Report on Tungurahua (Ecuador) — 6 June-12 June 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 June-12 June 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Tungurahua (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 6 June-12 June 2001. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
A SIGMET from the Guayaquil MWO noted that the IG reported ash to 7 km a.s.l. moving W on 5 June at 1200. Considerable cloudiness over and around the summit made it difficult to detect any ash in satellite imagery. Similar reports were made on 6 June at 2324 and on 11 June at 1602, but no estimates of ash cloud heights were possible. Based on the seismic record, the 11 June explosion was a small event. A lahar was also observed on the morning of 11 June that moved down the Quebrada Achupashal.
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.