New Mexico, Utah and Arizona 5000 feet above sea level. Erosion in the Pliocene downcut sedimentary rocks, reaching the Precambrian basement and forming the channels of Colorado River tributaries such as the Gunnison, Green, Dolores and Yampa rivers. During the Pleistocene, glaciers formed in the mountains, carving out valleys and straightening streams. See also Colorado Outline of Colorado Index of Colorado-related articles Bibliography of Colorado Climate change in Colorado Colorado statistical areas Front Range Urban Corridor North Central Colorado Urban Area South Central Colorado Urban Area Geography of Colorado Geology of Colorado History of Colorado List of territorial claims and designations in Colorado National Register of Historic Places listings in Colorado Prehistory of Colorado Timeline of Colorado history List of cities and towns in Colorado List of adjectivals and demonyms for Colorado cities List of census-designated places in Colorado List of city nicknames in Colorado List of Colorado municipalities by county Commons:Category:Cities in Colorado List of counties in Colorado Commons:Category:Counties of Colorado List of forts in Colorado List of ghost towns in Colorado List of places in Colorado Paleontology in Colorado References External links Colorado state government website Colorado Department of Transportation Colorado highway maps Colorado Travel Map Colorado counties Colorado municipalities Colorado special districts Colorado tourism List of searchable databases produced by Colorado state agencies hosted by the American Library Association Government Documents Roundtable. Colorado