Age of the Badlands Rocks

Although the formations of the badlands are young as compared to some rocks such as the granite in the Black Hills or the limestone in which Wind Cave is formed, they are ancient indeed when compared to human history. The geologic period (Tertiary) in which they originated began about 63 million years ago, and the Oligocene epoch of this period began about 36 million years ago and lasted for about 11 million years.

Most laymen are bewildered when confronted with a statement that a certain exposure of rock is 36 million years old. How do we known the age of anything so remote from human experience? The geologist has several ways of determining comparative ages; some are fairly accurate and some admittedly less so. The most accurate determinations are made when the rocks contain radioactive elements. Certain elements, after formation in the earth, break down into other elements at known rates of speed. By carefully controlled chemical and physical techniques, the amount of disintegration can be determined and the age of the mineral computed.

The most reliable estimates place the age of the badlands formations at about 36 million years—an almost incomprehensible figure. Try to visualize it this way: The width of this mark / is 1/64 of an inch. Let it represent 5,000 years, or about the sum total of recorded human history. Now place 7,200 of these lines side by side to make a solid black bar about 112 inches long and you will have a graphic comparison of the age of recorded history and the approximate age of the layers of rock in the badlands.

The first fossil described from the badlands—a fragment of the jawbone of a titanothere, a rhinoceros-like animal that lived here some 30 million years ago

GEOLOGIC TIME CHART