The natural world of Petrified Forest is far more complex than it seems on the surface. Located near the southern edge of the Colorado Plateau, the park is part of an amazing geological region. Some of the most famous geological parks are found on the Colorado Plateau, including Grand Canyon, Zion, Bryce, and Arches—just to name a few. Each has its own character, including which layer of the geological story is featured by that park. Petrified Forest has two geological formations, the Late Triassic Chinle Formation and the Mio-Pliocene Bidahochi Formation. Ancient environments are represented by these layers. The fossils that are found here help scientists reconstruct those ancient environments.
The colorful Painted Desert badlands are composed of bentonite, a product of altered volcanic ash. The clay minerals in the bentonite can absorb water and swell much as eight times their dry volume. The expansion and contraction properties of the bentonite cause rapid erosion including by preventing much vegetation from growing on—and thus fixing—the slopes of the hills.
Mesas and buttes are other features created by erosion. The flat tops are created by the presence of cap rocks, more erosion-resistant rock such as sandstone over softer clays. The softer rock is protected by the cap stones, but, as the sides weather and the protective rock falls down, the softer rock erodes away as it is exposed to the elements. Without the capstone, the feature becomes another rolling badland. Mesas typically are wider than they are tall while buttes are taller than they are wide. Towers, monuments, and hoodoos are even further eroded features.
The current environment is just as fascinating, a remnant of the Arizona native grassland. The types of plants and animals found in the park depend on the elevation, minerals in the soil and rock, and availability of moisture; it all ties together. Within the park, you may see open grassland, shrublands, little juniper-cliffrose woodlands, riparian and spring habitats. Explore the diverse natural world, both past and present, at Petrified Forest National Park.
Last updated: March 16, 2018