In a special report from 4 October IG stated that the current eruption at Sangay which began on 20 July continued, and that the activity had not changed significantly during the previous two months. Activity was characterized by explosions at the central vent and lava from the Ñuñurco lava dome flowing down the E and ESE flanks. On each day during the previous week there were about 65 explosions, 25 long-period events, and a few harmonic tremor signals. Ash plumes rose 1 km above the crater rim and caused ashfall in areas to the W and NW (Culebrillas and Licto (35 km NW)).

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)