IG-EPN reported a high level of eruptive activity at Sangay during 15-22 August, and seismic stations recorded 285-783 daily explosions. Crater incandescence was often visible in overnight webcam images, and during 16-18 August material on the S flank was incandescent up to 1 km from the crater. Several daily ash-and-gas plumes rose as high as 2.5 km above the crater rim and drifted mainly SW, W, and NW during 15-21 August. Ashfall was occasionally reported during 15-19 August in areas downwind, including Cebadas (35 km WNW), Guarguallá (25 km WNW), Retén (34 km WNW), and Palmira (46 km W), all located in the province of Chimborazo. Secretaría de Gestión de Riesgos maintained the Alert Level at Yellow (the second highest level on a four-color scale).

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.

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN), Secretaría de Gestión de Riesgos (SGR)