Report on Tungurahua (Ecuador) — 8 December-14 December 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 December-14 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, 8 December-14 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)
During 7-14 December, IG reported that ash-and-steam plumes from Tungurahua rose to altitudes of 6-9 km (19,700-30,000 ft) a.s.l. and drifted WNW, W, SSW, and SW. Ashfall was reported in areas as far as 8 km NW, 15 km W and SW, and 30 km S. Roars and sounds resembling "cannon shots" were noted almost daily. Explosions often caused windows and structures to vibrate. At night during 7-8 December Strombolian explosions ejected material 600 m above the crater. Blocks rolled 600-800 m down the flanks. On 9 December a pyroclastic flow traveled 3 km down the NW flank. During 9-10 and 12 December incandescent blocks rolled down the flanks. During 12-13 December incandescent blocks were ejected 500 m above the crater.
On 14 December, IG issued a special report stating that a lava flow with an estimated volume of hundreds of thousands of cubic meters traveled 1 km down the W flank on 4 December. The report noted that the flow was the second since the eruptions onset in 1999.
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.