How sailing rocks of Death Valley 'move on their own' revealed

A new study has helped researchers unveil the mystery behind "moving", sailing rocks of Death Valley's Racetrack Playa.

A team of researchers from the Scripps Institution of Oceanography at UC San Diego, brought in a high-resolution weather station to measure wind at one-second intervals, and brought in 15 rocks fitted with GPS devices to capture the movement of the rocks, CNet reported.

The movement requires the perfect concatenation of events. First, the playa has to fill with water, which must be deep enough to form floating ice during winter, but still shallow enough that the rocks are exposed.

When the temperature drops at night, this pond freezes into thin sheets of "windowpane" ice, which then must be thick enough to maintain strength, but thin enough to move freely. Finally, when the sun comes out, the ice melts and cracks into floating panels; these are blown across the playa by light winds, propelling the rocks in front of them.

The sheets of ice are only 0.25in thick, moving under winds of 10mph, pushing the rocks along at a speed of only a few inches per second, a speed which would almost be imperceptible at a distance unless someone knows what to look for.

The study is 'Sliding Rocks on Racetrack Playa, Death Valley National Park: First Observation of Rocks in Motion', is published in the journal PLOS One.