The moving rocks on the Race Track of Death Valley, California have defied explanation since they were first observed. All that had ever been seen are the rocks and their trails in the cracked mud of the playa. The rocks weigh as much as 318 kg and have moved as much as 250 meters. The mystery was finally solved when scientists from National Geographic tracked the rocks and were actually present when they moved. The movement was caused by ice forming a collar around an individual rock and, when additional water ran onto the playa, the rocks, buoyed by the ice collar, were pushed by the wind.