Overview of Devils Tower geology (Alt + 1)
Sedimentary Rocks (Alt + 2)
Igneous Rocks (Alt + 3)
Erosion (Alt + 4)
Review of Devils Tower geology (Alt + 5)
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1. Deposition of Sedimentary Rocks
The layers of sedimentary rocks in the Black Hills area are nearly two miles (3.2 km) thick. Most of these layers were deposited in shallow seas beginning about 500 million years ago.

The general sequence of events leading to the formation of Devils Tower is as follows: