Inyan Kara Mountain

Inyan Kara Mountain is a mountain associated with the Bear Lodge Mountains of Crook County, Wyoming, that is considered sacred by the Lakota people, particularly for mothers in childbirth. Inyan Kara stands apart from the main body of the Black Hills, with an elevation of. The mountain was stated to rumble on quiet days by the local Native Americans and by early explorers. No mention of the noises is found after 1833; the noise has been attributed to gas escaping from burning coal seams.
The peak was visited by George Armstrong Custer during Custer's 1874 Black Hills Expedition, reaching the summit on July 23.
The peak was placed on the National Register of Historic Places in 1973.

Geology

The mountain is a prominent "structural dome" and igneous intrusion, composed of a light-colored syenite porphyry or alkali rhyolite, which was emplaced as a small laccolith during the Eocene Epoch. This igneous activity occurred approximately 50 to 58 million years ago, as part of the broader volcanic event that formed other nearby landmarks such as Devils Tower and the Missouri Buttes. Magma did not reach the surface, but intstead pushed up the existing sedimentary rocks, creating the dome that is across. The intrusion pushed through roughly 4,000 feet of sedimentary rock, spanning in age from the Mississippian Age, to the Cretaceous. The oldest rocks are Pahasapa Limestone. This is overlain by Minnelusa, Opeche, Minnekahta, and red shale from the Spearfish Formation.