/reports/usgs/ Smithsonian Institution, National Museum of Natural History Department of Mineral Sciences, MRC-119 Washington, D.C., 20560 Phone: 202.633.1805 Fax: 202.357.2476 ============================================================== To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
