***************************************************************** GVP/USGS Weekly Volcanic Activity Report 8-14 Feb. 2006 ***************************************************************** From: Gari Mayberry <mayberry@xxxxxxxxxxxxxx> GVP/USGS Weekly Volcanic Activity Report 8-14 February 2006 http://www.volcano.si.edu/reports/usgs/ Ongoing Activity: | Augustine, USA | Cleveland, USA | Galeras, Colombia | Guagua Pichincha, Ecuador | Kilauea, USA | Santa Ana, El Salvador | Santa María, Guatemala | Soufrière Hills, Montserrat | St. Helens, USA | Tungurahua, Ecuador Ongoing Activity AUGUSTINE SW Alaska, USA 59.363°N, 153.43°W; summit elev. 1,252 m During 8-14 February, seismicity at Augustine remained at low levels, but was still above background. Also, low-level ash plumes and occasional pyroclastic flows occurred. Satellite and seismic data, and other remote observations indicated that a lava dome had been growing at the volcano's summit since 28 January. On the evening of 7 February, gas, ash, and incandescent blocks were observed descending the upper NE flank of Augustine. All available data indicated that as the lava dome grows, it periodically becomes unstable and small portions of it avalanche down the N flank, producing pyroclastic flows. The number of these flows gradually decreased during several days before 10 February, suggesting that the rate of lava extrusion also slowly declined. Data from continuous GPS receivers on the island indicated that the flanks of the volcano began to deflate around 28 January, marking a reversal in the swelling trend observed beginning in roughly June of 2005. AVO reported that based on all available data, eruptive activity associated with lava-dome building will continue over the next few days or weeks and may continue intermittently over the next several months. 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- CLEVELAND Aleutian Islands, USA 52.82°N, 169.95°W; summit elev. 1,730 m AVO decreased the Concern Color Code at Cleveland from Orange to Yellow on 11 February <http://www.avo.alaska.edu/color_codes.php>. They received no information about further eruptive activity or ash emissions after 6 February, and no ash clouds were detected on satellite imagery. Clouds obscured the volcano during 6-11 February, therefore, AVO could not verify that eruptive activity ended and it is possible that the volcano remains in a state of low-level unrest. Background. The symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited dumbbell-shaped Chuginadak Island in the east-central Aleutians. The 1,730-m-high stratovolcano is the highest of the Islands of Four Mountains group and is one of the most active in the Aleutians. Numerous large lava flows descend its flanks. It is possible that some 18th to 19th century eruptions attributed to Carlisle (a volcano located across the Carlisle Pass Strait to the NW) should be ascribed to Cleveland. In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mt. Cleveland have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks. 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 Cleveland Information from the Global Volcanism Program http://www.volcano.si.edu/ world/volcano.cfm?vnum=1101-24- GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4,276 m INGEOMINAS reported on 10 February that a lava dome was growing inside the main crater of Galeras. The lava dome was not seen during the previous observation flight on 16 January. Seismicity was dominated by long-period earthquakes, with an average of 150 occurring daily during 13 January to 8 February. On 5 February, strong degassing was visible from different parts of the active cone and around the lava dome. Cracks were visible on the high parts of the lava dome. During a field visit on 8 February, scientists found pyroclastic-flow deposits high on the SE flank of the volcano. The exact date of the small emission was not known, but it occurred after 26 November when scientists previously visited the area. Galeras remained at Alert Level 3 ("changes in the behavior of volcanic activity have been noted"). 