**************************************************************** GVP/USGS Weekly Volcanic Activity Report 23-29 January 2008 Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ **************************************************************** New Activity/Unrest: | Galeras, Colombia | Machín, Colombia Ongoing Activity: | Anatahan, Mariana Islands (Central Pacific) | Fuego, Guatemala | Kilauea, Hawaii (Hawaiian Islands) | Llaima, Central Chile | Pacaya, Guatemala | Popocatépetl, México | Rabaul, New Britain (SW Pacific) | Shiveluch, Sredinny Range | Soufrière Hills, Montserrat | St. Helens, Washington (USA) | Tungurahua, Ecuador New Activity/Unrest GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m INGEOMINAS reported that white plumes from Galeras's main crater and gas emissions from several points along the margins of the crater were observed during aerial observations on 23 January. Plumes drifted W. Several impact craters were spotted; the largest one was about 15 m in diameter and 5 m deep. Thermal images of the main crater revealed a maximum temperature of 150 degrees Celsius. 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. Longterm 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 (INGEOMINAS) http://www.ingeominas.gov.co// MACHIN Colombia 4.48°N, 75.392°W; summit elev. 2650+ m Observatory Vulcanológico and Sismológico de Manizales reported unusual seismicity at Machín during 6-8 January. Long-period earthquakes were detected S of the main lava dome. On 7 January, volcano-tectonic seismic signals were registered and occasionally felt and reported by near by residents. The simultaneous occurrence of both types of seismic signals was unusual for Machín. Geologic Summary. The small Cerro Machín stratovolcano lies at the southern end of the Ruiz-Tolima massif about 20 km WNW of the city of Ibagué. A 3-km-wide caldera is breached to the S and contains three forested lava domes. Voluminous pyroclastic flows traveled up to 40 km from the volcano during eruptions in the mid-to-late Holocene perhaps associated with formation of the caldera. Late-Holocene eruptions produced block-and-ash flows that traveled through the breach in the caldera rim to the W and S. The latest known eruption of Volcán Cerro Machín took place about 800 years ago. Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co// Ongoing Activity ANATAHAN Mariana Islands (Central Pacific) 16.35°N, 145.67°E; summit elev. 790 m The USGS reported that elevated seismic tremor levels at Anatahan detected on 16 January were sustained through 23 January and episodic during 23-28 January. During 20-28 January, a sulfur dioxide plume was detected by the satellite-based Ozone Monitoring Instrument (OMI) and drifted W and SW. A steam plume was also detected on satellite imagery. The Volcanic Alert Level remained at Advisory and the Aviation Color Code remained at Yellow. Geologic Summary. The elongate, 9-km-long island of Anatahan in the central Mariana Islands consists of large stratovolcano with a 2.3 x 5 km, E-W-trending compound summit caldera. The larger western caldera is 2.3 x 3 km wide, and its western rim forms the island's 790-m high point. Ponded lava flows overlain by pyroclastic deposits fill the floor of the western caldera, whose SW side is cut by a fresh-looking smaller crater. The 2-km-wide eastern caldera contained a steep-walled inner crater whose floor prior to the 2003 eruption was only 68 m above sea level. Sparseness of vegetation on the most recent lava flows on Anatahan had indicated that they were of Holocene age, but the first historical eruption of Anatahan did not occur until May 2003, when a large explosive eruption took place forming a new crater inside the eastern caldera. Source: Emergency Management Office of the Commonwealth of the Mariana Islands and the US Geological Survey Hawaiian Volcano Observatory http://volcano.wr.usgs.gov/ FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m INSIVUMEH reported on 24 January that explosions from Fuego produced ash plumes that rose to altitudes of 4.2-4.5 km (13,800-14,800 ft) a.s.l. ands drifted S, SW, and W. Some explosions produced shock waves that were detected 3 km away. At night, small avalanches of blocks traveled W towards the Taniluyá ravine. Based on reports from INSIVUMEH, CONRED reported on 28 January that the Alert Level was lowered to Green. Based on observations of satellite imagery, the Washington VAAC reported that a narrow plume of gas and possible ash drifted SW on 30 January. 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. Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/ Coordinadora Nacional para la Reducción de Desastres (CONRED) http://www.conred.org/principal.php Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html KILAUEA Hawaii (Hawaiian Islands) 19.421°N, 155.287°W; summit elev. 1222 m Based on observations during overflights, and web camera views when weather permitted, HVO reported that during 23-29 January activity from Kilauea's fissure segment D was concentrated at the Thanksgiving Eve Breakout (TEB) shield and satellitic shields to the SE. Lava flows issued from the tops and flanks of the shields. A crusted lava pond a few meters below the rim of the TEB shield was seen during an over flight on 25 January. A lava flow that advanced 1 km and started another rootless shield was also spotted during the aerial observations. On 28 January, low lava fountaining was seen from the TEB vent and a couple of the shields. The original perched lava channel formed from the 21 July fissure eruption refilled and overflowed the N end. On 29 January, a channelized 'a'a lava flow from a rootless shield that collapsed on 26 January advanced about 0.6 km into the Royal Gardens subdivision. The new 29 January flows mostly moved over older lava. Incandescence was observed in Pu'u 'O'o crater for less than 10 minutes at a time every day during the reporting period. During 22-23 January, the summit tiltmeter network recorded the first DI (deflation-inflation) tilt event that coinciding with rain. A few small earthquakes were located along the S-flank faults and SW rift zone. 