IG reported that the eruption at Cotopaxi continued during 24-31 January, characterized by almost daily gas-and-steam and ash emissions; inclement weather conditions prevented views of the volcano on 29 January. During 24-25 January steam-and-gas plumes rose to the crater level and drifted W. During 26-27 January gas-and-ash plumes rose less than 1 km above the crater rim and drifted SW and W. Minor ashfall was reported in San Agustín de Callo (18 km WSW), Lima Villacís, Mulaló, Barrancas, Ticatilín and Caspi (20 km WSW), and San Ramon (127 km W). Steam-and-gas emissions rose 600 m and drifted S on 28 January. A significant increase in the size and density of ash emissions was evident in satellite images at 0820 on 30 January. The plumes rose as high as 2.5 km above the crater rim and drifted SW, S, and SE. Minor amounts of ash fell in Mulaló and Latacunga (18 km WSW). Ash plumes rose as high as 1.7 km and drifted S and SE on 31 January. 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.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)