Report on Tungurahua (Ecuador) — 16 January-22 January 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 January-22 January 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 16 January-22 January 2008. 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 although visual observations were occasionally limited due to cloud cover, ash plumes were spotted and rose to altitudes of 5.5-9 km (18,000-29,500 ft) a.s.l. during 16-22 January. Ashfall was reported daily in areas mainly to the W, SW, and NW, and was heavy on 20 January. Roaring noises and "cannon shots" were heard frequently and windows and floors vibrated on 15, 20, and 21 January, as far away as the Tungurahua Observatory (OVT) in Guadalupe, about 13 km NW. On 16 January, incandescent blocks were propelled 200 m above the crater during a Strombolian eruption phase and blocks rolled 1 km down the flank. Three explosions produced blocks that rolled 2 km down the flanks. A small pyroclastic flow traveled 400 m down the NW side of the crater. Incandescence at the crater was again noted on 17 and 21 January.
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.