Report on Tungurahua (Ecuador) — 8 August-14 August 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 August-14 August 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, 8 August-14 August 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 during 8-13 August visual observations of Tungurahua were limited due to cloud cover. A vapor emission drifted W on 8 August. A small explosion on 10 August vibrated windows, and ash fell in Choglontús (SW). Three to four explosions on 11 and 12 August produced "gun shot" noises. At night incandescence from the crater was observed and sounds resembling blocks rolling down the flanks were reported. On 11 August an ash-and-steam plume rose from the crater, and the next day an ash plume rose 1 km and drifted W. During 12-13 August incandescent blocks were ejected 100 m above the crater and rolled 500 m down the flanks. Roaring was heard and ash fell in Cusúa (8 km NW) and Juive (7 km NNW). On 14 August seismicity increased and was accompanied by increased emissions. Ashfall was reported in Pillate (7 km W), Cusúa, and Choglontús.
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.