********************************************************* SI/USGS Weekly Volcanic Activity Report 22-28 October 2008 ********************************************************* Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Colima, México | Kliuchevskoi, Central Kamchatka (Russia) | Kuchinoerabu-jima, Ryukyu Islands (Japan) | Popocatépetl, México | Villarrica, Central Chile | White Island, New Zealand Ongoing Activity: | Chaitén, Southern Chile | Galeras, Colombia | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Nevado del Huila, Colombia | Rabaul, New Britain (SW Pacific) | Semeru, Eastern Java (Indonesia) | 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 COLIMA México 19.514°N, 103.62°W; summit elev. 3850 m Multiple white plumes from Colima were observed rising to altitudes of 3.9-4.1 km (12,800-13,500 ft) a.s.l. during 22-28 October. Gray plumes were observed during 25-28 October and rose to altitudes of 3.9-4.5 km (12,800-14,800 ft) a.s.l. Plumes drifted mainly SW, W, and NW. Geologic Summary. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4,320 m high point of the complex) on the N and the historically active Volcán de Colima on the S. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the S, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth. Source: Gobierno del Estado de Colima http://www.colima-estado.gob.mx/2006/seguridad/indvolcan.php KLIUCHEVSKOI Central Kamchatka (Russia) 56.057°N, 160.638°E; summit elev. 4835 m KVERT reported that seismic activity at Kliuchevskoi was above background levels during 17-24 October. Fumarolic activity was noted during 17-19 and 22-23 October by video and visual observations. Analysis of satellite imagery revealed a daily thermal anomaly in the crater. The Level of Concern Color Code remained Orange. Geologic Summary. Kliuchevskoi is Kamchatka's highest and most active volcano. Since its origin about 7,000 years ago, the beautifully symmetrical, 4,835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. More than 100 flank eruptions, mostly on the NE and SE flanks of the conical volcano between 500 m and 3,600 m elevation, have occurred during the past 3,000 years. The morphology of its 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included major explosive and effusive events from flank craters. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php KUCHINOERABU-JIMA Ryukyu Islands (Japan) 30.440°N, 130.219°E; summit elev. 657 m On 27 October, JMA raised the Alert Level for Kuchinoerabu-jima from 2 to 3 (on a scale of 1-5). GPS measurements indicated that inflation just below the summit crater, which had started in September, was continuing. Fumarolic activity near summit had also increased. On 4 September, JMA had raised the Alert Level for from 1 to 2 because of the increased seismicity. 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 POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m CENAPRED reported emissions of steam and gas from Popocatépetl during 22-28 October. The plumes occasionally contained slight amounts of ash on 27 and 28 October. 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/ VILLARRICA Central Chile 39.42°S, 71.93°W; summit elev. 2847 m SERNAGEOMIN reported that on 26 October three gray plumes with little ash content were emitted from Villarrica and rose to an altitude of 3.2 km (10,500 ft) a.s.l. The plumes quickly dispersed to the E. About 20 minutes later a darker gray plume rose to an altitude of 3.3 km (10,800 ft) a.s.l. Projecto Observación Visual Volcán Villarrica (POVI) reported that the latter plume deposited a thin layer of tephra several kilometers in length on the E flank. Geologic Summary. Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km wide caldera formed during the late Pleistocene, more than 0.9 million years ago. A 2-km-wide postglacial caldera is located at the base of the presently active, dominantly basaltic-to-andesitic cone at the NW margin of the Pleistocene caldera. About 25 scoria cones dot Villarrica's flanks. Plinian eruptions and pyroclastic flows have been produced during the Holocene from this dominantly basaltic volcano, but historical eruptions have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Lahars from the glacier-covered volcano have damaged towns on its flanks. Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/index.php, Projecto Observación Visual Volcán Villarrica (POVI) http://www.povi.cl/ WHITE ISLAND New Zealand 37.52°S, 177.18°E; summit elev. 321 m White Island's Crater Lake has continued to rise since December 2007, after being almost completely evaporated in late October 2007. By 23 October the lake was reported to have risen 15 m and was beginning to affect the geothermal features on the Main Crater floor. New springs formed on the floor and old springs flowed again. The lake temperature remained hot at 57 degrees Celsius and the color had changed to light green, reflecting a decrease in suspended sediment. High-temperature fumaroles (101-103 degrees Celsius) were located on the S side of the Main Crater floor. Steam, gas, and mud emissions had increased from the largest vent during the previous few weeks. The Alert Level remained at Level 1 (on a scale of 0-5), indicating signs of volcano unrest. Geologic Summary. The uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The 321-m-high island consists of two overlapping stratovolcanoes; the summit crater appears to be breached to the SE because the shoreline corresponds to the level of several notches in the SE crater wall. Throughout the short historical period beginning in 1826 the volcano has had long periods of continuous hydrothermal activity and steam release, punctuated by small-to-medium eruptions. Its activity also forms a prominent part of Maori legends. The most recent eruptive episode, which began on 7 March 2000, included the largest eruption at White Island in the past 20 years on 27 July. Source: GeoNet Data Centre http://www.geonet.org.nz/index.html Ongoing Activity CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m Based on web camera views and analysis of satellite imagery, the Buenos Aires VAAC reported that during 24 and 26-28 October, continuous ash plumes from Chaitén rose to altitudes of 2.1-7.3 km (7,000-24,000 ft) a.s.l. and drifted NE and E. A thermal anomaly was detected on 27 October. Geologic Summary. Chaitén is a small, glacier-free caldera with a Holocene lava dome located 10 km NE of the town of Chaitén on the Gulf of Corcovado. A pyroclastic-surge and pumice deposit considered to originate from the eruption that formed the elliptical 2.5 x 4 km wide summit caldera was dated at about 9400 years ago. A rhyolitic, 962-m-high obsidian lava dome occupies much of the caldera floor. Obsidian cobbles from this dome found in the Blanco River are the source of prehistorical artifacts from archaeological sites along the Pacific coast as far as 400 km away from the volcano to the north and south. The caldera is breached on the SW side by a river that drains to the bay of Chaitén, and the high point on its southern rim reaches 1122 m. Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m On 28 October, INGEOMINAS reported that during the previous week pulsating white plumes occasionally tinged gray rose from Galeras to altitudes of 4.7-5.5 km (15,400-18,000 ft) a.s.l. and drifted NW. 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 above background levels on 17 and 20 October and at background levels on the other days during 18-24 October. Possible explosions may have generated ash plumes to an altitude of 3.2 km (10,500 ft) a.s.l. Analysis of satellite imagery revealed a thermal anomaly in the crater on 17, 19, and 21 October; clouds prevented observations on the other days. The Level of Concern Color Code remained at Orange. Geologic Summary. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago. Construction of the Karymsky stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been Vulcanian or Vulcanian-Strombolian with moderate explosive activity and occasional lava flows from the summit crater. Most seismicity preceding Karymsky eruptions has originated beneath Akademia Nauk caldera, which is located immediately S of Karymsky volcano and erupted simultaneously with Karymsky in 1996. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m HVO reported that during 22-28 October lava flowed SE through a tube system from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex, reaching the Waikupanaha ocean entry. Lava flow production possibly paused during 26-27 October. Multiple surface lava flows on the pali were noted. On 23 October, a plume drifted above the County Viewing Area near the ocean entry and rained acid droplets, causing a closure. Explosions at the ocean entry were reported on 24 October. The sulfur dioxide emission rate at Pu'u 'O'o was 1,000 tonnes per day on 23 and 24 October, half of the background rate of the 2005-2007 average. Weak winds caused the viewing area to close again on 25 October. During the reporting period, Kilauea earthquakes were variously located beneath and to the S of the caldera, along the S-flank faults, and along the SW rift zone. Beneath Halema'uma'u crater