Report on Galeras (Colombia) — 10 October-16 October 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 October-16 October 2012
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2012. Report on Galeras (Colombia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 October-16 October 2012. Smithsonian Institution and US Geological Survey.
1.22°N, 77.37°W; summit elev. 4276 m
All times are local (unless otherwise noted)
INGEOMINAS reported that during 9-16 October cameras around Galeras recorded daily emissions; on 9 and 12 October ash was present in the emissions in small quantities. On 12 October a gas-and-ash plume rose 1 km above the crater, and staff at the Galeras National Park Wildlife Sanctuary reported sulfur gas odor in a cabin located on the E side of the volcano. Earthquakes were at most M 1.7 and occurred within 10 km of the crater at depths of less than 6 km. The Alert Level remained at 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.