Mount Rushmore community. Recent pine beetle infestations have threatened the forest. Mount Rushmore is largely composed of granite. The memorial is carved on the northwest margin of the Black Elk Peak granite batholith in the Black Hills of South Dakota, so the geologic formations of the heart of the Black Hills region are also evident at Mount Rushmore. The batholith magma intruded into the pre-existing mica schist rocks during the Proterozoic, 1.6 billion years ago. Coarse grained pegmatite dikes are associated with the granite intrusion of Black Elk Peak and are visibly lighter in color, thus explaining the light-colored streaks on the
Mount Rushmore in popular culture in the course of screenwriting, as Hitchcock and scriptwriter Ernest Lehman were struggling to develop an idea. As Lehman would later recall, Hitchcock "murmured wistfully, 'I always wanted to do a chase across the faces of Mount Rushmore.'" While writing the script, Lehman took a trip to Mount Rushmore to scale the faces of the famous monument; he only got halfway to the top, and bought a camera to give to the park ranger to photograph the famous monument for him. However, the scene was not actually filmed at the monument, since permission to shoot an attempted killing on the