************************************************************** SI/USGS Weekly Volcanic Activity Report 4-10 March 2009 ************************************************************** Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Koryaksky, Eastern Kamchatka | Sakura-jima, Kyushu | Semeru, Eastern Java (Indonesia) Ongoing Activity: | Batu Tara, Komba Island (Indonesia) | Chaitén, Southern Chile | Fuego, Guatemala | Galeras, Colombia | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Popocatépetl, México | Rabaul, New Britain | Redoubt, Southwestern Alaska | Sangay, Ecuador | Santa María, Guatemala | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Suwanose-jima, Ryukyu Islands (Japan) | Tungurahua, Ecuador | Ubinas, Perú 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 KORYAKSKY Eastern Kamchatka 53.320°N, 158.688°E; summit elev. 3456 m KVERT reported that seismic activity at Koryaksky was above background levels on 3 March and at background levels on the other days during 27 February-6 March. Observers reported that during 3-5 March gas plumes containing a small amount of ash rose to an altitude of 3.7 km (12,100 ft) a.s.l. and drifted ENE, E, and SE. The plumes were also seen on satellite imagery. Ash deposits were seen at the summit, and on the N flank at a thickness of about 4 cm. Ash deposits 1-2 mm thick had accumulated in an area between Koryaksky and Avachinsky volcanoes. A weak new fumarole was seen in the crater. The Level of Concern Color Code remained Orange. Based on information from the Yelizovo Airport, the Tokyo VAAC reported ash on 8 March. On 10 March, an ash plume rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted SE. 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.ssd.noaa.gov/VAAC/OTH/JP/messages.html, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m During 7-10 March, JMA reported that 12 Vulcanian explosions occurred from Showa Crater, on the E flank of Sakura-jima. Some explosions were seen from JMA's Kagoshima Observatory; observers reported that ejected bombs landed as far away as 800 m from the crater and plumes rose to an altitude of 2.9 km (9,500 ft) a.s.l. Based on information from JMA, the Tokyo VAAC reported that an eruption on 7 March, and explosions during 8-10 March, produced plumes that rose to altitudes of 1.8-2.7 km (6,000-9,000 ft) a.s.l. Plumes drifted N and S during 8-10 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/messages.html SEMERU Eastern Java (Indonesia) 8.108°S, 112.92°E; summit elev. 3676 m On 6 March, CVGHM reported that an ash eruption from Semeru was characterized by increased seismicity and booming sounds from the Jonggring Seloko crater; fog prevented visual observations. The Alert Level was raised to 3 (on a scale of 1-4). Based on analysis of satellite imagery, the Darwin VAAC reported that on 7 March a possible plume rose to altitudes of 3.7-4.3 (12,000-14,000 ft) a.s.l. Geologic Summary. Semeru is the highest volcano on Java and one of its most active. The symmetrical stratovolcano rises abruptly to 3,676 m above coastal plains to the S and lies at the southern end of a volcanic massif extending N to the Tengger caldera. Semeru has been in almost continuous eruption since 1967. Frequent small-to-moderate Vulcanian eruptions have accompanied intermittent lava dome extrusion, and periodic pyroclastic flows and lahars have damaged villages below the volcano. A major secondary lahar on 14 May 1981 caused more than 250 deaths and damaged 16 villages. Sources: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/, Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html Ongoing Activity 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 9 and 10 March ash plumes from Batu Tara rose to an altitude of 2.1 km (7,000 ft) a.s.l. Plumes drifted 37 km in areas NE to NW on 9 March, and NE and N on 10 March. Geologic Summary. The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow. Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m SERNAGEOMIN reported that during 28 February-3 March Chaitén's Domo Nuevo 1 and Domo Nuevo 2 lava-dome complex continued to grow. Collapses, originating from unstable slopes of the SE part of Domo Nuevo 1 and from a central spine complex, generated block-and-ash flows. Material from the collapses accumulated in the basal ring depression surrounding the dome complex and throughout the Chaitén (Blanco) River valley. Ash-and-gas plumes drifted mainly SE. Data collected during an overflight on 3 March revealed that temperatures of deposited material in the Chaitén River valley remained elevated. A steam-and-ash plume rose 1 km above the domes and drifted S. Based on web camera views and analysis of satellite imagery, the Buenos Aires VAAC reported that during 3 and 5-9 March ash plumes rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted SE, E, and NE. 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/index.php, Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m Based on analysis of satellite imagery, the Washington VAAC reported that on 5 March multiple ash plumes from Fuego drifted W. On 6 and 10 March, INSIVUMEH reported that explosions produced ash plumes that rose to altitudes of 4.2-4.8 km (13,800-15,700 ft) a.s.l. and drifted 12-15 km S and SW. Some strong explosions were accompanied by rumbling noises, shock waves detected 8 km away, avalanches of blocks down all flanks, and ash plumes that rose to an altitude of 5 km (16,400 ft) a.s.l. Ashfall was reported in areas to the SW. 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 GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m INGEOMINAS reported that on multiple occasions during 6-10 March white gas plumes from Galeras were occasionally tinged gray or brown and rose to altitudes less than 6.3 km (21,000 ft) a.s.l. An estimated 2 million cubic meters of material, or about 40 percent of the volume of the lava dome, was deposited during the eruptions that took place on 14 and 20 February. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity"). 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// KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m KVERT reported that seismic activity at Karymsky was at background levels during 27 February-6 March. Based on interpretations of seismic data, ash plumes likely rose to an altitude of 3.5 km (11,500 ft) a.s.l. Analysis of satellite imagery revealed a thermal anomaly on the lava dome during 27-28 February and 1-4 March, and an ash plume that drifted 120 km SE on 4 March. Ash deposits on the volcano were noted. On 3 March, pilots reported an ash plume that rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted E. 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 6 March produced a plume that rose to an altitude of 3 km (10,000 ft) a.s.l. Geologic Summary. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago. Construction of the Karymsky stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been Vulcanian or Vulcanian-Strombolian with moderate explosive activity and occasional lava flows from the summit crater. Most seismicity preceding Karymsky eruptions has originated beneath Akademia Nauk caldera, which is located immediately S of Karymsky volcano and erupted simultaneously with Karymsky in 1996. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html, 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 4-10 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 ocean entry and occasionally producing explosions. Thermal anomalies noted during most days on the coastal plain suggested surface flows. Scattered surface flows near the Prince lobe were noted on 5 and 9 March. The vent in Halema'uma'u crater continued to produce a predominantly white plume that drifted mainly SW; incandescence was intermittently seen. Small amounts of newly ejected tephra were collected on 5, 6, and 10 March. Geologists utilizing an infrared camera on 3 March saw two spattering vents and a hot area about 100 m below the vent rim. Hot areas were also visible during 4-5 March, and on 6 March they saw an enlarged puffing vent. The sulfur dioxide emission rate at the summit was 700 tonnes per day on 5 and 6 March; 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/ 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 4-10 March; the plumes contained slight amounts of ash on 5 March. 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 during 2-8 March white plumes and gray ash plumes from Rabaul caldera's Tavurvur cone rose a few hundred meters above the crater to 1.7 km (5,600 ft) a.s.l. and drifted NW and SE. Incandescence was seen most nights and incandescent tephra was ejected from the crater. Rumbling and roaring noises were reported during 4-6 March, and ashfall was reported in areas downwind. Based on analysis of satellite imagery, the Darwin VAAC reported that on 10 March an ash plume rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted N. Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the E, where its floor is flooded by Blanche Bay.Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city. Sources: Ima Itikarai, Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html REDOUBT Southwestern Alaska 60.485°N, 152.742°W; summit elev. 3108 m AVO reported that during 4-10 March seismic activity at Redoubt was variable but remained above background levels. Clear web camera views and satellite imagery on 7 and 8 March showed no unusual activity. On 10 March, AVO reported that although abnormally high gas emission rates continued to be detected and melting of the summit glacier was still evident, the new magma beneath the volcano did not show any signs of upward movement. The Aviation Color Code was lowered to Yellow and the Alert Level was lowered to Advisory. 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/ SANGAY Ecuador 2.002°S, 78.341°W; summit elev. 5230 m Based on pilot observations and analysis of satellite imagery, the Washington VAAC reported that on 10 March an ash plume from Sangay rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted W. A thermal anomaly was detected in satellite imagery. Geologic Summary. The isolated Sangay volcano, located E of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. It has been in frequent eruption for the past several centuries. The steep-sided, 5,230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the E, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. Sangay towers above the tropical jungle on the E side; on the other sides flat plains of ash from the volcano have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The more or less constant eruptive activity has caused frequent changes to the morphology of the summit crater complex. Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m Based on analysis of satellite imagery, the Washington VAAC reported that during 4-6 March ash plumes from Santa María's Santiaguito lava dome complex drifted W. On 6 and 10 March, INSIVUMEH reported that explosions produced ash plumes that rose to altitudes of 2.8-3.4 km (9,200-11,200 ft) a.s.l. and drifted SW, NW, and N. Ashfall was reported in areas downwind. Geologic Summary. Symmetrical, forest-covered Santa María volcano is one of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1-km-wide crater, which formed during a catastrophic eruption in 1902 and extends from just below the summit to the lower flank. The renowned Plinian eruption of 1902 followed a long repose period and devastated much of SW Guatemala. The large dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, accompanied by almost continuous minor explosions and periodic lava extrusion, larger explosions, pyroclastic flows, and lahars. 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 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 27 February-6 March. Based on interpretations of seismic data, ash plumes likely rose to an altitude of 5.4 km (17,700 ft) a.s.l. According to observers, fumaroles were active during 28 February and 3-5 March. Ash plumes rose to an altitude of 4.7 km (15,400 ft) a.s.l. and drifted NE during 3-4 March. Analysis of satellite imagery revealed a daily thermal anomaly on the lava dome and an ash plume that drifted 84 km E on 4 March. The Level of Concern Color Code remained at Orange. Based on information from KEMSD, the Tokyo VAAC reported that eruptions on 8 and 10 March produced plumes that rose to altitudes of 6.1-6.4 km (20,000-21,000 ft) a.s.l. Plumes drifted SE on 10 March. Geologic Summary. The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group and forms one of Kamchatka's largest and most active volcanoes. The currently active Molodoy Shiveluch lava-dome complex was constructed during the Holocene within a large breached caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. During the 1990s, intermittent explosive eruptions took place from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m MVO reported that during 27 February-6 March activity from the Soufrière Hills lava dome was at a low level. On 6 March, a pyroclastic flow traveled E down the Tar River Valley to the sea. The Hazard Level remained at 3. Geologic Summary. The complex dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. English's Crater, a 1-km-wide crater breached widely to the E, was formed during an eruption about 4,000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufrière Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption. Source: Montserrat Volcano Observatory (MVO) http://www.mvo.ms/ SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m Based on information from JMA, the Tokyo VAAC reported multiple explosions from Suwanose-jima on 6 March. 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 frequently prevented visual observations of Tungurahua during 4-10 March. Slight ashfall was reported in areas to the NW on 4 March. On 6 March, steam-and-ash plumes rose 500 m above the crater. On 8 March, a steam plumes rose 100 m above the summit and fumaroles on the E flank were active. 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/ UBINAS Perú 16.355°S, 70.903°W; summit elev. 5672 m Based on a SIGMET notice and analysis of satellite imagery, the Buenos Aires VAAC reported that on 4 March an ash plume from Ubinas rose to an altitude of 5.8 km (19,000 ft) a.s.l. and drifted SW. Geologic Summary. A small, 1.2-km-wide caldera that cuts the top of Ubinas, Peru's most active volcano, gives it a truncated appearance. Ubinas is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Peru. The upper slopes of the stratovolcano, composed primarily of Pleistocene andesitic lava flows, steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas extend 10 km from the volcano. Widespread Plinian pumice-fall deposits from Ubinas include some of Holocene age. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor explosive eruptions. Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html +++++++++++++++++++++++++++++++++++++ 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. ==============================================================
