Salar de Uyuni

Salar de Uyuni lies in southwestern Bolivia on the high Altiplano, an elevated basin within the Andes. NASA describes the salar as the world's largest salt flat; published area estimates vary, with NASA sources giving approximately 8,000 to 10,000 square kilometres. The basin is endorheic, meaning water does not drain to the sea, and its high, arid setting supports salt-pan landscapes.

The salt flat is the remnant of ancient lakes that evaporated in the Altiplano basin. The International Union of Geological Sciences describes the Uyuni Salt Flat as the product of evaporation of the Tauca paleolake and identifies alternating saline layers, composed largely of halite, and clay-rich lake sediments. NASA notes that basin sediments preserve evidence of changing lake levels and can serve as a regional paleoclimate record.

For much of the year, the surface is a broad expanse of pale salt crust. During the rainy season, standing water can cover parts of the flat, reflecting the sky and producing a mirror-like appearance. NASA's satellite observations of 2021–2022 documented unusually extensive and persistent seasonal water that year, illustrating that inundation varies with weather and is not a permanent feature.

The salar contains halite and other evaporite minerals, as well as lithium-rich brines beneath or within the salt-bearing deposits. A U.S. Geological Survey investigation reported lithium concentrations ranging from 80 to 1,500 parts per million in its sampled brines, with higher values concentrated in parts of the salar; those results refer to samples and do not by themselves indicate recoverable reserves. The flat's unusually even surface also makes it useful for calibrating satellite instruments, while its geological record attracts research into past climate and basin evolution.

Salar de Uyuni is a major landscape and tourist destination in Bolivia, valued for its striking scenery and natural history. The mineral resources have also drawn scientific and economic interest. Tourism, mineral development and the hydrology of the wider Altiplano basin are distinct aspects of the salar and should be considered alongside local environmental and community conditions.