The Great Basin Culture Area includes the high desert regions between the Sierra Nevada and the Rocky Mountains. It is bounded on the north by the Columbia Plateau and on the south by the Colorado Plateau. It includes southern Oregon and Idaho, a small portion of southwestern Montana, western Wyoming, eastern California, all of Nevada and Utah, a portion of northern Arizona, and most of western Colorado. This is an area which is characterized by low rainfall and extremes of temperature. The valleys in the area are 3,000 to 6,000 feet in altitude and are separated by mountain ranges running north and south that are 8,000 to 12,000 feet in elevation. The rivers in this region do not flow into the ocean, but simply disappear into the sand.