****************************************************** SI/USGS Weekly Volcanic Activity Report 25-31 March 2009 ****************************************************** Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Ambrym, Vanuatu (SW Pacific) | Gorely, Southern Kamchatka | Redoubt, Southwestern Alaska | Reventador, Ecuador Ongoing Activity: | Asama, Honshu | Barren Island, Andaman Is | Batu Tara, Komba Island (Indonesia) | Chaitén, Southern Chile | Colima, México | Fuego, Guatemala | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Koryaksky, Eastern Kamchatka | Krakatau, Indonesia | Rabaul, New Britain | Sakura-jima, Kyushu | Shiveluch, Central Kamchatka (Russia) | 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 AMBRYM Vanuatu (SW Pacific) 16.25°S, 168.12°E; summit elev. 1334 m Based on information from the Port Vila airport tower, the Wellington VAAC reported that on 25 March an ash plume from Ambrym rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted about 55 km S. The next day, a pilot reported that "smoke" rose to an altitude of 2.4 km (8,000 ft) a.s.l. Ash was not identified on satellite imagery. Geologic Summary. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major Plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations. Source: Wellington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/NZ/messages.html GORELY Southern Kamchatka 52.558°N, 158.03°E; summit elev. 1829 m KVERT reported that seismic activity from Gorely increased during 10-27 March. The Level of Concern Color Code was raised to Yellow. Geologic Summary. Gorely volcano, one of the most active in southern Kamchatka, consists of five small overlapping stratovolcanoes constructed along a WNW-ESE line within a large 9 x 13.5 km late-Pleistocene caldera. The massive Gorely complex contains 11 summit and 30 flank craters. During the early Holocene, activity was characterized by frequent mild eruptions with occasional larger explosions and lava flows that filled in the caldera. Quiescent periods became longer between 6,000 and 2,000 years ago, after which the activity was mainly explosive. About 600-650 years ago intermittent strong explosions and lava flow effusion accompanied frequent mild eruptions. Historical eruptions have consisted of vulcanian and phreatic explosions of moderate volume. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php REDOUBT Southwestern Alaska 60.485°N, 152.742°W; summit elev. 3108 m On 25 March, AVO reported that a small explosion from Redoubt produced an ash plume that rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted N to NW. Later that day AVO lowered the Volcanic Alert Level to Watch and the Aviation Color Code to Orange because seismicity had decreased during the previous 36 hours. On 26 March, multiple explosive eruptions produced plumes to altitudes of 6.1-19.8 km (20,000-65,000 ft) a.s.l. or greater. AVO raised the Alert Level to Warning and the Aviation Color Code to Red, the highest levels. The largest eruption, at 0924, also produced a lahar in the Drift River valley that was detected by seismic instruments. During 27-28 March, seven explosive eruptions produced ash plumes to altitudes of 7.6-15.2 km (25,000-50,000 ft) a.s.l. An ash plume on 29 March rose to an altitude of 6.1 km (20,000 ft) a.s.l. Seismic and infrasound data did not show clear evidence that the plume was generated by an explosion. On 30 March, continuously emitted ash plumes of varying intensities were observed in a web camera, on satellite and radar images, and by pilots, and rose to altitudes less than 6.1 km (20,000 ft) a.s.l. Occasionally, short-lived events produced ash plumes to an altitude of 8.2 km (27,000 ft) a.s.l. A thermal anomaly at the vent seen on satellite imagery was possibly due to the extrusion of a lava dome in the summit crater. On 31 March, emissions of steam, gas, and minor amounts of ash were seen on Redoubt Hut web camera. Resultant plumes rose to altitudes of 4.6-7.6 km (15,000-25,000 ft) a.s.l. Satellite images showed a broad layer of volcanic haze that extended E over the Kenai Peninsula, the Anchorage Bowl, and the Matanuska-Susitna Valley. According to news articles, 11 people were evacuated on 23 March from the Drift River Terminal, an oil storage facility about 35 km ENE of Redoubt that shut down because of the eruption. During 24-28 March, flights in and out of Anchorage and other local areas continued to be canceled or diverted; as many as 185 Alaska Airlines flights had been canceled since the beginning of the eruption. Ashfall was occasionally reported in Anchorage and areas NW. 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. Sources: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/, The Associated Press http://www.kgw.com/news-local/stories/kgw_032609_news_redoubt_volcano_alaska_eruptions.73d2de4a.html?npc, The Associated Press http://www.google.com/hostednews/ap/article/ALeqM5hcWJaxwgurm_TV9AVcObQBWbS25QD977EUS00 REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m The IG reported that seismicity from Reventador increased during 25-26 March. On 26 March, the seismic network detected an earthquake swarm consisting of long-period and hybrid events, interspersed with bands of harmonic tremor. Observers reported steam emissions with low ash content. Geologic Summary. