The "sailing rocks" of Death Valley have baffled scientists since the 1940s. 

How can large rocks, some even weighing hundreds of pounds, move across the waters of Racetrack Playa and leave trails on the earth?

Cousins Richard and James Norris of the Scripps Institution of Oceanography at the University of California, San Diego have solved the mystery through time-lapse video and GPS technology.

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The two were able to get permits from the National Park Service to install a weather station in Death Valley and place 15 stones mounted with global positioning devices on the southern end of the body of water. 

The southern end of the playa is where rocks journey after falling from a cliff.

After leaving their equipment for a year, when they returned, they saw that the water was covered with ice and, that there were new rock trails near thin ice stacked up on the shoreline.

The afternoon that followed gave them the answer to the question that has confused scientists over the years.

"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," Richard shared.

Overnight rainwater creates a shallow pond over the playa that turns to ice during winter. When the ice begins to melt from the hot sun of Death Valley, the ice breaks up into thin, large panels which shift with just a tiny nudge from the wind. The shifting pushes rocks that lie in the ice's path.

The duo catalogued 60 rocks moving across the water in December last year and published their findings in the journal Plos One last Wednesday.

"Observed rock movement occurred on sunny, clear days following nights of sub-freezing temperatures," they shared.

They observed that rocks moved around 15 feet per minute.

The Norris cousins stated that the "sailing rocks" phenomenon is rare because the area is usually very hot and dry.