PLATEAUS UINTA MTS. GREEN RIVER BASIN Yampa River Steamboat Springs UINTA BASIN White River WHITE RIVER PLATEAU ROAN PLATEAU Glenwood Springs Colorado River Grand Junction GRAND MESA Gunnison River UNCOMPAHGRE PLATEAU Dolores River PARADOX BASIN MESA VERDE MOUNTAINS NORTH PARK RABIT EARS RANGE PARK RANGE MIDDLE PARK GORE RANGE FRONT RANGE ELK MTS. Aspen SAWATCH RANGE Leadville MOSQUITO RANGE Fairplay SOUTH PARK WEST ELK MTS. Gunnison Salida WET MTS. SANGRE DE CRISTO RANGE SAN LUIS VALLEY Rio Grande Alamosa SAN JUAN MTS. Ouray Silverton Durango MESA DE MAYA PLAINS Fort Collins South Platte River Denver GREAT PLAINS Colorado Springs Arkansas River WET MT. VALLEY HUERFANO PARK La Junta Walsenburg I Colorado’s Three Provinces Scenically, Colorado is divided into three provinces: the Plains or Prairies on the east, the Rocky Mountains bisecting the state from north to south, and the Colorado Plateaus on the west. There are a number of local variations of course, but by and large the provinces are clearly defined. These three divisions will form the basis for our discussion of the geology of Colorado, for the scenic differences are almost exactly paralleled, and usually controlled, by differences in geologic structure. The Plains rise gently from an elevation of about 3350 feet at the eastern border of the state to 5000 feet where they meet the mountains 150 miles further west. Two major rivers cross the Colorado Plains: the South Platte River, flowing northeastward from the Denver region, and the Arkansas River, which leaves the mountains at Canon City south of Colorado Springs and travels eastward across the southern portion of the state. Tributaries of these two main river systems have etched the prairie surface, so that much of eastern Colorado has a gently rolling, hilly appearance.