How Death Valley’s ‘sailing stones’ move on their own

Becky Crew in Science Alert:

ScreenHunter_734 Aug. 02 22.52Located above the northwestern side of Death Valley in Eastern California's Mojave Desert, an exceptionally flat dried lake called Racetrack Playa contains a peculiar phenomenon. Dozens of large stone stabs made of dolomite and syenite – often weighing as much as 318 kilograms – move across the cracked mud, leaving a series of smooth trails behind them.

Some of these trails stretch for a whopping 250 metres. They often form a nice, lightly curved line, but sometimes they form sharp, zig-zagging angles, implying a sudden shift to the right or left. These ‘sailing stones’, as they’ve been nicknamed, are so common on the the Racetrack Playa, they make it look like a well-worn racetrack, hence the name. (Playa is another word for ‘dried lake’.)

It’s obvious that these stones are moving because of the trails, but how? No one knew. Since the 1900s researchers and casual observers were fascinated by the stones but no one could explain how they moved. And the biggest factor that kept the answer obscured over a century was that to this day, no one’s ever seen them move.

According to Marc Lallanilla at LiveScience, while the less informed guesses included everything from aliens and magnetic fields to good old-fashioned pranksters, a popular theory among researchers was that dust devils, which are strong, relatively long-lived whirlwinds, were pushing the stones around as they swept across the playa. But this theory, and others that cropped up, were all disproved.

And then in 2006, planetary scientist Ralph Lorenz from the Johns Hopkins University Applied Physics Laboratory in the US started investigating the sailing stones. He came to the Racetrack Playa with an interest in studying its similarities to a hydrocarbon lake on Saturn’s moon, Titan, and stayed to put an end to a long-standing mystery.

To do so, all he needed was a small rock, some water, and an ordinary Tupperware container. Lorez put the small rock in the bottom of the Tupperware container and filled it with a few centimetres of water. Then he put the whole thing in the freezer.

More here.