Report on Galeras (Colombia) — 13 June-19 June 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 13 June-19 June 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, 13 June-19 June 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 5-19 June seismicity at Galeras had increased in both magnitude and frequency since the previous week-long period, and indicated continuing ash and gas emissions. On 5, 6, and 12-19 June cameras recorded gas-and-ash emissions; an ash plume rose 1.4 and 2.4 km above the crater on 14 and 17 June, respectively. Ashfall was reported in Sandona (13 km NW), Samaniego (32 km NW), Mapachico (8 km NW), and Genoy (5 km NE). Sulfur dioxide emissions were moderate to high. 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.