********************************************************** GVP/USGS Weekly Volcanic Activity Report 12-18 April 2006 ********************************************************** From: Gari Mayberry <mayberry@xxxxxxxxxxxxxx> GVP/USGS Weekly Volcanic Activity Report 12-18 April 2006 http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Lascar, Chile | Merapi, Indonesia | Ubinas, Perú Ongoing Activity: | Augustine, USA | Fuego, Guatemala | Galeras, Colombia | Karymsky, Russia | Kilauea, USA | Manam, Papua New Guinea | Pacaya, Guatemala | Raoul Island, New Zealand | Santa Maria, Guatemala | Soufrière Hills, Montserrat | St. Helens, USA | Suwanose-jima, Japan | Tungurahua, Ecuador | Veniaminof, USA New Activity/Unrest LASCAR northern Chile 23.37°S, 67.73°W; summit elev. 5,592 m; All times are local (= UTC - 4 hours) ONEMI reported that two explosive eruptions occurred at Lascar on 18 April. The first ash emission began at 1120 and the second began at 1315. According to the Buenos Aires VAAC, a significant meteorological forecast (SIGMET) was issued for Lascar on 18 April stating that a "smoke" column was at a height of 8 km (26,250 ft) a.s.l. and was drifting eastward towards Argentina. The Aviation Color Code was at Red, the highest level. Activity ended later that day, so the Aviation Color Code was reduced to Green. The Villarica Volcano Visual Observation Project (POVI) website reported that a cloud rose to 3 km above the volcano (28,200 ft a.s.l.), no seismic activity was recorded in the area, and no evacuations occurred. Background. Lascar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters and lies 5 km W of an older, higher stratovolcano, Volcán Aguas Calientes. Lascar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption of Lascar took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9,000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded from Lascar in historical time since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away from the volcano. The largest historical eruption of Lascar took place in 1993 and produced pyroclastic flows that extended up to 8.5 km NW of the summit. Sources: Oficina Nacional de Emergencia Ministerio del Interior (ONEMI) http://www.onemi.cl/, Buenos Aires VAAC http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html, Villarica Volcano Visual Observation Project (POVI) http://www.povi.cl/ Lascar Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1505-10= MERAPI central Java, Indonesia 7.542°S, 110.442°E; summit elev. 2,947 m; All times are local (= UTC + 7 hours) According to CVGHM, volcanic activity began to increase at Merapi on 11 April, and on 12 April at 1500 they raised the Alert level from 2 to 3 (on a scale of 1-4). They reported that an eruption could occur at any time and no one was permitted within 8 km of the summit. According to news reports, authorities informed people living in villages near the volcano to be prepared for possible evacuations. Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately N of the major city of Yogyakarta. The steep-sided modern Merapi edifice, its upper part unvegetated due to frequent eruptive activity, was constructed to the SW of an arcuate scarp cutting the eroded older Batulawang volcano. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated and inhabited lands on the volcano's western-to-southern flanks and caused many fatalities during historical time. The volcano is the object of extensive monitoring efforts by the Merapi Volcano Observatory of the Volcanological Survey of Indonesia. Sources: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://www.vsi.esdm.go.id/portal/html/index.php, Associated Press http://news.yahoo.com/s/ap/indonesia_volcano, Reuters http://news.yahoo.com/s/nm/20060418/wl_nm/indonesia_volcano_dc_2 Merapi Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-25= UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m A significant meteorological forecast (SIGMET) was issued on 15 April for an ash cloud from Ubinas at a height of 6.1-7.3 km (20,000-24,000 ft) a.s.l., and later that day for a cloud at 6.1-9.1 km (20,000-30,000 ft) a.s.l. The Aviation Color Code was Red until 16 April when the Buenos Aires VAAC received a report that activity had ceased. According to a news report on 18 April, however, officials urged residents the town of Querapi ~5 km from the volcano to evacuate. Background. A small, 1.2-km-wide caldera that cuts the top of Ubinas, Peru's most active volcano, gives it a truncated appearance. Ubinas in 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. Sources: Buenos Aires Volcanic Ash Advisory Center http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html, Reuters http://news.yahoo.com/s/nm/20060418/sc_nm/peru_volcano_dc_1 Ubina Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1504-02= Ongoing Activity AUGUSTINE SW Alaska, USA 59.363°N, 153.43°W; summit elev. 1,252 m Activity at Augustine declined to low levels during 7-14 April, with seismicity decreasing to slightly above background levels, and rockfalls and avalanches decreasing in frequency in comparison to previous weeks. Low-level eruptive activity continued, consisting of slow effusion of lava at the summit accompanied by small rockfalls and avalanches on the volcano's flanks. Satellite imagery showed a decline in thermal output consistent with the decreased activity. Sulfur-dioxide gas measurements showed continued high levels of magmatic gas emissions that may have been associated with degassing of lava at the summit of the volcano. Augustine remained at Concern Color Code Orange <http://www.avo.alaska.edu/color_codes.php>. Background. Augustine volcano, rising above Kamishak Bay in the southern Cook Inlet about 290 km SW of Anchorage, is the most active volcano of the eastern Aleutian arc. It consists of a complex of overlapping summit lava domes surrounded by an apron of volcaniclastic debris that descends to the sea on all sides. Few lava flows are exposed; the flanks consist mainly of debris- avalanche and pyroclastic-flow deposits formed by repeated collapse and regrowth of the volcano's summit. The latest episode of edifice collapse occurred during Augustine's largest historical eruption in 1883; subsequent dome growth has restored the volcano to a height comparable to that prior to 1883. The oldest dated volcanic rocks on Augustine are more than 40,000 years old. At least 11 large debris avalanches have reached the sea during the past 1800-2000 years, and five major pumiceous tephras have been erupted during this interval. Historical eruptions have typically consisted of explosive activity with emplacement of pumiceous pyroclastic-flow deposits followed by lava dome extrusion with associated block-and-ash flows. Sources: Alaska Volcano Observatory http://www.avo.alaska.edu/activity/avoreport.php?view=update, Anchorage Volcanic Ash Advisory Center http://www.ssd.noaa.gov/VAAC/OTH/AK/messages.html Augustine Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1103-01- FUEGO Guatemala 14.47°N, 90.88°W; summit elev. 3,763 m On 17 April, explosions at Fuego ejected incandescent material ~50-75 m high, and gas plumes to ~150-200 m above the volcano (12,800-13,000 ft a.s.l.). Incandescent landslides traveled down the volcano's S and W flanks. Lava flowed ~400 m S towards Taniluyá ravine. Background. 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: Instituto Nacional de Sismologia, Vulcanologia, Meterologia, e Hidrologia, http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm 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 Galeras remained at a critical state during 10-17 April, with a partially solidified lava dome in the main crater. Seismicity continued to decrease, with an average of 70 small earthquakes occurring at the beginning of the report week, and an average of 45 occurring at the end of the week. In addition, there were small gas emissions from the volcano. Galeras remained at Alert Level 2 (likely eruption in days or weeks). Background. 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/tmsingeominas/ModuloPublicacionPortal/PublicacionP ortal.asp 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 Strombolian-to-Vulcanian activity continued at Karymsky during 7-14 April. Satellite imagery showed ash plumes extending ~40-145 km E and SE of the volcano, and a large thermal anomaly at the volcano's crater. Karymsky remained at Concern Color Code Orange <http://www.avo.alaska.edu/color_codes.php>. Background. 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 http://www.kcs.iks.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 During 13-17 April, lava from Kilauea continued to flow off of a lava delta into the ocean at the East Lae`apuki entry. Background volcanic tremor was at normal levels at Kilauea's summit, with small shallow also earthquakes occurring. Volcanic tremor reached moderate levels at Pu`u `O`o. Background. 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 about 104 km2 of land on the S flank of Kilauea and building more than 200 hectares of new land. Source: US Geological Survey Hawaiian Volcano Observatory http://volcanoes.usgs.gov/update.html Kilauea information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01- MANAM offshore New Guinea, Papua New Guinea 4.10°S, 145.06°E; summit elev. 1,807 m Based on information from an aircraft report, the Darwin VAAC reported that ash emitted from Manam reached ~2.7 km (9,000 ft) a.s.l. on 12 April and drifted WNW. No ash was visible on satellite imagery. According to RVO, low- level activity occurred at Manam during 13-15 April. Roaring was heard from Main Crater on 13 April, and both summit craters emitted white vapor on the 14th. Background. The 10-km-wide island of Manam is one of Papua New Guinea's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1,807-m-high stratovolcano to its lower flanks. These "avalanche valleys," regularly spaced 90 degrees apart, channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five satellitic centers are located near the island's shoreline. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during the past century into the SE avalanche valley. Frequent historical eruptions have been recorded since 1616. Sources: Darwin Volcanic Ash Advisory Center http://www.bom.gov.au/info/vaac/advisories.shtml, Rabaul Volcano Observatory Manam Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0501-02= PACAYA southern Guatemala 14.38°N, 90.60°W; summit elev. 2,552 m On 17 April, lava flowed from Pacaya from a parasitic crater at the NE base of a volcanic cone. Fumaroles were active at the volcano's central crater. Background. 