Report on Tungurahua (Ecuador) — 15 August-21 August 2007
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 15 August-21 August 2007
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2007. Report on Tungurahua (Ecuador) (Sennert, S, ed.). Weekly Volcanic Activity Report, 15 August-21 August 2007. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
Based on seismic interpretation, IG reported explosions and ash emissions from Tungurahua during 15-21 August. During 17-18 August, roaring and "cannon shot" noises were reported and ashfall occurred in areas to the W and SW. On 19 August, "cannon shot" noises were again reported and a gas-and-ash plume rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted W. Explosions on 20 and 21 August rattled windows at the Tungurahua Observatory (OVT) in Guadalupe, 11 km N, and in houses in areas to the W. Ashfall was reported in areas to the SW on 21 August. Inclement weather inhibited visual observations on other days.
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.