Why is this desert covered with white salt instead of sand?

When people think of deserts, they usually picture rolling sand dunes. However, some unique landscapes are covered in a thick crust of white salt. Salar de Uyuni in Bolivia is the world's largest salt flat, spanning 10,582 square kilometres. This white desert is not made of sand, but of concentrated minerals left behind by a specific geological process.

How closed basins trap water

Salt deserts, also known as salars or salt flats, form in closed desert basins. In these arid regions, water from rainfall or rivers flows into the basin, but it has no outlet to the sea. Because the climate is dry and evaporation rates are high, the trapped water eventually dries up. This natural process removes the water but leaves behind dissolved elements and salts on the surface.

The prehistoric lakes of Salar de Uyuni

The Bolivian salt flat sits at an elevation of 3,656 metres in the Andes. Its formation is tied to a prehistoric mega-lake known as Lake Minchin, which existed between 30,000 and 42,000 years ago. As the climate changed, this large body of water shrank into smaller lakes. Around 10,000 years ago, the final paleolake dried completely, leaving behind a solid crust of salt that continues to accumulate today.

A landscape built on lithium and brine

Unlike sandy deserts created by wind erosion, a salt flat sits on top of a concentrated underground pool of brine. Below the hard white surface of Salar de Uyuni lies a complex sequence of salt and mud layers. The brine underneath contains between 50 per cent and 70 per cent of the world's known lithium reserves. Because lithium is highly soluble, it remains in the water longer than other minerals as evaporation occurs.

Visiting a salt flat offers a factual look into thousands of years of geological history. While these bright white plains lack traditional sand dunes, they provide a vital source of minerals and an unusual travel experience.