The Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported high levels of eruptive activity at Sangay during 13-20 May. The seismic network recorded 98-194 daily explosions. Ash-and-gas plumes were observed in webcam and/or satellite images on most days rising as high as 2 km above the summit and drifting in multiple directions. Weather clouds often obscured observations, especially during the first half of the week. Crater incandescence was sometimes visible during dark hours from 17 May through 20 May. Incandescent avalanches of material descended the SE flank 600 m during 18-19 May. Secretaría de Gestión de Riesgos (SGR) 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)