In your article “Hidden Death Valley” (July ’18), you state that the rocks on the valley of Racetrack Playa are moved (pushed) by the wind. This is incorrect. They are moved by thin sheets of ice.
Second-in-command and Technical Editor Stuart Bourdon replies (it’s a little known fact that Editor Péwé is a formally trained geologist): “Both mechanisms are considered to be interacting during some winters to move the stones. An explanation of the complicated process was too detailed to fit into an easily readable photo caption. Those thin sheets of ice trapping the stones are moved by changes in water level and wind. Scripps Institution of Oceanography used timelapse cameras and GPS-device embedded stones during an especially cold and wet year to see the ice sheet–locked stones being dragged along the mud by water and wind flow.”