Salar Ignorado, Salt flat beach in Atacama Region, Chile

Salar Ignorado is a triangular salt flat of 0.7 square kilometres at 4,250 metres in the Chilean Andes, just south of the 5,400-metre Cerro Bayo volcano and near the Argentine border. Its surface is hummocky, rising about 2 metres, and roughly a third consists of pools up to 2 metres deep and 2 to 50 metres wide; the rest is sand dunes and salt flats, with salt-free benches along the shores.

Salar Ignorado and neighbouring Salar Gorbea may have been ordinary salt flats before hydrothermal alteration of the surrounding Miocene volcanoes made their waters acidic. A dry channel between the two basins suggests Ignorado once spilled into Gorbea. Solute input peaked between 120,000 and 11,000 years ago during a Pleistocene humid period, and volcanic uplift continues at about 2.5 cm per year.

The name Ignorado, "ignored", refers to how little the flat was studied; systematic reconnaissance was only reported in 2002. Diatoms, green algae such as Dunaliella and prokaryotes live inside the gypsum crystals and in their fluid inclusions, and microbial mats grow on the bottoms of the shallow pools. The bacterial variety and biomass are small, and no crustaceans have been found.

Reaching this location requires four-wheel-drive vehicles and preparation for high altitude conditions. Proper acclimatization and suitable equipment are essential for visiting this remote mountain area.

Salar Ignorado and neighbouring Salar de Gorbea are the only two salt flats in northern Chile and Bolivia known to have acidic waters. The acidity comes from sulfuric acid produced by hydrothermal and magmatic processes around the volcanoes, not from the salt itself.