********************************************************************* GVP/USGS Weekly Volcanic Activity Report 28 November-4 December 2007 http://www.volcano.si.edu/reports/usgs/ ********************************************************************* New Activity/Unrest: | Anatahan, Mariana Islands | Popocatépetl, México | Talang, Indonesia Ongoing Activity: | Bezymianny, Russia | Colima, México | Fuego, Guatemala | Galeras, Colombia | Jebel at Tair, Yemen | Karymsky, Russia | Kelut, Indonesia | Kilauea, USA | Shiveluch, Russia | Soufrière Hills, Montserrat | St. Helens, USA | Suwanose-jima, Japan | Tungurahua, Ecuador | Ubinas, Perú New Activity/Unrest ANATAHAN Mariana Islands, central Pacific Ocean 16.35°N, 145.67°E; summit elev. 788 m The amplitude of volcanic tremor at Anatahan gradually increased through October and November and small explosions occurred during the last week of November. On 29 November, the Volcanic Alert Level was raised to Advisory and the Aviation Color Code was raised to Yellow based on the increase in seismicity <http://www.avo.alaska.edu/color_codes.php>. Geologic Summary. The elongate, 9-km-long island of Anatahan in the central Mariana Islands consists of large stratovolcano with a 2.3 x 5 km, E-W-trending compound summit caldera. The larger western caldera is 2.3 x 3 km wide, and its western rim forms the island's 790-m high point. Ponded lava flows overlain by pyroclastic deposits fill the floor of the western caldera, whose SW side is cut by a fresh-looking smaller crater. The 2-km-wide eastern caldera contained a steep-walled inner crater prior to the 2003 eruption whose floor was only 68 m above sea level. Sparseness of vegetation on the most recent lava flows on Anatahan had indicated that they were of Holocene age, but the first historical eruption of Anatahan did not occur until May 2003, when a large explosive eruption took place forming a new crater inside the eastern caldera. Source: Emergency Management Office of the Commonwealth of the Mariana Islands and the US Geological Survey Hawaiian Volcano Observatory http://hvo.wr.usgs.gov/cnmi/index.html Anatahan Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0804-20= POPOCATÉPETL México 19.02°N, 98.62°W; summit elev. 5,426 m CENEPRED reported that multiple gas-and-steam plumes from Popocatépetl were observed during 28 November-4 December. On 1 December, high frequency seismic tremor was accompanied by an ash plume that rose to an altitude of 7.4 km (24,300 ft) a.s.l. and drifted N, and then NE. Ashfall was reported in areas downwind. Based on observations of satellite imagery, reports from the Mexico City MWO, and the web camera operated by CENEPRED, the Washington VAAC reported that the ash plume rose to an altitude of 9.1 km (30,000 ft) a.s.l. 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 (CENEPRED) http://www.cenapred.unam.mx/cgi-bin/popo/reportes/ultrep.cgi, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html Popocatépetl Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1401-09= TALANG Sumatra, Indonesia 00.98°S, 100.68°E; summit elev. 2,896 m CVGHM raised the Alert level for Talang from 2 to 3 (on a scale of 1-4) on 29 November based on visual observations and seismicity. Ash and steam plumes from multiple craters rose to altitudes of 3.1-4.1 km (10,200-13,500 ft) a.s.l. during 27-29 November. A strong smell of sulfur dioxide gas was also reported. Visitors and tourists were advised not to go within a 3-km radius of the summit. Geologic Summary. Talang, which forms a twin volcano with the extinct Pasar Arbaa volcano, has two crater lakes on its flanks. The largest of these is 1 x 2 km wide Danau Talang. No historical eruptions have occurred from the summit of the volcano, which lacks a crater. All historical eruptions from Gunung Talang volcano have involved small-to-moderate 19th-century explosive activity originating from a series of small craters in a valley on the upper NE flank. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ Talang Information from the Global Volcano Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0601-16= Ongoing Activity BEZYMIANNY Kamchatka Peninsula, Russia 55.98°N, 160.59°E; summit elev. 2,882 m Based on reports from KVERT, the Washington VAAC reported an ash plume from Bezymianny at an altitude of 4.3 km (14,000 ft) a.s.l. on 2 December. Ash was not identified on satellite imagery. The level of Concern Color Code remained at Yellow <http://www.avo.alaska.edu/color_codes.php>. Geologic Summary. Prior to its noted 1955-56 eruption, Bezymianny volcano had been considered extinct. The modern Bezymianny volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral volcano that was built between about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of Mount St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html Bezymianny Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-25= COLIMA Western México 19.514°N, 103.62°W; summit elev. 3,850 m Based on reports from the Mexico City MWO, the Washington VAAC reported that an ash plume from Colima rose to an altitude of 7.3 km (24,000 ft) a.s.l. and drifted W on 26 November. Observations of satellite imagery showed a plume to the NNE. Observers reported that steam and steam-and-ash plumes rose to altitudes of 3.9-4.6 km (12,800-15,100 ft) a.s.l. and drifted N and SW on 26, 27, and 29 November and during 3-4 December. 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. Sources: Gobierno del Estado de Colima http://www.colima-estado.gob.mx/2006/seguridad/indvolcan.php, Washington Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html Colima Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1401-04= FUEGO Guatemala 14.47°N, 90.88°W; summit elev. 3,763 m Based on observations of satellite imagery, the Washington VAAC reported that an ash plume from Fuego drifted W on 29 November. 