Volcanic Worldwide Weekly Activity Oct 7

29 September-5 October 2010

New Activity/Unrest: | Nevado del Huila, Colombia | Nevado del Ruiz, Colombia | Piton de la Fournaise, Reunion Island | Planchón-Peteroa, Central Chile-Argentina border | Reventador, Ecuador

Ongoing Activity: | Bagana, Bougainville | Batu Tara, Komba Island (Indonesia) | Dukono, Halmahera | Fuego, Guatemala | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaii (USA) | Kliuchevskoi, Central Kamchatka (Russia) | Pacaya, Guatemala | Popocatépetl, México | Sakura-jima, Kyushu | Sarychev Peak, Matua Island | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Suwanose-jima, Ryukyu Islands (Japan)

Updated every Wednesday, 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

NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5364 m

The Popayán Volcano Observatory (INGEOMINAS) reported that during 29 September-5 October gas plumes from Nevado del Huila, observed with the Tafxnú and Maravillas web cameras, rose 2.5 km above the summit. Incandescence from the extruding lava dome and collapsing material was also noted. Based on a SIGMET issued from the Bogota MWO, the Washington VAAC reported that on 1 October an ash plume rose to an altitude of 7.6 km (25,000 ft) a.s.l. Later that day, a 10-km-wide gas-and-ash plume was seen in satellite imagery drifting about 30 km S. The Alert Level remained at II (Orange; "probable eruption in term of days or weeks").

Geologic Summary. Nevado del Huila, the highest active volcano in Colombia, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. Two glacier-free lava domes lie at the southern end of the Huila volcanic complex. The first historical eruption from this little known volcano took place in the 16th century. Two persistent steam columns rise from the central peak, and hot springs are also present.

Sources: Instituto Colombiano de Geología y Minería (INGEOMINAS), Washington Volcanic Ash Advisory Center (VAAC)

Nevado del Huila Information from the Global Volcanism Program

NEVADO DEL RUIZ Colombia 4.895°N, 75.322°W; summit elev. 5321 m

INGEOMINAS reported a gradual increase in seismicity from Nevado del Ruiz on 30 September. Earthquakes were located beneath the Arenas crater at depths of 0.5-2 km. The largest earthquake was M 1.9. A plume of white gas rose 700 m above the caldera and a sulfur odor around the volcano was reported. The Alert Level was raised to III (Yellow; "changes in the behavior of volcanic activity") on 1 October. The report also noted changes in deformation and geochemistry during the previous few months. Seismic levels fluctuated during 2-3 October.

Geologic Summary. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers >200 sq km. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the summit caldera of an older Ruiz volcano. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. Steep headwalls of massive landslides cut the flanks of Nevado del Ruiz. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Source: Instituto Colombiano de Geología y Minería (INGEOMINAS)

Nevado del Ruiz Information from the Global Volcanism Program

PITON DE LA FOURNAISE Reunion Island 21.231°S, 55.713°E; summit elev. 2632 m

OVPDLF reported that on 29 September seismicity from Piton de la Fournaise remained high. Earthquakes were located at the base of the volcano, and inflation was noted particularly in the E. A significant number of landslides were detected in the crater. The Alert level remained at 1 ("probable or imminent eruption").

Geologic Summary. Massive Piton de la Fournaise shield volcano on the island of Réunion is one of the world's most active volcanoes. Most historical eruptions have originated from the summit and flanks of a 400-m-high lava shield, Dolomieu, that has grown within the youngest of three large calderas. This depression is 8 km wide and is breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows within the caldera, have been documented since the 17th century. The volcano is monitored by the Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris.

Source: Observatoire Volcanologique du Piton de la Fournaise (OVPDLF)

Piton de la Fournaise Information from the Global Volcanism Program

PLANCHON-PETEROA Central Chile-Argentina border 35.240°S, 70.570°W; summit elev. 4107 m

Based on analyses of satellite imagery, pilot observations, and SIGMET notices, the Buenos Aires VAAC reported that during 30 September-3 October ash plumes from Planchón-Peteroa rose to altitudes of 3-6.1 km (10,000-20,000 ft) a.s.l. and drifted NW, NNE, E, and SE.

Geologic Summary. Planchón-Peteroa is an elongated complex volcano along the Chile-Argentina border with several overlapping calderas. Activity began in the Pleistocene with construction of the basaltic-andesite to dacitic Volcán Azufre, followed by formation of basaltic and basaltic-andesite Volcán Planchón, 6 km to the N. About 11,500 years ago, much of Azufre and part of Planchón collapsed, forming the massive Río Teno debris avalanche, which reached Chile's Central Valley. Subsequently, Volcán Planchón II was formed. The youngest volcano, andesitic and basaltic-andesite Volcá Peteroa, consists of scattered vents between Azufre and Planchón. Peteroa has been active into historical time and contains a small steaming crater lake. Historical eruptions from the Planchón-Peteroa complex have been dominantly explosive, although lava flows were erupted in 1837 and 1937.

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)

Planchón-Peteroa Information from the Global Volcanism Program

REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m

According to the Washington VAAC, the IG reported ash over Reventador on 30 September. The VAAC stated that a diffuse plume was observed in satellite imagery drifting NW, although ash was not identified.

Geologic Summary. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well E of the principal volcanic axis. It is a forested stratovolcano that rises above the remote jungles of the western Amazon basin. A 3-km-wide caldera breached to the E was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1,300 m above the caldera floor. Reventador has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera.

Source: Washington Volcanic Ash Advisory Center (VAAC)

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