IG reported that the low-level eruption at Cotopaxi continued during 14-20 December, characterized by daily steam-and-gas emissions with low ash content. At 0626 on 14 December an ash emission rose 500 m above the crater rim and drifted W, causing ashfall within Parque Nacional Cotopaxi. Weather clouds sometimes obscured views of the volcano; between weather clouds during 14-16 December steam-and gas plumes with low ash content were seen rising as high as 500 m above the crater rim and drifting W. Several emissions with low or very low ash content rose as high as 800 m above the crater rim and drifted W and SW during 16-17 December; similar emissions rose as high as 1.1 km above the crater rim and drifted W and SW during 18-20 December based on webcam views and Washington VAAC notices. Ashfall was reported in San Pedro de Taboada (40 km N), Uyumbicho (30 km NNW), Güitig Alta, Güitig Baja, Conocoto (42 km N), Sur de Quito, Chimbacalle (48 km NNW), La Magdalena (48 km NNW), Barrio Nuevo, Villaflora (48 km NNW), Miraflores, and La Floresta (50 km N) during 19-20 December. 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)