During the week of 18-24 March seismicity and fumarolic activity at Tungurahua continued. The IG reported that at 1915 on 22 March an eruption column with an incandescent point rose to a height of 2 km and lasted 10 minutes. Another eruption on 23 March at 1014 lasted for 30 minutes, sending a column 2 km high that moved NW. Pilot reports indicated that the plume reached an altitude of 6 km. At night a point of incandescence in the crater was observed again. Extensive meteorological clouds prevented the Washington VAAC from obtaining good satellite imagery of the 22 and 23 March plumes.

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.

Sources: Washington Volcanic Ash Advisory Center (VAAC), Instituto Geofísico-Escuela Politécnica Nacional (IG)