Report on Tungurahua (Ecuador) — 11 January-17 January 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 January-17 January 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, 11 January-17 January 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 and increased seismicity from Tungurahua during 11-17 January. On 12 January ashfall was reported in Manzano (8 km SW), Cahuají (8 km SW), and Choglontus (13 km WSW). A lahar descended the Achupashal drainage, carrying blocks up to 1 m in diameter, and caused the road to Baños (9 km N) to be closed. Cloud cover prevented observations of the crater. On 13 January ash-and-gas emissions were observed, and ash plumes rose as high as 7 km (23,000 ft) a.s.l. and drifted W. Ash-fall was reported in Palitahua (6 km SSW) and roaring noises were heard in Cusúa (8 km NW) and Manzano. On 14 January ash emissions rose 500 m above the crater and drifted WSW; ashfall was reported in Choglontus, Palitahua, and Manzano. Clouds obscured views on 15 January; however ashfall was reported in Palitahua and Manzano. Lahars descended drainages in Juive (NW) and Pondoa (N), carrying blocks 10-20 cm in diameter.
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.