IG reported that eruptive activity at Cotopaxi was ongoing during 4-11 April. Gas, steam, and ash plumes visible in webcam images and reported by the Washington VAAC during 4-6 and 8 April rose 200-800 m above the summit and drifted E, SE, S, and SW. Minor ashfall was reported in Mulaló (9.5 km WSW) and San Agustín (10 km W). Gas-and-steam plumes rose 300 m and drifted S and SE on 7 April. On 10 April ash plumes rose 1-1.5 km and drifted W, SW, and SE. Weather clouds prevented visual observations on the other days. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest level on a four-color scale).

Geological Summary. The symmetrical, glacier-covered, 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 edifice has been constructed since a major collapse sometime prior to about 5,000 years ago. Pyroclastic flows (often confused in historical accounts with lava flows) have accompanied many explosive eruptions, and lahars have frequently devastated adjacent valleys. Strong 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. Smaller eruptions have been frequent since that time.

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN), Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE)