Report on Tungurahua (Ecuador) — 22 November-28 November 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 November-28 November 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, 22 November-28 November 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 21-28 November, emissions from Tungurahua produced ash and steam plumes that reached altitudes of 6-9 km (19,700-29,500 ft) a.s.l. and drifted predominantly NW and W. Ashfall about 1 mm thick was reported from areas 8 km WSW on 21 November and from areas 8 km W on 25 November. During 26-27 November, Strombolian activity propelled incandescent material up to 600 m above the summit. Blocks rolled 2 km down the flanks. Lightning was visible in an ash plume that reached 7 km (23,000 ft) a.s.l. and ashfall was reported from areas 8 km WSW. On 27 November, an ash plume rose to 9 km (29,500 ft) a.s.l. and drifted W.
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.