On 16 June the Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) declared a Yellow Alert for the province of Chimborazo due to a recent increase in ashfall from Sangay. IG reported a continuing high level of activity during 16-22 June, though weather clouds often prevented visual observations. According to the IG and Washington VAAC notices ash plumes rose 570-870 m above the summit and drifted W and SW. Incandescent blocks descending the SE flank were seen through breaks in cloud cover overnight during 17-18 June.

SNGRE reported that lahars in the Upano River in the morning of 21 June followed heavy rains two days earlier. In Macas (40 km SE) the lahars caused the closure of the E45 Macas-Puyo road, destroying a 27-m section and damaging a 30-m section, and the evacuation of 21 people.

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)