Rocks from a few hundred grams to 320 kilos sit on a dry lake bed in Death Valley with long tracks trailing behind them, and nobody had seen one move since the phenomenon was written up in 1948. Solved in 2014, and the answer is better than the guesses. Researchers put GPS units in fifteen boulders and time-lapse cameras on the corner of the playa and caught it: a shallow winter pond freezes into thin ice panels, the ice breaks up on a light 4 to 5 m/s wind, and the floating sheets shove the rocks along at up to 80 mm a second. Not wind on wet mud, ice. The playa is 2.8 miles by 1.2 at 3,714 feet. Getting there is 28 miles of rough gravel from Ubehebe Crater and you want high clearance and a spare; summer runs past 120 F, there is no signal, and the nearest fuel is 60 miles away.
Death Valley National Park, California
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