DEATH VALLEY NATIONAL PARK, Calif. — For years scientists have wondered how large rocks — some weighing hundreds of pounds — zigzag across a flat portion of desert in Death Valley National Park. As they moved on their own when no one watched them, the rocks would leave long trails etched in the earth.
Now two researchers have photographed these “sailing rocks.” How are they moving? It turns out they are being blown by light winds across the former lake bed known as the Racetrack Playa.
Cousins Richard Norris and James Norris said the movement is made possible when ice sheets that form after rare overnight rains melt in the rising sun, making the hard ground muddy and slick.
Last year, the cousins catalogued 60 rocks moving across the playa’s pancake-flat surface.
“Observed rock movement occurred on sunny, clear days, following nights of sub-freezing temperatures,” they wrote in their report.
The conclusion proves theories that have been floated since geologists began studying the moving rocks in the 1940s.
The phenomenon doesn’t happen often because it rarely rains in the notoriously hot and dry desert valley. Even more impressively, the rocks move about 15 feet per minute, the report says.
The Norrises launched their “Slithering Stones Research Initiative” in 2011. After getting permits from the National Park Service, they installed a weather station in the area and placed 15 stones equipped with global positioning devices on the desert surface.
The “GPS stones,” which were engineered to record movement and velocity, were stationed at the southern end of the playa. They were placed near where non-GPS-infused rocks begin their strange journeys after tumbling down a cliff.Read More