IG reported ongoing moderate eruptive activity at Cotopaxi during 26 April-2 May. Cloudy weather sometimes prevented webcam and satellite views, but emissions of steam-and-ash were visible on most days. On 26 April a gas plume with minor amounts of ash rose 500 m above the crater rim and drifted E. On 28 April an ash plume rose 800 m and drifted SE and W; ashfall was reported in the S part of Parque Nacional Cotopaxi. Gas-and-ash plumes rose 800 m and drifted W on 29 April, and two ash emissions rose 200-800 m and drifted SW and W on 30 April. At 0130 on 1 May the seismic network began recording a high-frequency signal that corresponded to the descent of a very small secondary lahar that remained within the bounds of Parque Nacional Cotopaxi. Gas-and-ash emissions rose 300 m and drifted W during 1-2 May. 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)