A badland is a type of landscape that has been deeply carved by erosion into a maze of steep ridges, gullies, and ravines, with little or no plant life clinging to its surface. These dramatic formations develop on soft rock over thousands of years, and once the process reaches its final stage, the terrain is essentially irreversible. The name itself comes from the Lakota word “mako sica,” meaning literally “bad lands,” a reference to how brutally difficult the terrain is to cross.
How Badlands Form
Badlands need four ingredients to develop: steep terrain or an actively changing base elevation, soft rock that weathers easily, a climate with intense rainfall events, and conditions that prevent protective vegetation from taking hold. When all four align, water does extraordinary damage in a short geological timeframe.
The process starts with soft sedimentary rocks like claystone, siltstone, and mudstone. These materials compact easily but erode even more easily. When rain hits exposed slopes, it cuts small channels called rills. Those rills deepen into gullies. The gullies multiply and branch, creating an extremely dense drainage network of V-shaped valleys separated by narrow, knife-edge ridges. Meanwhile, the cliff faces retreat as cycles of wetting and drying cause the rock surface to crack apart and crumble. At the base of retreating cliffs, broad sheets of runoff plane the surface into gentle slopes called pediments, which extend further with each storm.
The rock type underneath directly controls the texture of the landscape. In South Dakota’s Badlands National Park, for example, the Chadron formation produces fine-textured topography, while the overlying Brule formation creates ultra-fine textures with even more tightly spaced ridges and channels. Each slope eventually reaches a kind of equilibrium where the steepness matches the rock’s resistance to erosion, but that balance is constantly being reset by new storms.
The Rocks That Make It Possible
Not just any rock produces badlands. The formations depend on materials soft enough to erode rapidly but cohesive enough to hold steep faces temporarily. Claystone, siltstone, and sandstone are the most common parent rocks. Volcanic ash deposits play a special role in many badlands, particularly in the American West. Over millions of years, ash layers decompose into bentonite, a clay made primarily of a mineral called montmorillonite. Bentonite swells dramatically when wet and shrinks when dry, creating a cycle that constantly fractures the rock surface and accelerates erosion.
This swelling property is also what makes badlands so miserable to walk through. When it rains, the wet clay becomes slick and impossibly sticky, clinging to boots and hooves alike. When it dries, the surface hardens into a brittle crust that crumbles underfoot. Some badlands also contain lignite, a low-grade coal that can spontaneously ignite underground and burn for years, baking the surrounding rock into reddish, hardened masses called clinker.
How Fast Badlands Erode
Badlands are among the fastest-eroding landscapes on Earth. In southwestern Taiwan, where tectonic forces are actively pushing the land upward, badlands erode at roughly 11 millimeters per year over millennial timescales. On individual hillslopes in the same region, erosion rates can spike to 90 to 300 millimeters per year. To put that in perspective, most mountain landscapes lose a fraction of a millimeter annually. A badland hillslope losing 100 mm per year would drop by a full meter in a decade, which is fast enough to watch the terrain change within a human lifetime.
Where the Name Comes From
For hundreds of years, the Lakota people called the terrain in what is now southwestern South Dakota “mako sica.” When French fur trappers moved through the region, they adopted the concept, calling it “les mauvaises terres à traverser,” or “bad lands to travel across.” Since the French traders spent considerable time with the Lakota, the French name almost certainly came directly from the Lakota one.
The name stuck because it was accurate. Jagged canyons and buttes make navigation nearly impossible. The few water sources tend to be muddy and undrinkable. Winters are bitterly cold and windy, summers scorching and dry. Archaeological evidence suggests that even early human groups used the area only for seasonal hunting rather than permanent settlement.
Where Badlands Exist
The most famous badlands are in western South Dakota, preserved as Badlands National Park, but the landform type occurs worldwide. North Dakota’s Little Missouri National Grassland contains extensive badlands carved from similar sedimentary layers. Canada, Argentina, New Zealand, Italy, and Spain all have notable badlands formations. The common thread is always the same: soft, weatherable rock exposed to erosive rainfall in areas where vegetation can’t establish a protective cover.
Badlands can form in a surprisingly wide range of climates, from semi-arid plains to subtropical mountain fronts, as long as rainfall arrives in intense bursts rather than gentle, steady drizzle. It’s the energy of the water, not just the amount, that does the carving.
A Window Into Prehistoric Life
The same rapid erosion that creates badlands also makes them one of the best places on Earth to find fossils. As layers of rock wear away, they continuously expose bones and shells that have been buried for millions of years. At Badlands National Park, fossils range from 75 million to 28 million years old, and many are found in excellent condition because the sedimentary layers lie flat and undisturbed.
The most common fossils there are oreodonts, stocky herbivores roughly the size of a sheep that once roamed in enormous herds. But the park has also yielded brontotheres (massive rhino-like mammals), nimravids (false saber-toothed cats that predated true saber-tooths), and even mosasaurs, marine reptiles that swam through warm seas covering the region during the late Cretaceous period. In 2012, a remarkably well-preserved nimravid skull was discovered, and the park’s longest excavation, known as the Big Pig Dig, recovered nearly 20,000 individual fossils from a single site.
Life in the Badlands
Despite the hostile terrain, badlands are not lifeless. The eroded buttes and spires are largely barren, but the surrounding mixed-grass prairie supports a rich ecosystem. Badlands National Park alone is home to over 400 plant species. Western wheatgrass, a native perennial that grows one to three feet tall, is the dominant grass. Rarer species like Barr’s milkvetch and Dakota buckwheat are found almost nowhere else. Periodic wildfire maintains the prairie by burning dry grass tops while leaving root systems intact, allowing rapid regrowth.
The animal community is equally notable. American bison, which can weigh up to 2,000 pounds and sprint at 35 miles per hour, graze the prairie and travel roughly two miles each day. Black-tailed prairie dogs serve as a keystone species: their vast interconnected burrow systems loosen the soil, encourage new plant growth, and provide habitat for other animals. Black-footed ferrets, one of North America’s rarest mammals, live almost exclusively in abandoned prairie dog tunnels and hunt the prairie dogs themselves. Pronghorn, which can reach speeds of 55 miles per hour, use the open plains to outrun predators. The prairie rattlesnake, growing up to five feet long, is the only venomous snake in the ecosystem and preys on burrowing owls, prairie dogs, and small rodents.
The contrast is striking: a landscape too harsh for permanent human habitation supports one of the most intact prairie ecosystems remaining in the United States.