To most of us, deserts are landscapes of dryness, sparse vegetation and perpetual heat. But, in high deserts, the interplay of elevation and dry air produces wide temperature variations from day to night and from one season to another. Examples within the U.S. include the Great Basin Desert, with floor elevations from 5000 to 6000 feet, the Red Desert of southern Wyoming, ranging from 6000 to 8500 feet, and the San Luis Valley of Colorado, with an average elevation of 7600 feet. In all of these deserts, hemmed in by mountain ranges, the annual total precipitation is below 10 inches and surface temperatures may vary by as much as 70-80 degrees F between night and day.
However, the high deserts of the U.S. pale in comparison to the extreme conditions found in other regions of our globe. The Gobi Desert of Mongolia and the varied Patagonian Desert of Argentina are somewhat comparable with regard to elevation but are far larger and are affected by the extreme conditions of neighboring ecosystems. The Atacama Desert of Peru and Chile, the driest on Earth, stretches from the sea to the foot of the Andes and thus harbors varied life zones from zero to 11,000 feet or more. Among the highest deserts in the Western Hemisphere are the Bolivian Salt Flats (12,000 feet) and the Salinas Grandes of Argentina, 12,500 feet above sea level.
But the most impressive high deserts on our planet are the Tibetan Plateau, north of the Himalayas, averaging 14,500 feet in elevation, and the Antarctic Plateau of east-central Antarctica, with a mean elevation of 9800 feet. Despite the fact that its ice and snow harbor over 70% of the fresh water on Earth, Antarctica is our driest Continent, with most of its precipitation falling along the coastal shelves; ascending toward the great plateau, the dry polar air cools further, dropping its meager cargo of moisture on lower terrain.
