Racetrack Playa boasts a number of rocks with these weird trails behind them. You can also see some footprints around this rock. One theory for how the tracks are formed says that during the winter when there is more moisture than the spring (when we were there) the playa is covered with a layer of water or water plus ice. Then when the wind blows hard, it pushes the rocks around in the soft mud. I find it hard to believe that the wind would be capable of pushing such large rocks, so I favor the idea that ice must be involved, (the wind pushes on the ice and the rock, embedded in the ice, gets dragged along) but I'm not sure that theory makes perfect sense either.