***************************************************************** GVP/USGS Weekly Volcanic Activity Report 14-20 November 2007 http://www.volcano.si.edu/reports/usgs/ ***************************************************************** New Activity/Unrest: | Krakatau, Indonesia Ongoing Activity: | Arenal, Costa Rica | Bezymianny, Russia | Chikurachki, Russia | Fuego, Guatemala | Galeras, Colombia | Karymsky, Russia | Kilauea, USA | Pacaya, Guatemala | Santa María, Guatemala | Shiveluch, Russia | Soufrière Hills, Montserrat | St. Helens, USA | Tungurahua, Ecuador | Turrialba, Costa Rica | Ubinas, Perú | Villarrica, Chile New Activity/Unrest KRAKATAU Indonesia 6.10°S, 105.43°E; summit elev. 813 m According to a news article, lava flows and incandescent rocks from Anak Krakatau traveled down the flanks during 13-14 November. Incandescent material and "smoke" were propelled hundreds of meters from the summit on 14 November. Visitors and tourists were advised not to go within a 3-km radius of the summit. The Alert Level remained at 3 (on a scale of 1-4). Geologic Summary. The renowned Krakatau volcano lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 AD, resulted in a 7-km-wide caldera. Remnants of this volcano formed Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only a remnant of Rakata volcano. The post-collapse cone of Anak Krakatau (Child of Krakatau), constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan, has been the site of frequent eruptions since 1927. Source: Indo-Asian News Service (IANS) http://in.news.yahoo.com/071114/43/6n8en.html Krakatau Information from the Global Volcanism Program http://www.vsi.esdm.go.id/portal/html/index.php Ongoing Activity ARENAL Costa Rica 10.46°N, 84.70°W; summit elev. 1,657 m In October, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, lava flows traveling down the SW and S flanks, and occasional avalanches from lava-flow fronts. Volcanic activity was at relatively low levels and few eruptions occurred. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity. Geologic Summary. Conical Volcán Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1,657-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. The earliest known eruptions of Arenal took place about 7,000 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. Arenal's most recent eruptive period began with a major explosive eruption in 1968. Continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows has occurred since then from vents at the summit and on the upper western flank. Source: Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/ Arenal Information from the Global Volcanism Program http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1405-033 BEZYMIANNY Kamchatka Peninsula, Russia 55.98°N, 160.59°E; summit elev. 2,882 m KVERT reported that seismic activity at Bezymianny was above background levels on 12 November and at background levels during 9-11 and 13-16 November. Visual observations and video footage analysis indicated that gas-and-steam plumes drifted NE on 9 November and S on 13 November. Based on observations of satellite imagery, gas-and-steam plumes were observed during 9-11 and 13 November and a thermal anomaly was present in the crater during 9-13 November. Clouds obscured views of the volcano on other days. The level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. Based on observations of satellite imagery, the Washington VAAC reported that an ash plume at an altitude of about 6.4 km (21,000 ft) a.s.l. drifted E on 15 November. 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= CHIKURACHKI Kuril Islands, Russia 50.325°N, 155.458°E; summit elev. 1,816 m KVERT reported that clouds obscured satellite views of Chikurachki during 9-16 November. The Level of Concern Color Code was lowered to Yellow on 16 November <http://www.avo.alaska.edu/color_codes.php>. Geologic Summary. Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized scoria deposits covering the upper part of the young cone give it a distinctive red color. Lava flows from 1,816-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The more erosionally modified Tatarinov group of six volcanic centers is located immediately to the S of Chikurachki. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml Chikurachki Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0900-036= FUEGO Guatemala 14.47°N, 90.88°W; summit elev. 3,763 m Based on observations of satellite imagery and reports from INSIVUMEH, the Washington VAAC reported that an ash plume from Fuego rose to an altitude of 4.6 km (15,000 ft) a.s.l. on 20 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 INGEOMINAS reported that 16 ash plumes from Galeras, associated with episodes of seismic tremor, rose to altitudes of 4.5-7.2 m (14,800-23,600 ft) a.s.l. during 5-11 November. Ashfall was reported in areas to the NW and W on 7 and 9 November. On 13 November, a white plume rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted S. On 14 November, roaring noises and ashfall was reported in areas to the NW. 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= 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 9-16 November. Based on seismic interpretation, possible weak ash explosions occurred on 12 and 13 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= 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 an advancing lava flow that occasionally overflowed its channel edges during 14-19 November. On 15 November, crust overturns in a lava pond nearest to the vent were seen through the web camera. Three active pahoehoe lobes that were observed during an overflight on 17 November had advanced since 9 November. The first flow (located 1.7 km NE of Pu'u Kia'i) advanced 180 m, the second flow (about 700 m E of Pu'u Kia'i) advanced 150 m, and the third flow (1.85 km SE of Pu'u Kia'i) advanced about 500 m. A few small earthquakes were located beneath Halema'uma'u crater and along the lower 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- PACAYA southern Guatemala 14.38°N, 90.60°W; summit elev. 2,552 m Based on observations of satellite imagery, the Washington VAAC reported that an ash plume from Pacaya's MacKenney cone rose to an altitude of 4.3 km (14,000 ft) a.s.l. on 17 November and drifted NW. A thermal anomaly was also identified on the imagery. 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 Amatitlán 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. Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html Pacaya Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-11= SANTA MARÍA Guatemala 14.756°N, 91.552°W; summit elev. 3,772 m Based on observations of satellite imagery, the Washington VAAC reported that a diffuse ash plume from Santa María's Santiaguito lava dome complex rose to an altitude of 7.3 km (24,000 ft) a.s.l. and drifted W on 16 November. Geologic Summary. Symmetrical, forest-covered Santa María volcano is one of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1-km-wide crater, which formed during a catastrophic eruption in 1902 and extends from just below the summit to the lower flank. The renowned Plinian eruption of 1902 followed a long repose period and devastated much of SW Guatemala. The large dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, accompanied by almost continuous minor explosions and periodic lava extrusion, larger explosions, pyroclastic flows, and lahars. Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html Santa María Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-03= 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 9-16 November. Based on seismic interpretation, ash plumes rose to an altitude of 8 km (26,200 ft) a.s.l. and hot avalanches occurred. Visual observations and video footage analysis indicated that ash plumes rose to an altitude of 5 km (16,400 ft) a.s.l. on 8, 12, 13, and 14 November. A new lava flow that had effused onto the SW flank was noted during aerial observations on 9 November. Based on observations of satellite imagery, ash plumes drifted SE on 12 and 13 November and a thermal anomaly was present in the crater every day during the reporting period. Clouds obscured views of the volcano on other days. The Level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. 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. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml 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 MVO reported that during 9-16 November the lava dome at Soufrière Hills changed very little, based on limited visual observations due to cloud cover. Seismic activity was very low and low-level rockfall and pyroclastic flow activity continued. Fumarolic activity was concentrated on the N and S flanks. A vent located behind Gages Wall to the W was active and emitted a bluish sulfur dioxide gas. The Alert Level remained elevated at 4 (on a scale of 0-5). Based on observations of satellite imagery and information from the MVO, the Washington VAAC reported that ash and gas-and-ash plumes rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted NW during 15-16 November. The ash plumes were likely caused by strong winds. On 19 November, an ash plume resulting from a rockfall was detected on satellite imagery and drifted E. 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. Sources: Montserrat Volcano Observatory http://www.mvo.ms/, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html 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 14-20 November lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels, punctuated by M 1.5-2.5, and occasionally larger, earthquakes. 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- TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m IG reported that although visual observations were limited due to cloud cover, ash-and-steam and ash plumes from Tungurahua rose to altitudes of 5.8-6.5 km (19,000-21,300 ft) a.s.l. intermittently during 14-19 November. Plumes mainly drifted W and SW and ashfall was reported from multiple areas downwind. Roars and "cannon shots" were also reported from several areas. Incandescent blocks rolled down the flanks during 14-15 November. Based on pilot reports and observations of satellite imagery, the Washington VAAC reported that a gas plume with some ash rose to an altitude of 7.3 km (24,000 ft) a.s.l. and drifted SW on 20 November. A thermal anomaly was present in the crater. 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. Sources: Instituto Geofísico-Escuela Poltécnica Nacional http://www.igepn.edu.ec/, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html Tungurahua Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08= TURRIALBA Costa Rica 10.025°N, 83.767°W; summit elev. 3,340 m OVSICORI-UNA reported that fumarolic activity and gas discharge in and to the W of Turrialba's central crater continued throughout October. New points of gas discharge, small landslides, and accelerated vegetation die-off were noted from various locations within and around the crater. Fumaroles were active in almost all areas of the central crater; many exhibited sulfur deposits and those in the SW, W, and NW reached temperatures between 72-92 degrees C. Steam plumes from fumaroles on the W wall rose to an altitude of 3.8 km (12,500 ft) a.s.l. and were reported by settlers on the flanks. New fumaroles appeared on the SW flank and N and NW of the central crater. Some of the fumaroles corresponded to two widening cracks, to the SW of the W crater. Vegetation on the S and SE flanks affected from gas and steam discharge and sulfur deposits were noted. People living on the N flank and from areas to the NW and W reported gas emissions from cracks in an area of about 20 by 50 meters, NW of the W crater. Geologic Summary. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m wide summit depression that is breached to the NE. Most activity at Turrialba originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred at Turrialba during the past 3500 years. Turrialba has been quiescent since a series of explosive eruptions during the 19th century that were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters. Source: Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/ Turrialba Information from the Global Volcanism Program http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1405-07= UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m Based on Significant Meteorological Information (SIGMET) advisories and observations of satellite imagery, the Buenos Aires VAAC reported that ash plumes from Ubinas rose to altitudes of 5.5-7.9 km (18,000-26,000 ft) a.s.l. on 16, 18, and 20 November. Plumes drifted SW, SE, and NE. 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= VILLARRICA central Chile 39.42°S, 71.93°W; summit elev. 2,847 m Based on Significant Meteorological Information (SIGMET) advisories, the Buenos Aires VAAC reported that an eruption plume from Villarrica rose to an altitude of 3.8 km (12,500 ft) a.s.l. and drifted E on 14 November. Ash was not detected on satellite imagery. 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 Villarica'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. Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html Villarrica Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1507-12= +++++++++++++++++++++++++++++++++++++ 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. ==============================================================
