Report on Tungurahua (Ecuador) — 7 October-13 October 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 7 October-13 October 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 7 October-13 October 2015. 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-to-high seismic activity at Tungurahua during 7-13 October, characterized by long-period events, volcano-tectonic events, explosions, and signals indicating emissions. Cloud cover often prevented visual observations; steam-and-gas plumes were observed on a few days. Tremor began to be detected at 1340 on 11 October, and was accompanied by a gas-and-ash plume that rose 2 km above the crater. At 1906 incandescent blocks ejected from the crater rolled 500 m down the W flank. Later that night roaring, explosions, and falling blocks were heard, and structures in nearby towns vibrated. Ashfall was reported in Manzanó (8 km SW), Choglontus (13 km WSW), Pillate (8 km W), and Mocha (25 km W). Two small explosions took place on 12 October, ejecting blocks that rolled down the Cusúa (NW), Juive (NW), and Runtun drainages.
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.