Just before midnight on August 17, 1959, a massive earthquake measuring 7.5 on the Richter scale jolted Yellowstone and the Madison River canyon, sending large chunks of mountain into the river. A campsite just below the mountain was covered with rubble and 19 people were buried alive. The rubble that collapsed into the river created a dam and the aptly named Quake Lake. The ghostly fingers of trees that died when they were swamped still poke skyward from the lake. The visitor center on the north side of the highway offers exhibits, a video every half-hour, and an observation area from which you can see the massive slides. The area around Yellowstone and Quake Lake is still very seismically active, and southwest Montana is second only to California in terms of earthquake frequency. The visitor center has a great deal of information about the area's seismic activity and hypotheses of how it got this way.