The cracking sounds were ferocious. An ankle-deep, frozen lake in Death Valley National Park was breaking apart under sunny skies. As cousins Richard Norris and James Norris watched, a light wind began moving huge floes of ice across the surface of the water and into rocks weighing up to 200 pounds. Propelled by the ice masses, the rocks began to slide across the slick, muddy bottom of the normally dry lake bed, known as the Racetrack playa. “My god, Jim, it’s happening,” Richard yelled. James Norris grabbed a camera. Their photos last Dec. 21 provided the final evidence in solving a mystery of the Racetrack Playa that has long puzzled visitors and scientists: What mechanism moves rocks across flat dirt in the heart of the hottest, driest place on earth? Read more via LA Times.