IG reported a high level of activity at Sangay during 1-8 November. Almost daily thermal anomalies were identified in satellite images, though weather clouds often prevented views. Incandescence at the summit was periodically visible at night. Daily ash-and-gas plumes were identified in either or both IG webcam photos and satellite images according to the Washington VAAC. Plumes generally rose as high as 2.1 km above the volcano and drifted NW, W, and SW. Ash emissions were first observed at 0520 on 4 November and then the amplitude of tremor signals increased at 0650. A pyroclastic flow descended the Volcán River drainage on the SE flank at 0700. The emissions intensified at 0840 and a plume rose 8.3 km above the crater rim and drifted NW, W, and SW. Minor-to-moderate amounts of ash fell in several cities including Riobamba (50 km NW), Guamote (42 km WNW), Colta (55 km NW), Alausí (60 km SW), Pallatanga (70 km W), Chambo (40 km NW), and Chunchi (73 km SW) during 4-5 November.

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)