Report on Tungurahua (Ecuador) — 19 September-25 September 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 19 September-25 September 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, 19 September-25 September 2001. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
During the week several moderate-sized explosions and low-level emissions of ash and gas occurred. An explosion on 20 September at 1044 produced an ash cloud that rose to 2 km above the volcano and drifted to the WSW. The explosion was accompanied by loud roaring and the sound of rockfalls. Small amounts of ash fell in Pillate, Juive, and Runtún. The explosion was preceded by tremor for approximately 3 hours. On 21 September at 1625 another moderate-sized explosion produced an ash cloud that rose to 3 km above the volcano's summit and drifted to the NW. During the night incandescence was visible at the volcano's crater.
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.