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: Instituto Nacional de Sismologia, Vulcanologia, Meterologia, e Hidrologia, http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm Pacaya Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-11= RAOUL ISLAND Kermadec Islands, New Zealand 29.27°S, 177.92°W; summit elev. 516 m As of 13 April, seismicity at Raoul Island had returned to normal and Green Lake's water level was dropping. Raoul Island remained at Alert Level 2 (minor eruptive activity). Background. Anvil-shaped Raoul Island, the largest and northernmost of the Kermadec Islands, has been the source of vigorous eruptive activity during the past several thousand years that was dominated by dacitic explosive eruptions. Two Holocene calderas are found at Raoul. The older caldera cuts the center of Raoul Island and is about 2.5 x 3.5 km wide. Denham caldera, formed during a major dacitic explosive eruption about 2,200 years ago, truncated the western side of the island and is 6.5 x 4 km wide. Historical eruptions at Raoul during the 19th and 20th centuries have sometimes occurred simultaneously from both calderas, and have consisted of small-to-moderate phreatic eruptions, some of which formed ephemeral islands in Denham caldera. A 240-m-high unnamed submarine cone, one of several located along a fissure on the lower NNE flank of Raoul Island volcano, has also erupted during historical time. Source: Institute of Geological & Nuclear Sciences (GNS) http://data.geonet.org.nz/geonews/index.html Raoul Island Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0402-03= SANTA MARÍA Guatemala 14.756°N, 91.552°W; summit elev. 3,772 m Explosions at Santa Maria's Santiaguito lava-dome complex on 17 April produced ash plumes that reached heights between 500 and 900 m above the volcano (14,000-15,300 ft a.s.l.). Several pyroclastic avalanches occurred that sent material down the volcano's S flank. Background. 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: Instituto Nacional de Sismologia, Vulcanologia, Meterologia, e Hidrologia, http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm Santa María Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-03= SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m; All times are local (= UTC - 4 hours) Observations of the lava dome at Soufrière Hills suggested that lava extrusion continued during 7-14 April. Growth occurred over a sector extending E to N, and an eastward-facing lobe developed on the NE side of the dome. Numerous small rockfalls continued from the active eastern flanks of the dome, adding to the talus in the upper reaches of the Tar River valley. Rockfalls were accompanied by minor ash venting. Due to the wind coming from the S in contrast to the normal prevailing wind direction (from the E) during the second half of the report period, ash fell over many parts of Montserrat: notably after a minor pyroclastic flow occurred at 0645 on 14 April. During the report period, the sulfur-dioxide flux averaged 540 metric tons per day. The hydrogen chloride to sulfur dioxide ratio on 12 April was 3.75, higher than 2.64 measured the previous week. Background. 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 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 Growth of the new lava dome inside the crater of Mount St. Helens continued during 12-17 April, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. The eruption continued unabated as was demonstrated by a steady background of small earthquakes and steady westward movement (~1 m per day) of a GPS (global positioning system) station on the active lava dome. St. Helens remained at Volcano Advisory (Alert Level 2); aviation color code Orange. Background. 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: USGS 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 and an aircraft report, the Tokyo VAAC reported that ash from Suwanose-jima was visible at a height of ~1.5 km (5,000 ft) a.s.l. on 16 April. Background. 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 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 During 11-17 April, small-to-moderate explosions at Tungurahua produced gas, steam, and small amounts of ash. Seismicity was at relatively high levels. Plumes rose to ~2 km above the volcano (or 23,000 ft a.s.l.) on 13 April. A small amount of ash fell in the Pondoa sector N of the volcano. Background. 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 Geofisico-Escuela Poltecnica Nacional http://www.igepn.edu.ec/vulcanologia/tungurahua/actividad/informet.htm, Washington Volcanic Ash Advisory Center 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= VENIAMINOF Alaska Peninsula, USA 56.17°N, 159.38°W; summit elev. 2,507 m During 7-14 April, seismicity at Veniaminof remained at low levels, but above background. Views of the volcano were obscured by clouds during the report period, and AVO received no information about ash clouds or activity at the volcano. Veniaminof remained at Concern Color Code Yellow <http://www.avo.alaska.edu/color_codes.php>. Background. Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the N, is deeply notched on the W by Cone Glacier, and is covered by an ice sheet on the S. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which reaches an elevation of 2,156 m and rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface. Source: Alaska Volcano Observatory http://www.avo.alaska.edu/avo4/updates/updates.htm Veniaminof Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1102-07- ********************************************************* Gari Mayberry US Geological Survey/Global Volcanism Program Smithsonian Institution National Museum of Natural History MRC-119 Dept. of Mineral Sciences Washington, DC 20560-0119 Phone: 202.633.1805 Fax: 202.357.2476 mayberry@xxxxxxxxxxxxxx http://www.volcano.si.edu/reports/usgs/ ********************************************************** ----- End forwarded message ----- ============================================================== 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. ==============================================================
