A trail left by a rock implanted with a motion-activated Global Positioning System (GPS) unit is seen in the so-called Racetrack Playa of California's Death Valley in this undated handout photo provided by the Scripps Institution of Oceanography. A solution to the longstanding mystery of why rocks move erratically across the isolated patch of California's Death Valley finally emerged on August 28, 2014, when researchers published a study showing the driving force was sheets of wind-driven ice. (Photo by Reuters/Scripps Institution of Oceanography, University of California, San Diego)
|