Report on Tungurahua (Ecuador) — 14 March-20 March 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 March-20 March 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, 14 March-20 March 2007. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
IG reported that during 14-20 March, explosions from Tungurahua were accompanied by noises that resembled "cannon shots." On 16, 18, and 20 March, explosions rattled windows at the observatory in Guadalupe, about 11 km N. Incandescent material was ejected 100-200 m above the summit on 14, 16, and 20 March and rolled 500-800 m down the flanks on 16,18, and 20 March. Ash plumes rose to altitudes of 6.5-12 km (21,300-39,400 ft) a.s.l. during the reporting period and drifted mainly NW and W. Ashfall was reported as far as Cotaló (13 km NW) on 16 March and from other areas S, W, and NW during 14-20 March. Rainfall contributed to lahars in valleys W and NW on 15 and 16 March.
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.