Report on Tungurahua (Ecuador) — 25 April-1 May 2007
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 25 April-1 May 2007
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2007. Report on Tungurahua (Ecuador) (Sennert, S, ed.). Weekly Volcanic Activity Report, 25 April-1 May 2007. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
IG reported that during 25, 27-29 April, and 1 May, ash plumes from Tungurahua rose to altitudes of 5.8-7.5 km (19,000-24,600 ft) a.s.l. and drifted SW and W. Ashfall was reported in areas to the SW, W, and NW during 25, 29-30 April, and 1 May. On 25 April, muddy water flowed down river valleys to the NW and disrupted the road between Ambato and Baños. The next day, lahars traveled down almost all of the river valleys, but were most concentrated in valleys to the W. Lahars and muddy water flowed down NW and W river valleys on 27 and 30 April.
Geological Summary. 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 collapsed about 3,000 years ago and produced a large debris-avalanche deposit to the west. The modern glacier-capped stratovolcano (Tungurahua III) was constructed within the landslide scarp. 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.