IG-EPN reported that high levels of eruptive activity continued at Sangay during 23-30 April. The seismic network recorded 388-1,167 daily explosions during the week. Daily gas-and-ash plumes visible in webcam and/or satellite images generally rose as high as 2 km above the summit and drifted NW, W, and SW; weather conditions often hindered views during the week. Incandescent material was visible daily during dark hours descending the SE flank as far as 1.8 km. Several episodes of explosions were visible in webcam images during 25-28 April and pyroclastic density currents descended the SE flank during 27-29 April. Ash plumes possibly rose as high as 7 km above the summit and drifted W and SW during 28-29 April. 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)