Report on Tungurahua (Ecuador) — 22 February-28 February 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 February-28 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, 22 February-28 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 moderate activity at Tungurahua during 22-28 February. Steam plumes with some ash content rose to altitudes of 1-2 km (3,300-6,500 ft) a.s.l. and drifted W during 22-24 February. Ash fall was reported in Palitahua (6 km SSW), Choglontus (13 km WSW), and Manzano (8 km SW) on 23 February, and in the Mapayacu (SW) and Achupashal (NW) gorges on 24 February. Strombolian activity was observed on 24 February, and incandescence material that rose as high as 500 m above the crater fell on the W and NW flanks. Ashfall was reported to the SW in Manzano again on 25 February. A steam-and-ash plume rose as high as 800 m above the crater and drifted W on 26 February. Crater incandescence was observed on 23 and 27 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.