In a special report from 3 August, IG reported that a new eruptive phase at Sangay began on 20 July, after 8 months without major surface activity. The recent activity was characterized by low-energy ash plumes rising no more than 3 km above the crater rim, incandescent rocks rolling as far as 1 km down the ESE flank, and a possible lava flow on the same flank. Minor amounts of ash fell in uninhabited areas to the W.

Based on Washington VAAC reports, IG noted two ash plumes on 20 July and one on 2 August that rose 2.3-3 km above the crater and drifted W and NW. Numerous thermal anomalies detected during 2-3 August were aligned on the ESE flank. Based on numerical weather prediction (NWP) models, satellite data, and information from the Guayaquil Meteorological Watch Office (MWO), the Washington VAAC reported that on 6 August an ash plume drifted W.

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), Washington Volcanic Ash Advisory Center (VAAC)