Most rocks are boring. Some can be interesting which is why some people collect them. For their interesting textures or colors or what have you. Though when it comes to action, rocks are not exactly known to be powerhouses of fun and joy, unless they are flat and smooth and there happens to be a lake or a pond near by. Rocks and stones, for the most part, just sit there, doing nothing except being hard and old. As with most things however, there are exceptions such as the so-called “Sailing Stones” in California’s Death Valley.
Like a rolling stone
One of the strangest natural mysteries around, the sailing stones have perplexed scientists and laymen alike for decades. Basically rocks seemingly like any other, some of them as small as six to eight inches in diameter, the Sailing Stones, most famously, though not exclusively found in a dried lakebed called Racetrack Playa in Death Valley have a habit of moving, with no apparent outside force making them do so. This evident freedom of movement extends to direction as well, many stones found to have been moving in opposite directions to each other and in some case seven turning off course up to 90 degrees.
The hows and the whys of the Sailing Stones
As with any great mystery there are a great number of theories and also with a great mystery many of these theories are fairly silly. One of the most sensible seeming but incorrect ideas has to do with some sort of hitherto unnoticed magnetic activity in the area. While not patently absurd, there have been cases of magnetic activity in such desert areas before, it is unlikely to be the answer in the case of the sailing stones. The reason this theory has been discounted is that not all of the stones in Death Valley move, there are stones outside of Death Valley that move in a similar manner, the stones that do move do not contain high enough levels of magnetic materials and move in markedly different directions.
If a magnetic field were the culprit, all of the stones would move exactly the same direction, drawn to the same point. Another theory, no less simple but more likely given the available evidence is that strong winds have moved the stones when the lakebed has become slick, the movement not being something that happens regularly, as well as having gone largely unobserved.
What REALLY happened
The most likely theory and the most scientifically sound and least otherworldly, has to do with a combination of factors. While Racetrack Playa may well be a dried lakebed in an expansive desert, this is not to say that it is always, literally dry. Moisture can build up from occasional rain or melting snow from nearby mountains. As researcher Brian Dunning pointed out, even the temperatures can drop below freezing and if they do, this can cause a thin sheet of ice on the lakebed. To quote him directly from the Skeptoid podcast: “Solid ice, moving with the surface of the lake and with the inertia of a whole surrounding ice sheet, would have no trouble pushing a rock along the slick muddy floor… As the wind shifts and the flow ebbs, these ice floes drag the rocks across the slippery mud surface in zig-zagging paths, even moving heavy rocks and sometimes dragging some but washing past others nearby.”