Report on Tungurahua (Ecuador) — 24 December-30 December 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
24 December-30 December 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Tungurahua (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 24 December-30 December 2003. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
During 24-30 December, there were emissions of gas, steam, and ash, and low levels of seismicity at Tungurahua. On 28 December emissions sent plumes ~1.5 km above the volcano's summit that drifted E and NE. Ash fell in the sector of Runtún NNE of the volcano and in the city of Baños on the volcano's N flank. On 30 December aircraft personnel reported an ash cloud ~800 m above the volcano. According to the Washington VAAC, during the report period ash was visible on satellite imagery to a maximum height of ~3 km above the volcano.
Geological Summary. 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.