Report on Sangay (Ecuador) — 22 December-28 December 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 December-28 December 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Sangay (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 22 December-28 December 2004. Smithsonian Institution and US Geological Survey.
2.005°S, 78.341°W; summit elev. 5286 m
All times are local (unless otherwise noted)
According to the Washington VAAC, on 28 December around 0715 satellite imagery showed a plume from Sangay that was most likely composed of steam with little ash. The plume was E of the volcano's summit at a height of ~6.4 km a.s.l. A hotspot was prominent on satellite imagery, but ash was more difficult to distinguish.
Geologic Background. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.