Report on Tungurahua (Ecuador) — 8 August-14 August 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 August-14 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, 8 August-14 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)
Ongoing eruptions occurred at Tungurahua since at least 6 August at 0703, sending steam-and-ash clouds to 7.5-11.6 km a.s.l. The ash clouds primarily drifted towards the W. On 13 August three particularly strong emissions occurred at about 0630, 1200, and 1315. Afterward, two distinct areas of ash were visible in satellite imagery; one contained ash from the strong emissions, rose to ~11.6 km a.s.l. and drifted to the E; the other ash cloud was fed from continuous emissions and possibly rose to ~10 km a.s.l. and drifted to the SW.
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.