IG reported a high level of activity at Sangay during 16-22 December. Seismicity was characterized by 20-127 daily explosions, occasional harmonic tremor, long-period earthquakes, and signals indicating emissions. Weather clouds often prevented visual observations of the volcano, but the Washington VAAC and IG webcams recorded daily ash plumes that rose as high as 2.4 km above the summit and drifted mainly NW, W, and SW. Seismic signals signifying lahars were recorded during 16-18 December.

Geological Summary. 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 the open 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 eroded by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an eruption was in 1628. Almost 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.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)