IG-EPN reported that an eruption at Reventador was ongoing during 13-20 August. Seismicity was characterized by 43-100 daily explosions on most days, along with long-period earthquakes, harmonic tremor, and tremor associated with emissions during the beginning of the week; data transmissions from the seismic station were occasionally interrupted. Several ash-and-gas plumes were observed on most days rising 300-800 m above the crater rim and drifting N, WNW, and W. Weather conditions occasionally prevented visual observations, particularly on 16 August. Thermal anomalies in the crater were identified in satellite images on most days. Secretaría de Gestión de Riesgos maintained the Alert Level at Orange (the second highest level on a four-color scale).

Geological Summary. Volcán El Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic stratovolcano has 4-km-wide avalanche scarp open to the E formed by edifice collapse. A young, unvegetated, cone rises from the amphitheater floor to a height comparable to the rim. It has been the source of numerous lava flows as well as explosive eruptions visible from Quito, about 90 km ESE. Frequent lahars in this region of heavy rainfall have left extensive deposits on the scarp slope. The largest recorded eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN), Secretaría de Gestión de Riesgos (SGR)