Report on Tungurahua (Ecuador) — 22 August-28 August 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 August-28 August 2007
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2007. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 August-28 August 2007. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
IG reported that ash plumes from Tungurahua rose to altitudes of 6-9 km (19,700-29,500 ft) a.s.l. during 22-28 August and drifted mainly NW, W, and SW. Noises resembling the sounds made by blocks rolling down the flanks were reported during 22-26 August and explosions rattled windows in surrounding areas, including Baños 8 km to the N, on 24 and 25 August. Ashfall was reported in nearby areas, especially to the NW, W, and SW, during 25-28 August. On 28 August, lahars affected W and NW drainages, the Pampas sector, and interrupted traffic on the route between Ambato and Baños. Incandescent blocks rolled down the flanks.
Geologic Background. 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 itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. 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.