Based on Air Force Weather Agency (AFWA) reports, pilot observations, and analyses of satellite imagery, the Washington VAAC reported that on 22 November an eruption from Tungurahua produced an ash plume that rose to an altitude of 7.6 km (25,000 ft) a.s.l. and drifted 37 km SW. Subsequent satellite images showed a detached ash cloud that became difficult to discern in images about 230 km SW of the volcano. Pilots reported additional ash emissions that rose to an altitude of 6.4 km (21,000 ft) a.s.l. On 23 November satellite images showed an ash plume drifting S. IG reported that an ash plume rose to an altitude of 7 km (23,000 ft) a.s.l.

Geological Summary. Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II collapsed about 3,000 years ago and produced a large debris-avalanche deposit to the west. The modern glacier-capped stratovolcano (Tungurahua III) was constructed within the landslide scarp. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Source: Washington Volcanic Ash Advisory Center (VAAC)