Mystery: For hundreds of years,people have been baffled by the mysterious 'sailing stones' that occasionally appear at certain locations; most notably in Racetrack Playa, Death Valley National Park. Drag-marks appeared to have been left behind by even exceptionally large rocks, as if they had been moving in erratic patterns along the floor. Explanation: The main hypothesis was that when a small amount of water was on the surface of the ground, a sheet of ice would form, trapping the rocks. Wind would then move the whole thing, with the reduced friction allowing the rocks to travel along the muddy ground. This idea had been theorised for a while, but it was confirmed in August 2014, after time lapsed video footage showed the rocks moving during low wind speeds, across the thin, melting sheets of ice.
