Report on Tungurahua (Ecuador) — 15 August-21 August 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 15 August-21 August 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Tungurahua (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 15 August-21 August 2001. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
The series of eruptions that began at Tungurahua on 6 August continued during the week. Seismic activity was characterized by many long-period earthquakes and seismic signals that represented ash emissions. Several sporadic explosions occurred, with the largest explosion beginning on 15 August at 2231. The eruption produced an ash cloud that rose to 12.2 km a.s.l. IG reported that on 17 August volcanic activity increased slightly and incandescent material was ejected up to 1 km W of the crater. According to news reports, as of 15 August ash affected more than 23,000 people, blanketed approximately 89,000 acres of crops, and killed an undetermined number of livestock. The Alert Level remained at Yellow in the town of Baños and at Orange for the rest of the population in the high-risk zone, as it has since 5 September 2000.
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.