The Clarno Unit is located 18 miles west of the town of Fossil. The Palisades are the most prominent landform. 44 million years ago a series of volcanic mudflows, swept up and preserved a diverse assortment of plants and animals that inhabited a near-tropical forest. Tiny four-toed horses, huge rhino-like brontotheres, crocodilians, and meat-eating creodonts that once roamed ancient jungles are now found in the rocks of the Clarno Unit, as well as an incredibly diverse range of plant life. Leaves, fruits, nuts, seeds, and petrified wood from 173 species of trees, vines, shrubs, and other plants have been found here thus far.

The modern vegetation is typical of Central Oregon’s near-desert environment with a variety of grasses, sagebrush and juniper.