The Mystery Behind The Giant Moving Rocks Of Death Valley Has Finally Been Solved (Photos)

Death Valley is one of the most enigmatic places on earth, but its most enduring mystery—the sliding stones—appears to have finally been solved.

The Racetrack Playa, a dry lake bed in a remote part of the national park, is home to what geologists call "sailing stones"—rocks weighing up to 700 pounds that appear to move on their own and leave behind zig-zagging tracks in the dried mud. Ever since they were first known to have been observed almost 100 years ago, the mechanism behind the movement of the rocks was speculated to have been everything from hurricane-force winds to aliens. It seems all it takes is the right set of conditions, including a little bit of rain in the desert, freezing temperatures, and wind to get the seemingly-immovable objects moving.

Researchers lead by Richard Norris of UC San Diego's Scripps Institute were lucky to be out in Racetrack Playa back in December of 2013 after a winter storm had flooded the plain with a shallow level of water. With Death Valley's frigid winter nights dipping into freezing temperatures, a very thin layer of ice had formed. The desert sun beaming down during the day cracked the "windowpane" ice into smaller panels that were still strong enough to push the rocks through the mud as the wind blew. The conditions observed by the team were much less extreme than previously theorized. As opposed to the hurricane-force winds or massive layers of ice, all the rocks needed for a little push were less than a quarter-inch thick layer of ice and winds less than 10 mph, according to a press release from UC San Diego.

Richard Norris explains how the rocks move

Once the water evaporates, the tracks of the moving stones are left behind in the dried mud. It is these tracks that have puzzled observers for decades.

Because the set of environmental conditions necessary for the movement is so rare, it was pure luck that the scientists were on hand at the site to observe it in action. In 2011, Norris and his colleagues launched the "Slithering Stones Research Initiative" to study the rocks, installing a weather station at the location and planting 15 GPS-outfitted rocks on the plain in what they dubbed would be "the most boring experiment ever." When they visited the playa in December of 2013, they were fortunate to witness the phenomenon and record it on video. The rocks themselves don't move very fast, only about 15 feet per minute. Probably not fast enough for SpongeBob. Their findings have been published in the scientific journal PLOS ONE.

Tune to about 2:00 for your moving rock action

"We were sitting on a mountainside and admiring the view when a light wind kicked up and the ice started cracking. Suddenly, the whole process unfolded before our eyes," Norris told the LA Times. The rocks are thought to move once every few years, with lapses in activity lasting as long as a decade. The last suspected movement was back in 2006, and may be even more rare now because of climate change.

"There was a side of me that was wistful. Because the mystery was no more," he added.

"While it takes away the mystery, it also underscores what an amazingly rare and wonderful mechanism is at work there," said study co-author Ralph Lorenz of Johns Hopkins University.

The Racetrack Playa is certainly one of the national park's more fascinating attractions, but it is not easily accessible. The site sits at the end of a 26-mile unpaved road that requires vehicles designed for off-road use. Park officials worry that the renewed interest in the stones will attract more visitors to the site, leading to unprepared drivers getting stranded on the road, foot traffic disturbing the fragile site, and possible thefts of some of the stones.

Rangers might take solace in learning that the latter might not be an issue after all. The team also noted trails formed in the mud without any rocks. The movement of some of the ice panels left the marks in the mud.

The case may seem to be closed, but Norris still thinks there's more to learn. "We have not seen the really big boys move out there. Does that work the same way?"