Report on Cotopaxi (Ecuador) — 14 October-20 October 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 October-20 October 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Cotopaxi (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 14 October-20 October 2015. Smithsonian Institution and US Geological Survey.
0.677°S, 78.436°W; summit elev. 5911 m
All times are local (unless otherwise noted)
IG reported that during 14-20 October cloud cover sometimes obscured views of Cotopaxi although emissions were observed daily. Gas, steam, and ash plumes rose as high as 2 km above the crater and drifted W, NW, N, and E. Small lahars descended the NW flank during 14-15 October, and a small lahar traveled down the Agualongo gorge on 16 October. Ashfall was reported during 16-17 and 19-20 October in Ticatilín, Lasso (60 km N), Chasqui (48 km NNW), Agualongo, Mariscal Sucre (50 km NNW), Rumipamba, San Fernando (58 km NNW), Selva Alegre (54 km NNW), Rumiñahui (61 km N), Vallecito, Aloasí (23 km NW), Aloag (28 km NW), Jambelí, El Chaupi (24 km WNW), Tanicuchi (25 km SW), and Maldonado.
Geologic Background. Symmetrical, glacier-clad Cotopaxi stratovolcano is Ecuador's most well-known volcano and one of its most active. The steep-sided cone is capped by nested summit craters, the largest of which is about 550 x 800 m in diameter. Deep valleys scoured by lahars radiate from the summit of the andesitic volcano, and large andesitic lava flows extend to its base. The modern conical edifice has been constructed since a major collapse sometime prior to about 5000 years ago. Pyroclastic flows (often confused in historical accounts with lava flows) have accompanied many explosive eruptions, and lahars have frequently devastated adjacent valleys. The most violent historical eruptions took place in 1744, 1768, and 1877. Pyroclastic flows descended all sides of the volcano in 1877, and lahars traveled more than 100 km into the Pacific Ocean and western Amazon basin. The last significant eruption took place in 1904.