Report on Tungurahua (Ecuador) — 27 February-5 March 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 27 February-5 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, 27 February-5 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 seismicity at Tungurahua increased on 28 February. The next day an increase in the number of long-period earthquakes was accompanied by small explosions, roaring, and ash emissions. At around 1600 on 1 March a plume of water vapor and gas containing small amounts of ash rose a few hundred meters above the crater and drifted WNW. Ashfall was reported in areas on the SW flank including Choglontús (SW) and Manzano (8 km SW). On 2 March an explosion at 1106 produced noises from blocks rolling down the flanks. Instruments detected deformation on the NW flank. Cloud cover during 1-2 March inhibited visual observations.
At night during 2-3 March incandescent blocks were ejected from the crater and rolled 300 m down the flanks. Seismicity again increased on 3 March. Ash plumes rose from the crater and produced ashfall in Manzano and Penipe (15 km SW). Cloud cover prevented views on 4 March, however ashfall was reported in Manzano. On 5 March explosions produced an ash plume that rose 1-1.5 km above the crater and drifted W.
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.