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Racetrack Playa (Google Maps view here) is a 2.8 mile long, 1.5 mile wide dry lake in California’s Death Valley.  It is over 3,800 feet above sea level and is unconnected from any other waterway. During the summer and again in early winter, the area receives some rain, and every few years, Racetrack Playa collects some water. The water leads to a layer of mud which dries come spring and fall, creating a patchwork of cracked, dried up mud shapes across the Playa’s entire surface.

On top of that dried mud are the sailing stones.

Pictured above, the sailing stones are a curiosity uniquely found at Racetrack Playa. Without even so much as a push from animals or people, these stones — some weighing hundreds of pounds — make their way across the landscape leaving telltale tracks in their wakes. Their patterns are not simply straight shots, either; as seen here, sometimes, they zig zag. If you want to watch a video of these stones’ movements in action, you can’t — they move rarely (only once every few years), and therefore their movement has never been caught on film.  But the tracks they leave behind — which last years — are more than enough evidence to demonstrate that they move.  But how?  What is making these stones sail?

There are a few theories, and no, UFOs aren’t one of them (at least not to any serious degree, with apologies to this guy). Some suggest that a combination of rain  – which make the playa’s surface slippery — and winds of 90 miles per hour can cause the movement. This theory is buttressed by the fact that these conditions do, indeed, happen, but only rarely; and that the stones seem to move in the same direction as the prevailing winds at Racetrack Playa.  Another theory adopts the view that ice forms on and around the rocks when the area gets sufficient rain and low enough temperatures; this, combined with even a light wind, allows the stones to move around in a more chaotic pattern.

Regardless of reason, these stones, set on the backdrop of the Racetrack Playa, provide both mystery and beauty.  Wikipedia has a panoramic photo of a sailing stone against the night sky, seen here. It is a picture more Mars than Earth, but rest assured: no Martians were involved.

Bonus fact: In Yap, Micronesia, locals use large stones called rai as currency. The value of each stone is a function of, among other things, the stone’s size, leading to gargantuan ones such as the one seen here. Extraordinarily large rai stones can be 10 feet in diameter and weigh over 8,000 pounds.

From the ArchivesThe Strategy Behind Rock Paper Scissors.  Well, at least it’s tangentially related to rocks/stones.

Related: Probably the closest thing you’ll get to having your own sailing stones on your desk. As a bonus, you can also use it to play shuffleboard and bowl a little, too.

Originally published

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