Geological History
Bear Butte is not strictly a butte (created primarily by erosion of sedimentary strata), but a laccolith: an intrusive body of igneous rock, uplifting the earlier sedimentary layers, which have since largely eroded away. This is the result of the forcible entry (or intrusion) of magma into cooler crustal rock in the Black Hills area during the Eocene Epoch. In this, Bear Butte shares a similar geological history with other formations in the region, including the Black Hills, Devils Tower, the Missouri Buttes, and some parts of the Rocky Mountains. It is possible that when the intrusion was emplaced, some magma may have breached the surface, forming a volcano; however, it would have eroded away long ago.
The peak rises 1,253.5 feet (382.1 m) above the surrounding plain and is 4,426 feet (1,349 m) above sea level.
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