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. Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html Fuego Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-09= GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4,276 m Based on visual observations during clear weather, INGEOMINAS reported that steam-and-gas plumes from Galeras rose to a maximum altitude of 5.3 km (17,400 ft) a.s.l. during 21-23 November and 3 December. The plumes occasionally contained small volumes of ash and were associated with seismic tremor. Gas and ash plumes that rose to an altitude of 4.4 km (14,400 ft) a.s.l. and drifted NW were observed during an overflight on 27 November. Thermal images indicated an increase in temperatures since a 2 October overflight at the point sources of emissions. The Alert Level remained at 3 (changes in the behavior of volcanic activity have been noted) on a scale of 4-1. 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. Long-term 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 http://www.ingeominas.gov.co/ Galeras Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1501-08= JEBEL AT TAIR Red Sea, Yemen 15.55°N, 41.82°E; summit elev. 244 m Since the beginning of an eruption of Jebel at Tair on 30 September, the MODIS satellite detected thermal anomalies over the island every day through 4 December. According to a news article, an eruption took place on 4 December and lava flows intermittently occurred since 30 September. Geologic Summary. The basaltic Jebel at Tair volcano rises from a 1200 m depth in the south-central Red Sea, forming an oval-shaped island about 3 km long. Jebel at Tair (one of many variations of the name, including Djebel Teyr, Jabal al Tayr, and Jibbel Tir ) is the northernmost known Holocene volcano in the Red Sea and lies SW of the Farisan Islands. Youthful basaltic pahoehoe lava flows from the steep-sided central vent, Jebel Duchan, cover most of the island. They drape a circular cliff cut by wave erosion of an older edifice and extend beyond it to form a flat coastal plain. Pyroclastic cones are located along the NW and southern coasts, and fumarolic activity occurs from two uneroded scoria cones at the summit. Radial fissures extend from the summit, some of which were the sources of lava flows. The island is of Holocene age, and explosive eruptions were reported in the 18th and 19th centuries. Sources: Hawai'i Institute of Geophysics and Planetology (HIGP) Moderate Resolution imaging Spectroradiometer (MODIS) Thermal Alert System http://modis.higp.hawaii.edu/, Integrated Regional Information Networks (IRIN) http://www.irinnews.org/Report.aspx?ReportId=75671 Jebel at Tair Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0201-01= KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m KVERT reported that seismic activity at Karymsky was at background levels during 24-25 November and slightly above background levels on 26 November. Seismic data was unavailable on the other days during 23-30 November. The Level of Concern Color Code <http://www.avo.alaska.edu/color_codes.php> 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/updates.shtml Karymsky Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-13= KELUT Java, Indonesia 7.93°S, 112.31°E; summit elev. 1,731 m CVGHM reported that on 29 November, the Alert level for Kelut was lowered from 3 to 2 (on a scale of 1-4), due to a decrease in seismicity and a lack of deformation. Observations of video footage from a camera on 25 November revealed that the lava dome was still active. Visitors and tourists were advised not to go within a 1.5-km radius of the crater lake. Geologic Summary. The relatively inconspicuous 1,731-m-high Kelut stratovolcano contains a summit crater lake that has been the source of some of Indonesia's most deadly eruptions. A cluster of summit lava domes cut by numerous craters has given the summit a very irregular profile. More than 30 eruptions have been recorded from Gunung Kelut since 1000 AD. The ejection of water from the crater lake during Kelut's typically short, but violent eruptions has created pyroclastic flows and lahars that have caused widespread fatalities and destruction. After more than 5,000 people were killed during the 1919 eruption, an ambitious engineering project sought to drain the crater lake. This initial effort lowered the lake by more than 50 m, but the 1951 eruption deepened the crater by 70 m, leaving 50 million cubic meters of water after repair of the damaged drainage tunnels. After more than 200 people were killed in the 1966 eruption, a new deeper tunnel was constructed, lowering the lake's volume to only about 1 million cubic meters prior to the 1990 eruption. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ Kelut Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-28= KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m Based on overflights and web camera views, HVO reported that fissure segment D from Kilauea's 21 July fissure eruption continued to feed a lava channel and perched lava ponds that occasionally overflowed their edges during 28 November-3 December. Views were blocked by fumes on 4 December. The small lava pond at the top of the Thanksgiving Eve Breakout (TEB) shield, built directly over the fissure, occasionally overflowed and fed lava flows in multiple directions. On 1 December, one of these flows was L-shaped and 2.1 km long, but mostly active within the upper 800 m. A few small earthquakes were located beneath Halema'uma'u crater and along the SW rift zone and S-flank fault. 