Report on Tungurahua (Ecuador) — 26 July-1 August 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
26 July-1 August 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 26 July-1 August 2006. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
On 26 July, the United Nations Office for the Coordination of Humanitarian Affairs (OCHA) reported that, according to the Ecuadorian Civil Defense, approximately 13,000 people had been severely affected by the eruption of Tungurahua. About 815 remained in shelters.
During 26 July-1 August, eruption columns with small-to-moderate ash content reached an altitude of ~9 km (~30,000 ft) a.s.l. Ash fall was reported in Pillate, ~ 7 km to the W on 27-29 and 30 July, as far as Baños ~12 km N and Puela ~8 km S on 29 July and Cotaló ~13 km NW on 30 July. On 27 July, incandescent material from explosions descended ~1 km down the flanks. A thermal anomaly was observed on satellite imagery during the reporting period.
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.