Parallel trails carved in the wet, mud-cracked surface of the Death Valley playa. (Credit: Jim Norris)
In California’s Death Valley, the stones on the desert floor have been known to move on their own accord, leaving trails in the sand that have bamboozled onlookers for decades. But with the help of GPS transponders and a video camera, one geologist from the Scripps Institution of Oceanography believes he’s found the answer to this ongoing riddle, NPR reported.
The boulders — some weighing up to 500 pounds — seem to skate across the playa sand in a variety of patterns, from straight to crooked and even reversing course. Geologist Richard Norris tagged one stone with a GPS unit and set up a camera nearby.
He found that a thin layer of ice would occasionally form over the playa, then melt and shift, moving the boulders as well. However, the phenomenon requires specific conditions: rain, then cold air and sunshine with a little breeze.
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Top image: Parallel trails carved in the wet, mud-cracked surface of the Death Valley playa. (Credit: Jim Norris)