************************************************************ SI/USGS Weekly Volcanic Activity Report 29 April-5 May 2009 ************************************************************ Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Bagana, Bougainville | Fernandina, Galápagos Islands | Galeras, Colombia | Krakatau, Indonesia | Reventador, Ecuador | Rinjani, Lombok Island (Indonesia) | Shiveluch, Central Kamchatka (Russia) | Slamet, Central Java (Indonesia) Ongoing Activity: | Asama, Honshu | Batu Tara, Komba Island (Indonesia) | Chaitén, Southern Chile | Cleveland, Chuginadak Island | Dukono, Halmahera | Ebeko, Paramushir Island | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Popocatépetl, México | Rabaul, New Britain | Redoubt, Southwestern Alaska | Sakura-jima, Kyushu | 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 BAGANA Bougainville 6.140°S, 155.195°E; summit elev. 1750 m Based on analysis of satellite imagery, the Darwin VAAC reported that on 2 and 4 May ash plumes from Bagana rose to altitudes of 2.4-3 km (8,000-10,000 ft) a.s.l. and drifted 45-55 km NE. Geologic Summary. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. Bagana is a massive symmetrical lava cone largely constructed by an accumulation of viscous andesitic lava flows. The entire lava cone could have been constructed in about 300 years at its present rate of lava production. Eruptive activity at Bagana is 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 volcano's flanks on all sides. Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html FERNANDINA Galápagos Islands 0.37°S, 91.55°W; summit elev. 1476 m According to a news article, the eruption of Fernandina that began sometime between 2200 on 10 April and 0030 on 11 April continued after about 20 days. Variable activity included steam-and-gas emissions and lava flows. 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. Source: Antena 3 http://www.antena3noticias.com/PortalA3N/noticia/ciencia-y-tecnologia/Volcan-Cumbre-continua-expulsando-lava-despues-dias/5809819 GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m INGEOMINAS reported that on 29 April an eruption from Galeras was detected by the seismic network. Observers to the N and NW reported that an ash plume drifted NW; ash fell in areas up to 35 km downwind. During 4-5 May, ash plumes drifted NE and ashfall was reported in multiple areas of Pasto (about 10 km E). The Alert Level remained at II (Orange; "probable eruption in term of days or weeks"). Geologic Summary. Galeras, a stratovolcano with a large breached caldera located immediately W of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic Galeras volcanic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Longterm extensive hydrothermal alteration has affected the volcano. This has contributed to large-scale edifice collapse that has occurred on at least three occasions, producing debris avalanches that swept to the W 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. Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co// KRAKATAU Indonesia 6.102°S, 105.423°E; summit elev. 813 m CVGHM reported that the number of eruptions from Anak Krakatau increased significantly at the end of March and continued through 5 May. Seismic data were not collected during 26 April-29 April due to instrument malfunctions. Direct observations of the crater on 24, 25, and 29 April revealed that the eruption originated from a crater on the W slope of Anak Krakatau. Ash plumes generally drifted E and caused ashfall within a 5 km radius of the crater. Clear weather on 5 May allowed for visual observations; "smoke" rose 500 m above the crater. On 6 May, the Alert Level was raised to 3 (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/ REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m Based on analysis of satellite imagery, the Washington VAAC reported that on 1 May a thermal anomaly over Reventador was noted along with a possible low-level plume drifting W. The IG reported to the VAAC lava and gas emissions, and possible smoke from burning vegetation, but little to no ash. 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: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html RINJANI Lombok Island (Indonesia) 8.42°S, 116.47°E; summit elev. 3726 m CVGHM reported than during 29 April-2 May seismicity from Rinjani increased and tremor was detected. On 2 May, an eruption produced dense brown "smoke" that rose 1 km from Barujari cone and was accompanied by a booming noise. On 4 May, an eruption of ash produced a white to brown plume that rose 500-700 m above the cone and drifted N. Fog often prevented observations. The Alert Level was raised to 2 (on a scale of 1-4). According to a news article, ash fell in the local village of Senaru. Geologic Summary. Rinjani volcano on the island of Lombok rises to 3,726 m, second in height among Indonesian volcanoes only to Sumatra's Kerinci volcano. Rinjani has a steep-sided conical profile when viewed from the E, but the W side of the compound volcano is truncated by the 6 x 8.5 km, oval-shaped Segara Anak caldera. The western half of the caldera contains a 230-m-deep lake whose crescentic form results from growth of the post-caldera cone Barujari at the