At 11:37 p.m. on Aug. 17, 1959, a 7.5 earthquake shook this area and triggered a massive landslide in which 80 million tons of rock, half a mountain, crashed down. The slide blocked the rushing currents of the Madison River and created a massive rock dam, causing water to churn behind it and rise quickly, submerging Rock Creek Campground by 6:30 a.m. the following morning. The landscape instantly changed, lives were lost, and a lake formed. The trees standing in the middle of the lake remain reminders of the dynamic forces that formed Earthquake Lake. More than three miles of former U.S. Highway 287 lie under Earthquake Lake and landslide debris, and a new road now runs along the north shore. At the end of the lake, a spillway channel cuts through the slide, made in haste by the U.S. Army Corps of Engineers to avert a possible flood downstream. Earthquake Lake is now 4 miles long and 120 feet deep.