************************************************************* SI/USGS Weekly Volcanic Activity Report 6-12 May 2009 ************************************************************* Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Galeras, Colombia | Nyiragongo, Democratic Republic of Congo | Rinjani, Lombok Island (Indonesia) | Veniaminof, Alaska Peninsula Ongoing Activity: | Arenal, Costa Rica | Batu Tara, Komba Island (Indonesia) | Chaitén, Southern Chile | Dukono, Halmahera | Ebeko, Paramushir Island | Kilauea, Hawaii (USA) | Llaima, Central Chile | Nevado del Huila, Colombia | Rabaul, New Britain | Redoubt, Southwestern Alaska | 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 GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m On 6 May, INGEOMINAS reported that gas-and-ash plumes from Galeras rose to an altitude of 5.8 km (19,000 ft) a.s.l. and drifted NE. An overflight revealed incandescence from a vent, 90-100 m in diameter, in the main crater that corresponded to a 500 degree Celsius temperature anomaly. Blocks, 9-13 m in diameter, scattered on the S and SE flanks were part of the 2008 lava dome that had been ejected during the 24 April 2009 eruption. White plumes originated from multiple points inside and outside of the crater. Volcanic tremor seldom occurred during the previous week. The Alert Level was lowered to III (Yellow; "changes in the behavior of volcanic activity"). On 9 May, a M 2.2 volcano-tectonic earthquake occurred 6 km to the NE of the main crater at a depth of 10 km. On 11 May, seismicity increased, and hybrid earthquakes and tremor were detected. The recent seismicity, along with incandescence in the crater, and low sulfur dioxide values suggested to INGEOMINAS that the volcano may become overpressurized. The Alert Level was raised to II (Orange; "probable eruption in term of days or weeks"). Steam plumes rose 250 m and drifted NW on 12 May. 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// NYIRAGONGO Democratic Republic of Congo 1.52°S, 29.25°E; summit elev. 3470 m According to a news article on 8 May, the air in the city of Goma, 18 km S of Nyiragongo, was thick with "volcanic dust." Residents reported seeing incandescent lava flowing from the summit crater at night. The article also stated that the scientist-in-charge of Goma Volcano Observatory (GVO) reported that significantly increased temperatures were measured around Nyiragongo and that larger-than-usual plumes of "volcanic dust" were being ejected. The news account did not mention any GVO statements about lava flows. Geologic Summary. One of Africa's most notable volcanoes, Nyiragongo contained an active lava lake in its deep summit crater that drained catastrophically through its outer flanks in 1977. In contrast to the low profile of its neighboring shield volcano, Nyamuragira, Nyiragongo displays the steep slopes of a stratovolcano. Benches in the steep-walled, 1.2-km-wide summit crater mark the levels of former lava lakes, which have been observed since the late 19th century. About 100 parasitic cones are located on the volcano's flanks and along a NE-SW zone extending as far as Lake Kivu. Monitoring is done from a small observatory building located in Goma, ~18 km S of the Nyiragongo crater. Source: BBC News http://news.bbc.co.uk/2/hi/africa/8040855.stm RINJANI Lombok Island (Indonesia) 8.42°S, 116.47°E; summit elev. 3726 m CVGHM reported than during 3-7 May seismicity from Rinjani continued to be elevated and tremor was detected. On 4 May, an eruption of ash produced a white-to-brown plume that rose 500-700 m above the Barujari cone and drifted N. No eruption plumes were seen during times of clear weather on 5 and 6 May. On 7 May, thick white "smoke" from Rinjani was noted. The Alert Level remained at 2 (on a scale of 1-4). 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. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ VENIAMINOF Alaska Peninsula 56.17°N, 159.38°W; summit elev. 2507 m During 6-7 May, seismic activity from Veniaminof increased, prompting AVO to raise the Volcanic Alert Level to Advisory and the Aviation Color Code to Yellow. Small magnitude earthquakes occurred at rates of 5-10 per hour during quieter periods and 1-3 per minute during periods of more intense activity. Visual observations indicated typical steaming from the summit caldera cone. Seismicity remained elevated during 8-12 May. Minor ash-producing explosions last occurred in March 2008. Geologic Summary. Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the N, is deeply notched on the W by Cone Glacier, and is covered by an ice sheet on the S. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which reaches an elevation of 2,156 m and rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface. Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/ Ongoing Activity ARENAL Costa Rica 10.463°N, 84.703°W; summit elev. 1670 m OVSICORI-UNA reported that during April activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches that traveled down the SW, S, and N 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) http://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 on 5 May an ash plume from Batu Tara rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 55 km 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 SERNAGEOMIN reported that during 29 April-4 May gas-and-ash plumes rose up to 2 km from Chaitén's growing Domo Nuevo 1 and Domo Nuevo 2 lava-dome complex. Collapses originating from unstable slopes generated block-and-ash flows. An overflight on 1 May revealed a large central spine fractured into three main blocks. The surface of the lava dome complex was very irregular and several spines had grown 100 m above the dome surface. Seismicity remained high. The Alert Level remained at Red. Based on analysis of satellite imagery, SIGMET notices, web camera views, and information from the Puerto Montt Flight Information Region (FIR), the Buenos Aires VAAC reported that during 5 and 10-12 May, ash plumes rose to altitudes of 2.1-4.6 km (7,000-15,000 ft) a.s.l. and drifted N, NE, and ENE. 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 DUKONO Halmahera 1.68°N, 127.88°E; summit elev. 1335 m Based on analysis of satellite imagery, the Darwin VAAC reported that during 5-7 May ash plumes from Dukono rose to altitudes of 3-3.7 km (10,000-12,000 ft) a.s.l. and drifted 20-110 km SE. 