IG-EPN reported that the eruption at Reventador was ongoing during 18-25 July. Seismicity was characterized by 16-40 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Weather clouds often hindered visual observations, though crater incandescence was visible on most nights and early mornings, and material was seen descending the flanks. Ash-and-gas plumes rose 400 m above the crater rim and drifted NW on 19 July. Crater incandescence was visible during the night of 20-21 July and incandescent blocks rolled 500 m down the flanks. An explosion at 0804 on 22 July produced a plume with moderate amounts of ash that rose 500 m above the crater rim. An explosion at 0509 on 23 July ejected incandescent material onto the flanks that descended 500 m. Ash emissions on 24 July rose less than 200 m and drifted NW. Incandescent material was ejected as far as 400 m onto the flanks. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) 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: Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE), Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)