Report on Tungurahua (Ecuador) — 20 June-26 June 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 June-26 June 2007
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2007. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 20 June-26 June 2007. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
The IG reported that during 20-25 June mudflows and lahars traveled on the S, W, NW, and N flanks of Tungurahua and interrupted traffic. A steam plume with little ash content was observed on 21 June. On 22 June, ashfall was reported SW in Choglontus and roaring noises were heard. A small landslide occurred on the edge of the Chambo river; another landslide affected a highway. On 23 June, a steam plume with little ash content rose to an altitude of 5.8 km (19,000 ft) a.s.l. and drifted W. The next day, ashfall was reported. During 23-24 June, roaring noises were heard.
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.