Report on Tungurahua (Ecuador) — 6 January-12 January 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 January-12 January 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, 6 January-12 January 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 5-6 January a gas-and-ash plume from Tungurahua rose to an altitude of 6.5 km (21,300 ft) a.s.l. and drifted NW. The sulfur dioxide emission rate was 3,200 tons per day, ten times the value measured during the previous months. On 7 January seismic tremor duration and amplitude increased, and signals indicative of explosions were detected. On 6 and 7 January, incandescent blocks were ejected and fell back into the crater. During 8-10 January, cloud cover often prevented observations; on 10 January a steam-and-ash plume rose to an altitude of 6.5 km (21,300 ft) a.s.l. and drifted W. Incandescence from the crater was sometimes seen at night. Ashfall up to 5 mm thick was reported in areas W and SW on 9 and 10 January. Roaring noises and vibrating glass were occasionally noted during the reporting period.
During 11-12 January, activity increased; ash plumes rose to higher altitudes and more explosions were detected. Incandescent blocks were ejected almost 1 km above the crater and 1.5 km away from the crater, onto the flanks. Gas-and-ash plumes rose to an altitude of 8 km (26,200 ft) a.s.l. and drifted in multiple directions. Ashfall was reported in areas to the NNW, W, SW, and S.
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.