La Pacana Caldera is the most important caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

 of the La Pacana Complex in the Antofagasta Region

Antofagasta Region

The II Antofagasta Region is one of Chile's fifteen first-order administrative divisions. It comprises three provinces, Antofagasta, El Loa and Tocopilla...

, northern of Chile, East of the Salar de Atacama

Salar de Atacama

Salar de Atacama is the largest salt flat in Chile. It is located south of San Pedro de Atacama, is surrounded by mountains and has no drainage outlets. To the east is enclosed by the main chain of the Andes, while to the west lies a secondary mountain range of the Andes called Cordillera de Domeyko...

. The La Pacana Complex belongs to the Altiplano-Puna Volcanic Complex. Chilean, Bolivian and Argentinian borders meet on the Northeast of the resurgent center (Cerro La Pacana), the Salar Aguas Calientes is on the Southwest of the resurgent center. The size of the caldera depression is 70 kilometres (43.5 mi) x 35 kilometres (21.7 mi). A large (VEI

Volcanic Explosivity Index

The Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....

 8) eruption c. 4 million years ago produced 2500 cubic kilometres (600 cu mi) of tephra

Tephra

200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....

.