Report on Tungurahua (Ecuador) — 7 July-13 July 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 7 July-13 July 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 7 July-13 July 2010. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
Observations of Tungurahua's summit area during 7-13 July were often not possible due to inclement weather. On 7 July steam-and-ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. and drifted WSW. The next day explosions were accompanied by acoustic waves. A steam plume rose to an altitude of 8 km (26,200 ft) a.s.l. and drifted NW. Ashfall was reported in Cusúa about 8 km downwind. Incandescence from the crater was seen during both nights. Ash-and-steam plumes were seen on 9 July. Ashfall was reported in a few areas 8 km SW and W. On 10 and 12 July plumes with low ash content drifted W. Ashfall was reported 7-8 km to the W and NNW on 12 July. Incandescent blocks descended the flanks at night to 500 m below the crater on 9 and 12 July.
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.