The IG reported that, although cloud cover occasionally prevented visual observation during 18-24 February, ash plumes from Tungurahua were seen and rose to altitudes of 6-8 km (19,700-26,200 ft) a.s.l. The plumes drifted mainly W and NW. Ashfall was reported almost daily and was noted in areas to the SW, W, and NW. Blocks were often seen or heard rolling down the flanks, and roaring or explosion noises were noted. On 18 February, incandescence in the crater was seen and a lahar traveled down a drainage to the W. Strombolian activity at the summit was observed during 19-20 and 22-23 February.

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: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)