Death Valley's Sailing Stones Captured Moving On Camera

What mechanism moves rocks across flat dirt in the heart of the hottest, driest place on Earth? Geologists have been studying the moving rocks since 1948, when the first scientific study suggested they were driven by dust devils. Theories over the decades have included sporadic hurricane-force winds when the surface is covered with rain water, or rocks carried across the mud by small rafts of ice, or UFOs. But until the Norrises had an incredible stroke of luck that day last December, no one had scientifically verified the phenomenon.

http://www.thestar.com.my/Lifestyle/Features/2014/09/03/Solved-The-riddle-of-the-rolling-rocks/

https://en.wikipedia.org/wiki/Sailing_stones