Report on Tungurahua (Ecuador) — 1 April-7 April 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 April-7 April 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, 1 April-7 April 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 that, although cloud cover often prevented visual observations of Tungurahua’s crater during 1-5 April, minor steam emissions were occasionally seen. On 6 April at 0356 tremor began to be detected and was associated with steam-and-ash emissions which rose 1 km above the crater. Noises were reported at 0730 and ashfall was reported in Cahuaji (8 km SW), Chacauco (NW), Manzano (8 km SW), and Punzupal Alto. Later that day an ash plume drifted W. Emissions in the early afternoon rose no higher than 1 km. On 7 April cloud cover prevented views of the crater most of the day; ashfall was reported in Palitahua (6 km SSW), and a water vapor-and-ash plume rose 1 km and drifted NW. Two explosions were detected by the seismic network.
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.