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 Pilchuck State Park Mount Pilchuck State Park Mount Pilchuck State Park is a public recreation area located east of Granite Falls, Washington, on the western edges of the Cascade Mountains. The state park features of alpine scenery, recreational activities, and Mount Pilchuck itself. The main point of interest is the trail to the peak and the old fire lookout located on the summit, above sea level. The name "Pilchuck" originated from the Native American name of "red water" for a creek in the area. The U.S. Forest Service built a fire lookout on the summit in 1918 which was staffed until the 1960s.