Report on Tungurahua (Ecuador) — 5 November-11 November 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 5 November-11 November 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Tungurahua (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 5 November-11 November 2003. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
Tungurahua maintained a generally low level of activity, with occasional plumes (often ash-poor) rising to less than 1 km above the summit. In contrast, a few ash-bearing emissions occurred. For example, on 5, 6, and 7 November there were ash falls of low intensity in the volcano's eastern sector. On the 6th two larger than average explosions were recorded seismically, one associated with an ash column rising to 2 km a.s.l. On the latter day there was also a modest. During this week, tremor represented a key seismic signal, with relatively few earthquakes.
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.