Death Valley lies within the Mojave Desert of southeastern California and in the southwestern arm of the vast Basin and Range Province. The latter, which stretches from western Utah to the Sierra Nevada and from southern Idaho to the Sea of Cortez, is characterized by numerous fault-block mountain ranges (running north to south), separated by long, flat valleys. The crust of this region has been under tension for the past 16 million years, stretching it from east to west and causing it to rupture along numerous fault lines; this process (which continues today) has produced the basin and range topography. Filled with lakes during the cool, wet climate of the Pleistocene, the valleys now harbor vast salt pans and stark desert landscapes.
During the above process, Death Valley has dropped lower as its surrounding mountains have risen and, despite a thick layer of erosional debris, its floor still dips to 282 feet below sea level at Badwater Basin, the lowest point in North America. Cut off from Pacific moisture by the high spine of the Sierra Nevada and by other coastal and desert ranges, the air that reaches the Valley is especially dry and dense, increasing its capacity to retain heat. High atmospheric pressure and the surrounding wall of mountains trap this heat in the valley; furthermore, any air that flows into the Valley must descend from the surrounding highlands, a process that compresses and warms the air. Intense sunshine and a rocky, barren landscape magnify heat production at ground level and, as this hot air rises along the valley walls, it cools just enough to sink back toward the valley floor, reinforcing the heat at lower elevations. Finally, unlike the nocturnal, radiation cooling that occurs in the thin air of the high deserts, the dense surface air of Death Valley retains much of its heat through the night.
For all of the above reasons, Death Valley is the site of the highest temperature ever recorded in the Western Hemisphere: 134 F at Furnace Creek, in 1913. Daily high temperatures range from an average of 64 in mid winter to 116 in mid summer; corresponding lows average 40 to 88 degrees. As one might expect, the average annual precipitation in this low desert is less than 2 inches.
