During 26 November- 1 December, Reventador mainly emitted gas and steam and occasionally small amounts of ash, and seismicity was low. IG stressed to the public that the sulfuric odor in the city of Quito was not indicative of renewed volcanism. During a flight over the volcano on 27 November, IG scientists determined that reports of a second lava flow made the previous week were false; rather, a pyroclastic flow had descended the volcano's NE flank. They also confirmed that a lava flow on the volcano's E flank had been emitted from a small crater that opened ~600 m below the volcano's summit. They believe it began to flow on 24 November and was accompanied by the emission of ash and incandescent rocks. On 2 December incandescence was visible on the E flank of the cone, which was thought to be from a new pulse of lava emitted from the 24 November flow the night of 1 December. On 2 December mudflows traveled down the Montana River, causing problems at a highway.

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 about 1,300 m 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 constructed a debris plain on the eastern floor of the scarp. 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), Washington Volcanic Ash Advisory Center (VAAC)