IG reported a high level of activity at Sangay during 27 January-4 February, though weather clouds often prevented visual confirmation. Ash, steam, and gas plumes rose 880-1,200 m above the summit and drifted W and SW during 27-29 January. Minor ashfall was reported in Púngala and in several Chimborazo province communities during 27-28 February. A pyroclastic flow descended the SE flank on 28 January, reaching the Volcán River and causing secondary lahars in the river. Incandescent blocks rolled down the SE flank on 29 January. Minor ashfall was reported in the province of Chimborazo (W), particularly in the towns of Cebadas (35 km WNW) and Palmira (46 km W). On 30 January residents in the town of Alao (20 km NW) reported that vegetation was covered with fine white ash. An ash emission rose 570 m above the summit and drifted W on 31 January. Ashfall was reported in Macas (42 km SE) the next day. Gas-and-steam plumes rose up to 200 m and drifted W on 2 February. Incandescent blocks rolled down the SE flank on 3 February.

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.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)