********************************************************** SI/USGS Weekly Volcanic Activity Report 8-14 April 2009 ********************************************************** Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Ebeko, Paramushir Island | Fernandina, Galápagos Islands, Ecuador | Kliuchevskoi, Central Kamchatka (Russia) | Llaima, Central Chile | Miyake-jima, Japan | Redoubt, Southwestern Alaska | Sakura-jima, Kyushu Ongoing Activity: | Arenal, Costa Rica | Batu Tara, Komba Island (Indonesia) | Chaitén, Southern Chile | Colima, México | Dukono, Halmahera (Indonesia) | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Koryaksky, Eastern Kamchatka | Rabaul, New Britain | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Suwanose-jima, Ryukyu Islands (Japan) | Tungurahua, Ecuador 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 EBEKO Paramushir Island 50.68°N, 156.02°E; summit elev. 1156 m KVERT reported that during 3-10 April observers from Severo-Kurilsk, about 7 km E of Ebeko, observed continued activity. Gas-and-steam plumes with some ash content rose to an altitude of 3.4 km (11,200 ft) a.s.l. and drifted 8 km in southerly directions. Light ashfall was reported in Severo-Kurilsk on 5 April. The Level of Concern Color Code remained at Yellow. Based on analysis of satellite imagery and information from Yelizovo Airport, the Tokyo VAAC reported that on 12 April an ash plume drifted 6 km SE at an altitude of 1.5 km (5,000 ft) a.s.l. Geologic Summary. 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. The eastern part of the southern crater of Ebeko contains strong solfataras and a large boiling spring. The central crater of Ebeko 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 of Ebeko, on the outer flanks of the cone, and in lateral explosion craters. 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 FERNANDINA Galápagos Islands, Ecuador 0.37°S, 91.55°W; summit elev. 1,476 m Based on analysis of satellite imagery, IG reported that an eruption of Fernandina started sometime during 2200 on 10 April and 0030 on 11 April. Several thermal anomalies were seen on satellite imagery, possibly indicating active lava flows. A representative of the Galápagos National Park reported that tourists and park employees observed the eruption during the early hours of 11 April. According to news articles, Galápagos National Park personnel conducting an overflight indicated that the eruption occurred from a fissure on the SW flank, about 500 m from the summit crater. The fissure was 200 m long and 10 m wide, and ejected lava fountains 15 m high. A gas-and-ash plume drifted SW. The eruption took place near the site of the previous eruption in 2005. Based on analysis of satellite imagery, the Washington VVAC reported that during 11-14 April gas and possible ash plumes drifted up to 370 km W, SW, S, and N. On 14 April, a large thermal anomaly and sulfur dioxide were detected. The observatory also reported smoke from burning vegetation. Geologic Summary. Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic "overturned soup bowl" profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as a lava flow that reached the coast from a SW-flank vent. Collapse of a nearly 1 cu km section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake. Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html, Agence France-Presse http://www.google.com/hostednews/afp/article/ALeqM5jMJ2XdjTAuNRBTt-CTsIs11mZrxQ KLIUCHEVSKOI Central Kamchatka (Russia) 56.057°N, 160.638°E; summit elev. 4835 m KVERT reported that fumarolic activity from Kliuchevskoi was observed during 3-10 April. Satellite imagery indicated a thermal anomaly over the volcano on 5 and 6 April, and weak volcanic tremor was detected during 5-8 April. Based on analysis of satellite imagery, the Tokyo VAAC reported that a possible eruption on 9 April produced a plume that rose to an altitude of 4.9 km (16,000 ft) a.s.l. and drifted NE. Imagery later indicated that any ash that may have been present had dissipated. On 11 April, imagery again indicated a possible eruption; any resultant ash plumes had dissipated by a few hours later. The Level of Concern Color remained at Yellow. Geologic Summary. Kliuchevskoi is Kamchatka's highest and most active volcano. Since its origin about 7,000 years ago, the beautifully symmetrical, 4,835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. More than 100 flank eruptions, mostly on the NE and SE flanks of the conical volcano between 500 m and 3,600 m elevation, have occurred during the past 3,000 years. The morphology of its 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 major explosive and effusive events from flank craters. 