Report on Tungurahua (Ecuador) — 21 March-27 March 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 21 March-27 March 2012
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2012. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 21 March-27 March 2012. 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 of Tungurahua during 21-25 March were occasionally limited due to cloud cover, steam plumes rose 0.5-4 km above the crater and drifted SW, W, NW, and NNE. On 21 March incandescence from the crater was observed and roaring noises were noted. The next day a steam-and-ash plume rose to a low height, and during 22-23 March ashfall was reported in Runtún (6 km NNE). Heavy rain during 24-25 March generated lahars in the Pampas area to the S and caused flooding in the sectors of Puela (8 km SW), Palitahua (S) and Ulba (NNE). Activity increased on 26 March. Roaring was heard in multiple areas. An ash plume rose 3 km above the crater and drifted NNE; ashfall was reported in Ventanas, Cusúa (8 km NW), Pondoa (about 8 km N), Baños (9 km N), San Francisco, and Río Verde.
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.