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= GUAGUA PICHINCHA north-central Ecuador 0.17°S, 78.60°W; summit elev. 4,784 m; All times are local (= UTC - 5 hours) On 5 February, beginning around 1300, three small gas emissions occurred at Guagua Pichincha. IG reported that this phreatic activity was associated with accumulated rainfall that was heated by magmatic material from the previous eruptive period, and was not related to renewed volcanic activity. After the emissions, a series of seismic signals associated with rockfalls and long-period earthquakes were recorded. The signals were related to degassing that commonly occurs after emissions. Cloudy conditions prevented observations of the volcano. IG recommended that people should not visit Guagua Pichincha's crater since emissions or explosions can occur at any time. Background. Guagua Pichincha rises immediately west of Quito, Ecuador's capital city. The broad volcanic massif is cut by a large horseshoe-shaped summit caldera, ~6 km in diameter and 600 m deep, that was breached to the W during a slope failure ~50,000 years ago. Subsequent late-Pleistocene and Holocene eruptions from the central vent consisted of explosive activity with pyroclastic flows accompanied by periodic lava dome growth and destruction. A major eruption in 1660 deposited 30 cm of ash in Quito, but most of the many eruptions since the Spanish colonial era have been minor. The latest eruptive period began with phreatic explosions in 1998. Magmatic eruptions first occurred in October 1999, and intermittent eruptions of varying scale since then have blanketed Quito and surrounding towns with ash. Source: Instituto Geofísico-Escuela Politécnica Nacional http://www.igepn.edu.ec/ Guagua Pichincha Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-02= KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m During 8-14 February, surface lava flows were not visible on Kilauea's Pulama pali fault scarp due to lava traveling underground through the PKK lava tube until reaching the East Lae`apuki lava delta and flowing into the sea. Observations on 7 February revealed that the lava delta had broadened 120 m westward since 30 January. During the report period, background volcanic tremor was near normal levels at Kilauea's summit, with numerous sporadic shallow earthquakes continuing to occur at the summit and upper E rift zone. Volcanic tremor reached moderate levels at Pu`u `O`o. Slow, steady inflation continued at Kilauea's summit as it has more-or-less since mid-January. 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- SANTA ANA El Salvador 13.853°N, 89.630°W; summit elev. 2,365 m During 3-10 February, volcanic activity was at moderate levels at Santa Ana. Seismicity was relatively stable, and steam plumes rose to low levels above the volcano. The sulfur- dioxide flux averaged 1,200 metric tons per day. The Alert Level at Santa Ana remained at Red, the highest level, within a 5-km radius around 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= SANTA MARÍA Guatemala 14.756°N, 91.552°W; summit elev. 3,772 m During 9-14 February, weak-to-moderate explosions at Santa María's Santiaguito lava- dome complex produced plumes that rose to a maximum height of 1.2 km above the volcano (or 16,300 ft a.s.l.) on the 9th. Several explosions were accompanied by small pyroclastic flows that traveled down the SW and SE sides of Caliente Dome. 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 MVO reported to the Washington VAAC that increased activity began at Soufrière Hills on 10 February. That day, satellite imagery showed a prominent hotspot at the volcano and a NW-drifting ash plume at a height of ~3 km (10,000 ft) a.s.l. Ash-and-gas emissions continued through 15 February, producing plumes to a height of ~2.7 km (9,000 ft) a.s.l. MVO reported that on 15 February, there was markedly less volcanic activity, with steam and a small amount of ash emitted to ~1.4 km (4,450 ft) a.s.l. 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. Source: 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 8-15 February, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. Comparison of photos taken between 17 December and 7 February showed that the base of the active lobe of the lava dome enlarged by about 100 meters. A series of photographs taken during the week of 5 February showed that the active part of the new lava dome continued to extrude, with points on the surface of the dome moving a couple of meters per day. 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; All times are local (= UTC - 5 hours) During 6-14 February, several moderate-sized emissions of gas and ash occurred at Tungurahua, with plumes rising to ~500 m above the volcano (or 18,100 ft a.s.l.). On the 6th, the number of long-period earthquakes increased. An explosion around midnight on 12 February expelled incandescent volcanic material that traveled down the N flank of the volcano. A small amount of ash fell in the town of Puela, SW 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= ********************************************************* 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/ ********************************************************** ============================================================== 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. ==============================================================
