Report on Tungurahua (Ecuador) — 10 February-16 February 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 February-16 February 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 February-16 February 2010. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
The IG reported that during 10-16 February explosions from Tungurahua were detected by the seismic network. The explosions often produced sounds resembling "cannon shots" and caused windows and structures to occasionally vibrate. Blocks ejected from the crater fell onto the flanks and rolled as far as 2 km from the crater. Ash plumes rose to altitudes of 5.5-9 km (18,000-29,500 ft) a.s.l. On 11 February, a small pyroclastic flow seen from Tungurahua Observatory (OVT) in Guadalupe, 11 km N, descended the N and NNW flanks. Ashfall was seen daily and impacted areas to the NW, W, SW, and S. Ashfall was 3 mm thick in Choglontus, Cahuají, and Pillate on 12 February, and 1 mm thick in Choglontus on 14 February.
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.