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Report on Galeras (Colombia) — 25 February-3 March 2009

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 February-3 March 2009
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2009. Report on Galeras (Colombia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 February-3 March 2009. Smithsonian Institution and US Geological Survey.

Volcano Profile |  Weekly Report (25 February-3 March 2009)


Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


INGEOMINAS reported that on several occasions during 25 February-2 March white gas plumes from Galeras with variable ash content rose to a peak altitude of 5.4 km (17,700 ft) a.s.l. and drifted NNW. On 3 March, the Alert Level was lowered from II (Orange; "probable eruption in term of days or weeks") to III (Yellow; "changes in the behavior of volcanic activity").

Geologic Background. Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic 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 contributed to large-scale edifice collapse on at least three occasions, producing debris avalanches that swept to the west 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: Servicio Geológico Colombiano (SGC)