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 1-8 May observers from Severo-Kurilsk, about 7 km E of Ebeko, observed continued activity. Gas-and-steam plumes containing a small amount of ash were noted on 2 May. 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 during 9-11 May ash plumes rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted SW and SE. 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 KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m During 6-12 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. On 6 May, a bench collapse from Kupapa'u was detected by seismic signals. Tour pilots reported an active surface lava flow above the pali that was less than half a kilometer long. A thermal anomaly corresponding to the flow was detected on satellite imagery. Geologists on an overflight on 7 May mapped a stalled 'a'a flow that broke out from the TEB lava tube and was being covered by pahoehoe from the breakout point. They also saw that the Waikupanaha delta had built out to the furthest point in its over 13-month history and that bus-sized chunks of delta were scattered on the beach fronting the Kupapa'u entry, as a result of the 6 May collapse. Some explosions occurred at the Waikupanaha ocean entry on 10 May. The vent in Halema'uma'u crater continued to produce a white plume that that drifted W and SW. A molten lava pool near the base of the cavity, deep below the floor of the crater, produced the brightest incandescence from the summit vent since early December 2008. Sounds resembling rushing gas and falling rocks were sometimes heard in the vicinity of the crater. Fresh spatter was retrieved from collection bins placed near the plume during 6-7 May. The sulfur dioxide emission rate at the summit was elevated; measurements were 1,100 and 700 tonnes per day on 8 and 10 May, 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/ LLAIMA Central Chile 38.692°S, 71.729°W; summit elev. 3125 m During 28 April-11 May, SERNAGEOMIN reported sporadic incandescence from an area in the SW part of Llaima's main crater, corresponding to a small outcrop of lava. Blocks occasionally rolling down the W flank were seen on a web camera. During 5-11 May, tephra was ejected from an area on the E flank and, during the night, incandescence originated from this area. During the daytime, observers reported that an almost continuous orange brown plume rose 200 m. The Volcano Alert Level remained at Yellow. 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/ NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5364 m INGEOMINAS reported images of Nevado del Huila taken during overflights on 7 and 9 May revealed thermal anomalies, volume increases, and changes in the color of the lava dome, indicating the extrusion of juvenile material. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity"). Geologic Summary. Nevado del Huila, the highest active volcano in Colombia, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. Two glacier-free lava domes lie at the southern end of the Huila volcanic complex. The first historical eruption from this little known volcano took place in the 16th century. Two persistent steam columns rise from the central peak, and hot springs are also present. Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co// RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m Based on analysis of satellite imagery, the Darwin VAAC reported that on 9 May ash plumes from Rabaul caldera's Tavurvur cone rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted about 35 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: 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 AVO reported that during 6-12 May seismicity from Redoubt remained above background levels, indicating ongoing growth of the lava dome in the summit crater. Occasional rockfalls originating from the lava dome's flanks and steam-and-gas emissions were observed on the web camera. The emissions may have contained some ash. During 5-6 May, seismicity intensified and nearly continuous small earthquakes near the summit were recorded. Steam emissions were vigorous and minor ash was detected in emission by satellite imagery. Rockfalls also triggered ash emissions near the summit. On 6 May, tremor nearly doubled in intensity and the number of events increased. An ash emission produced a plume that rose to an altitude of 3.7 km (12,000 ft) a.s.l. Seismicity declined during 6-7 May but continuous small earthquakes continued to be recorded by stations near the summit. On 12 May, seismicity decreased to low levels compared to other phases of the eruption. 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 and pilot observations, the Tokyo VAAC reported that on 9 May eruptions from Sakura-jima produced plumes that rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted S. On 12 May, an ash plume drifted E at an altitude of 1.8 km (6,000 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 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 1-8 May. Based on interpretations of seismic data, ash plumes likely rose to an altitude of 6.7 km (22,000 ft) a.s.l. Analysis of satellite imagery revealed a thermal anomaly from the lava dome every day. The Level of Concern Color Code remained at Orange. Geologic Summary. The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group and forms one of Kamchatka's largest and most active volcanoes. The currently active Molodoy Shiveluch lava-dome complex was constructed during the Holocene within a large breached caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. 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. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php 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 during 7-9 and 12 May. Details of possible resultant ash plumes 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 The IG reported that inclement weather sometimes prevented observations of Tungurahua during 6-12 May. On 6 May, ashfall was reported in Baños, about 8 km N. Steam plumes rose to altitudes below 6.5 km (21,300 ft) a.s.l. during 6-8 May and drifted W. During 9-11 May, roaring noises, "cannon shots," and sounds resembling rolling blocks were reported. On 9 May, an ash plume rose to an altitude of 6 km (19,700 ft) a.s.l. The next day ash plumes rose to an altitude of 8 km (26,200 ft) a.s.l. while roaring noises were very strong. 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. ==============================================================
