Report on Tungurahua (Ecuador) — 22 December-28 December 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
22 December-28 December 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 December-28 December 2010. 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 21-23 December steam-and-ash plumes rose from Tungurahua and drifted NW, W, and SW. Ash fell in Bilbao, 8 km W, on 22 December. On 23 December explosions caused windows to vibrate in Cusúa (8 km NW), Pondoa (8 km N), and Baños (9 km N), producing sounds resembling "cannon shots." One of the explosions ejected incandescent material that rolled down to the lower flanks. Another produced a steam-and-ash plume that rose to an altitude of 11 km (36,100 ft) a.s.l. and drifted W and NW.
On 24 December steam-and-ash plumes rose 8 km (26,200 ft) a.s.l. and drifted NW and SW. Explosions caused windows to vibrate and sounds resembling "cannon shots" were noted. On 25 December incandescent material was ejected from the crater and rolled 2 km down the flanks. Steam-and-ash plumes rose from the crater during 25-27 December; ashfall was reported in Choglontús (SW) on the 25th. Ash plumes observed on 28 December drifted W. Incandescence from the crater was also noted.
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 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.