Hay Butte, Badlands National Park

The colorfully banded escarpments of Badlands National Park in South Dakota reveal a complex history of deposition and erosion of sedimentary rock layers overlying even more ancient igneous and metamorphic bedrock. The different bands testify to changing geologic forces such as the uplift of the Black Hills to the west, which were subsequently eroded, their deposits flowing into the basin to the east that would eventually become the Badlands. Ancient volcanic activity to the west of the Badlands deposited layers of dark ash carried by the wind. As climate and physiography changed, inland seas alternately flooded and exposed the area, creating habitat for the many animals and plants whose fossils can be found in various layers.

While the dramatic formations of the Badlands seem at first glance fixed, erosion continues to wear away the soft rock at a rate of up to one inch per year. Even more changeable are the colors of the landscape. When wet, the red bands stand out. In full sun, contrast among the bands can fade. This photograph was made in twilight as a line of storms approached from the south, the reflected blue of the lowering clouds lending a unique hue to the Badlands.

For a brief overview of Badlands geology, see Geologic Formations; for a more detailed account, see “Geology of Badlands National Park: A Preliminary Report.”