1. Puyehue-Cordón Caulle, Chile (308)
The winner of the 2011 Pliny for Volcanic Event of the Year - and by a longshot - was the stunning and long-lived eruption of Puyehue-Cordón Caulle near the Chilean-Argentine border. In early May, the volcano was placed on "Yellow Alert" status by the SERNAGEOMIN but a strong increase in seismicity was observed starting in late April. Almost exactly one month later, Puyehue-Cordón Caulle showed that it meant business, producing a giant explosive eruption that reached 10 km / 35,000 feet and was spotted from space punching through the cloud deck. Eventually, a lava flow was spotted coming from the fissure vent on Cordón Caulle as well. For the rest of the winter and into the spring and summer the volcano caused periodic air traffic closures and brought towns near the volcano, like Bariloche, to a standstill. Lakes and land around Puyehue-Cordón Caulle were choked with pumice and ash from the eruption and ash continues to fall even as 2011 draws to a close.
Image: The ash plume from Puyehue-Cordón Caulle captured via webcam on June 13, 2011.