Glacial erratic boulders atop Olmsted Point, with the massive granite monoliths Half Dome and Clouds Rest in the background. Erratics are huge boulders left behind by the passing of glaciers which carved the granite surroundings into their present-day form. When the glaciers melt, any boulders and other geologic material that it was carrying are left in place, sometimes many miles from their original location.
Location: Yosemite National Park
Image ID: 23264