Report on Tungurahua (Ecuador) — 20 September-26 September 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
20 September-26 September 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, 20 September-26 September 2006. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
During 20-26 September seismicity remained low, as Tungurahua continued to generate ash eruptions. Ash rose 2 km above summit (23,000 ft a.s.l.) on the afternoon of 21 September. Moderate ash emissions occurred again on 22 September. Three more ash emissions on 23 September caused ashfall in Penipe; one plume rose 3 km above the summit (26,000 ft a.s.l.), and another 4 km (29,500 ft a.s.l.). Ash plumes were seen again on 25 September.
Geological Summary. 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.