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well E of the principal volcanic axis. It is a forested stratovolcano that rises above the remote jungles of the western Amazon basin. A 3-km-wide caldera breached to the E was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1,300 m above the caldera floor. Reventador 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. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/ Ongoing Activity ASAMA Honshu 36.403°N, 138.526°E; summit elev. 2568 m JMA reported weak incandescence from Asama on 23 March. Strong steam emissions were seen on 30 March by an observer in Maebashi, 50 km E. Geologic Summary. Asama, Honshu's most active volcano, is located at the junction of the Izu-Marianas and NE Japan arcs and has an historical record dating back at least to the 11th century. The modern cone of Maekake-yama is situated E of the horseshoe-shaped remnant of an older andesitic volcano, Kurofu-yama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic and rhyolitic lava cone was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 years BP, and by growth of the Ko-Asama-yama lava dome on the E flank. Maekake-yama is probably only a few thousand years old, but has had several major Plinian eruptions, the last two of which occurred in 1108 and 1783 AD. Sources: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/indexe.html, Yukio Hayakawa, personal communication BARREN ISLAND Andaman Is 12.278°N, 93.858°E; summit elev. 354 m Based on analysis of satellite imagery, the Darwin VAAC reported that during 25-26 March ash plumes from Barren Island rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted about 110 km S. Geologic Summary. 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-trending volcanic arc extending between Sumatra and Burma (Myanmar). The 354-m-high island is the emergent summit of volcano that rises from a depth of about 2,250 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 W, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. The morphology of a fresh pyroclastic cone that was constructed in the center of the caldera has varied during the course of historical eruptions. Lava flows fill much of the caldera floor and have reached the sea along the western coast during historical eruptions. Source: Darwin Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html 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 25-27 March ash plumes from Batu Tara rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted about 30-110 km 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 during 17-23 March Chaitén's lava-dome complex continued to grow from an area that includes the central spines and part of Domo Nuevo 1. This was also the main area where collapses from unstable slopes caused block-and-ash flows. Continuously emitted steam plumes with varying amounts of tephra and gas-and-ash plumes generated by block-and-ash flows drifted N and ESE. The block-and-ash flow volume was smaller compared to the previous week. The Alert Level remained at Red. 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. Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/index.php COLIMA México 19.514°N, 103.62°W; summit elev. 3850 m During 25-29 and 31 March, white and gray plumes from Colima rose to altitudes of 3.9-4.6 km (12,800-15,100 ft) a.s.l. and occasionally drifted SW, SE, E, and NE. 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 FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m On 27 and 30 March, INSIVUMEH reported that explosions from Fuego produced ash plumes that rose to altitudes of 4.1-4.8 km (13,500-15,700 ft) a.s.l. and drifted S and SW. Some explosions were accompanied by rumbling noises, shock waves detected 10 km away, and avalanches of blocks down the W and SW flanks. Fumarolic plumes drifted NE and SW. On 30 March, incandescent material was ejected 75 m into the air. Based on analysis of satellite imagery, the Washington VAAC reported that on 31 March an ash plume drifted E. Geologic Summary. Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3,763-m-high Fuego and its twin volcano to the N, Acatenango. Construction of Meseta volcano continued until the late Pleistocene or early Holocene, after which growth of the modern Fuego volcano continued the southward migration of volcanism that began at Acatenango. Frequent vigorous historical eruptions have been recorded at Fuego since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows. The last major explosive eruption from Fuego took place in 1974, producing spectacular pyroclastic flows visible from Antigua. Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m KVERT reported that seismic activity at Karymsky was elevated during 19-22 March and at background levels during 23-24 March. Based on interpretations of seismic data, ash plumes likely rose to an altitude of 2 km (6,600 ft) a.s.l. On 26 March, ash deposits extending 30 km S of the volcano were seen 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. 