Report on Tungurahua (Ecuador) — 4 April-10 April 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
4 April-10 April 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, 4 April-10 April 2007. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
IG reported that during 3-5 April, ash plumes from Tungurahua rose to altitudes of 8-9 km (26,200-29,500 ft) a.s.l. and drifted NW and W. Ashfall was reported at areas to the SW on 4 April. On 3 April, blocks rolled 800 m down the W flank; noises indicating rolling blocks were heard on 5 and 6 April. Lahars descended the W flank on 6 April. During 6-8 April, ash plumes, occasionally accompanied by roaring noises and "cannon shots", rose to altitudes of 7-10.5 km (23,000-34,400 ft) a.s.l. and drifted mainly W and NW. Ashfall was reported from areas about 8 km NW and SW from the summit on 6 April. On 9 April, ashfall was reported from areas 8 km W. On 10 April an explosion occurred. Incandescence was seen at the summit and blocks rolled about 100 m down the flanks. Clouds occasionally inhibited visual observations 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 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.