Report on Tungurahua (Ecuador) — 2 June-8 June 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 2 June-8 June 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, 2 June-8 June 2010. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
Although storm clouds often prevented observations of Tungurahua's summit area during 1-8 June, steam-and-ash plumes generated by explosions were sometimes seen and rose to altitudes of 6-8 km (19,700-26,200 ft) a.s.l. Larger explosions occasionally produced ash plumes that rose as high as an altitude of 9 km (29,500 ft) a.s.l. Daily reports of ashfall came from multiple areas within about 8 km NW, W, and SW. Explosions ejected blocks (that were occasionally incandescent) almost daily as high as 1 km above the crater rim. The blocks that fell outside of the crater descended the flanks a maximum distance of 2 km. Noises resembling "cannon shots" associated with explosions were often followed by vibrating windows and doors in local areas; on 6 June large windows vibrated at Tungurahua Observatory (OVT) in Guadalupe, 11 km N.
On 2 June a pyroclastic flow traveled 1.5 km down the NW flank. During 5-7 June ashfall was noted in areas farther away, including at OVT and Cevallos, 23 km NW. Explosions on 7 and 8 June generated ash plumes that rose to altitudes of 9-10 km (29,500-32,800 ft) a.s.l. and drifted W. On 7 June another small pyroclastic flow traveled 1.5 km down the NW flank.
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.