Eroded Spires of the Badlands Wall, South Dakota

The Badlands Wall formation stretches roughly 60 miles through Badlands National Park, separating the upper prairie from the lower prairie along the White River Valley. These sedimentary layers—bands of volcanic ash, claystone, and sandstone—were deposited between 75 and 28 million years ago and have been eroding at a rate of about an inch per year since the process began roughly 500,000 years ago. The park protects more than 244,000 acres, much of it co-managed with the Oglala Sioux Tribe as part of the adjacent Pine Ridge Reservation's South Unit. Fossil beds within these formations have yielded remains of ancient horses, rhinoceroses, and saber-toothed cats, making the area one of the richest Oligocene fossil deposits in the world.

Photo taken in July 2017.