Report on Tungurahua (Ecuador) — 14 July-20 July 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 July-20 July 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 14 July-20 July 2010. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
Observations of Tungurahua's summit area during 13-20 July were sometimes not possible due to inclement weather. On 13 July incandescent blocks were seen rolling down the flanks at night and ashfall was reported in areas 8 km SW. Incandescence from the crater was seen the next night and ashfall was again reported in areas to the SW. During 15-18 July steam-and-ash plumes were observed and occasionally drifted SW. Ashfall was noted in areas within 8 km SW, W, and NW. Lahars descended drainages to the SW, NW, and N on 15 July. Rolling blocks on the flanks were seen after explosions on 18 July. During 19-20 July steam plumes drifted NW and 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.