******************************************************************** GVP/USGS Weekly Volcanic Activity Report 29 March- 4 April 2006 ******************************************************************** From: Gari Mayberry <mayberry@xxxxxxxxxxxxxx> GVP/USGS Weekly Volcanic Activity Report 29 March-4 April 2006 http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Ol Doinyo Lengai, Tanzania | Ubinas, Peru Ongoing Activity: | Arenal, Costa Rica | Augustine, USA | Bagana, Papua New Guinea | Colima, México | Galeras, Colombia | Kilauea, USA | Langila, Papua New Guinea | Poas, Costa Rica | Popocatépetl, México | Raoul Island, New Zealand | Santa Ana, El Salvador | Soufrière Hills, Montserrat | St. Helens, USA | Tungurahua, Ecuador New Activity/Unrest OL DOINYO LENGAI Tanzania, eastern Africa 2.751°S, 35.902°E; summit elev. 2,890 m According to news reports, an eruption began at Ol Doinyo Lengai around 30 March, forcing villagers living near the volcano to evacuate. An article stated that, "Eyewitnesses said they heard a rumbling noise before the volcano began discharging ash and lava, prompting local residents to flee the area in their hundreds. District officials estimated that about 3,000 people from Nayobi, Magadini, Engaruka, Malambo, Ngaresero, Gelai Bomba, and Kitumbeine villages left their homes within a few hours of the eruption?" There were reports of polluted water sources and destroyed vegetation, but no reports of deaths or injuries. Background. The symmetrical Ol Doinyo Lengai stratovolcano is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent volcano, known as "The Mountain of God," rises abruptly above the broad plain S of Lake Natron. The cone-building stage of the volcano ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatite and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra eruptions and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater. Petrologists first observed the eruption of carbonatitic lava flows in the 1960s. Subsequent more frequent visits have documented long-term lava effusion in the summit crater that would not have been seen from the foot of the volcano. Sources: Guardian News http://www.ippmedia.com/ipp/guardian/2006/04/01/63338.html, Associated Press http://edition.cnn.com/2006/WORLD/africa/04/04/volcano.ap/ Ol Doinyo Lengai Reports from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0202-12= UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m Increased fumarolic activity occurred at Ubinas during the end of March. A Universidad de San Agustin scientist who visited the volcano on 31 March found strong steam-and-ash emissions occurring. Also, leaves of nearby crops were burned and a sound similar to a jet engine emanated from the vent area. 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. Source: Randall White, USGS/OFDA Volcano Disaster Assistance Program and Victor Aguilar, Universidad de San Agustin, Peru Ubinas Information from the Global Volcanism Program http://www.volcano.si.edu/world/ volcano.cfm?vnum=1504-02= Ongoing Activity ARENAL Costa Rica 10.46°N, 84.70°W; summit elev. 1,657 m; All times are local (= UTC - 6 hours) OVSICORI reported that on 2 April around 1000 a small pyroclastic flow traveled down Arenal's W flank. Background. 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.una.ac.cr/ovsi/ Arenal Information from the Global Volcanism Program http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1405-033 AUGUSTINE SW Alaska, USA 59.363°N, 153.43°W; summit elev. 1,252 m Low-level eruptive activity continued at Augustine during 24-31 March. Signals continued to be recorded by the seismic network that were associated with occasional hot block-and-ash flows, rock avalanches, rockfalls, and lava flows. Small and dilute ash clouds resulting from these processes were likely confined to the immediate vicinity of the volcano. Satellite imagery continued to show a thermal anomaly related to the new lava dome and lava flow. Airborne sulfur-dioxide gas measurements showed continued high levels of magmatic gas output. Low-light camera observations indicated that activity was restricted mainly to the summit lava dome. Augustine remained at Concern Color 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- BAGANA Bougainville Island, Papua New Guinea 6.14°S, 155.19°E; summit elev. 1,750 m During 16 February to 31 March, activity at Bagana was at moderate levels. Mostly gas emissions occurred, but on 27 March an ash cloud was emitted. During 15-31 March, observers noted moderate-to-bright incandescence, projections of lava fragments, and a lava flow traveling down the volcano's SSW flank. Background. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. Bagana is a massive symmetrical lava cone largely constructed by an accumulation of viscous andesitic lava flows. The entire lava cone could have been constructed in about 300 years at its present rate of lava production. Eruptive activity at Bagana is characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50-m-thick with prominent levees that descend the volcano's flanks on all sides. Source: Rabaul Volcano Observatory via the Darwin Volcanic Ash Advisory Center http:// www.ssd.noaa.gov/VAAC/OTH/AU/messages.html Bagana Information from the Global Volcanism Program http://www.volcano.si.edu/world/ volcano.cfm?vnum=0505-02= COLIMA Western México 19.514°N, 103.62°W; summit elev. ~3,850 m; All times are local (= UTC - 6 hours) Based on information from the Mexico City MWO, the Colima Observatory, and satellite data, the Washington VAAC reported that there were several eruptions at Colima during 1-3 April. The highest rising resultant ash plume reached ~7.9 km (26,000 ft) a.s.l. after an eruption on 2 April at 1052. Background. 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: Washington Volcanic Ash Advisory Center 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= GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4,276 m An increase in the energy of earthquakes at Galeras, which began on 28 March, ended on the 29th. The number of earthquakes beneath the volcano decreased during 28 March to 3 April (an average of 66 earthquakes was recorded daily), in comparison to the previous week (an average of 89 earthquakes was recorded daily). During the report period, steam columns rose up to ~500 m above the volcano (or 15,700 ft a.s.l.) and the outer layer of the lava dome at the volcano's summit cooled in comparison to previous weeks. 