Report on Galeras (Colombia) — 10 December-16 December 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 December-16 December 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Galeras (Colombia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 December-16 December 2008. 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 thermal images of the lava dome in Galeras's crater were taken during an overflight on 11 December. The images revealed temperatures as hot as 530 degrees Celsius on the N side of the dome and temperatures near 80 degrees Celsius on the W side. Temperatures had declined compared to thermal images taken in October 2008. On 16 December, INGEOMINAS reported that during the previous few days, gas plumes rose to altitudes of 5.9-6.7 km (19,400-22,000 ft) a.s.l. and drifted NW.
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.