E end of the caldera. Historical eruptions at Rinjani dating back to 1847 have been restricted to Barujari cone and consist of moderate explosive activity and occasional lava flows that have entered Segara Anak lake. Sources: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/, Bali Discovery Tours http://www.balidiscovery.com/messages/message.asp?Id=5219 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 28 April-1 May. Based on interpretations of seismic data, ash plumes likely rose to altitudes of 5-6 km (16,400-19,700 ft) a.s.l. During 29-30 April, observers reported active fumaroles. Ash plumes generated by hot avalanches rose to an altitude of 6 km (19,700 ft) a.s.l. and drifted SE. Analysis of satellite imagery revealed an intense thermal anomaly on the lava dome every day. The Level of Concern Color Code remained at Orange. Based on information from KEMSD and analysis of satellite imagery, the Tokyo VAAC reported that an eruption on 5 May produced a plume that rose to an altitude of 6.7 km (22,000 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. Intermittent explosive eruptions began in the 1990s 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 SLAMET Central Java (Indonesia) 7.242°S, 109.208°E; summit elev. 3428 m During 23 April-5 May, CVGHM reported that seismicity from Slamet increased and an eruption originating from the western part of the crater continued. During times of clear weather, observers reported that incandescent lava, ejected 25-100 m above the crater, fell back into and around the active crater. Gray and white "smoke" rose 100-800 m from the crater. Occasionally a "thunderous" noise accompanied eruptions of ash. The Alert Level remained at 3 (on a scale of 1-4). Geologic Summary. Slamet, Java's second highest volcano at 3428 m and one of its most active, has a cluster of about three dozen cinder cones on its lower SE-NE flanks and a single cinder cone on the western flank. Slamet is composed of two overlapping edifices, an older basaltic-andesite to andesitic volcano on the west and a younger basaltic to basaltic-andesite one on the east. Gunung Malang II cinder cone on the upper eastern flank on the younger edifice fed a lava flow that extends 6 km to the east. Four craters occur at the summit of Gunung Slamet, with activity migrating to the SW over time. Historical eruptions, recorded since the 18th century, have originated from a 150-m-deep, 450-m-wide, steep-walled crater at the western part of the summit and have consisted of explosive eruptions generally lasting a few days to a few weeks. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ Ongoing Activity ASAMA Honshu 36.403°N, 138.526°E; summit elev. 2568 m Based on information from JMA, the Tokyo VAAC reported that on 30 April and 2 May eruptions from Asama produced plumes that rose to altitudes of 3-3.4 km (10,000-11,000 ft) a.s.l. and drifted NE. 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. Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/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 29-30 April and 3-4 May ash plumes from Batu Tara rose to altitudes of 2.4-3 km (8,000-10,000 ft) a.s.l. and drifted 45-185 km NW and W. 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 Based on web camera views and analysis of satellite imagery, the Buenos Aires VAAC reported that on 29 April an ash plume from Chaitén's Domo Nuevo 1 and Domo Nuevo 2 lava-dome complex rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted NW. 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: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html CLEVELAND Chuginadak Island 52.825°N, 169.944°W; summit elev. 1730 m On 1 May, AVO decreased the Aviation Color Code and the Volcano Alert Level for Cleveland to "Unassigned" because no volcanic activity had been detected since late January. Cleveland is not monitored by a real-time seismic network, thus the levels "Green" or "Normal" do not apply because background activity is not defined. Geologic Summary. Symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited dumbbell-shaped Chuginadak Island in the east-central Aleutians. The 1,730-m-high stratovolcano is the highest of the Islands of Four Mountains group and is one of the most active in the Aleutians. Numerous large lava flows descend its flanks. It is possible that some 18th to 19th century eruptions attributed to Carlisle (a volcano located across the Carlisle Pass Strait to the NW) should be ascribed to Cleveland. In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mt. Cleveland have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks. Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/ DUKONO Halmahera 1.68°N, 127.88°E; summit elev. 1335 m Based on analysis of satellite imagery and pilot observations, the Darwin VAAC reported that during 29 April-4 May ash plumes from Dukono rose to an altitude of 3.7-4.5 km (12,000-14,000 ft) a.s.l. and drifted 45-165 km E and NE. 