Report on Tungurahua (Ecuador) — 18 October-24 October 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 18 October-24 October 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 18 October-24 October 2006. 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 during 18-19 October, emissions from Tungurahua increased in intensity and ash content and seismic tremor was continuous. During the night, lava fountains reached heights of 6 km (19,800 ft) a.s.l. and blocks rolled 800 m down the flanks. According to the Washington VAAC, a pilot reported an ash plume to an altitude of 8.5 km (28,000 ft) a.s.l. Ash plumes drifted NE and E and generated ashfall about 50 km E, in Puyo. According to news articles, about 300 villagers evacuated from the flanks. During 20-24 October, emissions continued and produced plumes to 7-8 km (23,000-26,000 ft) a.s.l. Ashfall was reported from towns on the N, NW, W, SW, and E flanks.
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.