Salar de Aguas Calientes IV, Salt flat in Antofagasta Region, Chile

Salar de Aguas Calientes IV is a salt pan of 19.5 km² at 3,665 m in the Antofagasta Region, south of the Llullaillaco volcano (6,739 m) and beside Llullaillaco National Park. It is a "playa" type flat, with a subterranean brine table 1 to 2 m below the surface and lagoons of 1 to 3 km².

The site developed from a large ancient lake that gradually transformed into the current salt deposits through evaporation. Volcanic activity from nearby mountains contributed material to the basin, shaping the landscape into what exists today.

The name Aguas Calientes is common across the Chilean altiplano, so Hans Niemeyer distinguished the salt pans by their latitude; this one lies at 25° 00' S. Luis Risopatrón's 1924 dictionary already listed it under that coordinate, noting two springs of dense mineralisation at 24 °C emerging from beneath lava layers to the northwest.

Visit during the drier months when road conditions are more stable and weather is more predictable. Prepare for the extreme altitude with proper acclimatization, carry plenty of water, and wear sun protection since the open terrain offers no shade.

The salt pan is a "playa" type, with a brine sheet only 1 to 2 metres below the surface. Luis Risopatrón's 1924 geographic dictionary already noted two springs of dense mineralisation welling from beneath lava layers at 24 °C on its north-west side.