The stones that move alone in Death Valley, USA

In the famous Death Valley in the United States there is a single phenomenon, these stones appear floating above the barren wasteland that was once mud. For decades, scientists have theorized a reasonable explanation for this anomaly, in which a stone weighing several pounds can travel several hundred meters "course."

Many believe that this movement is due to strong winds, but that does not explain that rocks of different size and weight of a parallel move with different speeds and directions. In addition, the calculation of physics do not support this theory, because for some stones will be needed to move wind speeds of hundreds of kilometers per hour higher. The wind can move the small stones, but how do you move a few tens of pounds?.