Report on Tungurahua (Ecuador) — 9 May-15 May 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 9 May-15 May 2007
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2007. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 9 May-15 May 2007. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
During 9-12 and 14 May, IG reported that ash plumes were visible from Tungurahua and rose to an altitude of 5.1 km (16,700ft) a.s.l. during 11-12 May. Plumes drifted W and NW. Ashfall was reported on 9 May in areas about 8 km to the SW and W and trace ashfall was reported about 30 km NW in Ambato. Incandescence at the summit was noted that evening. Ashfall was also reported on 10, 11, and 14 May from areas NW, SW, and W; on 11 May, the ashfall was red in color. Lahars and muddy waters that traveled into the Pampas sector and in NW ravines blocked the Baños-Penipe highway during the morning of 10 May. Muddy waters traveled in W ravines on 12 May and SW ravines on 14 May.
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.