The Painted Desert is a United States desert of badlands in the Four Corners area from the Grand Canyon National Park into the Petrified Forest National Park. Much of the area within the Petrified Forest National Park is protected as the Petrified Forest National Wilderness Area. Much of the Painted Desert region is within the Navajo Nation (Navajo and Hopi have lived in the region for at least five hundred and one thousand years, respectively.)
The desert is composed of stratified layers of easily erodible siltstone, mudstone, and shale of the Triassic Chinle Formation. These fine grained rock layers contain abundant iron and manganese compounds which provide the pigments for the various colors of the region. Thin resistant lacustrine limestone layers and volcanic flows cap the mesas. Numerous layers of silicic volcanic ash occur in the Chinle and provide the silica for the petrified logs of the area. The erosion of these layers has resulted in the formation of the badlands topography of the region
In the southern portions of the desert the remains of a Triassic period coniferous forest have fossilized over millions of years. Wind, water and soil erosion continue to change the face of the landscape by shifting sediment and exposing layers of the Chinle Formation. An assortment of fossilized prehistoric plants and animals are found in the region, as well as dinosaur tracks and the evidence of early human habitation.
The Painted Desert extends roughly from Cameron-Tuba City, Arizona, southeast to past Holbrook, Arizona, and the Petrified Forest National Park. The distances are approximately 120-miles in length, and a width of about 60-mi, making it roughly 7,500 square miles (19,425 sq km). Bordering southwest and south is the Mogollon Plateau, and on the plateau's south border the Mogollon Rim-(the north border of the Arizona transition zone).