Report on Tungurahua (Ecuador) — 17 May-23 May 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 17 May-23 May 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, 17 May-23 May 2006. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
During 17-20 May, ash emissions from Tungurahua increased. On 18 May, an ash plume reached a height of 5.2 km (17,000 ft) a.s.l. and extended NW, according to Washington VAAC reports. The Washington VAAC also noted that on 19 May, the Instituto Geofísico observed an ash plume that reached a height of 12 km (40,000 ft) a.s.l. On satellite imagery, ash plumes were visible on 20 and 23 May and extended SW. Hotspots were visible on satellite imagery 19-20 and 23 May. The ash plume and incandescence on 23 May were also observed by Instituto Geofísico staff.
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.