Authorized as a National Monument in 1929 and redesignated as a National Park in 1978, Badlands National Park in southwestern South Dakota is over 240,000 acres of wilderness, pinnacles, spires, eroded buttes, and mixed grass prairie. It has been the home of Native American Ghost Dances, a United States Air Force bomb and gunnery range, and the reintroduction of the black-footed ferret—North America’s most endangered land mammal. But what makes these badlands, so bad?
Broadly, the term “badlands” refers to a specific type of terrain of clay-rich soil and soft sedimentary rock that has been heavily eroded by wind and water. Badlands are often devoid of vegetation, have incredibly steep slopes, highly varied rock striations and coloration, and are mainly characterized by a lack of regolith. Regolith, in geologic speak, is loose material. Think soil, pebbles, gravel, volcanic ash, dust, etc.
It takes two things to form badlands. Deposition and erosion. Deposition is the accumulation of mineral material over a long period of time. Approximately 47 million years in the case of Badlands National Park. Sedimentary rock forms from deposition. Material gets deposited, more materials deposits on top of that, and the process of cementation occurs where water moves out of the deposits and they harden. Voila, rock.
The next step in the process is erosion. Sedimentary rocks are far more prone to erosion that either igneous or metamorphic rocks. As water, wind, or ice move across sedimentary rocks, significant erosion occurs. In badlands, deep, intricate canyons are formed. Any material loosened from the rock is quickly transported out of the area due to the high drainage density—a lot of steep slopes where water doesn’t stay around too long. Remember that regolith stuff? If all your regolith is removed, you never get real soil formation, and if you don’t make soil, you don’t get a lot of vegetation. Get the picture?
Badlands do offer a striking portrait of one major tenet of geology–the law of superposition. Simply, the law of superposition states that the oldest strata, or layers, will be at the bottom, and new strata will be at the top. This is crucial for fields like geology and archaeology and offers a form of relative dating—basically that what is lower in the strata is older than on top. In the badlands, there are sharp contrasts between strata that are clearly evident. If geology is your thing, the Badlands is a playground.
But Badlands National Park, while serving as a living geology textbook, is also home to the largest undisturbed mixed-grass prairie in the United States.
Mixed-grass prairies are transitional areas between tall-grass and short-grass prairies. As you can probably guess, mixed-grass prairies have both tall and short grasses. Mixed-grass prairies range from northern Texas through the central plains of the US, into southern Manitoba and Alberta. Prairies, broadly, occur in areas where there is not quite enough rainfall for trees, but enough to support grasses, forbs, and sedges. In North America, the Great Plains make an ideal home from prairies ecosystems. During the last glaciation, this area was almost completely leveled. As the glaciers receded, nutrient rich glacial till was deposited. Of course, the great expanse of the Rocky Mountains had to interfere, casting a huge rain shadow across the Great Plains. Not enough rain fell for forests to develop, but there was just enough rain and great soil conditions for expansive grasslands to spring up. A perfect home for vast herds of bison, elk, big-horn sheep, along with room for many other animals from porcupines to badgers to prairie dogs.
This rich geologic and biological diversity made this area into a rich hunting ground. The area that is now Badlands National Park, for nearly 11,000 years, was home to the Lakota people—members of the confederation of Sioux Tribes. The Lakota considered the areas around the Badlands and the Black Hills to be sacred ground, and objected to settlement and mining in the area during westward expansion in the 1800s. Tensions between the Lakota and the US Government led to bloody skirmishes, broken treaties, and ultimately to the Lakota’s forced removal to reservations and a loss of their hunting grounds.
History runs even deeper in Badlands National Park. Pre-historic camels, three-toed horses, rhinoceroses, and many other mammals roamed this area thousands of years ago. In the 1840’s, rich fossil beds with many late Eocene and Oligocene mammal fossils were discovered. In the Pierre Shale and Fox Hills Formations, Cretaceous era fossils dating back 70 million years have also been found. To this day, the Badlands and Black Hills of South Dakota are popular fossil hunting destinations.
While average winter temperatures in the Badlands hover around freezing, summer is great time to visit this wonderfully diverse and spectacularly scenic area. Few areas of the globe offer such a rich dive into deep history where the narrative of geologic change can be so clearly read in the rock. Badlands National Park offers a glimpse into how dramatic climate change and human-disturbance can alter a system. A lesson we all need a reminder of as we grapple with how to manage and prepare for the present and future impacts of human-catalyzed global climate change.