Report on Tungurahua (Ecuador) — 1 February-7 February 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 February-7 February 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, 1 February-7 February 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 a new episode of activity from Tungurahua on 4 February with an explosion that produced roaring heard 14 km NW in Palitahua and Guadalupe. On 4 February an ash plume rose to altitudes of 7-8 km above the crater and drifted NE; lapilli fall was reported in Baños (9 km N), Pillate (7 km W), and Juive (7 km NNW). IG staff aboard a commercial flight on 4 February observed an ash plume that rose to an altitude of 1 km above the crater and drifted W. Ashfall and roaring noises were reported in Baños, Pillate, Juive, Pondoa (8 km N), Pelileo ( about 7 km NW), Guadalupe, Cevallos (23 km NW), and Patate (NW). A pyroclastic flow descended into the Achupashal drainage (NW). At night incandescent blocks ejected by an explosion traveled 1 km down the flanks. On 5 February clouds prevented views of the volcano, though loud "cannon shots" were heard in Baños and Juive, and ashfall was reported in Manzano (8 km SW). Clouds prevented views of the volcano during 6-7 February.
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.