Pastos Grandes Caldera or Cerro Pastos Grandes (a resurgent centre) is an old 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...

 in the Potosí Department

Potosí Department

Potosí Department is a department in southwestern Bolivia. It comprises 118,218 km² with 709,013 inhabitants . The capital is the city of Potosí....

, Bolivia

Bolivia

Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

, which belongs to the Altiplano-Puna Volcanic Complex. Lagunas Pastos Grandes

Laguna Pastos Grandes

Laguna Pastos Grandes is a lake in the Potosí Department, Bolivia. At an elevation of 4330 m, its surface area is 120 km²....

, Khara and Cachi may be remnants of a greater caldera lake. Size of the caldera: 50 km x 40 km. 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....

 7) eruption c. 2.9 million years ago produced 820 cubic kilometres (197 cu mi) of tephra.