Report on Tungurahua (Ecuador) — 11 October-17 October 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 October-17 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, 11 October-17 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 an increase in emissions and seismicity at Tungurahua on 11 and 12 October. Steam plumes with slight to moderate amounts of ash reached heights of 9-12 km (29,500-39,500 ft) a.s.l. and resulted in light ashfall in areas NW and W. During 13-17 October, seismicity decreased and emissions produced plumes that reached heights of 7-8 km (23,000-26,000 ft) a.s.l. On 16 October, a small lava flow produced incandescent blocks and gas plumes. Lahars traveled NNW and NNE down the gorges of Vazcún and Ulba, respectively. Incandescence from the crater could be seen during most of the reporting period.
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.