Report on Galeras (Colombia) — 10 April-16 April 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 April-16 April 2013
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2013. Report on Galeras (Colombia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 April-16 April 2013. 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 10-16 April earthquakes at Galeras were located in various areas as far as 13 km from the crater, at depths no greater than 14 km and with maximum magnitudes of 2. Moderate levels of sulfur dioxide were detected; plumes drifted NW. Cameras recorded ash emissions all week, especially on 9, 11, 12, and 14 April, when pulsating activity produced plumes that drifted W. Plumes rose no more than 1 km above the crater. 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.