Racetrack Playa Death Valley, California—Self-propelled rocks

The Mystery: In the vast, flat desert of Death Valley, a series of colossal boulders, weighing up to 700 pounds each, appear to move on their own. There are no traces of bulldozers, footprints, or tire tracks. Not only that, these sliding rocks leave behind deep "scars" that disappear in less than seven years. Gravity was once thought to be the culprit, until researchers discovered that many of these massive stones were skittering uphill.
The Reality: One recent study using differential GPS and rock-trail analysis suggests that a potent combination of blasting winds, whirling dust devils, and the slick playa surface causes the rocks to inch ever so slowly along the desert floor.
Photo Portfolio: Uta Kögelsberger

Racetrack Playa is a flat lake bed located between the Cottonwood Mountains and Last Chance Range. This trail sign at Teakettle Junction in Death Valley points toward the playa.

Racetrack Playa is a very remote place. To find it, you have to travel almost 60 miles past the Death Valley Visitor Center, then go 30 more miles down a rough dirt road, and hike half a mile from the parking lot. Uta says it was very peculiar to come across dozens of photographers in this vast, stark landscape kneeling with their cameras to shoot photos of the rocks.
Adding to the strangeness was the noise of jets from Edwards Air Force Base breaking the sound barrier above their heads. "Being in the middle of nowhere with a military exercise going on above my head was spooky," says Uta.
Photo: Uwe Zirpner

The rocks trails aren't permanent. A rainstorm can wash away the paths of smaller rocks, and none last more than six to seven years.
 http://www.wired.com/culture/culturereviews/magazine/17-05/ff_mysteryspots?currentPage=all