Sailing Stones

geology · desert · mysterious movement

Rocks that move. Sailing stones are rocks that slide across smooth valley floors on their own, leaving long tracks in the dirt and mud behind them. Scientists studied these mysterious trails for a long time before figuring out what was actually happening.

Ice does the pushing. The rocks move when thin sheets of ice form on winter ponds during cold nights. Wind breaks the ice into pieces, and as these floating ice sheets push and slide across the pond, they nudge the rocks along with them.

Famous racetrack. The most famous sailing stones are found at Racetrack Playa in Death Valley, California, where rocks leave trails that stretch dozens of feet long. The smooth, flat ground there is perfect for the rocks to slide great distances.

Needs water first. The rocks can only move during winter when water freezes into sheets of ice on ephemeral ponds, which are temporary bodies of water that form and disappear seasonally.

Solved mystery. For decades, people wondered how rocks could move on their own, but scientists eventually figured out it was the floating ice sheets doing all the work, not anything magical or mysterious.