earthquakes ranged from less than 30 per day to 70 (background is about 40), but were too small to be located more precisely. The vent in Halema'uma'u crater continued to produce a predominantly white plume that drifted mainly SW. Night-time incandescence was intermittently seen at the base of the plume, and sounds resembling distant surf, rock clattering, and rock impacts were heard in the vicinity of the crater. Weak winds resulted in poor air quality at the summit during 21 and 25-28 October. During an overflight on 24 October, HVO geologists used a FLIR (Forward Looking InfraRed) camera to view the vent. The vent (about 80 m by 60 m) was wider than a lower orifice (about 30 m by 15 m), but narrower than a chamber above the orifice, resulting in an over-hanging vent rim prone to collapse. The sulfur dioxide emission rate was 500-900 tonnes per day during 22-24 October. The 2003-2007 rate average 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/ NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5365 m INGEOMINAS reported that on 26 October an episode of tremor at Nevado del Huila lasted about 1 hour and 40 minutes, and was interpreted to have possibly been associated with ash emissions. On 28 October local residents and passengers aboard a commercial flight reported smelling sulfur. 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 (SW Pacific) 4.271°S, 152.203°E; summit elev. 688 m RVO reported that during 21-26 October ash plumes from Rabaul caldera's Tavurvur cone rose to an altitude of 2.7 km (8,900 ft) a.s.l. and drifted NW and W. During 21-24 October ashfall was reported in areas downwind, continuous incandescence from the vent was observed, and loud rumbling and roaring noises were reported. During 24-25 October ash plumes drifted to the NW area between Namanula Hill and Rabaul town. On 26 October, ash plumes rose to an altitude of 1.7 km (5,600 ft) a.s.l. and drifted NW, creating hazy conditions in Rabaul town (3-5 km NW). 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: Ima Itikarai, Rabaul Volcano Observatory (RVO) SEMERU Eastern Java (Indonesia) 8.108°S, 112.92°E; summit elev. 3676 m Based on analysis of satellite imagery, the Darwin VAAC reported that on 22 October a plume from Semeru rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted WSW. 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. Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/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 17-24 October. Based on interpretations of seismic data, a large number of hot avalanches were inferred to have descended the lava dome and produced ash plumes that rose to an altitude of 6.7 km (22,000 ft) a.s.l. Significant hot avalanches that produced ash plumes to altitudes of 5 km (16,400 ft) a.s.l. were seen on 16 and 20 October. Fumarolic activity was visible on the web camera during 17-20 and 22-23 October. Analysis of satellite imagery revealed a daily thermal anomaly on the lava dome, and ash plumes drifted 60 km E on 20 October. Ash plumes about 10 by 11 km and 10 by 5 km in horizontal dimensions drifted about 30-40 km SE on 19 and 22 October, respectively. 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 during 17-24 October the activity level at the Soufrière Hills lava dome was slightly higher than the previous week and consisted mainly of volcanic seismicity. There was no evidence of lava extrusion. On the evening of 17 October several points of incandescence from locations previously glowing on 8 October were observed through binoculars. On 20 October three pyroclastic flows descended the Tar River Valley. They generated small ash plumes that drifted over unpopulated areas to the W and SW, towards Plymouth. 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 that Suwanose-jima produced explosion or eruption plumes that rose to altitudes of 1.5-3 km (5,000-10,000 ft) a.s.l. and drifted W and E during 21, 23, 25-26, and 28 October. 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 mostly prevented observations of Tungurahua during 22-28 October; fumarolic activity was noted on 22 October. On 23 October muddy waters descended the Vascún River to the N, causing a landslide and a ruptured water pipe that serviced Baños. 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 SIGMET notices, the Buenos Aires VAAC reported that on 22 October ash plumes were continuously emitted from Ubinas and rose to altitudes of 5.5-6.7 km (18,000-22,000 ft) a.s.l. The plumes drifted S. 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. ==============================================================
