Although storm clouds occasionally prevented observations of Tungurahua's summit area during 9-12 June, steam-and-ash plumes were seen and rose to altitudes of 5.5-8 km (18,000-29,500 ft) a.s.l. Daily reports of ashfall came from multiple areas within about 8 km NW, W, and SW, but ash was noted as far away as 22 km NW and 25 km W on 9 June. Blocks, including some that were incandescent, occasionally ejected by explosions rolled at most 1 km down the flanks. Explosions caused noises resembling "cannon shots" and vibrating windows almost daily. During 13-14 June steam plumes from the crater and the NW flank rose 500-1,000 m above the crater and drifted W. An explosion on 15 June generated an ash plume that rose to an altitude of 7 km (23,000 ft) a.s.l. and drifted W.

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)