Report on Tungurahua (Ecuador) — 2 January-8 January 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 2 January-8 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, 2 January-8 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-and-steam and ash plumes from Tungurahua were seen and rose to altitudes of 5.5-8 km (18,000-26,200 ft) a.s.l. during 2-8 January. Plumes drifted NW and W. Ashfall was reported in areas to the W and SW during 3-4 and 7-8 January.
On 1 January, ash emissions were continuous and incandescent blocks rolled down the flanks. Roaring noises and "cannon shots" were heard, and the ground and windows vibrated in areas to the NNE and NNW. On 3 January, the seismic network recorded a high number of explosions. Some explosions caused acoustic waves similar to "cannon shots" that vibrated windows in areas to the W and NW. These explosions ejected incandescent blocks from the summit crater that rolled 500 m down the flanks. On 4 January, "cannon shots" were again noted as far as 13 km away; this caused large windows to vibrate in areas to the W and glass to break in Puñapí. Explosions vibrated the ground in one town and generated ash plumes that rose to an altitude less that 6 km (19,700 ft) a.s.l. During 5-8 January, roaring noises and "cannon shots" continued; windows and floors vibrated as far as the Tungurahua Observatory (OVT) in Guadalupe, about 13 km NW, on 6 January.
According to news articles, nearly 1,000 people were evacuated on 6 January to spend the night in evacuation shelters. They were allowed to return to their villages in the daytime to tend to homes, crops, and animals.
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.