Racetrack Playa is a dry lake bed located 3,608 feet above sea level in Death Valley National Park, California. The playa is named after the "racetracks" left by stones that mysteriously skid across its surface.
The Racetrack is primarily covered with hexagonal saucers of dry mud, left after a very short season when the lake bed is covered with a shallow layer of water after rains wash down from the surrounding mountains and into the playa. But marring this surface is the creepy evidence of stones that move on their own.
Sliding slowly without any intervention for distances as long as 1,500 feet, the sailing stones have never been filmed in motion, yet they're definitely on the move. The strange phenomenon only happens every few years, and the tracks are left for several years for visitors to ponder. One hypothesis is that winds -- which can howl at up to 90 mph -- push the stones across the slick mud left as the lake bed dries up after a downpour. A second similar hypothesis poses that after a thin sheet of rain falls over the playa and night temperatures drop to below freezing, a layer of ice forms across the surface of the lake bed and the stones slide across the ice with the wind.
The only way to find out for sure would be to set up cameras and environmental sensor tools to understand just what makes these rocks move. Until then, they will remain a mind-blowing mystery!