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Report on Tungurahua (Ecuador) — 12 September-18 September 2001

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 12 September-18 September 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, 12 September-18 September 2001. Smithsonian Institution and US Geological Survey.

Volcano Profile |  Weekly Report (12 September-18 September 2001)


Tungurahua

Ecuador

1.467°S, 78.442°W; summit elev. 5023 m

All times are local (unless otherwise noted)


During the week volcanic activity at Tungurahua was characterized by a large number of long-period earthquakes, near-summit ash-and-gas emissions, and sporadic small-to-moderate explosions. The highest ash cloud reached ~8 km a.s.l. On 11 September, and to a lesser extent on 12 September, ash fell to the N of the volcano in the towns of Pondoa, Runtun, and Baños. In addition, ash fell to the SW in Quero and Penipe, and mud flows were reported in Penipe. Explosions on 13 September deposited ash to the W of the volcano, affecting the towns of Juive, Cotalo, and Bibao. On the 15th ash fell to the SW in Riobamba and Penipe. On 16 September incandescent material was emitted from the volcano along with ash and gas. The Alert Level remained at Yellow in the town of Baños and at Orange for the rest of the population in the high-risk zone, as it has since 5 September 2000.

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.

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG), Washington Volcanic Ash Advisory Center (VAAC)