Report on Tungurahua (Ecuador) — 3 February-9 February 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 February-9 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, 3 February-9 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 14-51 explosions from Tungurahua were detected by the seismic network during 3-9 February. Inclement weather often prevented observations of the volcano; an ash plume was seen rising to an altitude of 7 km (23,000 ft) a.s.l. Ashfall was noted almost daily in areas to the SW, W, and NW, and was particularly heavy towards the end of the reporting period. Roaring noises and sounds resembling "cannon shots" were heard. Explosions sometimes caused windows and structures to vibrate, including large windows at the Tungurahua Observatory (OVT) in Guadalupe, 11 km N. Occasionally at night incandescence emanated from the crater and incandescent blocks rolled down the flanks as far as 1 km. On 3 February lahars descended drainages to the W and SW, carrying tree trunks and blocks up to 1 m in diameter, and causing the road from Riobamba to Baños to close. Strombolian activity from the crater was seen during 6-8 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.