During 3-9 September IG reported moderate activity including explosions, long-period earthquakes, harmonic tremor, and tremor at Reventador. While cloud cover frequently limited observations, on 5-8 September steam emissions were observed with small quantities of ash. In the morning of 5 September an explosion generated a plume and ejected blocks from the crater that fell ~500 m below the summit on the W flank. A thermal camera detected an explosion on the following day that also included ballistics. Rumbling sounds were heard in the morning of 7 September, and that evening a 1 km plume was observed. The following morning a vapor plume persisted from the summit, and in the afternoon it contained a small amount of ash.

The MODIS sensor onboard the Terra satellite detected thermal anomalies from the region of Reventador’s summit during 4-6 September.

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), Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts Team