******************************************************** SI/USGS Weekly Volcanic Activity Report 18-24 March 2009 ******************************************************** Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Galeras, Colombia | Hunga Tonga-Hunga Ha'apai, Tonga | Koryaksky, Eastern Kamchatka | Redoubt, Southwestern Alaska Ongoing Activity: | Batu Tara, Komba Island (Indonesia) | Chaitén, Southern Chile | Dempo, Sumatra (Indonesia) | Etna, Sicily (Italy) | Gamkonora, Halmahera | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Kuchinoerabu-jima, Ryukyu Islands (Japan) | Lewotobi, Flores Island (Indonesia) | Okmok, Fox Islands | Popocatépetl, México | Rabaul, New Britain | Sakura-jima, Kyushu | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | 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 GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m On 24 March, INGEOMINAS lowered the Alert Level for Galeras to III (Yellow; "changes in the behavior of volcanic activity"). During the previous week daily sulfur dioxide levels were high. Earthquake levels were low in both intensity and occurrence. During 21-23 March, white-colored gas plumes rose to an altitude of 5.4 km (17,700 ft) a.s.l. and drifted in multiple directions. 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// HUNGA TONGA-HUNGA HA'APAI Tonga 20.57°S, 175.38°W; summit elev. 149 m Based on information from Tonga Meteorological Services, analysis of satellite imagery, and pilot observations, the Wellington VAAC reported that during 18-19 March ash plumes from Hunga Tonga-Hunga Ha'apai rose to altitudes of 4-5.2 km (13,000-17,000 ft) a.s.l. and drifted NE and about 480 km ENE. On 20 March, steam plumes rose to an altitude of 1.8 km (6,000 ft) a.s.l. Wide-spread haze was reported in areas downwind, below an altitude of 1.5 km (5,000 ft) a.s.l., including in Vava'u, a group of islands about 255 km NE of Hunga Tonga-Hunga Ha'apai. On 21 March, an eruption plume rose to an altitude of 0.8 km (2,500 ft) a.s.l. According to news articles, the eruption started on 16 March from two vents, one on Hunga Ha'apai and another about 100 m offshore. Video footage and photographs taken from a nearby boat and posted on 20 March showed repeated dark, ash-rich Surtseyan explosions and associated base surges from two vents. A journalist that visited the area reported that the island was covered with black ash, and coconut trees were reduced to black stumps. Dead birds and fish were seen in the water. Geologic Summary. The small islands of Hunga Tonga and Hunga Ha'apai cap a large seamount located about 30 km SSE of Falcon Island. The two linear andesitic islands are about 2 km long and represent the western and northern remnants of a the rim of a largely submarine caldera lying east and south of the islands. Hunga Tonga and Hunga Ha'apai reach an elevation of only 149 m and 128 m above sea level, respectively, and display inward-facing sea cliffs with lava and tephra layers dipping gently away from the submarine caldera. A rocky shoal 3.2 km SE of Hunga Ha'apai and 3 km south of Hunga Tonga marks the most prominent historically active vent. Several submarine eruptions have occurred at Hunga Tonga-Hunga Ha'apai since the first historical eruption in 1912. Sources: Wellington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/NZ/messages.html, Agence France-Presse http://www.google.com/hostednews/afp/article/ALeqM5j6VD1Pdx9mNNXjovtdfyKtB2WXVQ, Infobae http://www.infobae.com/contenidos/437492-101275-0-Impactantes-im%C3%A1genes-una-erupci%C3%B3n-volc%C3%A1nica-el-mar KORYAKSKY Eastern Kamchatka 53.320°N, 158.688°E; summit elev. 3456 m KVERT reported that seismic activity at Koryaksky was elevated on 13 March and at background levels on the other days during 14-20 March. Observers reported that gas plumes containing a small amount of ash rose to an altitude of 4 km (13,200 ft) a.s.l. and drifted in easterly directions during the reporting period. The plumes were also seen on satellite imagery drifting 140 km away from the volcano. Ash was emitted from the upper fumarolic vent and covered the flanks. The Level of Concern Color Code remained Orange. Geologic Summary. The large symmetrical Koryaksky stratovolcano is the most prominent landmark of the NW-trending Avachinskaya volcano group, which towers above Kamchatka's largest city, Petropavlovsk. Erosion has produced a ribbed surface on the eastern flanks of the 3456-m-high volcano; the youngest lava flows are found on the upper western flank and below SE-flank cinder cones. No strong explosive eruptions have been documented during the Holocene. Extensive Holocene lava fields on the western flank were primarily fed by summit vents; those on the SW flank originated from flank vents. Lahars associated with a period of lava effusion from south- and SW-flank fissure vents about 3900-3500 years ago reached Avacha Bay. Only a few moderate explosive eruptions have occurred during historical time. Koryaksky's first historical eruption, in 1895, also produced a lava flow. