Puyehue and Cordon Caulle are two coalesced volcanic edifices that form a major mountain massif in Puyehue National Park in the Andes of Ranco Province, Chile. In volcanology this group is known as the Puyehue-Cordón Caulle Volcanic Complex (PCCVC). Four different volcanoes constitute the volcanic group or complex, the Cordillera Nevada Caldera, the Pliocene Mencheca volcano, Cordón Caulle fissure vents and the Puyehue stratovolcano. As with most stratovolcanoes on the Southern Volcanic Zone of the Andes, Puyehue and Cordon Caulle are located along the intersection of a traverse fault with the larger north-south Liquine-Ofqui Fault. The volcanic complex has shaped the local landscape and produced a huge variety of volcanic landforms and products over the last 300,000 years. Cinder cones, lava domes, calderas and craters can be found in the area apart from the widest variety of volcanic rocks in all the Southern Volcanic Zone, for example both primitive basalts and rhyolites. Cordón Caulle is notable for having erupted following the 1960 Valdivia earthquake, the largest recorded earthquake in history.
Apart from this, the Puyehue-Cordon Caulle area is one of the main sites of exploration for geothermal power in Chile. Geothermal activity is manifested on the surface of Puyehue and Cordón Caulle as several boiling springs, solfataras and fumaroles.
Renewed activity at the volcano resulted in the highest alert level, 4, being declared on 3 June 2011. A new eruption started on 3 June, 20:30 UTC. On 4 June the ash cloud reached a height of 12,000 metres (39,370 ft).