Report on Tungurahua (Ecuador) — 30 June-6 July 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 30 June-6 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, 30 June-6 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 30 June-6 July were mostly not possible due to inclement weather. On 2 July, gas plumes were seen drifting WSW during breaks in the cloud cover. Ashfall was reported in areas 8-9 km W and SW, and as far away as 40 km WSW in San Juan. Incandescence from the crater was seen at night and slight roaring was heard. Ashfall was again reported in areas 8-9 km W and SW during 3-4 July. Steam-and-ash plumes were seen on 5 July and rose to an altitude of 7 km (23,000 ft) a.s.l. Ash fell in areas 8 km to the SW. Steam-and-ash plumes were again seen on 6 July; ashfall was reported in areas 8 km W, NW, and N.
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.