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Maps

• Map of American drylands on the basis of annual precipitation averages, 1971-2000
  [NOTE: Arid lands have less than 250 millimeters (about 10 inches) of annual rainfall, and semiarid lands have a mean annual precipitation of between 250 and 500 millimeters (between about 10 and 20 inches). Extremely arid lands have at least 12 consecutive months without rainfall. Arid and extremely arid lands are called deserts, and semiarid grasslands are commonly referred to as steppes.]
• Map of Distribution of non-polar arid land
• Generalized geologic map of the southwestern United States showing locations of the Mojave Desert and the Colorado Plateau