Report on Tungurahua (Ecuador) — 24 December-30 December 2008
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 24 December-30 December 2008
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2008. Report on Tungurahua (Ecuador) (Sennert, S, ed.). Weekly Volcanic Activity Report, 24 December-30 December 2008. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
The IG reported that during 23 and 25-29 December ash plumes from Tungurahua rose to altitudes of 6-9 km (19,700-29,500 ft) a.s.l. and drifted mostly S, SW, W, and NW. On 23 December incandescent material rolled down Tungurahua's flanks and a possible pyroclastic flow traveled 700 m down the NW flank. Ashfall was reported and explosions vibrated windows and the ground in areas to the SW. During 24-29 December roaring and "cannon shot" noises were reported almost daily; windows and the ground vibrated on 24, 28, and 30 December. A lahar traveled SW down the Mapayacu ravine on 27 December. Incandescence at the summit and ashfall in areas downwind were noted on 25, 26, 28, and 29 December. Explosions ejected blocks that rolled 500 m down the flanks on 25 December, 1500 m on 29 December, and 800 m on 30 December. On 30 December heavy black ash fell in areas to the SW.
Geological Summary. 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 collapsed about 3,000 years ago and produced a large debris-avalanche deposit to the west. The modern glacier-capped stratovolcano (Tungurahua III) was constructed within the landslide scarp. 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.