The Clarno Unit is 1,969 acres in size and is located 18 miles west of the town of Fossil. It features hiking trails, exhibits, and a picnic area; The modern vegetation here is typical of Central Oregon's near-desert environment with a variety of grasses, sagebrush and juniper.

The cliffs of the Palisades are the most prominent landform in the Clarno Unit. The Palisades were formed 44 million years ago by a series of volcanic mudflows called lahars . The Palisades, preserved a great diversity of fossils in an environment very different from that of today. At that time, volcanoes towered over a landscape covered by near-tropical forest fed by approximately 100 inches of rain per year. Tiny four-toed horses, huge rhino-like brontotheres, crocodilians, and meat-eating creodonts roamed the ancient jungles.