Planchón-Peteroa is a complex volcano extending in a north–south direction along the border between Argentina and Chile. It consists of volcanoes of various ages with several overlapping calderas. Those include Volcán Planchón, Volcán Peteroa and Volcán Azufre. A partial collapse of the complex about 11,500 years ago produced a major debris avalanche, which followed the course of the Teno River until reaching the Chile Central Valley. Peteroa has a crater lake. Lagunas de Teno lies at the foot of Planchón volcano. In this area also is the Vergara International Pass.

September 6, 2010 eruption

Planchón-Peteroa Volcano erupted on September 6, followed by a stronger eruption on September 18. On September 21, the volcano erupted once again, emitting a dark gray plume of volcanic ash. As winds blew the ash southeast into Argentina, residents there were warned by authorities to evacuate the nearby areas before Planchón-Peteroa would erupt again.