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 24-31 March, 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. Daily thermal anomalies seen on satellite imagery suggested surface flows on the coastal plain. The vent in Halema'uma'u crater continued to produce a predominantly white plume that drifted mainly SW. Incandescence was intermittently seen from the vent, and sounds resembling rushing gas were sometimes heard in the vicinity of the crater. Variable amounts of tephra and some Pele's hair were retrieved almost daily from collection bins placed near the plume. On 24 March, a dusty brown plume rose from the vent. Geologists utilizing an infrared camera saw at least two spattering openings deep below the vent rim. On 25 March, two more brown plumes were emitted. A larger collapse was followed by a large, dense, brown plume, and several more brown plumes over the next two hours. The rockfalls within the vent covered the previously seen hot vents. During 26-28 March, infrared camera views revealed a rising and falling lava surface deep below the crater floor. The lava surface was static, but circulating on 29 March. The sulfur dioxide emission rate at the summit was 500, 900, and 1,000 tonnes per day on 25, 26, and 30 March, respectively; the 2003-2007 average rate was 140 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/ KORYAKSKY Eastern Kamchatka 53.320°N, 158.688°E; summit elev. 3456 m KVERT reported that seismic activity at Koryaksky was at background levels during 20-27 March. Gas plumes containing a small amount of ash rose to an altitude of 4 km (13,200 ft) a.s.l. and drifted S, SE, W and NW during the reporting period. On 25 and 26 March, gas-and-ash plumes were also seen on satellite imagery and drifted 225 km SE. The Level of Concern Color Code remained Orange. Based on information from the Yelizovo Airport and KEMSD, and analysis of satellite imagery, the Tokyo VAAC reported that during 26-27 and 29 March ash plumes rose to altitudes of 3-3.7 km (10,000-12,000 ft) a.s.l. and drifted S, SW, and W. 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. 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 KRAKATAU Indonesia 6.102°S, 105.423°E; summit elev. 813 m CVGHM reported that seismicity from Krakatau increased during 19-25 March. Fog prevented observations on 24 March. During periods of clear weather on 25 March, white-to-gray plumes rose 400 m above Anak Krakatau. The Alert Level remained at 2 (on a scale of 1-4). Geologic Summary. Renowned Krakatau volcano lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 AD, resulted in a 7-km-wide caldera. Remnants of this volcano formed Verlaten and Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only a remnant of Rakata volcano. The post-collapse cone of Anak Krakatau (Child of Krakatau), constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan, has been the site of frequent eruptions since 1927. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m RVO reported that during 21-26 March white and occasional gray ash plumes from Rabaul caldera's Tavurvur cone rose 500 m above the crater and drifted in variable directions. Incandescence from the summit crater was seen at night. Light ashfall was reported S of Duke of York Islands, about 20 km E. 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: Herman Patia, Rabaul Volcano Observatory (RVO) SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m Based on information from JMA, the Tokyo VAAC reported that an explosion from Sakura-jima on 26 March produced a plume that rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted SE. JMA reported occasional weak eruptions during 27-30 March. 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/MSG0871505.01.txt 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 20-27 March. Based on interpretations of seismic data, ash plumes likely rose to an altitude of 6 km (19,700 ft) a.s.l. According to observers, fumaroles were active during 23-26 March and explosions produced ash plumes that rose to an altitude of 8 km (26,200 ft) a.s.l. on 24 March. Analysis of satellite imagery revealed a daily thermal anomaly on the lava dome and an ash plume that drifted 40 km S on 25 March. The Level of Concern Color Code remained at Orange. Based on information from KEMSD, the Tokyo VAAC reported that eruptions during 27-28 March produced plumes that rose to altitudes of 4.3-5.5 km (14,000-18,000 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.kscnet.ru/ivs/kvert/index_eng.php, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m Based on information from JMA, the Tokyo VAAC reported an explosion from Suwanose-jima on 28 March. JMA reported three explosions on 30 March. 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. 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/MSG0871505.01.txt TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m During 25-27 and 30-31 March, IG reported that steam-and-ash plumes from Tungurahua rose to altitudes of 5.5-7 km (18,000-23,000 ft) a.s.l. and drifted NW, NE, E, and SW. On 25 March, ashfall was reported in areas to the SW and lahars traveled down a drainage to the W. On 26 March, lahars traveled down multiple drainages to the W, SW, and S; a lahar in the Mapayacu drainage to the SW carried blocks up to 2 m in diameter. Inclement weather impaired visual observations during 28-29 March. 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. ==============================================================
