Report on Tungurahua (Ecuador) — 10 December-16 December 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 December-16 December 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 December-16 December 2008. 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 activity from Tungurahua on 15 December was characterized by increased seismicity, ash emissions, and the ejection of incandescent blocks. Ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. and drifted NE. Ashfall was reported 6 km NNE in Runtún. Observers at the Tungurahua Observatory (OVT) in Guadalupe, 11 km N, saw incandescent blocks ejected from the summit fall onto the W flank. Later that night, ash plumes rose to altitudes of 7 km (23,000 ft) a.s.l. and incandescence was seen at the summit. Emissions with variable ash content were seen on 16 December.
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.