TIME Environment

Solved: Mystery of Moving Stones in Death Valley

A sailing stone in Racetrack playa, Death Valley, CA.
A sailing stone in Racetrack playa, Death Valley, in California Mark Newman—Getty Images

A group of scientists say they've figured out how the "sailing stones" glide along the desert floor on their own

So-called sailing stones in California’s Death Valley National Park have perplexed tourists and scientists alike for their apparent ability to move on their own, leaving sometimes meter-long tracks in their wake.

But after years of speculation, researchers with patience, remote weather monitors, cameras, and stones that are fitted with GPS say they have discovered the force behind the phenomenon.

Wind (very strong winds) and ice (very thick ice) have long been considered as possible explanations for why the rocks, sometimes weighing hundreds of pounds, move. It’s actually a combination of a little of both, the team of researchers say in their study, published in the journal PLOS One this week.

Rainwater in what is known as the Racetrack Playa creates a shallow pond over the playa that, in cold winter temperatures, freezes over. When the ice begins to melt under the sun, it first breaks up into large panels thin enough that, with a nudge from even light winds, they shift — and push whatever rocks may lie in their path.

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