The IG reported that field observations of Reventador on 16 and 17 September confirmed the presence of a lava flow on the S flank of the cone. Gas and steam emissions were noted, as was growth of the lava dome. Thermal anomalies over the crater area were detected in satellite imagery on 6, 11, and 13 October. On 14 October, seismicity increased and harmonic tremor was detected. A seismic station on the NE flank of the cone detected rockfalls. Several people living in the area reported roaring noises and observed slight incandescence from the crater during the previous few nights.

During an overflight on 16 October, scientists saw the lava dome and a lava flow on the N flank. Bluish gases were emitted. According to a thermal camera, the incandescent parts in the crater were about 300 degrees Celsius. Other observers heard roaring noises and sounds resembling "cannon shots." Incandescent blocks were ejected from the crater, and steam and gases rose 100 m and drifted SW. Incandescent material was seen on the S flank. On 17 October, incandescence on the S flank was seen and noises similar the previous day were again heard. A small gray plume was seen the next day. On 19 October, thermal anomalies were again detected on satellite imagery. During an overflight, blue gas plumes were seen. The lava flow on the S flank occupied a large area and was divided into two branches.

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.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)