Report on Tungurahua (Ecuador) — 11 March-17 March 2009
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 11 March-17 March 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, 11 March-17 March 2009. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
On 11 March, IG reported that a steam-and-ash plume from Tungurahua rose 600 m above the summit and drifted E and NE. Fumaroles on the NE flank were active. On 12 and 16 March, plumes with low ash content rose to altitudes of 6-7 km (19,700-23,000 ft) a.s.l. and drifted NE. Steam plumes were occasionally seen during 13-14 and 17 March, and a plume rose 300-500 m above the summit and drifted E and W on 15 March.
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.