Largest salt flat

The world's largest salt flat is the Salar de Uyuni in south-west Bolivia. At an altitude of 3,650 metres (11,975 feet) above sea level, this flat expanse of salt covers an area of approximately 9,500–10,000 square kilometres (3,668–3,861 square miles), and contains an estimated 10 billion tonnes of salt.

The precise boundaries of the salt flat are difficult to define, depending on criteria such as the thickness of the salt layer. Some estimates put the area of Salar de Uyuni as small as 8,000 km2 (3,088 sq mi) and others as large as 12,000 km2 (4,633 sq mi).

Salar de Uyuni is the lowest part of the lakebed of the giant prehistoric Lake Minchin, which started to dry up around 30,000–40,000 years ago. As the lake evaporated, the salt it contained became more and more concentrated. When the salt finally crystallized, it formed a crust that is as thick as 10 m (32 ft) in some areas.

The much smaller Salar de Coipasa – around 2,500 km2 (965 sq mi) in area – lies 120 km (75 mi) north-west of Uyuni surrounding Lake Coipasa; this salt flat also originally formed part of Minchin's lakebed.