Report on Tungurahua (Ecuador) — 11 February-17 February 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 February-17 February 2009
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 11 February-17 February 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 although visual observations of Tungurahua were occasionally limited due to cloud cover; gas-and-ash plumes were seen and rose to altitudes of 5.5-7.5 km (18,000-24,600 ft) a.s.l. during 11-17 February. Plumes drifted W, NE, E, and SE. On 11 February, small lahars descended multiple gorges to the NW and S. Incandescence in the crater was seen at night on 11 and 12 February, and roaring was heard on 12 and 16 February. Ashfall was reported in areas to the SW on 12 February and to the N on 14 February. An explosion on 16 February that vibrated windows was followed by ash emissions that generated a plume to an altitude of 8 km (26,200 ft) a.s.l. The plume drifted W.
Geologic Background. 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 itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. 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.