The Patagonian Desert, also known as the Patagonia Desert or the Patagonian Steppe, is the largest desert in Argentina and is the 7th largest desert in the world by area, occupying 673,000 square kilometers (260,000 mi²). It is located primarily in Argentina with small parts in Chile and is bounded by the Andes, to its west, and the Atlantic Ocean to its east, in the region of Patagonia, southern Argentina. To the north the desert grades into the semi-arid Cuyo Region and the Dry and Humid Pampas. The central parts of the steppe are dominated by shrubby and herbaceous plant species albeit to the west, where precipitation is higher, bushes are replaced by grasses. Topographically the deserts consist of alternating tablelands and massifs dissected by river valleys and canyons. The more western parts of the steppe host lakes of glacial origin and grades into barren mountains or cold temperate forests along valleys.
Inhabited by hunter-gatherers since Pre-Hispanic times the desert faced in the 19th century migration of Mapuches, Chileans, Argentines, Welshs and other European peoples transforming it from a conflictive borderland zone to an integral part of Argentina with cattle, sheep and horse husbandry being the primary land use.
The Patagonian Desert is the largest continental landmass of the 40° parallel and is a large cold winter desert, where the temperature rarely exceeds 12°C and averages just 3°C. The region experiences about seven months of winter and five months of summer. Frost is not uncommon in the desert but, due to the very dry condition year round, snow is. The Andes, to the desert's west, are the primary reason for the Patagonian desert status as they inhibit the westerly flow of moisture from the southern Pacific from reaching inland. This creates a rain shadow that accounts for the formation of the desert and is why, despite approximately half of the desert being only about 200 miles from the ocean, such a large desert is found in the region. The cold Falkland Current off the Atlantic coast of South America also contributes to the area's aridity.