Report on Tungurahua (Ecuador) — 8 April-14 April 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 April-14 April 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, 8 April-14 April 2015. 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 minor ash emissions from Tungurahua were seen almost daily during 8-14 April, although cloud cover often prevented visual observations. During 7-8 April ash emissions rose 500-800 m above the crater and drifted NW, W, and SW; ashfall was reported in Quero (20 km NW), Guanto, Guazmo, Mirador, Santuario, and in the sectors of El Manzano (8 km SW), Pillate (8 km W), and Choglontus (13 km WSW). Ashfall was reported in Chonglontus on 9 April. Later that day a plume with low ash content drifted W. During 9-10 April seismicity increased to a high level, and "drumbeat" events were detected there for the first time during 16 years of monitoring. Ashfall was reported in El Manzano and Chonglontus. On 11 April an emission with low ash content drifted W. On 13 April a steam-and-ash plume drifted W and SW, causing ashfall in El Manzano. On 14 April an emission with low ash content drifted W; ash fell in Mapayacu.
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.