SALAR DE UYUNI

While relatively few people have ever visited the immense salt flat known as Salar de Uyuni (sa-LAR day ooh-yooni), millions have seen it on the big screen. In the 2017 movie Star Wars: The Last Jedi, Salar de Uyuni was the filming location for the fictional Crait, a small planet where white salt covers bright-red, mineral-rich soil, and the Resistance fought the First Order in a climactic battle.

- STEVE VOYNICK

But the notoriety of Salar de Uyuni, located at the lofty elevation of 12,000 feet in remote southwestern Bolivia, goes far beyond its Star Wars connection. Visible from space, it’s the world’s most extensive salt flat, flattest large land area and largest natural mirror. And perhaps most importantly, Salar de Uyuni is also the largest known deposit of lithium.

AN ANCIENT LAKE

Familiarly known as “the Salar,” Salar de Uyuni is hidden away in the Bolivian Altiplano, a broad, high-elevation plateau in the Andes Mountains. Some 40,000 years ago, this region was covered by a huge lake that a changing climate later transformed into Salar de Uyuni.

The Salar is an endorheic or closed drainage basin. With no outflow, water loss occurs only through evaporation. Incoming water from snowmelt and wet-season rain contains dissolved mineral salts, which seasonal evaporation causes to precipitate from solution onto the lake bed. Thousands of these annual, repetitive replenishment-and-evaporation cycles eventually created a massive salt deposit.

Salar de Uyuni is nearly the size of the state of Connecticut and 100 times larger than Utah's better-known Bonneville Salt Flats. The Salar lake bed consists of interbedded layers of fine-grained lacustrine mud and salt immersed in a brine saturated with the dissolved chlorides of sodium, magnesium and lithium. Its surface crust varies in thickness from mere inches to several feet. In its entirety, the Salar contains some 10 billion tonnes of mixed-chloride salts.