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/PublicacionPortal.asp Galeras Information from the Global Volcanism Program http://www.volcano.si.edu/world/ volcano.cfm?vnum=1501-08= KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m During 29 March to 3 April, lava from Kilauea flowed 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. Small, shallow earthquakes continued beneath the summit area and upper E rift zone at a fluctuating rate. Volcanic tremor reached moderate levels at Pu`u `O`o. Slight inflation and deflation occurred at the volcano. 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- LANGILA New Britain Island, Papua New Guinea 5.53°S, 148.42°E; summit elev. 1,330 m During 16 February to 31 March, low-level Vulcanian activity continued at Langila's Crater 2. Eruptive activity was characterized by low-energy emissions of diffuse pale gray ash between 30 January and 7 February. Activity changed to subcontinuous forceful emissions of dark gray ash on 1, 2, 6, 7, and 9 March. The resultant plumes did not rise higher than 2 km above the summit crater (or 10,900 ft a.s.l.) before drifting WSW of the volcano. Weak-to-bright glow and weak projections of incandescent lava fragments were visible on 22, 23, and 28 February, and on 1, 2, and 6 March. There was no activity at Crater 3. Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5- km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the N and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m. Source: Rabaul Volcano Observatory via the Darwin Volcanic Ash Advisory Center http:// www.bom.gov.au/info/vaac/advisories.shtml Langila Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-01= POÁS Costa Rica 10.20°N, 84.233°W; summit elev. 2,708 m Following phreatic eruptions that began at Poás on 24 March, seismicity decreased at the volcano by 27 March. In addition, harmonic tremor that was recorded during the heightened activity ceased. As of the 27th, no significant deformation was recorded at the volcano and abundant evaporation continued at Caliente Lake. Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2,708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7,500 years ago. The more prominent geothermally heated northern lake is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Poás eruptions often include geyser-like ejection of crater-lake water. Source: Observatorio Vulcanológico y Sismológico de Costa Rica , Universidad Nacional (OVSICORI- UNA) http://www.una.ac.cr/ovsi/informes.html Poás Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1405-04= POPOCATÉPETL México 19.02°N, 98.62°W; summit elev. 5,426 m; All times are local (= UTC - 6 hours) The Washington VAAC reported that ash from Popocatépetl was visible on satellite imagery on 3 April at 0245 at a height of ~7.3 km (~24,000 ft) a.s.l., drifting S. The Mexico City MWO indicated that there was an eruption around this time that emitted small amounts of ash. Background. 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: Washington Volcanic Ash Advisory Center 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= RAOUL ISLAND Kermadec Islands, New Zealand 29.27°S, 177.92°W; summit elev. 516 m As of 31 March, no new eruptive activity had occurred at Raoul Island after the 17 March eruption. Seismicity continued to decline and Green Lake's water level continued to rise in response to the eruption. 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 ANA El Salvador 13.853°N, 89.630°W; summit elev. 2,365 m During 24-31 March, activity at Santa Ana decreased to low levels in comparison to the previous 4 months of moderate activity. During the report period, seismicity was at relatively low levels, steam plumes occasionally rose ~200 m above the volcano (or 8,400 ft a.s.l.), and the daily sulfur- dioxide flux was between 500 and 1,000 metric tons. The Alert Level remained at red, the highest level, within 5 km of the volcano's summit crater. Background. Santa Ana, El Salvador's highest volcano, is a massive stratovolcano immediately W of Coatepeque caldera. Collapse of the volcano during the late Pleistocene or early Holocene produced a massive debris avalanche that swept into the Pacific, forming the Acajutla Peninsula. Reconstruction of the volcano rapidly filled the collapse scarp. The broad summit of the volcano is cut by several crescentic craters, and a series of parasitic vents and cones have formed along a 20- km-long fissure system that extends from near the town of Chalchuapa NNW of the volcano to the San Marcelino and Cerro Chino cinder cones on the SE flank. Historical activity, largely consisting of small-to-moderate explosive eruptions from both summit and flank vents, has been documented since the 16th century. The San Marcelino cinder cone on the SE flank produced a lava flow in 1722 that traveled 11 km to the E. Source: Servicio Nacional de Estudios Territoriales http://www.snet.gob.sv/ Santa Ana Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1403-02= SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m During 24-31 March, lava-dome growth at Soufrière Hills was focused towards the E, with a lava lobe growing in that direction and the majority of rockfalls and pyroclastic flows occurring in the SE and NE sectors of the volcano. The largest pyroclastic flows traveled as far as 2 km NE down Tar River Valley. The sulfur-dioxide flux averaged 523 metric tons per day. 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 29 March to 3 April, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. Although the overall level of seismicity remained low, the eruption of lava into the crater continued as was evidenced by ongoing rockfalls and continuous GPS measurements made on the growing lava lobe. 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- TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m During 29 March to 2 April, small-to-moderate explosions at Tungurahua consisted of gas, steam, and small amounts of ash. During the report period, ash fell in the Bilbao, Choglontos, Puela, and Manzano sectors, and incandescent blocks rolled down the volcano's NW flank. 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= ============================================================== 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. ==============================================================
