Sailing stones (also known as sliding rocks or moving rocks) are a mysterious geological phenomenon in which large rocks move along the floor of a valley, seemingly by themselves, leaving tracks in their wake. Rocks that start off beside each other may go in different directions. The phenomenon has been studied at Racetrack Playa in Death Valley, California, where the rocks move once every two to three years, leaving behind tracks lasting for three or four years.
Theories about what makes these rocks move include:
- Strong winter winds -- gusts of wind start the movement, then sustained wind keeps the rocks moving
- Strong winds that move the rocks in combination with wet mud
- Ice floes that drag the rocks along with them
- Ice sheets surrounding the rocks that give them more surface area for the wind to catch
- Ice collars around the rocks that enable them to float when water levels rise
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