************************************************************* SI/USGS Weekly Volcanic Activity Report 29 October-4 November 2008 ************************************************************* Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Chaitén, Southern Chile | Colima, México | Galeras, Colombia | Kliuchevskoi, Central Kamchatka (Russia) | Nevado del Huila, Colombia Ongoing Activity: | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Kliuchevskoi, Central Kamchatka (Russia) | Masaya, Nicaragua | Pacaya, Guatemala | Piton de la Fournaise, Reunion Island | Popocatépetl, México | Rabaul, New Britain (SW Pacific) | 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 CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m On 29 October, SERNAGEOMIN received reports of an increase in activity at Chaitén characterized by several explosions that darkened the plume and caused it to rise from about 1.6 km (5,200 ft) a.s.l to about 3.1 km (10,200 ft) a.s.l. SERNAGEOMIN reported that variations in seismicity remained similar to patterns detected during the pervious weeks. A gas plume was continually emitted to an altitude of 3.1 km (10,200 ft) a.s.l. during the previous week. ONEMI reported that during an overflight on 30 October, scientists observed a landslide that had originated from the active lava dome. The next day observers described a plume emitted from multiple areas that rose to an altitude of 2.1 km (6,900 ft) a.s.l. The white component of the plume (steam and gas) emitted mainly from the center and S parts of the lava dome. Vents on the N and NE area produced a gray plume. The Alert Level remained Red. Based on observations of satellite imagery, Puerto Montt Flight Information Region (FIR) notices, web camera views, SIGMET notices, and pilot reports, the Buenos Aires VAAC reported that during 29-30 October and 1-3 November ash plumes from Chaitén rose to altitudes 2.4-3.7 km (8,000-12,000 ft) a.s.l. and drifted N, NE, and E. Thermal anomalies were present on 30 October and 2 November. On 4 November, SERNAGEOMIN reported that a recent overflight confirmed the presence of a second new lava dome. The new dome grew in the NE part of the first dome that started to form in May 2008, and had a diameter of about 300 m and a height of about 150 m. Spines protruded from the top. Seismicity was concentrated underneath that area. 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, Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI) http://www.onemi.cl/, Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html COLIMA México 19.514°N, 103.62°W; summit elev. 3850 m White plumes from Colima were observed rising to altitudes of 4.1-4.3 km (13,500-14,100 ft) a.s.l. during 30-31 October and 2 November. Gray plumes seen on 2 November rose to an altitude of 4.6 km (15,100 ft) a.s.l. Plumes drifted mainly SW and E. 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 GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m On 4 November, INGEOMINAS reported that during the previous week pulsating white plumes, occasionally tinged gray or blue, rose from Galeras to altitudes of 4.5-6.8 km (14,800-22,300 ft) a.s.l. and drifted W. During an overflight on 30 October, incandescence was observed on some parts of the lava dome. 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// 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 24-31 October. Video and visual observations showed fumarolic activity during 24-25 and 28-30 October. "Bursting" sounds from the volcano were heard in Klyuchi, about 30 km to the NE. 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 NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5365 m INGEOMINAS reported that on 3 November residents in an area to the S of Nevado del Huila observed intense fumarolic activity from at or near the summit that was white in color and turned grayish for short intervals. Residents of Wila, Tóez, and Plan de Caloto, to the SW, reported ashfall and strong sulfur odors. 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// Ongoing Activity KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m KVERT reported that seismic activity at Karymsky was above background levels during 24-27 October and at background levels during 28-31 October. Possible explosions may have generated ash plumes to an altitude of 2.8 km (9,200 ft) a.s.l. Analysis of satellite imagery revealed a thermal anomaly in the crater on 23, 24, and 28 October; clouds prevented observations on the other days. The Level of Concern Color Code remained at Orange. Based on analysis of satellite imagery and information from KEMSD, the Tokyo VAAC reported that an eruption generated a plume to an altitude of 4 km (13,000 ft) a.s.l. on 2 November. 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 HVO reported that during 29 October-4 November lava flowed SE through a tube system from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex, reaching the Waikupanaha ocean entry. Thermal anomalies detected on satellite imagery indicated active surface flows, especially in the abandoned Royal Gardens subdivision. Explosive activity at the ocean entry was reported on 31 October and 1 November. The sulfur dioxide emission rate at Pu'u 'O'o was 1,200 and 1,700 tonnes per day on 30 October and 3 November, respectively, half of the background rate of the 2005-2007 average. During the reporting period, Kilauea earthquakes were variously located beneath and to the S of the caldera and along the S-flank fault. Beneath Halema'uma'u crater earthquakes ranged from 40 to 60 (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 and rock clattering were heard in the vicinity of the crater. The sulfur dioxide emission rate was 500-700 tonnes per day during 29-31 October and 3 November. 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/ MASAYA Nicaragua 11.984°N, 86.161°W; summit elev. 635 m Based on analysis of satellite imagery, the Washington VAAC reported that on 4 and 5 November possible diffuse ash and steam plumes from Masaya drifted SW and S. Geologic Summary. Masaya is one of Nicaragua's most unusual and most active volcanoes. It is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high that is filled on its NW end by more than a dozen vents erupted along a circular, 4-km-wide fracture system. The twin volcanoes of Nindiri and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters. A major basaltic Plinian tephra was erupted from Masaya about 6,500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the N caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted several attempts to extract the volcano's molten "gold." Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html PACAYA Guatemala 14.381°N, 90.601°W; summit elev. 2552 m Based on analysis of satellite imagery, the Washington VAAC reported that on 2 November a possible ash-and-gas plume was emitted from Pacaya and drifted E. On 3 November, INSIVUMEH reported that fumarolic plumes drifted S at a low altitude. Ash occasionally entrained by strong winds drifted S. Multiple lava flows on the S and SW flanks of MacKenney cone traveled a maximum distance of 400 m on 3 and 4 November, and continued to fill in the area between the cone and Cerro Chino crater to the N. Fumarolic plumes drifted E on 4 November. Geologic Summary. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. Pacaya is a complex volcano constructed on the southern rim of the 14 x 16 km Pleistocene Amatitlan caldera. A cluster of dacitic lava domes occupies the caldera floor. The Pacaya massif includes the Cerro Grande lava dome and a younger volcano to the SW. Collapse of Pacaya volcano about 1,100 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (MacKenney cone) grew. During the past several decades, activity at Pacaya has consisted of frequent Strombolian eruptions with intermittent lava flow extrusion on the flanks of MacKenney cone, punctuated by occasional larger explosive eruptions. 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 PITON DE LA FOURNAISE Reunion Island 21.231°S, 55.713°E; summit elev. 2632 m OVPDLF reported that a seismic crisis at Piton de la Fournaise on 31 October was characterized by hundreds of earthquakes. The Alert Level was not changed. Geologic Summary. Massive Piton de la Fournaise shield volcano on the island of Réunion is one of the world's most active volcanoes. Most historical eruptions have originated from the summit and flanks of a 400-m-high lava shield, Dolomieu, that has grown within the youngest of three large calderas. This depression is 8 km wide and is breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows within the caldera, have been documented since the 17th century. The volcano is monitored by the Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris. Source: Observatoire Volcanologique du Piton de la Fournaise (OVPDLF) http://ovpf.univ-reunion.fr/ POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m CENAPRED reported that emissions of steam and gas from Popocatépetl were visible during 29 October-4 November. The plumes occasionally contained slight amounts of ash. 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 (SW Pacific) 4.271°S, 152.203°E; summit elev. 688 m RVO reported that during 27 October-2 November ash plumes from Rabaul caldera's Tavurvur cone rose to an altitude of 1.7 km (5,600 ft) a.s.l. and drifted NW and SE. Ashfall was reported in areas downwind. Sub-continuous incandescence from the vent was observed and rumbling and roaring noises were reported on some days. Explosions or forceful emissions sometimes ejected incandescent lava fragments. Based on analysis of satellite imagery, the Darwin VAAC reported that on 3 November ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. 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 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 24-31 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 5.2 km (17,100 ft) a.s.l. Ash plumes that rose to an altitude of 5 km (16,400 ft) a.s.l. were seen on 24 October. Fumarolic activity was visible on the web camera during 23-25 and 28-30 October. Analysis of satellite imagery revealed a daily thermal anomaly on the lava dome. The Level of Concern Color Code remained at Orange. Based on information from KEMSD and analysis of satellite imagery, the Tokyo VAAC reported that on 2 and 4 November eruption plumes rose to altitudes of 5.2 and 4.6 km (17,000 and 15,000 ft) a.s.l., respectively. 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.kscnet.ru/ivs/kvert/index_eng.php, 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 24-31 October the activity level at the Soufrière Hills lava dome was low. There was no evidence of lava extrusion. On 26 October, observers aboard a fixed-wing aircraft confirmed that a few small pyroclastic flows traveled about 1.5 km down the Tar River Valley. Erosion down several V-shaped chutes continued at the E and SE bases of the dome further deepened the moat in the talus around the dome. Ongoing erosion of the talus pile on the W flank resulted in a well-incised network of gullies leading into the White River. On 27 October, a small pyroclastic flow seen from MVO traveled about 1 km down the Tar River Valley and generated a small ash plume 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 during 29-30 October and 3 November Suwanose-jima produced explosion or eruption plumes that rose to altitudes of 1.5-1.8 km (5,000-6,000 ft) a.s.l. and drifted E. Explosions were reported on 31 October and 1 November, but details of possible 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 mostly prevented observations of Tungurahua from 28 October to 4 November; steam plumes were noted on 2 November. On 28 October a lahar lasting about 30 minutes descended the Vascún River to the N. Lahars caused by rain descended multiple drainages on 1 November. Blocks about 50-70 cm in diameter were reported in Juive, (about 7 km NNW), La Pampas, (about 6 km S), and Bilbao (about 8 km N). Rolling blocks up to 1 m in diameter were reported in the SW. Residents bordering the Vascún River temporarily evacuated and then returned to their homes after the rain stopped. 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 31 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 E. 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. ==============================================================
