This province consists primarily of mountains composed of igneous, volcanic, and sedimentary rocks adjacent to alluvial valleys. In this province, the mountains define the eastern boundary of the study unit. The mountains are rugged and have significant relief above the alluvial valleys. In the mountains soils are shallow or nonexistent and spruce, pine, and aspen trees are common. Sagebrush and low grasses are common in the valleys.
Many streams exist in the mountains because of the large quantity of precipitation.
Areas of the study unit in the Colorado Plateau Province are generally south and west of the Southern Rocky Mountains Province and north and west of the Basin and Range Province. Rocks range in age from Mississippian to Tertiary. Although the rock strata are relatively flat-lying, erosion has greatly dissected the topography and there are areas of local uplift. The area is a succession of low mesas and erosional valleys resulting from the erosion of rocks with different resistances to weathering in an arid climate. In the higher altitudes, ponderosa pine trees are common, but throughout most of the area scattered pinon, juniper trees, and low bushes are the most common vegetation.