It's a strange and seemingly wicked place. From the ragged ridges and sawtooth spires to the wind-ravaged desolation of Sage Creek Wilderness Area, Badlands National Park is an awe-inspiring sight and an unsettling experience. Few leave here unaffected by the vastness of this geologic anomaly, spread across 381 square miles of moonscape.
The Sioux Indians who once traversed this incredible land named it mako sica or "land bad." Early French-Canadian trappers labeled it les mauvaises terres a traverser or "bad lands to travel across."
Steep canyons, towering spires, and flat-topped tables are all found among Badlands buttes. Yet, despite their apparent complexity, the unusual formations of the Badlands are essentially the result of two basic geologic processes: deposition and erosion.
The layered look of the Badlands comes from sedimentary rocks composed of fine grains that have been cemented into a solid form. Layers with similar characteristics are grouped into units called formations. The bottom formation is the Pierre Shale, deposited 68 million to 77 million years ago during the Cretaceous period, when a shallow, inland sea stretched across the present-day Great Plains. The black mud of the sea floor hardened into shale, leaving fossil clamshells and ammonites that today confirm a sea environment. The sea eventually drained away, and the upper layers of shale were weathered into soil, now seen as yellow mounds.
The Chadron Formation, deposited 32 million to 37 million years ago during the Eocene epoch, sits above the Pierre Shale. By this time, a floodplain had replaced the sea and each time the rivers flooded, they deposited a new layer of sediment on the plain. Alligator fossils indicate that a lush, subtropical forest covered the region. However, mammal fossils dominate. The Chadron is best known for its large, elephantlike mammals called titanotheres.
Some of the sediment carried by rivers and wind was volcanic ash, the product of eruptions associated with the creation of the Rocky Mountains. This ash mixed with river and stream sediments to form clay stone, the main material from which Badlands buttes are constructed. After the Eocene epoch, the climate began to dry and cool and tropical forests gave way to open savanna. Rivers deposited the Brule and Sharps Formations during the Oligocene epoch from 26 million to 32 million years ago, and today these formations contain the most rugged peaks and canyons of the Badlands.
Actually, the impressive serrated ridges and deep canyons of the Badlands did not exist until about 500,000 years ago, when water began to cut through the layers of rock, carving fantastic shapes into what had been a flat floodplain. Once again, the ancient fossil soils, buried for millions of years, became exposed. That erosion is ongoing, and every time it rains, or snow melts in spring, more sediment is washed from the buttes in this endless work of sculpting the earth. On average, the buttes erode 1 inch each year, and scientists believe that the buttes will be gone in another 500,000 years.
In addition to its scenic wonders, the Badlands are one of the richest Oligocene fossil beds known to exist. Remains of three-toed horses, dog-sized camels, saber-toothed cats, giant pigs, and other species have been found here, all dating from 25 million to 35 million years ago.
