Report on Tungurahua (Ecuador) — 10 January-16 January 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 January-16 January 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, 10 January-16 January 2001. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
The IG reported that since 3 January, Tungurahua has had an increase in vapor-and-ash emissions from its 300-m-diameter summit crater. Planes have observed the ash plumes up to 7 km altitude. From the Guadalupe observatory, 11 km N of the cone, ash-laden columns to 3-4 km altitude were observed. No new explosive activity or incandescence has been seen since 22 October 2000. SO2 values, which had been at about 1,000 metric tons/day (t/d) have now risen to 2,000-2,400 t/d. Seismicity remains very low. New fumaroles have been observed since late November at 4,400 m elevation on the NW flank.
Based on reports from the IG, the Washington VAAC issued aviation notices of ash over the volcano on the afternoon of 10 January to an altitude of 6.4 km. Cloudiness made satellite observations difficult, but a pilot reported ash to 7 km altitude over the volcano in the early afternoon of the 11th.
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.