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 of lava flows less than about 1,100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island. Source: US Geological Survey Hawaiian Volcano Observatory http://volcano.wr.usgs.gov/ LLAIMA Central Chile 38.692°S, 71.729°W; summit elev. 3125 m SERNAGEOMIN reported that eruptive activity at Llaima continued from the main crater and from multiple areas on the E flank during 23-27 January. On 23 January, a brown ash plume rose to an altitude of 3.5 km (11,500 ft) a.s.l and drifted W. Based on observations during an overflight later that day, Strombolian eruptions took place from a central pyroclastic cone in the main crater and were accompanied by emissions of brown ash. A small hornito emitting bluish gas and a lava field were noted between the pyroclastic cone and the inner margins of the crater. On 24 January, explosions from the E flank were detected and on 26 January, steam plumes were observed. Strombolian eruptions in the main crater accompanied by gas and ash emissions continued during 24-27 January. Ash plumes rose to altitudes of 3.3-4.1 km (10,800-13,500 ft) a.s.l. and drifted NW, E, SE, and S. Geologic Summary. Llaima, one of Chile's largest and most active volcanoes, contains two historically active craters, one at the summit and the other to the SE. The massive 3,125-m-high, glacier-covered stratovolcano has a volume of 400 cu km. A Holocene edifice built primarily of accumulated lava flows was constructed over an 8-km-wide caldera that formed about 13,200 years ago, following eruption of the 24 cu km Curacautín Ignimbrite. More than 40 scoria cones dot the volcano's flanks. Following the end of an explosive stage about 7,200 years ago, construction of the present edifice began, characterized by Strombolian, hawaiian, and infrequent subplinian eruptions. Frequent moderate explosive eruptions with occasional lava flows have been recorded since the 17th century. Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/ PACAYA Guatemala 14.381°N, 90.601°W; summit elev. 2552 m INSIVUMEH reported on 24 January that white and blue fumarolic plumes from Pacaya's MacKenney cone drifted S and SW. Four lava flows traveled about 100 m to the W. Based on reports from INSIVUMEH, CONRED reported on 28 January that the Alert Level was lowered to Green. 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 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. Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/ Coordinadora Nacional para la Reducción de Desastres (CONRED) http://www.conred.org/principal.php POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m CENAPRED reported that emissions of steam and gas from Popocatépetl were visible during 23-29 January. The plumes occasionally contained slight amounts of ash. On 28 January, an ash plume rose to an altitude of 8.6 km (28,200 ft) a.s.l. and drifted NW. Geologic Summary. 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: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.unam.mx/es/ RABAUL New Britain (SW Pacific) 4.271°S, 152.203°E; summit elev. 688 m RVO reported that white plumes from Rabaul caldera's Tavurvur cone rose to an altitude of 1.5 km (4,900 ft) a.s.l. and drifted E and NE during 24-25 January. Incandescence at the summit was seen at night. On 26 January, ash plumes that were emitted about every 10-20 minutes rose to an altitude of 1.7 km (5,600 ft) a.s.l. and drifted NE. Slight ashfall was reported in areas on the E coast. Deformation-monitoring instruments indicated that uplift started on 23 January and peaked during 25-26 January with 2 cm of inflation. On 28 January, white plumes rose to an altitude of 1.7 km (5,600 ft) a.s.l. and drifted W. On 29 and 30 January, ash-and-gas plumes rose to the same altitude as the previous day but drifted SW, W, and E. Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the E, where its floor is flooded by Blanche Bay.Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city. Source: Steve Saunders, Rabaul Volcano Observatory SHIVELUCH Sredinny Range 56.653°N, 161.360°E; summit elev. 3283 m KVERT reported that seismic activity at Shiveluch was slightly above background levels during 18-25 January. Based on seismic interpretation, ash plumes rose to an altitude of 4.3 km (14,100 ft) a.s.l. during 17-18, 20, and 23 January. Fumarolic activity was noted on 19, 20, and 22 January. Based on observations of satellite imagery, a thermal anomaly was present in the crater every day during the reporting period. The Level of Concern Color Code remained at Orange. 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 breached 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 SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m MVO reported that the lava dome at Soufrière Hills had changed very little, based on visual observations during an over flight on 23 January. Visual observations were limited during 22-29 January. Seismic activity was very low and low-level rockfall activity continued. Fumarolic activity on the N and E flanks also continued, along with active fumaroles in the Galway's area to the S of the dome and W in the Gages Wall area. The Alert Level remained elevated at 4 (on a scale of 0-5). 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 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 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: Montserrat Volcano Observatory (MVO) http://www.mvo.ms/ ST. HELENS Washington (USA) 46.20°N, 122.18°W; summit elev. 2549 m Data from deformation-monitoring instruments indicated that during 23-29 January lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels, punctuated by M 1.5-2.5, and occasionally larger, earthquakes. A steam plume that rose from the dome and slightly above the crater rim was visible on 25 January. 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: Cascades Volcano Observatory (CVO) http://volcano.wr.usgs.gov/cvo/current_updates.php TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m IG reported that although visual observations were occasionally limited due to cloud cover, ash plumes were spotted and rose to altitudes of 5.5-9 km (18,000-29,500 ft) a.s.l. during 23-29 January. Ashfall was reported daily in areas mainly within 10 km to the SW, W, NW, and NE. On 24 January, ashfall was reported from San Juan, about 40 km WSW and from Bilbao, 8 km W, where the ashfall was 2 mm thick. On 25 January, ashfall was reported in Riobamba, 30 km S. During 22-25, 27, and 29 January, incandescence at the summit was observed at night and incandescent blocks that were propelled from the summit by explosions rolled 500-800 m down the flanks. Roaring noises and "cannon shots" were heard almost daily during 23-29 January. Lahars descend multiple drainages on 29 January and blocked the road to Baños in the La Pampas sector to the S. 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 all originated from 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. Source: Instituto Geofísico-Escuela Politécnica Nacional http://www.igepn.edu.ec/ +++++++++++++++++++++++++++++++++++++ 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. ==============================================================
