The ridges form as the salt crystallises from the evaporating water following the rains each year.
Salar de Uyuni (or Salar de Tunupa) is the world's largest salt flat at 10,582 km² (4,085 square miles). It is located in the Potosí and Oruro departments in southwest Bolivia, near the crest of the Andes, 3,650 meters high. The major minerals found in the salar are halite and gypsum.
Some 40,000 years ago, the area was part of Lake Minchin, a giant prehistoric lake. When the lake dried, it left behind two modern lakes, Poopó Lake and Uru Uru Lake, and two major salt deserts, Salar de Coipasa and the larger Uyuni. Uyuni is roughly 25 times the size of the Bonneville Salt Flats in the United States.
Salar de Uyuni is estimated to contain 10 billion tons of salt, of which less than 25,000 tons is extracted annually. All miners working in the Salar belong to Colchani's cooperative. They work from dawn to dusk and most of them do not take a lunch break in order to take advantage of time, getting energy by chewing coca leaves. Every November, Salar de Uyuni is also the breeding grounds for three species of South American flamingos: the Chilean, James's and Andean flamingos. It is also a significant tourist destination; highlights include a salt hotel and several so-called islands. en.wikipedia.org/wiki/Salar_de_Uyuni