Report on Tungurahua (Ecuador) — 23 September-29 September 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 September-29 September 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 23 September-29 September 2015. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
In a special report from 21 September, IG noted increased activity at Tungurahua during the previous two weeks, characterized by an increase in seismicity and the intensity of gas-and-ash emissions. An explosion on 19 September generated an ash plume that rose 2 km. Later that night weak glow from the crater was observed. Moderate levels of activity at Tungurahua were reported during 23-29 September; inclement weather often prevented visual observations. Seismicity significantly increased on 26 September, accompanied by emissions with high ash content that rose 500 m and ejected incandescent blocks that rolled 500 m down the NW flank. Ashfall was reported in Manzanó (8 km SW), Choglontus (13 km WSW), Caguají, and Palitahua (6 km SSW).
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.