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Scientist Figures Out How Those Big-Ass 'Sailing Stones' Move Themselves Across Death Valley
By Rain Noe - Jun 12, 2013
"Racetrack Playa" sounds like the screenname of an online teenager you're competing against in Need for Speed, but scientists recognize it as the name of a dried-up lake in Death Valley. For a century, scientific minds have been puzzled by a well-documented, poorly-understood phenomenon occuring at Racetrack Playa: Enormous stones, some up to 700 pounds, appear to have somehow moved themselves across the lakebed floor in random patterns, leaving a furrowed trail behind them.
No one had ever seen these "sailing stones" move, but many photographed the end result. The original thought was that the lakebed forms a thin sheet of ice on it, and that the wind then blows the rocks across it; but that theory was discounted after researchers calculated it would take wind speeds of hundreds of miles per hour to move the rocks, while the wind at the Racetrack maxes out around 90 m.p.h. And if you're wondering why they don't just strap a GoPro camera onto a rock to see what's going on, scientists returning to the site over the years have calculated that the rocks move for short periods of time, just once every three years. That's a bit longer than your battery's likely to last.
However, a fortunate collision between two of these magic rocks provided planetary scientist Ralph Lorenz with an interesting discovery:Lorenz, studying the trails left by the stones, observed that one rock had collided against another and been deflected. "There was a rock trail and it looked like it hit another rock and bounced, but the trail didn't go all the way up to other the rock, like it was repelled somehow," Lorenz told Smithsonian Magazine. In other words, there was some kind of force-field-like barrier around each rock that prevented total contact.
What would spontaneously form a barrier around a rock, then later disappear? Lorenz realized that as moisture levels changed with the seasons, a collar of ice could form around the rock. With the rest of the lakebed covered in a thin, cold-but-not-frozen sheet of water, this ice collar would enable the rock it encased to float—slightly. It would lift it to the top of the water, but the rock's bottom, the part that was resting directly on the ground, would not have ice on it. Wind could then blow the rock across the water, and the bottom of the rock would dig a furrow into the lakebed. Later the ice and water would melt and recede.
Eventually, Lorenz employed a tried-and-true method for testing his nascent idea: the kitchen-table experiment. "I took a small rock, and put it in a piece of Tupperware, and filled it with water so there was an inch of water with a bit of the rock sticking out," he says. "I put it in the freezer, and that then gave me a slab of ice with a rock sticking out of it." He flipped the rock-ice hybrid upside down and floated it in a tray of water with sand on the bottom. By merely blowing gently on the ice, he realized, he could send the embedded rock gliding across the tray, scraping a trail in the sand as it moved. After decades of theoretical calculations by countless scientists, the answer seemed to be sitting on his tabletop.
Lorenz's full research paper, entitled "Ice Rafts, Not Sails," is available here.
Rain Noe
Rain Noe is a writer and industrial designer based in New York City.
18 Comments
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Curt,
You base your arguments on the point that all stones move at the same time, therefore they should have tracks going in the same direction if wind is the reason. It's probably not that common for the stones to freeze and float away, so some stones may freeze and move, making tracks as they go, while others are at rest. At a later point, they may also freeze, but the winds is blowing in a different direction.!Report as spam -
gods pushing them, duh!!Report as spam
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Is there a way to date the various rocks movement based on the organic content in the track? Then the movement could be matched to weather events to be seen in year rings of ancient trees? I am assuming that the events took place a very long time ago when the climate may have been different?!Report as spam
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Hi, could you tell me where the last photograph is from?!Report as spam
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It might be magnetic, as the earth orbits, there might be a magnetic force that keeps the rock on its diametrical place. The earth simply spins under the rock, but the rock stays in its place.!Report as spam
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Wouldn't scientists find something better to do than study some stupid rocks? Put your brain to some good use.!Report as spam
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The lifting of the stones due to moisture would account for the movement and trail but not for the selected time period (every 3 years) unless the required humidty/rainfall requirements are only met every 3 years.!Report as spam
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I reckon Steve and Ross have the most reasonable explanation. The hypothesis in the article is nice.. provided that someone does come along at night, puts the rock in a tupperware container in the freezer and then puts is back on the lakebed while the lakebed is flooded. The amount of ice and the depth of water required would have to be pretty substantial.
I wouldn't be surprised if it had something to do with the thawing characteristics of ice underneath the rock as the rock is heated by the morning sun. Still hard to believe it would cause this phenomenon, but a lot more reasonable imo.!Report as spam -
I'd say stoners.
Give it a minute, you'll get it.!Report as spam -
I think Steve is right. My thought is, what little water there is condenses on the underside of the rocks during the day. It freezes at night and thaws again through the day. This layer of water below the ice acts as a lubricant to allow the rock to shift in the direction of the path of least resistance, just as water moves. It's the same way glacial fields move.!Report as spam
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if they move in different directions with the same wind then it must be dependent on the rock itself - what if when the ground is frozen the rock warms up in the sunlight - it is a relatively good conductor and could build up heat while the ground could not - and it slightly melts the ice under it asymmetrically based on the shape of the rock and "falls" microscopically towards the thawed ground. at night the ground freezes and pushes the rock back up. this would account of the rocks moving in different directions and also why they leave relatively deep paths behind them.!Report as spam
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Are large amounts of frozen water, enough to cover most of the rock in a large frozen sheet, common in Death Valley during the winter? According to the national parks service, "Average rainfall is less than 2 inches (5cm), a fraction of what most deserts receive."
Seems like the mystery remains...!Report as spam -
And what are the conditions where the lake is covered by water and the rock is covered in ice? Is it early autumn?!Report as spam
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so...couple of problems, the amount of water required to lift a 700lb rock encased in ice would require the area to flood, also you would need a decent amount of wind at the same time and cold enough temperatures that would freeze the water on the stone, not on the ground below. the area just doesnt get that way. see?
http://www.desertusa.com/dv/du_dvpmap.html
and of course there's one major problem with that whole idea of the wind moving the rocks while they are floating or sitting or otherwise. wind only blows one way at a time. the rocks are moving in all different directions. if the wind was in play, and strong enough to move a 700lb "race rock" then all the smaller rocks would have been moved in the same direction over different distances. but they are not, they all move random directions. to make it more so, smaller rocks have been documented with shorter race trails than larger ones in the same area, meaning that either the wind is selective in that area or there are just no laws of the universe on that playa...
this cats got a good hypothesis, there are more holes in it than a block of swiss cheese, but its a good hypothesis...
!Report as spam -
Maybe aliens are landing in the desert, getting out of their spaceship, picking up and moving the rocks ever so slightly while we're not looking, getting back in their spaceship, and leaving, just to mess with us.!Report as spam
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has anyone considered magnetic force?!Report as spam
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This is not proof. This is a good hypothesis, but it is not proof the rocks in the playa move this way.!Report as spam
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can you believe people iceblock like this for fun?
!Report as spam
Continued Reading
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