Report on Tungurahua (Ecuador) — 30 January-5 February 2008
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 30 January-5 February 2008
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2008. Report on Tungurahua (Ecuador) (Sennert, S, ed.). Weekly Volcanic Activity Report, 30 January-5 February 2008. 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 that although visual observations were limited due to cloud cover, ash plumes were spotted and rose to altitudes of 6-9 km (19,700-29,500 ft) a.s.l. during 30 January-5 February. Ash plumes drifted mainly W, NW, and E, and ashfall was also reported in areas to the SW, N, and NE. Roaring noises and "cannon shots" were heard almost everyday and the seismic network detected between 65-208 explosions daily.
On 30 January, incandescence at the summit was observed at night and incandescent blocks that were propelled from the summit by explosions rolled 600 m down the W flank. Explosions rattled windows as far away as the Tungurahua Observatory (OVT) in Guadalupe, about 13 km NW. A lahar descended the Mandur drainage, to the NW. On 1 and 4 February, incandescence at the summit was again noted and incandescent blocks traveled down the flanks. On 4 February, heavy ashfall to the SW was reported and explosions rattled windows in near-by areas. On 5 February, ashfall was reported in areas to the NW.
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.