Report on Tungurahua (Ecuador) — 2 March-8 March 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 2 March-8 March 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2016. Report on Tungurahua (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 2 March-8 March 2016. 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 moderate-to-high levels of Strombolian activity at Tungurahua continued during 2-8 March. Daily explosions were often accompanied by roaring and sounds resembling gunshots, and often caused local structures to vibrate. Steam-and-ash plumes rose from the crater daily often to heights less than 2.5 km above the crater and drifted NW, WNW, W, and SW; ash plumes rose 5 km on 4 March and to 6 km with a SE drift on 8 March. Ashfall was also reported daily in areas including Chontapamba (W), Pillate (8 km W), Bilbao (8 km W), Chacauco (NW), Juive (NW), Quero (20 km NW), Cusúa (NW), Choglontús (13 km WSW), Pelileo (8 km N), El Manzano (8 km SW), Vazcún (N), and Pondoa (N). Strombolian explosions observed nightly ejected incandescent blocks that rolled as far as 2 km down the flanks.
At 1020 on 4 March an explosion vibrated windows and generated an ash plume that rose 3 km above the crater. A pyroclastic flow traveled 1 km down the Romero drainage, and at 1152 another pyroclastic flow traveled 500 m down Achupashal (NW) drainage. On 6 March another explosion was followed by pyroclastic flows that traveled 1 km down the Achupashal, Rea, Pondoa (N), and Mandur (NW) drainages. Pyroclastic flows on 8 March traveled as far as 2.2 km down the Mandur, Romero, Bilbao, Juive, and Achupashal drainages.
On 5 March lahars descended the ravines of Achupashal, Juive, Pondoa, Mandur, Pingullo, Rea and Chontapamba; lahars in Pingullo and Cusúa led to the closure of the road.
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.