Death Valley’s rocks “wander” due to ice shove

Nature : For the first time, the so-called sliding rocks of California’s Death Valley National Park have been recorded in motion. For more than half a century people have noticed that stones on the flat desert lake bed of Racetrack Playa appear to have moved because of the long trails they’ve left behind them in the ground. But no one had ever observed the rocks moving. Now Richard Norris of the Scripps Institution of Oceanography in La Jolla, California, and colleagues have used time-lapse photography and rocks instrumented with GPS trackers to record their movements. In their paper published in the journal PLOS ONE, the researchers report that the rocks’ motion cannot be blamed on thick ice and strong winds. Actually, windowpane-thin ice sheets melt, break into pieces, and push the rocks slowly along paths determined by the direction and velocity of the wind and of the water flowing under the ice.