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 EBEKO Paramushir Island 50.68°N, 156.02°E; summit elev. 1156 m KVERT reported that during 24 April-1 May 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 3.5 km (11,500 ft) a.s.l. and drifted 6 km in multiple directions. On 23 April, a small amount of ash fell in Severo-Kurilsk. Satellite imagery revealed strips of ash deposits radiating from the crater in different directions on 29 and 30 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 30 April an ash plume rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted 20 km E. 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 KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m Based on analysis of satellite imagery, KVERT reported that a weak thermal anomaly over Karymsky was noted on 26 April. The Level of Concern Color Code was lowered to Yellow. 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 29 April-5 May, 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. Some explosions occurred at the Waikupanaha ocean entry. The vent in Halema'uma'u crater continued to produce a white plume that sometimes caused poor air quality in nearby areas. Sounds resembling rushing gas were sometimes heard in the vicinity of the crater. Various amounts of tephra, spatter, and ash were retrieved from collection bins placed near the plume during the reporting period. On 3 May, unusually bright incandescence seen from the vent on the web camera was accompanied by a decrease in summit tremor levels of about 40 percent. During 4-5 May, bright incandescence was again noted; summit tremor levels were variable but never exceeded moderate values. 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/ POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m CENAPRED reported that emissions of steam and gas from Popocatépetl were visible during 29 April-5 May; the plumes contained slight amounts of ash on 29 April. Geologic Summary. Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5,426 m 70 km SE of Mexico City and is North America's second-highest volcano. Frequent historical eruptions have been recorded since the beginning of the Spanish colonial era. A small eruption on 21 December 1994 ended five decades of quiescence. Since 1996 small lava domes have incrementally been constructed within the summit crater and destroyed by explosive eruptions. Intermittent small-to-moderate gas-and-ash eruptions have continued, occasionally producing ashfall in neighboring towns and villages. Source: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.unam.mx/es/ RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m RVO reported that on 27 April white and occasionally gray plumes from Rabaul caldera's Tavurvur cone rose 0.5-1 km above the crater. Ashfall was reported in Kokopo, about 20 km SE, along with infrequent roaring noises. Activity decreased during 28 April-2 May; white and, less frequently blue, plumes were emitted. Incandescence from the summit crater was seen at night. Based on analysis of satellite imagery, the Darwin VAAC reported that during 3-4 May ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted about 35 km NE. 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: Herman Patia, Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html REDOUBT Southwestern Alaska 60.485°N, 152.742°W; summit elev. 3108 m During 29 April-5 May, AVO reported that elevated seismicity from Redoubt and a persistent thermal anomaly over the summit lava dome detected on satellite imagery were consistent with continued lava-dome growth. Changes in the size and shape of the dome confirmed growth; the volume of the dome was an estimated 25-30 million cubic meters. Occasional small rock avalanches originating from the N side of the lava dome produced minor low-level ash emissions. The web camera showed steam-and-gas plumes ash rising from the lava dome. During 2-3 May, seismicity increased markedly and minor ash emissions were seen on the web camera. More frequent rockfalls were also detected. On 4 May, steam plumes with possible minor amounts of ash rose several thousand feet above the summit and drifted SE. Seismicity during 4-5 May continued to slowly increase. AVO warned that a significant explosive event was likely in the coming days. 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 during 3-4 May eruptions from Sakura-jima produced plumes that rose to altitudes of 2.4-3.7 km (8,000-12,000 ft) a.s.l. 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 SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m Based on information from JMA, the Tokyo VAAC reported that eruptions from Suwanose-jima during 29 April-1 May produced plumes that rose to altitudes of 1.5-1.8 km (5,000-6,000 ft) a.s.l. Plumes drifted W on 30 April and 1 May. 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 28 April-5 May, IG reported that, although inclement weather often prevented observations of Tungurahua, steam-and-gas plumes were seen almost daily. The plumes rose to altitudes below 6.8 km (22,300 ft) a.s.l. and rifted SW and W. Lahars descended the Achupashal drainage to the NW on 28 April and the Motilones drainage to the W on 1 May. Incandescence in the crater was seen at night on 30 April. During 29 April and 2-3 May, noises and explosions rattled structures and windows. On 3 May, ashfall was reported in areas to the SW, NW, and 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. ==============================================================
