Report on Tungurahua (Ecuador) — 25 February-3 March 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 February-3 March 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, 25 February-3 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)
The IG reported that, although cloud cover occasionally prevented visual observation during 24 February-3 March, ash plumes from Tungurahua were seen and rose to altitudes of 5.5-10 km (18,000-32,800 ft) a.s.l. The plumes drifted in multiple directions. Ashfall was reported almost daily in areas to the SW, W, NW, N, and NE. Blocks were sometimes seen or heard rolling down the flanks, and roaring or explosion noises were noted. Strombolian activity at the summit was observed at night on 24 and 25 February. On 25 February, explosions caused the ground and large windows to vibrate. An explosion on 1 March was followed by an ash plume that rose to an altitude of 10 km (32,800 ft) a.s.l. and drifted NW. Incandescence at the crater was noted at night on 2 March.
According to a news article from 3 March, ash covered at least 250 hectares of cropland, and additional land for cattle grazing.
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.