Report on Tungurahua (Ecuador) — 19 December-25 December 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 19 December-25 December 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, 19 December-25 December 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 although visual observations were occasionally limited due to cloud cover, ash-and-steam and ash plumes from Tungurahua were observed and rose to altitudes of 6-8.5 km (19,700-28,000 ft) a.s.l. during 19-25 December. Plumes drifted SE, SW, and WNW. Ashfall was reported in areas to the SW, W, NW, and N. Roaring noises and "cannon shots" were heard almost daily and windows and floors vibrated on 19, 21, and 23-24 December. On 19, 22, and 23 December, incandescent blocks were seen rolling hundreds of m down the flanks. Sounds indicating rolling blocks on the flanks were reported during 20-22 December, but were not observed due to cloud cover.
According to news articles, nearly 1,200 people in Penipe were evacuated nightly by security and specific communities around the volcano remained at an Orange Alert level.
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.