Scientists have observed that huge stones in the Death Valley desert have been moving by themselves. Experts are stumped as to why and what caused the movement. Is it the heat? Or is it gravity?

Photos of the massive rocks show long stretch of trails that the rocks leave behind in Racetrack Playa. Some of the rocks are the size of a loaf of bread and weigh about 25 pounds.

So why and how did the stones cross the desert? Maybe aliens moved them. HAHA.

Here are photos:

Lines were made by rock tracks. (NASA/GSFC/Maggie McAdam)

Lines were made by rock tracks. (NASA/GSFC/Maggie McAdam)

Large rocks move around the Racetrack Playa.

Large rocks move around the Racetrack Playa.

The sailing stones. (Tahoenathan/Wikimedia)

The sailing stones. (Tahoenathan/Wikimedia)

Some researchers studying the rock movements. (NASA/GSFC/Leva McIntire/LPSA intern)

Some researchers studying the rock movements. (NASA/GSFC/Leva McIntire/LPSA intern)

Note: A paper was published in 2011 discussing this phenomenon. Lorenz, R.D. et al. 2011. “Ice rafts not sails: Floating the rocks at Racetrack Playa”, American Journal of Physics, 79, 1, p.37. [Full Text in PDF]