IG-EPN reported that high levels of eruptive activity continued at Sangay during 12-19 March. The seismic network recorded 61-319 daily explosions during 12-18 March, though there were 3,838 explosions during 18-19 March with most of the events attributed to a period of heightened activity. Inclement or cloudy weather prevented views on most days, though incandescent material was visible descending the SE flank as far as 2 km during dark hours on most days. Crater incandescence was sometimes visible. A series of explosions began at 1540 on 18 March and lasted several hours. The explosions produced ash-and-gas plumes that rose as high as 2.5 km above the crater rim and drifted W and SW. Ashfall was reported in several towns including Palmira (46 km W), Alausí (60 km SW), and Achupallas (56 km SW) in the province of Chimborazo. Incandescent material was ejected above the crater and descended the upper SE flanks. Pyroclastic flows traveled as far as 1.8 km down the SE flank. During the afternoon and into the night roaring noises and vibrations were reported in areas surrounding the volcano. 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)