Arizona. The plateau is cut by deep canyons and dotted with worn-out volcanoes. Rivers and the wind have caused erosion of the soil. Erosion wears down the land. Some examples of different extremes of erosion are Monument Valley, the Grand Canyon, and the Petrified Forest. Arizona’s highest mountain is found on the Colorado Plateau. Mt. Humphreys is part of the San Francisco Peaks. Its elevation is 12,633 feet. It is found near the city of Flagstaff. Some of Arizona’s greatest natural wonders are found on the Colorado Plateau. The Grand Canyon, Monument Valley, the Painted Desert, and the Petrified Forest are found here. Three Indian nations are also found on the plateau. The San Juan Paiutes, the Hopi, and the Navajo nations make their homes on this beautiful Arizona land. Many historical sites are located on the Colorado Plateau. Canyon de Chelly, Wupatki, and Walnut Canyon National Monuments are all found here. Sunset Crater National Monument allows visitors to walk on an ancient volcano. Petrified Forest National Park was established in 1962. Here the wood of an ancient forest of giant trees has been replaced by quartz crystals and silica to make this beautiful rock forest. Wupatki is a Hopi Indian word that means “tall house.” Wupatki National Monument covers 54 square miles. The ruins we see today were built by the Sinagua Indians during the 12th century. Chapter 2 • The Land  19