****************************************** GVP/USGS Weekly Volcanic Activity Report 18-24 January 2006 ****************************************** From: Ed Venzke <venzke@xxxxxxxxxxxxxx> URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Lopevi, Vanuatu Ongoing Activity: | Augustine, USA | Fuego, Guatemala | Karymsky, Russia | Pacaya, Guatemala | Santa Ana, El Salvador | Santa Marma, Guatemala | Soufrihre Hills, Montserrat | St. Helens, USA | Tungurahua, Ecuador The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network. Note: Many news agencies do not archive the articles they post on the Internet, and therefore the links to some sources may not be active. To obtain information about the cited articles that are no longer available on the Internet contact the source. New Activity/Unrest LOPEVI Central Islands, Vanuatu 16.5070S, 168.3460E; summit elev. 1,413 m; All times are local (= UTC + 11 hours) Pilots reported a vertical plume rising from Lopevi on 24 January 2006 to an altitude of 2.1-2.4 km (7,000-8,000 feet) a.s.l. The plume extended S and SE, and was reportedly at 2.7 km (9,000 feet) a.s.l. about 24 hours later. Background. The small 7-km-wide conical island of Lopevi is one of Vanuatu's most active volcanoes. A small summit crater containing a cinder cone is breached to the NW and tops an older cone that is rimmed by the remnant of a larger crater. The basaltic-to-andesitic volcano has been active during historical time at both summit and flank vents, primarily on the NW and SE sides, producing moderate explosive eruptions and lava flows that reached the coast. Historical eruptions at the 1,413-m-high volcano date back to the mid-19th century. The island was evacuated following eruptions in 1939 and 1960. The latter eruption, from a NW-flank fissure vent, produced a pyroclastic flow that swept to the sea and a lava flow that formed a new peninsula on the western coast. Sources: Wellington VAAC Ongoing Activity AUGUSTINE SW Alaska, USA 59.3630N, 153.430W; summit elev. 1,252 m; All times are local (= UTC - 9 hours) Observations made during an overflight on 18 January indicated that the summit was steaming vigorously, consistent with the formation of a new lava dome. Observers also noted ballistic bombs, block and ash flow deposits, and dilute-cloud surge deposits on the volcano's flanks. A white ash-poor steam plume was observed rising to about 2.6 km (8,500 feet) a.s.l. Seismicity decreased significantly over 19-20 January, but remained above background levels through 24 January. Night-time satellite views during 22-24 January showed faint thermal anomalies. 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 FUEGO Guatemala 14.470N, 90.880W; summit elev. 3,763 m Weak to moderate explosions continued at Fuego during 18-24 January 2006, sending dark gray ash plumes as high as 800 m (2,600 feet) above the crater. Explosion noises could be heard 25-30 km away. Incandescent lava ejections rising 100 m above the crater were seen on the night of 22-23 January that resulted in block avalanches down the SW flank. Background. Volcan 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. Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia KARYMSKY Kamchatka Peninsula, Russia 54.050N, 159.430E; summit elev. 1,536 m; All times are local (= UTC + 12 hours [or 13 hours in March-late October]) Seismic activity indicated that ash explosions from the summit crater of Karymsky continued during 14-20 January 2006. Ash plumes extending 6-9 km S from the volcano were registered on 12 January. A thermal anomaly over the dome was noted during 13-15 January. According to seismic data on 14-15 January, two possible ash plumes rose up to 3.0-3.4 km (9,800-11,200 feet) a.s.l. Karymsky remained at Concern Color Code Orange. 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 PACAYA southern Guatemala 14.380N, 90.600W; summit elev. 2,552 m; All times are local (= UTC - 6 hours) Weak incandescence was noted from the Pacaya crater during 18-24 January. A white- and blue-colored fumarolic gas plume rising from the crater frequently extends many kilometers downwind. 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 Amatitlan 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, Meteorologia, e Hidrologia SANTA ANA El Salvador 13.8530N, 89.6300W; summit elev. 2,365 m Seismicity at Santa Ana during 14-20 January 2006 was at normal levels. Degassing continued, with sporadic gas-and-steam emissions that rose about 200 m before dispersing. Sulfur dioxide flux, measured 6 km SW of the volcano, ranged from 163 to 1,578 metric tons/day. The hazard status remained at Alert Red, the highest level, within a 5-km radius of the central 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. Sources: Servicio Nacional de Estudios Territoriales (SNET) SANTA MARMA Guatemala 14.7560N 91.5520W; summit elev. 3,772 Volcanism continued from the Santiaguito lava-dome complex at Santa Maria during 18-24 January 2006. Intermittent ash explosions sent gray ash as high as 800 m (2,600 feet) above the crater, causing ashfall in some local communities. Avalanches of blocks and finer material from lava-flow collapses is constant on the S and SW flanks. Background. Symmetrical, forest-covered Santa Marma 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, Meteorologia, e Hidrologia SOUFRIHRE HILLS Montserrat, West Indies 16.720N, 62.180W; summit elev. 1,052 m Activity at Soufrihre Hills remained elevated during 13-20 January 2006. The seismic network recorded 61 rockfall signals, 17 long-period earthquakes, and 15 long-period rockfall signals. Measured sulfur dioxide fluxes ranged between 350 and 1,160 metric tons/day (t/d); the weekly average was 767 t/d. Images taken by the remote camera on Perches Mountain show that the dome continued to grow over a broad sector extending from the SW around to the NE. A central spine was first observed on 17 January when cloud cleared briefly from the. Continuing small rockfalls from the S, E, and NE flanks of the dome are visible at, and are adding to the talus in the upper reaches of the Tar River valley. Background. The complex dominantly andesitic Soufrihre 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 E, was formed during an eruption about 4,000 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 Soufrihre Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption. Source: Montserrat Volcano Observatory ST. HELENS Washington, USA 46.200N, 122.180W; summit elev. 2,549 m Growth of the new lava dome inside the crater of Mount St. Helens continued during 18-24 January 2006, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. The dome-building eruption has proceeded at a slow and steady pace, quietly extruding dacitic lava. Seismometers, GPS receivers, and tiltmeters show patterns basically unchanged since the first of January. With the first clear weather in over a month on 23 January, crews were in the field observing the new dome, repairing instruments, replacing batteries, and exhuming cameras from ice and snow. The new dome is noticeably taller and broader than when last viewed in December. Rockfalls from its summit generated small ash plumes that slowly rose above the crater rim and dissipated as they drifted E. 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: US Geological Survey Cascades Volcano Observatory TUNGURAHUA Ecuador 1.470S, 78.440W; summit elev. 5,023 m At the beginning of January there was an increase in volcanic activity, and explosions generated moderate amounts of ash; seismicity remained low. Though clouds obscured the volcano during much of 18-24 January 2006, steam clouds with minor ash content were seen on 20 and 22 January. Muddy, sediment-laden water discharge down the W flank on 23-24 January blocked a highway. 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 initially prompted temporary evacuation of the entire town of Baqos on the N side of the volcano. Source: Instituto Geofisico-Escuela Politicnica Nacional Contact: Gari Mayberry - Weekly Report Editor ============================================================== 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. ==============================================================
