La Pacana  La Pacana is a Miocene age caldera in northern Chile's Antofagasta Region. Part of the Central Volcanic Zone of the Andes, it is part of the Altiplano-Puna volcanic complex, a major caldera and silicic ignimbrite volcanic field. This volcanic field is located in remote regions at the Zapaleri tripoint between Chile, Bolivia and Argentina. La Pacana along with other regional volcanoes was formed by the subduction of the Nazca Plate beneath the South American Plate in the Peru-Chile Trench. La Pacana is situated in a basement formed by various Paleozoic formations and Tertiary ignimbrites and volcanoes. Several major faults cross the region at La Pacana and have influenced its volcanic activity. La Pacana is a supervolcano and is responsible for the eruption of the giant Atana ignimbrite, which reaches a volume of and constitutes the fifth-largest explosive eruption known. The Atana ignimbrite was erupted 3.8 ± 0.1 and 4.2 ± 0.1 million years ago, almost simultaneously with the much smaller (volume of ) Toconao ignimbrite. The Pujsa ignimbrite was erupted by La Pacana before the Atana/Toconao ignimbrites, and the Filo Delgado and Pampa Chamaca/Talabre ignimbrites afterwards. La Pacana lies in the Antofagasta Region of Chile, in the Andes just north of the Tropic of Capricorn. The border between Chile and Bolivia crosses the northern sector of the caldera. The area of La Pacana is largely uninhabitated; small settlements such as Socaire, Talabre and Toconao exist close to the Salar de Atacama, where streams descend the mountain slopes to the salar. The caldera was discovered during mapping efforts in the region between 1980–1985. La Pacana is part of the Central Volcanic Zone, one of the four volcanic zones that make up the Andean Volcanic Belt and which are separated from each other by gaps without ongoing volcanic activity. A number of stratovolcanoes and ignimbrite-forming centres have erupted in the Central Volcanic Zone since the Miocene, about 50 of which are considered to be active. In addition, the Central Volcanic Zone features about 18 minor volcanic fields. The largest historical eruption of the Andes occurred in 1600 at Huaynaputina in Peru in the Central Volcanic Zone, and the most active volcano of the Central Volcanic Zone is Láscar in Chile.