Report on Tungurahua (Ecuador) — 13 June-19 June 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 13 June-19 June 2007
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2007. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 13 June-19 June 2007. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
The IG reported that heavy and occasionally continuous rains resulted in mudflows and lahars on the flanks of Tungurahua during 12 and 14-16 June. On 12 June, lahars in the Pampas sector disrupted traffic on the route between Ambato and Baños for several hours. Traffic was again disrupted on 14 June and lahars occurred in W and SW drainages. A potable water system in a locality to the SW was affected by one of the lahars. Slight ashfall was reported from Bilbao, about 8 km to the W. On 15 June, lahars traveled in NW, W, and SW drainages. Mudflows interrupted traffic on the route between Ambato and Baños and dragged blocks 1 m in diameter in the W-flank Mandur drainage. According to the Washington VAAC, IG reported that an ash plume rose to an altitude of 5 km (16,500 ft) a.s.l. and drifted WSW. Ash was not visible on satellite imagery. During 15-16 June, heavy rains led to a landslide in the Peras Pamba sector near Cusúa (8 km NW) that blocked the flow of the Chambo river for about 20 minutes. Mudflows continued to affect the Pampas sector on 16 June. On 18 June, an ash plume rose to an altitude of 7 km (23,000 ft) a.s.l. and drifted W.
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.