Smithsonian/USGS Weekly Volcanic Activity Report

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Smithsonian/USGS Weekly Volcanic Activity Report

Post by Joe Bese on Thu Feb 10, 2011 8:45 am

I don't think copyright is an issue, since it's from the US govt, but if you disagree, let me know.

Smithsonian/USGS Weekly Volcanic Activity Report
2-8 February 2011

New Activity/Unrest: | Fuego, Guatemala | Galeras, Colombia | Kirishima, Kyushu | Nyiragongo, Democratic Republic of Congo

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

FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m

INSIVUMEH reported that during 2-3 February Fuego produced 27 explosions with ash plumes that rose 300-500 m above the crater and drifted 7 km W and SW. The explosions generated shock waves detected as far away as 5 km W and SW, in Sangre de Cristo, Panimache I and II, and Morelia. Block avalanches descended the Santa Teresa, Taniluyá, Cenizas, and Trinidad drainages to the SW. During 6-8 February explosions produced ash plumes that rose 500 m above the crater and drifted W and SW. At night incandescence was observed emanating from the crater and explosions sometimes ejected incandescent material 100 m above the crater rim.

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.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm


GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m

On 8 February, INGEOMINAS reported that "tornillo-type" earthquakes from Galeras had not been detected since 5 February. Seismic levels continued to fluctuate. On 6 February an overflight revealed that gas emissions had increased in comparison to the previous week, forming plumes that drifted NW. The Alert Level was lowered to III (Yellow; "changes in the behavior of volcanic activity").

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//


KIRISHIMA Kyushu 31.931°N, 130.864°E; summit elev. 1700 m

According to a news article, explosions on 2 February from Shinmoe-dake (Shinmoe peak), a stratovolcano of the Kirishima volcano group, disrupted flights to Tokyo. The article also noted that JMA widened the restricted zone to a 4-km-radius around the crater. About 600 people from Miyazaki (55 km E) had evacuated.

Based on reports from JMA, analyses of satellite imagery, and pilot observations, the Tokyo VAAC reported that during 2-8 February ash plumes rose to altitudes of 1.5-4.6 km (5,000-15,000 ft) a.s.l. and drifted SE. On 3 February, a pilot noted that an ash plume rose to an altitude of 9.1 km (30,000 ft) a.s.l. and drifted NE.

According to JMA, scientists observed Shinmoe-dake during an overflight on 6 February and noted that the lava dome was about 600 m in diameter, similar to observations from four days prior. Gas plumes rose from the edges of the lava dome, from multiple areas on the E side of the dome, and from a central vent. Ash plumes rose 1.5 km above the crater rim and drifted SE.

Geologic Summary. Kirishima is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene volcano group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located, 1,700-m-high Karakuni-dake being the highest. Onami-ike and Mi-ike, the two largest maars, are located SW of Karakuni-dake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Mi-ike to Ohachi, and at Shinmoe-dake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century.

Sources: Earthquake Research Institute http://www.eri.u-tokyo.ac.jp/,
Japan Meteorological Agency http://www.jma.go.jp/jma/indexe.html,
Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html,
Asia One http://www.asiaone.com/News/Latest+News/Asia/Story/A1Story20110202-261714.html


NYIRAGONGO Democratic Republic of Congo 1.52°S, 29.25°E; summit elev. 3470 m

The Toulouse VAAC reported that during 4-5 February diffuse plumes, likely composed primarily of sulfur dioxide gas, were observed in satellite imagery.

Geologic Summary. One of Africa's most notable volcanoes, Nyiragongo contained an active lava lake in its deep summit crater that drained catastrophically through its outer flanks in 1977. In contrast to the low profile of its neighboring shield volcano, Nyamuragira, Nyiragongo displays the steep slopes of a stratovolcano. Benches in the steep-walled, 1.2-km-wide summit crater mark the levels of former lava lakes, which have been observed since the late 19th century. About 100 parasitic cones are located on the volcano's flanks and along a NE-SW zone extending as far as Lake Kivu. Monitoring is done from a small observatory building located in Goma, ~18 km S of the Nyiragongo crater.

Source: Toulouse Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/FR/messages.html
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Joe Bese

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