Mount Rushmore National Memorial - Natural Features

Afternoon thunder showers can produce rainbows over the Black Hills during the summer. Blaine Kortemeyer/NPS If you go for a walk on the Presidential Trail or hike to Old Baldy or into Starling Basin you should touch the granite. How do you think it will feel under your fingers?

Granite is one of the primary rock types in the Black Hills. Mount Rushmore is carved from a granite formation locally known as Harney Peak granite. The core of the Black Hills is made of this granite that formed underground as a batholith. A batholith is a large plume of magma that cools and hardens underground. About 60 to 70 million years ago the batholith was uplifted during the Laramide Orogeny, creating the Black Hills. After being uplifted the Black Hills may have been twice as tall as they are now. Time, wind, rain, snow, and ice have reduced the Black Hills to their present height. Harney Peak is the tallest peak in the Black Hills at 7,242 feet above sea level. Mount Rushmore is 5,725.

Granite isn"t the only rock in the Black Hills, mica schist can be found in many areas. Mica schist is a metamorphic rock, a rock that has been changed to it present form by heat and pressure, but did not become molten. Mica schist is a very brittle rock and proved to be uncarvable when work was attempted on it during the carving of Mount Rushmore.

The rocks that you can feel under your fingers here at Mount Rushmore have had an influence on the landscape and the features you will see all around you. Whether the rock is broken down into soil, eroded by streams into V-shaped valleys or still stands tall providing you with lofty places to climb and hike, these natural features will leave your senses full.