Lastarria is a volcano that lies on the border between Chile and Argentina. It is part of the Central Volcanic Zone, one of the four segments of the volcanic arc of the Andes. Several volcanoes are located in this chain of volcanoes, which is formed by subduction of the Nazca Plate beneath the South American Plate.
Lastarria is formed by two volcanic edifices and one subsidiary lava flow field. There is no recorded eruptive activity, but the volcano displays vigorous fumarolic activity. It is located on top of older volcanic rocks and features both andesite and dacite.
Lastarria has produced a large landslide deposit as well as flows of molten sulfur. A progressive uplift of the terrain around Lastarria and farther south has been recognized.