Report on Tungurahua (Ecuador) — 29 April-5 May 2009
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 29 April-5 May 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, 29 April-5 May 2009. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
During 28 April-5 May, IG reported that, although inclement weather often prevented observations of Tungurahua, steam-and-gas plumes were seen almost daily. The plumes rose to altitudes below 6.8 km (22,300 ft) a.s.l. and drifted SW and W. Lahars descended the Achupashal drainage to the NW on 28 April and the Motilones drainage to the W on 1 May. Incandescence in the crater was seen at night on 30 April. During 29 April and 2-3 May, noises and explosions rattled structures and windows. On 3 May, ashfall was reported in areas to the SW, NW, and N.
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.