Report on Tungurahua (Ecuador) — 28 February-6 March 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 28 February-6 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, 28 February-6 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 noises produced by material rolling down the flanks of Tungurahua, roars, and "cannon shots" were heard during 28 February-6 March. Visual observations were limited due to cloud cover. Based on pilot reports, the Washington VAAC reported on 28 February that an ash plume rose to an altitude of 7.6 km (25,000 ft) a.s.l. and drifted W. On 1 and 2 March, gas-and-ash plumes rose to altitudes of 7-10 km (23,000-32,800 ft) a.s.l. and also drifted W. Incandescent material was ejected above the summit and rolled down the N and NW flanks. During 4-5 March, ash plumes rose to altitudes of 10-12 km (32,800-39,400 ft) a.s.l. and drifted W and NW. During 4-6 March, explosions rattled windows in Guadalupe, about 11 km N, and Baños, about 8 km N. Ashfall was reported from areas to the SW during the reporting period.
According to news articles, authorities conducted a voluntary evacuation of about 100 families on 5 March due to increased activity at Tungurahua.
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.