Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that an eruption at Reventador was ongoing during 18-22 October. Seismicity was characterized by 59-92 daily explosions, 17-23 long-period earthquakes, and 5-17 tremor events associated with emissions. During 19-22 October there were 2-5 harmonic tremor events recorded. Ash-and-gas plumes were observed in webcam images and/or satellite images rising 200-1,000 m above the crater and drifted in different directions. Crater incandescence was visible during 18-21 October and incandescent material was reported descending the flanks as far as 1,000 m below the crater. According to a webcam image, a pyroclastic flow occurred at 1701 on 19 October, traveling 800 m below the crater on the SE flank. 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)