IG-EPN reported that the eruption at Reventador was ongoing during 12-19 December. Seismicity was characterized by 23-51 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions; data reception was interrupted during 13-14 December. Several daily ash-and-gas plumes rose as high as 1 km above the crater rim and drifted in multiple directions, though cloudy conditions prevented views at times during 18-19 December. Crater incandescence was often visible during both overnight and morning hours, and avalanches of incandescent material frequently descended the flanks to distances as far as 800 m from the summit. Weather conditions sometimes prevented views of the volcano. 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), Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE)