Northern Arizona is an unofficial, colloquially-defined region of the U.S. state of Arizona. Generally consisting of Coconino County, Yavapai County, Navajo County, and Apache County, it is geographically dominated by the Colorado Plateau, the southern border of which in Arizona is called the Mogollon Rim. It is home to dozens of mountain ranges, including the state's highest, the San Francisco Peaks. It also contains most of the state's natural lakes. In the West lies the Grand Canyon, which was cut by the flow of the Colorado River while the land slowly rose around it. The elevation ranges from 2200 feet at the bottom of the Grand Canyon to 12,633 feet at Humphrey's Peak. In the central portion lies the Painted Desert, consisting of sedimentary rocks eroded by water and wind, exposing thick, brightly colored layers. In the East are the very large Hopi and Navajo reservations, parts of which overlap, leading to occasional territorial disputes. In this area travelers may tune their radios to hear native-language broadcasts.