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php REDOUBT Southwestern Alaska 60.485°N, 152.742°W; summit elev. 3108 m On 18 March, AVO lowered the Alert Level for Redoubt to Advisory and Aviation Color Code to Yellow because seismicity declined to levels recorded prior to the ash emission on 15 March. Seismicity remained low the next day. Shallow earthquake activity was noted again on 20 March. On 21 March, a steam plume rose to an altitude of 3.4 km (11,200 ft) a.s.l. Later that day, the rate of seismic events continued to increase, prompting AVO to raise the Alert Level to Watch and the Aviation Color Code to Orange. On 22 March, an explosive eruption began at 2238, prompting AVO to raise the Alert Level to Warning and the Aviation Color Code to Red, the highest levels. Four more explosive eruptions occurred, with each lasting between 4-30 minutes. Ash plumes rose to an altitude of 18.2 km (60,000 ft) a.s.l., with the bulk of the ash volume between 7.6-9.1 km (25,000-30,000 ft) a.s.l. Ashfall was reported in areas 190-250 km NE. The last explosion ended at 0500 on 23 March. No ash was detected afterwards utilizing radar data, suggesting that if ash emissions were occurring, plumes would be below approximately 4 km (13,000 ft) a.s.l. and/or contain particles too fine to be detected. Poor weather hindered visual observations of the volcano. The sixth explosion began on 23 March at 1941, lasted about 17 minutes, and produced an ash plume that rose to an altitude of 15.2 km (50,000 ft) a.s.l. and drifted W and N. Pyroclastic flows were visible traveling down the N flank in web camera images. According to news articles, Alaska Airlines cancelled 19 flights on 23 March due to ash plumes. On 23 March, AVO staff visited areas around Redoubt and saw large lahar and flood deposits in the Drift River valley. The eruptions caused melting of the Drift Glacier and greatly increased discharge down the Drift River, causing lahars that traveled more than 35 km, reaching the Cook Inlet. In the middle to upper Drift River valley, high-water marks reached 6-8 m above the valley floor. At the AVO hut (roughly 11 km NNW of the summit), a 6-cm-thick fall deposit was observed. On 24 March, AVO reported that a steam plume rose to an altitude of 6.1 km (20,000 ft) and drifted about 65 km NW. Geologic Summary. Redoubt is a 3108-m-high glacier-covered stratovolcano with a breached summit crater in Lake Clark National Park about 170 km SW of Anchorage. Next to Mount Spurr, Redoubt has been the most active Holocene volcano in the upper Cook Inlet. Collapse of the summit of Redoubt 10,500-13,000 years ago produced a major debris avalanche that reached Cook Inlet. Holocene activity has included the emplacement of a large debris avalanche and clay-rich lahars that dammed Lake Crescent on the south side and reached Cook Inlet about 3500 years ago. Eruptions during the past few centuries have affected only the Drift River drainage on the north. Historical eruptions have originated from a vent at the north end of the 1.8-km-wide breached summit crater. The 1989-90 eruption of Redoubt had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano. Sources: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/, The Associated Press http://www.myfoxchicago.com/dpp/news/dpg_Alaska_Redoubt_Volcano_Erupts_fc_200903242303249 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 20 March an ash plume from Batu Tara rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted NW. Geologic Summary. The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow. Source: Darwin Volcanic Ash Advisory 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 10-16 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 was channeled towards the Chaitén (Blanco) River valley. Ash-and-gas plumes drifted mainly SE. Based on web camera views and SIGMET notices, the Buenos Aires VAAC reported that during 20-21 and 23 March ash plumes rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted 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 DEMPO Sumatra (Indonesia) 4.03°S, 103.13°E; summit elev. 3173 m On 23 March, CVGHM lowered the Alert Level for Dempo from 2 to 1 (on a scale of 1-4) based on visual observations of the crater lake during 5-6 January and 2-4 March, and decreased seismicity since a phreatic eruption on 1 January. Visitors and residents were advised not to go within a 1-km radius of the summit. Geologic Summary. Dempo is a prominent 3173-m-high stratovolcano that rises above the Pasumah Plain of SE Sumatra. Remnants of 7 craters are found at or near the summit, with volcanism migrating to the WNW with time. The historically active summit crater of Gunung Dempo contains a 400-m-wide lake, located at the NW end of the crater complex. Historical eruptions have been restricted to small-to-moderate explosive activity that produced ashfall near the volcano. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ ETNA Sicily (Italy) 37.734°N, 15.004°E; summit elev. 3330 m INGV-CT reported that after a week of Strombolian activity and ash emission from the top of Etna's 2008 eruptive fissure, activity from the summit craters during 16-22 March consisted of degassing from the Northeast Crater, the NW Bocca Nuova vent, from the E flank of the Southeast Crater, and along summit fumarolic fields. The activity was observed directly and by utilizing surveillance cameras situated in Milo (about 11 km ESE). The NW-SE-trending fissure E of the summit craters continued (since 13 May 2008) to produce active lava flows to the N of the SE end of the fissure, along the W wall of the Valle del Bove. Geologic Summary. