Report on Tungurahua (Ecuador) — 15 December-21 December 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 15 December-21 December 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, 15 December-21 December 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 14-15 December gas-and-ash plumes from Tungurahua rose to an altitude of 8 km (26,200 ft) a.s.l. and drifted SW, NE, and E. Slight ashfall was reported in Puto, 50 km E. Explosions caused "cannot shot" noises, and blocks rolled down the flanks. Incandescence from the crater was observed at night. The next day steam-and-gas plumes, with occasional pulses of ash, rose to an altitude of 7 km (23,000 ft) a.s.l. and drifted E and W. Roaring was heard and ashfall was reported in Palictagua.
Although storm clouds occasionally prevented observations of the summit area, steam-and-gas plumes were seen during 17-18 and 21 December drifting S, SW, and W, and a plume was observed drifted S on 19 December. On 20 December ashfall was reported in areas to the N and NNW. Lahars descended the Mapayacu (SW) and Bramaderos drainages, carrying blocks up to 90 cm in diameter and depositing them in the Puela river to the S. Later that day, an explosion caused windows to vibrate in multiple areas. Incandescent blocks rolled 2 km down the flanks. A plume rose to an altitude of 7 km (23,000 ft) a.s.l. and drifted W.
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.