On a quiet August night at a Forest Service campground below Hebgen Dam, an earthquake suddenly tore through the area, slicing across the campground and Cabin Creek as the ground trembled, jolted, and widened into a crack while one side dropped between 5 and 20 feet. Campers saw a newly exposed wall of earth and a short-lived waterfall created by subsidence along the Hebgen Fault at Cabin Creek. The 20-foot cliff appeared on the night of August 17, 1959, when the Hebgen Lake Fault Block, a large section of the Earth’s crust covering about 125 square miles across the West Yellowstone Basin, dropped along a normal fault caused by stretching of the crust. Eyewitnesses said the descent may have happened in abrupt jerks as the bedrock walls of the deep fault rubbed against each other. Scarps like this one reveal the dynamic history of the Basin and Range Province, where older scarps show that other earthquakes also created similar displacements.