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BC. Historical lava flows cover much of the surface of this massive basaltic stratovolcano, the highest and most voluminous in Italy. Two styles of eruptive activity typically occur at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater. Flank eruptions, typically with higher effusion rates, occur less frequently and originate from fissures that open progressively downward from near the summit. A period of more intense intermittent explosive eruptions from Etna's summit craters began in 1995. The active volcano is monitored by the Instituto Nazionale di Geofisica e Volcanologia (INGV) in Catania. Source: Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania (INGV-CT) http://www.ct.ingv.it/ GAMKONORA Halmahera 1.38°N, 127.53°E; summit elev. 1635 m On 23 March, CVGHM lowered the Alert Level for Gamkonora from 2 to 1 (on a scale of 1-4) based on visual observations and decreased seismicity since January. Diffuse white plumes rose 50-150 m above the crater. Residents and visitors were reminded not to approach or climb the crater. Geologic Summary. The shifting of eruption centers on Gamkonora, at 1635 m the highest peak of Halmahera, has produced an elongated series of summit craters along a N-S trending rift. Youthful-looking lava flows originate near the cones of Gunung Alon and Popolojo, south of Gamkonora. Since its first recorded eruption in the 16th century, Gamkonora has typically produced small-to-moderate explosive eruptions. Its largest historical eruption, in 1673, was accompanied by tsunamis that inundated villages. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m KVERT reported that seismic activity at Karymsky was above background levels on 12 and 18 March; no data was collected during 13-17 March due to technical reasons. According to reports from Yelizovo Airport, pilots saw an ash plume that rose to an altitude of 3.9 km (12,800 ft) a.s.l. and drifted E on 12 March. Analysis of satellite imagery revealed a thermal anomaly on the lava dome during 12-14 and 16-17 March, and ash plumes that drifted 200 km in easterly directions during 12-13 and 16-17 March. The Level of Concern Color Code remained at Orange. Based on information from the Yelizovo Airport, the Tokyo VAAC reported that on 19 March an ash plume rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted W. 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.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 18-24 March, HVO reported that lava flowed SE from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex through a lava tube system, reaching the Waikupanaha and Kupapa'u ocean entries. Activity near the Prince Lobe was noted, and thermal anomalies seen on satellite imagery during most days suggested surface flows on the coastal plain. Explosions from the Waikupanaha ocean entry were seen on 19 March. During 19-20 March, the Kupapa'u bench was 450 m wide (along shore) and extended 70 m into the ocean. The vent in Halema'uma'u crater continued to produce a predominantly white plume, occasionally tinged brown, that drifted mainly SW. Incandescence was intermittently seen from the vent, and sounds resembling rushing gas were sometimes heard in the vicinity of the crater. Tephra and some glassy spatter were retrieved almost daily from collection bins placed near the plume. On 20 March, geologists utilizing an infrared camera saw that a single small spattering vent (another was out of sight to the E) at the bottom of a large overhung cavity beneath the Halema'uma'u crater floor emitted gas and steam. The sulfur dioxide emission rate at the summit was 500 and 900 tonnes per day on 19 and 23 March, respectively; the 2003-2007 average rate was 140 tonnes per day. Geologic Summary. Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world's most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed of lava flows less than about 1,100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island. Source: US Geological Survey Hawaiian Volcano Observatory (HVO) http://hvo.wr.usgs.gov/ KUCHINOERABU-JIMA Ryukyu Islands (Japan) 30.440°N, 130.219°E; summit elev. 657 m On 18 March, JMA lowered the Alert Level for Kuchinoerabu-jima from 3 to 2 (on a scale of 1-5). Sulfur dioxide emissions decreased in January and the rate of deformation decreased in February. Seismicity was also low. The volcano had been in a state of unrest since September 2008. Geologic Summary. A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabu-jima in the northern Ryukyus, 15 km west of Yaku-shima. Furu-take, Shin-take, and Noike were erupted from south to north, respectively, to form a composite cone that is parallel to the trend of the Ryukyu Islands. The youngest cone, 640-m-high Shin-take, was formed after the NW side of Furu-take was breached by an explosion. All historical eruptions have occurred from Shin-take, although a lava flow from the south flank of Furu-take that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shin-take since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few km of the active crater of Shin-take and have suffered damage from eruptions. Source: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/indexe.html LEWOTOBI Flores Island (Indonesia) 8.542°S, 122.775°E; summit elev. 1703 m On 23 March, CVGHM lowered the Alert Level for Lewotobi from 2 to 1 (on a scale of 1-4) based on visual observations and decreased seismicity during March. Rarely seen diffuse white plumes rose 25 m above the crater and drifted E. Visitors and residents were advised not to approach the crater. Geologic Summary. The Lewotobi "husband and wife" twin volcano (also known as Lewetobi) in eastern Flores Island is composed of the Lewotobi Lakilaki and Lewotobi Perempuan stratovolcanoes. Their summits are less than 2 km apart along a NW-SE line. The conical 1,584-m-high Lewotobi Lakilaki has been frequently active during the 19th and 20th centuries, while the taller and broader 1,703-m-high Lewotobi Perempuan has erupted only twice in historical time. Small lava domes have grown during the 20th century in the crescentic summit craters of both volcanoes, which are open to the N. A prominent flank cone, Iliwokar, occurs on the E flank of Lewotobi Perampuan. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ OKMOK Fox Islands 53.43°N, 168.13°W; summit elev. 1073 m On 20 March, AVO lowered the Volcano Alert Level for Okmok to Normal and the Aviation Color Code to Green. Seismic activity had been at low to near background levels and satellite views showed no activity during the previous two weeks. The last confirmed ash emission at Okmok occurred on 19 August 2008. Geologic Summary. The broad, basaltic Okmok shield volcano, which forms the NE end of Umnak Island, has a dramatically different profile than most other Aleutian volcanoes. The summit of the low, 35-km-wide volcano is cut by two 10-km-wide calderas formed during eruptions about 8,250 and 2,400 years ago that produced dacitic pyroclastic flows that reached the coast. Numerous satellitic cones and lava domes dot the flanks of the volcano down to the coast. Some of the post-caldera cones show evidence of wave-cut lake terraces; the more recent cones, some of which have been active historically, were formed after the caldera lake disappeared. Hot springs and fumaroles are found within the caldera and at Hot Springs Cone, 20 km to the SW. Historical eruptions have occurred since 1805 from cinder cones within the caldera. Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/ 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 18-24 March; the plumes contained slight amounts of ash during 20-21 and 23 March. An explosion on 23 March ejected incandescent fragments that landed near the crater. Based on information from CENEPRED, the Washington VAAC reported that a minor emission on 23 March produced a plume that rose to an altitude of 6.7 km (22,000 ft) a.s.l. A small ash plume was seen on satellite imagery drifting SE. 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. Sources: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.unam.mx/es/, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m RVO reported that during 16-20 March gray ash plumes from Rabaul caldera's Tavurvur cone rose to a maximum altitude of 1.7 km (5,600 ft) a.s.l. and drifted E. Blue vapor was visible during intervals between ash cloud emissions. Incandescence from the summit crater was seen at night, and incandescent tephra was occasionally ejected from the crater during periods of heightened activity. Light ashfall was reported in areas downwind, including in the Duke of York Islands about 20 km E. Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the E, where its floor is flooded by Blanche Bay.Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city. Source: Herman Patia, Rabaul Volcano Observatory (RVO) SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m Based on information from JMA, the Tokyo VAAC reported explosions from Sakura-jima on 20 and 23 March. Additional information on possible resultant plumes was not reported. 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 during 13-20 March seismic activity at Shiveluch was above background levels. 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 12-14 and 16-19 March. Strong fumarolic activity was seen on 13, 14, and 18 March, and incandescence from the lava dome was seen at night on 14 and 18 March. 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. 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. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m MVO reported that observations during an overflight of the Soufrière Hills lava dome on 18 March confirmed that a seismic signal recorded earlier that day was from a pyroclastic flow; the flow traveled E down the Tar River Valley, almost reaching the sea. 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/ TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m The IG reported that during 17-18 and 22 March ash plumes from Tungurahua rose to altitudes of 5.5-7.5 km (18,000-24,600 ft) a.s.l. and drifted W, NW, and NNE. Ashfall was reported in areas downwind on 17 and 20 March. On 21 March, lahars carrying blocks up to 30 cm in diameter traveled down the Mapayacu drainage to the SW. Lahars were also seen in the Mandur drainage to the NW. 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 pilot observations, the Buenos Aires VAAC reported that a plume from Ubinas rose to an altitude of 7.9 km (26,000 ft) a.s.l. on 18 March. Ash was not identified in satellite imagery. 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. ==============================================================