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 LLAIMA Central Chile 38.692°S, 71.729°W; summit elev. 3125 m On 8 April, SERNAGEOMIN reported that, after 74 hours of a vigorous Strombolian eruption from Llaima and accompanying lava flow emissions, activity declined quickly on 6 April until reaching a low level characterized by small amounts of ash emissions. On 7 April, weak emissions of gas and ash were observed. An overflight revealed that the main crater was completely obscured by a large pyroclastic cone with four inactive craters. Sulfur dioxide and hydrochloric gasses were emitted. Two lava flows descended the W flank. The more southerly lava flow was about 4.5 km long and melted part of the glacier, causing a lahar to travel towards the Calbuco River. The more northerly lava flow was similar in length, and branched off into two 1-km-long flows. It too caused a lahar. On the NE flank, a lava flow that originated from the base of the pyroclastic cone caused lahars that descended into the valley between Curacautín (30 km NNW) and the Conguillío National Park. During 7-10 April, intermittent incandescence from a lava flow at the SW base of the pyroclastic cone was observed. Incandescent blocks originating from the lava flow descended W. On 8 April, gasses emitted from multiple points on the pyroclastic cone formed a plume that drifted NE. Preliminary calculations indicated that the height of the pyroclastic cone exceeded the top of the main crater by 70 m, making the summit elevation 3,240 m a.s.l. During 9-10 and 13-14 April, gas and steam plumes rose from the pyroclastic cone; views were obscured by clouds on 11 and 12 April. On 14 April, fumarolic activity from the pyroclastic cone was again noted. The Volcano Alert Level remained at Red. Geologic Summary. Llaima, one of Chile's largest and most active volcanoes, contains two main historically active craters, one at the summit and the other to the SE. The massive 3,125-m-high, glacier-covered stratovolcano has a volume of 400 cu km. A Holocene edifice built primarily of accumulated lava flows was constructed over an 8-km-wide caldera that formed about 13,200 years ago, following eruption of the 24 cu km Curacautín Ignimbrite. More than 40 scoria cones dot the volcano's flanks. Following the end of an explosive stage about 7,200 years ago, construction of the present edifice began, characterized by Strombolian, Hawaiian, and infrequent subplinian eruptions. Frequent moderate explosive eruptions with occasional lava flows have been recorded since the 17th century. Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/index.php MIYAKE-JIMA Japan 34.079°N, 139.529°E; summit elev. 815 m JMA reported that on 1 April an eruption from Miyake-jima produced an ash plume that rose 600 m above the crater and drifted E. They also stated that the last eruption was on 8 May 2008. Geologic Summary. The circular, 8-km-wide island of Miyake-jima forms a low-angle stratovolcano that rises about 1100 m from the sea floor in the northern Izu Islands about 200 km SSW of Tokyo. Parasitic craters and vents, including maars near the coast and radially oriented fissure vents, dot the flanks of the volcano. Frequent historical eruptions have occurred since 1085 AD at vents ranging from the summit to below sea level, causing much damage on this small populated island. After a three-century-long hiatus ending in 1469, activity has been dominated by flank fissure eruptions sometimes accompanied by minor summit eruptions. A 1.6-km-wide summit caldera was slowly formed by subsidence during an eruption in 2000; by October of that year the crater floor had dropped to only 230 m above sea level. Source: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/indexe.html REDOUBT Southwestern Alaska 60.485°N, 152.742°W; summit elev. 3108 m Based on seismic data and satellite imagery, AVO reported that Redoubt’s lava dome continued to grow during 8-14 April. On 8 April, a small steam plume possibly containing ash was seen on satellite imagery and on the web camera, and drifted NE at low altitudes. A continuous sulfur dioxide plume seen on satellite imagery drifted 965 km. On 9 April, RADAR data showed no significant ash emissions. An M 3.3 earthquake was located about 4 km ENE of the summit. Observations showed that the lava dome grew in the same location as the previous lava dome, was circular in shape, and 400 m in diameter. A report on 10 April indicated that seismicity had remained steady since the last explosion on 4 April; small repetitive volcanic earthquakes were detected. Gas, steam, and ash emitted from the vent formed a plume that rose to an altitude less than 4.6 km (15,000 ft) a.s.l. On 11 April, A vigorous steam plume that may have contained small amounts of ash was visible on the web camera. Satellite imagery showed a plume that drifted NW at altitudes below 6.1 km (20,000 ft) a.s.l. Observations on 13 and 14 April were obscured by clouds. The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange. Geologic Summary. Redoubt is a 3108-m-high glacier-covered stratovolcano with a breached summit crater in Lake Clark National Park about 170 km SW of Anchorage. Next to Mount Spurr, Redoubt has been the most active Holocene volcano in the upper Cook Inlet. Collapse of the summit of Redoubt 10,500-13,000 years ago produced a major debris avalanche that reached Cook Inlet. Holocene activity has included the emplacement of a large debris avalanche and clay-rich lahars that dammed Lake Crescent on the south side and reached Cook Inlet about 3500 years ago. Eruptions during the past few centuries have affected only the Drift River drainage on the north. Historical eruptions have originated from a vent at the north end of the 1.8-km-wide breached summit crater. The 1989-90 eruption of Redoubt had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano. Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/ SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m Based on information from JMA, the Tokyo VAAC reported that on 8 April an eruption from Sakura-jima produced a plume that rose to an altitude of 2.7 km (9,000 ft) a.s.l. JMA reported that on 9 April a Vulcanian explosion from Showa crater on the E flank ejected bombs as far away as 1.3 km. A plume rose to an altitude of 4.8 km (15,700 ft) a.s.l. and drifted SW; JMA stated that the plume altitude was the highest altitude a plume reached since June 2006. A pyroclastic flow traveled 1 km E. According to a news article, heavy ashfall was reported in Kagoshima City (about 10 km W), the first ashfall reported there since October 2002. On 10 April, the Tokyo VAAC reported that eruptions produced plumes that rose to altitudes of 2.1-2.7 km (7,000-9,000 ft) a.s.l. and drifted W and 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. Sources: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/indexe.html, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html, Asahi http://www.asahi.com/national/update/0409/SEB200904090017.html Ongoing Activity ARENAL Costa Rica 10.463°N, 84.703°W; summit elev. 1670 m OVSICORI-UNA reported that during March activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches from the fronts of lava flows that traveled down the SW flanks. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity. Geologic Summary. Conical Volcan Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1,657-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. The earliest known eruptions of Arenal took place about 7,000 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. Arenal's most recent eruptive period began with a major explosive eruption in 1968. Continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows has occurred since then from vents at the summit and on the upper western flank. Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) www.ovsicori.una.ac.cr/ BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m Based on analysis of satellite imagery, the Darwin VAAC reported that during 11-12 and 14 April ash plumes from Batu Tara rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted 35-90 km W and NW. 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 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 cloudy weather often prevented observations of Chaitén's Domo Nuevo 1 and Domo Nuevo 2 lava-dome complex during 30 March-6 April. Occasional clear views revealed that collapses from the central spine continued, and a new smaller spine grew on the southern area of Domo Nuevo 1. On 8 April, seismic activity gradually increased. During 11-12 April, the numbers and magnitudes of earthquakes were the highest; magnitudes reached M 4.5. The Alert Level remained at Red. Based on analysis of satellite imagery and web camera views, the Buenos Aires VAAC reported that during 9-11 and 14 April, ash plumes rose to altitudes of 1.5-2.4 km (5,000-8,000 ft) a.s.l. and drifted NE, ENE, and ESE. 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. Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/, Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html COLIMA México 19.514°N, 103.62°W; summit elev. 3850 m During 8-10 and 12-13 April, white and gray plumes from Colima rose to altitudes of 3.9-5.2 km (12,800-17,100 ft) a.s.l. and occasionally drifted E, S, SW, and W. Geologic Summary. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4,320 m high point of the complex) on the N and the historically active Volcán de Colima on the S. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the S, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth. Source: Gobierno del Estado de Colima http://www.colima-estado.gob.mx/2006/seguridad/indvolcan.php DUKONO Halmahera 1.68°N, 127.88°E; summit elev. 1335 m Based on analysis of satellite imagery, the Darwin VAAC reported that on 12 April an ash plume from Dukono rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 55 km NW. Geologic Summary. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the N-flank cone of Gunung Mamuya. Dukono is a complex volcano presenting a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of Dukono's summit crater complex, contains a 700 x 570 m crater that has also been active during historical time. 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 above background levels on 2 and 3 April and at background levels on 4 April; no data was collected during 5-10 April due to technical reasons. Analysis of satellite imagery revealed a weak thermal anomaly on the volcano on 5 April. Fumarolic activity was seen by volcanologists on 9 April. 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. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m During 8-14 April, HVO reported that lava flowed SE from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex through a lava tube system, reaching the Waikupanaha and Kupapa'u ocean entries. Occasional explosions occurred from the Waikupanaha ocean entry. Surface flows on the coastal plain or from the Prince lobe were seen or detected by satellite imagery. The vent in Halema'uma'u crater continued to produce a white plume occasionally tinged brown that drifted mainly SW. Incandescence was intermittently seen from the vent. The sulfur dioxide emission rate at the summit was elevated; measurements were 1,000, 900, and 1,000 tonnes per day on 8, 9, and 13 April, respectively. The 2003-2007 average rate was 140 tonnes per day. On 13 April, Pele's hair, tiny glass spheres, and ash were retrieved from collection bins placed near the plume. On 14 April, ash was collected from the bins. Seismic instruments recorded a M 5 earthquake beneath the S flank, 12 km SE of the summit, at a depth of 10 km. 