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 by lava flows less than about 1,100 years old; 70% of the volcano's surface is younger than 600 years. The latest Kilauea eruption began in January 1983 along the E rift zone. This long-term ongoing eruption from Pu'u 'O'o-Kupaianaha has produced lava flows that have traveled 11-12 km from the vents to the sea, paving broad areas on the S flank of Kilauea and adding new land beyond the former coastline. Source: US Geological Survey Hawaiian Volcano Observatory http://volcano.wr.usgs.gov/hvostatus.php Kilauea Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01- SHIVELUCH Kamchatka Peninsula, Russia 56.653°N, 161.360°E; summit elev. 3,283 m KVERT reported that seismic activity at Shiveluch was above background levels during 23-30 November. Based on seismic interpretation, ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. and hot avalanches occurred. Visual observations and video footage analysis indicated that gas-and-steam plumes rose to an altitude of 5 km (16,400 ft) a.s.l. on 22 and 26-29 November. Based on observations of satellite imagery, ash plumes drifted SW, NW, N, and SE on 26, 27, and 28 November and a thermal anomaly was present in the crater every day during the reporting period. The Level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. Based on information from the KEMSD, the Tokyo VAAC reported that eruption plumes rose to altitudes of 5.5 km and 5.8 km (18,000 ft and 19,000 ft) a.s.l. on 30 November and 2 December, 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 horseshoe-shaped 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/updates.shtml, Tokyo Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html Shiveluch Information from the Global Volcanism Program http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1000-27= SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m; All times are local (= UTC - 4 hours) MVO reported that during 23 November-3 December the lava dome at Soufrière Hills changed very little, based on visual observations. Seismic activity was very low and low-level rockfall and pyroclastic flow activity continued. Fumarolic activity on the N and E flanks of the dome were observed. On 29 November, a regional M 7.4 earthquake occurred at 1500. A few minutes later, a small pyroclastic flow traveled down the E flank. At 1530, three more pyroclastic flows traveled E down the Tar River Valley. The Alert Level remained elevated at 4 (on a scale of 0-5). 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 east, was formed during an eruption about 4000 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 http://www.mvo.ms/ Soufrière Hills Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1600-05= ST. HELENS Washington, USA 46.20°N, 122.18°W; summit elev. 2,549 m Data from deformation-monitoring instruments indicated that during 28 November-4 December lava-dome growth at Mount St. Helens continued. Small inflation-deflation events occurred which were interpreted as dome-growth pulses. Seismicity persisted at low levels, punctuated by M 1.5-2.5, and occasionally larger, earthquakes. A GPS receiver on the W part of the active spine showed continued SW advance at a rate of 3-4 mm per day since September 2007. An image from a camera on the NE flank from 28 November showed no notable landscape changes. Clouds occasionally inhibited visual observations. Geologic Summary. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago, and has been the most active volcano in the Cascade Range during the Holocene. The modern edifice was constructed during the last 2,200 years, when the volcano produced basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the N flank, and were witnessed by early settlers. Source: US Geological Survey Cascades Volcano Observatory http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity/framework.html St. Helens Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05- SUWANOSE-JIMA Ryukyu Islands, Japan 29.53°N, 129.72°E; summit elev. 799 m Based on information from JMA, the Tokyo VAAC reported that eruption plumes from Suwanose-jima rose to altitudes of 1.2-1.8 km (4,000-6,000 ft) a.s.l. during 29 November-2 December and drifted E. Ash was not visible on satellite imagery. 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 E 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 around 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 Suwanose-jima Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0802-03= TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m IG reported that although visual observations were occasionally limited due to cloud cover, ash-and-steam and ash plumes from Tungurahua rose to altitudes of 6-8 km (19,700-26,200 ft) a.s.l. during 27 November-4 December. During 28 November-1 December, seismic activity was elevated and multiple explosions were associated with almost continuous emissions of steam and ash. Explosions and "cannon shots" vibrated large windows and the ground within a 13 km radius of the summit on 28 and 29 November, and during 1-3 December. Ashfall was reported in areas to the SW, W, NW, N, and NE on 28 November, and 3-4 December. Incandescent blocks rolled 500-1000 m down the flanks on 28 November, 1 December, and 3 December. Roaring noises were occasionally reported. 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 been restricted to 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 Poltécnica Nacional http://www.igepn.edu.ec/ Tungurahua Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08= UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m Based on a pilot report and observations of satellite imagery, the Buenos Aires VAAC reported that ash plumes from Ubinas rose to altitudes of 6.7-7.6 km (22,000-25,000 ft) a.s.l. and drifted SW and NE during 28-29 November. 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 Ubinas Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1504-02= +++++++++++++++++++++++++++++++++++++ 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. ==============================================================
