Report on Galeras (Colombia) — February 1992
Bulletin of the Global Volcanism Network, vol. 17, no. 2 (February 1992)
Managing Editor: Lindsay McClelland..
Galeras (Colombia) Occasional ash emissions
Please cite this report as:
Global Volcanism Program, 1992. Report on Galeras (Colombia). In: McClelland, L. (ed.), Bulletin of the Global Volcanism Network, 17:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199202-351080.
1.22°N, 77.37°W; summit elev. 4276 m
All times are local (unless otherwise noted)
Occasional emissions of fine ash, sometimes associated with long-period earthquakes or variations in tremor, punctuated the continuous emission of gas and vapor in February. Although seismicity oscillated in February, it has remained stable since the increased activity associated with dome growth in October-November. On 11 February, a M 3.1 earthquake occurred roughly 2 km W of the crater, and was felt 9 km away (in Pasto and Consacá). Electronic tiltmeter measurements [at the Crater and Peladitos stations] were essentially stable, with the latter showing a slight tendency toward inflation.
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.
Information Contacts: J. Romero, INGEOMINAS-Observatorio Vulcanológico del Sur.