IG described the ongoing eruption at Reventador as moderate during 17-24 January. Daily seismicity was characterized by explosions, long-period earthquakes, periods of harmonic tremor, and signals that indicated emissions. The daily count of explosions ranged from 22-96; seismic data transmission was interrupted during 22-23 January. Although weather clouds often prevented observations of the summit, daily gas, steam, and ash plumes were observed in IG webcam images and described in Washington VAAC volcanic activity notifications almost daily. The plumes rose as high as 2.2 km above the volcano and drifted in multiple directions. Crater incandescence was visible nightly and incandescent blocks were ejected onto the flanks sometimes in all directions; incandescent blocks were also visible rolling as far as 800 m down 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: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN), Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE)