Report on Tungurahua (Ecuador) — 22 April-28 April 2009
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 22 April-28 April 2009
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2009. Report on Tungurahua (Ecuador) (Sennert, S, ed.). Weekly Volcanic Activity Report, 22 April-28 April 2009. 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 22-28 April steam-and-gas plumes occasionally containing ash rose from Tungurahua to an altitude of 6.5 km (21,300 ft) a.s.l. and drifted SW and W. Roaring noises were reported. Ashfall was noted in areas to the SW on 21 April. During 21-22 April, incandescence from the crater was seen; incandescent blocks ejected from the crater on 22 April rolled down the flanks. On 25 April, a lahar descended the Patacocha drainage.
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.