How the Badlands Keep Changing

From a grassy prairie in South Dakota, the land suddenly seems to drop away. Below are striped cliffs, narrow spires, and deep gullies. These shapes in Badlands National Park may look still, but water and wind are slowly changing them. Their story begins long before the shapes appeared.

Layers from the past

Millions of years ago, this region looked very different. Rivers and streams carried sand, silt, and mud across broad areas. When the water slowed, it dropped, or deposited, these materials. Layers built up over long periods of time. Volcanic ash from distant eruptions also settled over the region and became part of the layers.

As more material piled on top, the lower layers were pressed together. Over time, they hardened into sedimentary rock. Different layers contain different materials, which help give the Badlands their bands of gray, tan, red, and other colors. The bands are like pages in a long history, although some pages are missing because material has worn away.

Water shapes the land

Erosion is the wearing away and movement of rock and soil. In the Badlands, rain is especially important. Water runs down slopes, carrying loose grains into small channels. As more water follows these paths, the channels can deepen and widen into gullies and canyons.