Report on Tungurahua (Ecuador) — 9 January-15 January 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 9 January-15 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, 9 January-15 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 released a special report on 9 January noting that increased seismic activity at Tungurahua was comparable to that of the few days prior to the eruption of 14 July, 2006.
IG reported that although visual observations were occasionally limited due to cloud cover, ash-and-steam and ash plumes were observed and rose to altitudes of 6-9 km (19,700-29,500 ft) a.s.l. during 9-15 January. Ashfall was reported almost daily in areas to the NE, N, NW, W, and SW. Roaring noises and "cannon shots" were heard daily and windows and floors vibrated on 9, 10, 12, and 15 January, as far away as the Tungurahua Observatory (OVT) in Guadalupe, about 13 km NW. Incandescence at the summit was observed and incandescent blocks rolled 0.5-1 km down the flanks. On 11 January, Strombolian activity at the summit crater was observed and blocks rolled 600 m down the flank.
According to news articles, residents from two provinces continued to evacuate at night and about 20,000 health masks were distributed to residents from Baños and Quero.
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.