Report on Tungurahua (Ecuador) — 21 January-27 January 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
21 January-27 January 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Tungurahua (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 21 January-27 January 2004. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
During 21-26 January, Tungurahua continued to emit gas, steam, and ash. Emissions rose to ~1 km above the crater, with variable amounts of ash in the resultant plumes. On 22 January at 0626 an explosion sent a plume to ~2 km above the volcano. On the evening of 24 January ash fell in the areas of Puela and Penipe (~ 8 km SW of the volcano), and ash fell during 24-25 January in the city of Riobamba (~ 30 km SW of the volcano). During the report period, low-level seismicity occurred.
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 collapsed about 3,000 years ago and produced a large debris-avalanche deposit to the west. The modern glacier-capped stratovolcano (Tungurahua III) was constructed within the landslide scarp. 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.