Report on Tungurahua (Ecuador) — 20 March-26 March 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 March-26 March 2013
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2013. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 20 March-26 March 2013. 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 during 18-20 March seismicity at Tungurahua was high. Although cloud cover often prevented observations, steam-and-ash plumes were observed rising as high as 1 km above the crater. Slight ashfall was reported in Riobamba (30 km S) on 18 March. Seismicity declined on 21 March and continued to trend downward during 22-26 March. A small lahar descended the Chontapamba drainage (W) on 21 March. Steam plumes drifted W on 22 March, and were again observed during 25-26 March. A plume with low ash content rose 1 km above the crater on 24 March and drifted N. Slight roaring was reported from El Manzano (8 km SW).
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.