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/ KORYAKSKY Eastern Kamchatka 53.320°N, 158.688°E; summit elev. 3456 m KVERT reported that seismic activity at Koryaksky was elevated on 7 and 8 April and at background levels on the other days during 3-10 April. Weak volcanic tremor was detected on 7 April. Gas plumes containing a small amount of ash originating from two vents on the NW flank rose to an altitude of 5.4 km (17,700 ft) a.s.l. and drifted NE, NW, SE, and SW during the reporting period. Gas-and-ash plumes were also seen on satellite imagery and drifted 290 km in multiple directions. On 11 April, KVERT staff reported ashfall in Petropavlovsk-Kamchatsky (30 km S). Ash accumulated to 0.1-2.5 cm thickness near the Institute of Volcanology and Seismology (IVS) FED RAS. The Level of Concern Color Code remained Orange. Geologic Summary. The large symmetrical Koryaksky stratovolcano is the most prominent landmark of the NW-trending Avachinskaya volcano group, which towers above Kamchatka's largest city, Petropavlovsk. Erosion has produced a ribbed surface on the eastern flanks of the 3456-m-high volcano; the youngest lava flows are found on the upper western flank and below SE-flank cinder cones. No strong explosive eruptions have been documented during the Holocene. Extensive Holocene lava fields on the western flank were primarily fed by summit vents; those on the SW flank originated from flank vents. Lahars associated with a period of lava effusion from south- and SW-flank fissure vents about 3900-3500 years ago reached Avacha Bay. Only a few moderate explosive eruptions have occurred during historical time. Koryaksky's first historical eruption, in 1895, also produced a lava flow. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m RVO reported that during 3-9 April white and gray plumes from Rabaul caldera's Tavurvur cone rose 1 km above the crater. Plumes drifted SE and NW. Occasionally, incandescence from the summit crater was seen at night and roaring noises were reported. Light ashfall was reported in Kokopo, about 20 km SE. Based on analysis of satellite imagery, the Darwin VAAC reported that during 11-12 April ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted up to 75 km NW. On 14 April, ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted W and up to 120 km NW. 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. Sources: Ima Itikarai, Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m KVERT reported that seismic activity at Shiveluch was above background levels during 3-10 April. Based on interpretations of seismic data, ash plumes likely rose to an altitude of 7.5 km (24,600 ft) a.s.l. during 3-5 and 8-9 April. According to observers, fumaroles were active during 3-7 and 9 April. Analysis of satellite imagery revealed a daily thermal anomaly on the lava dome. The Level of Concern Color Code remained at Orange. Based on information from KEMSD, the Tokyo VAAC reported that eruptions during 11-14 April produced plumes that rose to altitudes of 4.6-5.5 km (15,000-18,000 ft) a.s.l. 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. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m MVO reported that during 3-10 April activity from the Soufrière Hills lava dome was at a low level. Heavy rainfall during 8-9 April caused lahars in multiple river valleys. The Hazard Level remained at 3. 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/ SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m Based on information from JMA, the Tokyo VAAC reported explosions from Suwanose-jima on 8 and 10 April. Details of possible resultant ash plumes on either day were not reported. Geologic Summary. The 8-km-long, spindle-shaped island of Suwanose-jima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. Only about 50 persons live on the sparsely populated island. 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. Suwanose-jima, one of Japan's most frequently active volcanoes, was in a state of intermittent Strombolian activity from On-take, the NE summit crater, that began in 1949 and lasted nearly a half century. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, after which the island was uninhabited for about 70 years. The SW crater produced lava flows that reached the western coast in 1813, and lava flows reached the eastern coast of the island in 1884. Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m During 8-14 April, IG reported that clouds mostly prevented observations of Tungurahua; a steam plume seen on 9 April rose 300 m above the crater and drifted SW. On 10 April, slight ashfall was reported in areas to the SW. The next day, a lahar traveled SW down the Mapayacu drainage. On 14 April, a steam-and-gas plume containing some ash rose to an altitude of 7.5 km (24,600 ft) a.s.l. and drifted N. 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/ +++++++++++++++++++++++++++++++++++++ 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. ==============================================================
