The Arizona desert region known for colorful badlands in Petrified Forest National Park is the Painted Desert.
The Painted Desert occupies part of the Four Corners region and stretches from near the eastern Grand Canyon area southeast through Petrified Forest National Park. Its exposed hills and mesas display red, orange, yellow, gray, lavender, and purple tones, giving the landscape its famous name. The area is a desert of badlands rather than a single sharply bounded sand sea.
Most of the colors come from layers of the Triassic Chinle Formation, deposited more than 200 million years ago. Iron and manganese compounds tint the mudstone, siltstone, and shale, while wind and water erosion carve the soft layers into gullies, rounded hills, cliffs, and mesas. The same geological formation helped preserve the fossil logs that make the national park famous.
The Painted Desert is often confused with Petrified Forest National Park because the two landscapes overlap, but they are not identical names: the Painted Desert is the broader regional landform, while the national park is the protected unit containing its southern portion. A Spanish expedition associated with Francisco Vázquez de Coronado reportedly called the colorful area El Desierto Pintado in 1540.