Report on Tungurahua (Ecuador) — 24 November-30 November 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 24 November-30 November 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, 24 November-30 November 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 on 22 November an explosion ejected incandescent blocks that fell onto the flanks 1.5 km below the crater rim, and produced an ash plume that rose to altitudes of 11-12 km (36,100-39,400 ft) a.s.l. Ashfall was reported in multiple areas to the W and SW. Smaller explosions produced ash plumes that rose to altitudes of 7-8 km (23,000-26,200 ft) a.s.l. and drifted NE and E. Lahars descended a SW drainage and temporarily dammed the Puela river. During 23-25 November, explosions produced ash plumes that rose less than 7 km (23,000 ft) a.s.l. Ashfall was reported in areas within 8 km N, NNE, W, and SW. Strombolian activity was seen at night.
During 25-26 and 29 November incandescent blocks were observed rolling down the flanks. During 26-30 November, steam-and-ash plumes rose to altitudes of 5.5-9 km (18,000-29,500 ft) a.s.l. and drifted SW and W. Plumes also drifted NW on 28 November. Ashfall was reported in areas within 8 km downwind, and roaring was occasionally reported. At night during 28-29 November Strombolian activity ejected blocks that rolled 400 m down the flanks. Satellite imagery on 29 November showed an increase in sulfur dioxide concentrations.
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.