IG reported that the eruption at Sangay continued at a high level during 30 May-6 June, though weather clouds often prevented visual observations. The seismic network recorded 504-528 explosions per day during 30 May-2 June and 158-384 per day during the rest of the week. Periods of occasional-to-frequent ash plumes were reported almost daily. Incandescence at the crater was visible during 31 May and 3-4 June; incandescent material traveled 1 km down the SE flank. Ashfall was reported on 1 June in Cebadas Parish, Chimborazo Province (33 km WNW). On 4 June an ash plume rose to 1.1 km above the crater and drifted W and SW. During 4-5 June incandescent material traveled 1 km down the SE flank. Several steam-and-ash plumes rose as high as 1.1 km above the summit and drifted W. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest 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), Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE), Washington Volcanic Ash Advisory Center (VAAC)