Report on Tungurahua (Ecuador) — 11 April-17 April 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 April-17 April 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, 11 April-17 April 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 based on visual observations and reports from pilots, ash plumes from Tungurahua rose to altitudes of 6.7-8 km (22,000-26,200 ft) a.s.l. and drifted NNW on 11 April. Fumarolic activity originated from the NE and E edges of the crater. During 12-17 April, ash plumes, occasionally accompanied by roaring, rose to altitudes of 5.8-8 km (19,000-26,200 ft) a.s.l. and drifted mainly W. Ashfall was reported from areas downwind on 12 April. During 13-14 April, Strombolian activity was observed; incandescent material was ejected about 200-300 m above the summit and blocks descended 500-800 m down the flanks. During 15-17 April, lahars descended several NW, W, and SW valleys. In the Pampas sector, lahars with blocks 50 cm in diameter disrupted the roads between Ambato and Baños, and between Baños and Penipe.
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.