Report on Tungurahua (Ecuador) — 15 February-21 February 2012
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 15 February-21 February 2012
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2012. Report on Tungurahua (Ecuador) (Sennert, S, ed.). Weekly Volcanic Activity Report, 15 February-21 February 2012. 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 continuing activity at Tungurahua during 15-21 February. Increased seismicity and constant harmonic tremor were detected on 16 February. Based on information from the Guayaquil MWO and IG, the Washington VAAC reported that during 17-18 February emissions rose to an altitude of 6 km (19, 500 ft) a.s.l. IG also noted that a steam plume with small amounts of ash drifted WSW on 19 February and W on 21 February.
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.