Report on Tungurahua (Ecuador) — 30 July-5 August 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 30 July-5 August 2014
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2014. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 30 July-5 August 2014. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
During 30 July-5 August IG reported that Tungurahua had moderate and increasing levels of seismicity. On 1-4 August ash plumes rose 1-4 km (3,300-13,100 ft) a.s.l. and drifted N, NW, W, SW, and E. Incandescent blocks ejected 700-1000m above the crater and traveled 500-700m down the flanks of Tungurahua from an explosion on 1 August, followed by 4 small to moderate explosions on 3 August and an explosion 4 August that rattled the observatory. IG reported incandescence within the crater on 2-4 August; observations were supplemented with a thermal camera when the summit was obscured by clouds. Washington VAAC reported ash emissions on 1-5 August that rose 6-8.5 km (20,000-28000 ft) a.s.l. Ashfall was reported in Choglontús, El Manzano, Motilones, Cusúa, Tisaleo, Mocha, Bilbao, Pillate, Chacauco, Pondoa, Sua, Cevallos, Motilones, Quero, Rumipamba, Yanayacu, Pinchicoto, and Tizaleo.
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.