Which desert covers about 647,500 square kilometers of South America?

The desert covering about 647,500 square kilometres of South America is the Patagonian Desert.

Also called the Patagonian Steppe, it occupies much of southern Argentina and extends into parts of Chile. It is the largest desert in Argentina and is commonly ranked among the world’s largest deserts, although estimates vary because different sources draw its boundaries differently and may include adjacent steppe environments.

The Andes help create its dry conditions. Moisture-bearing air from the Pacific rises over the mountains, loses much of its moisture, and descends on the eastern side as relatively dry air. This rain-shadow effect combines with strong winds and cool temperatures, making Patagonia a temperate desert rather than a hot subtropical one.

The landscape is not uniformly sandy. It includes shrublands, gravelly plains, grass-covered steppe, cliffs and river valleys. A common mix-up is to treat the Argentine Monte as the same desert: the Monte lies to the north and is a neighbouring arid region, while the Patagonian Desert occupies the colder southern steppe. The Atacama, by contrast, is farther north along the Pacific side of the Andes.