Based on a SIGMET notice of a pilot observation, the Washington VAAC reported that on 26 February an ash plume from Sangay rose to an altitude of 7.3 km (24,000 ft) a.s.l. Satellite images only detected an intermittent thermal anomaly. According to the VAAC, on 27 February IG reported a lava flow and a possible diffuse ash plume that rose to an altitude below 5.5 km (18,000 ft) a.s.l. within 15 km of the summit. On 2 March a local pilot observed an ash plume that rose to an altitude of 7.6 km (25,000 ft) a.s.l. On 3 March an ash plume rose to an estimated altitude of 5.2 km (17,000 ft) a.s.l. and drifted 13 km 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.

Source: Washington Volcanic Ash Advisory Center (VAAC)