What are sailing stones? Maybe you’ve seen galleries of these things online over the years: mysterious stones in Death Valley with long trails behind them, moved hundreds of feet, it appears, by unexplainable forces. How can a 200-pound stone move like that? Wind? Telekinesis? Aliens? Scientists have studied them since at least the 1940s, and in 2013, they finally made a breakthrough discovery: they actually saw them move, thanks to GPS tracking, time-lapse photography, and a whole lot of luck.
So how do sailing stones form? Here’s the big reveal: “Wind-driven ice that forms and then breaks up under certain conditions.” Super-rare “ice rafts,” basically, move the stones every decade or so, but only if the weather conditions are perfect. That might not sound like a very sexy explanation, but the science behind it is actually pretty amazing. Read on for more fascinating sailing stone facts.
A breakthrough study of the so-called “sailing stones” involved something you—and definitely your grandmother—have in the kitchen: Tupperware. NASA scientist Ralph Lorenz told The Smithsonian Magazine he used sand, a rock, and some water in a large Tupperware container to conduct an experiment that helped him and his team discover the model for how the stones “sail” at Racetrack Playa in Death Valley. He created a thin slab of ice-covered sand in a freezer with a small rock sticking out of it. By gently blowing on the ice, the rock is floated out of the mud, leaving a little trail in its wake.
Starting in 1968, researchers decided to assign the stone women’s names to help track them. Karen, for example, is a 700-pound stone. Hortense is pretty speedy: she moved 820 feet one winter. Other names include Ossie, Bessie, Bep, Alanis, Layla, Goldy, and Xeino. The scientists also tagged the stones using washable ink.
A 2013 Los Angeles Times report shows that Death Valley National Park officials actually had to investigate the theft of “several” sailing stones at Racetrack Playa. A park ranger told Smithsonian Magazine that he has a guess at a possible motive: “I don't know whether people think they're ‘magic rocks,’” he said. “But of course, as soon as you remove them from the playa, all ‘magic’ is lost.” A park spokesman agrees that “outside of the Racetrack, these marvelous rocks have no value.” The stones are, after all, simply caused by erosion from the surrounding mountains.
The researchers that eventually discovered how the “sailing stones” move were definitely in the right place at the right time. As The Verge puts it, “conditions need to be perfect” to catch the stones in action. This includes rain (in Death Valley!) combined with below-freezing temperatures (in Death Valley!), followed by a warm-up to melt the ice. Oh yeah: there also needs to be wind to push and break the ice. Fortunately for the researchers, a “freak storm” struck at the right time.