Report on Tungurahua (Ecuador) — 20 February-26 February 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
20 February-26 February 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Tungurahua (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 20 February-26 February 2002. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
During 19-24 February relatively low-intensity Strombolian activity continued at Tungurahua. In addition, there were several emissions of steam, gas, and ash. On the afternoon of 19 February a mixture of rain and ash fell in the Puela sector, and a small lahar traveled W to the Chontapamba sector. That evening, low-intensity Strombolian activity was observed. On the 20th at 2127, incandescent blocks were emitted that rolled down the flank to the Refugio de Pondoa. The next day during 0752-0905 ash columns reached 2 km above the volcano and drifted to the SW. Since 5 September 2000 the volcano has been at Alert Level Yellow for the town of Baños and at Orange for the rest of the population in the high-risk zone.
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.
Sources: Washington Volcanic Ash Advisory Center (VAAC), Instituto Geofísico-Escuela Politécnica Nacional (IG)