For at least a century, the moving rocks of Death Valley have presented a puzzle, and researchers have been trying to solve it since 1948.  The rocks, some of them boulders weighing more than 600 pounds, show signs of movement across the desert floor by leaving long trails behind them.

Explanations including dust devils, flooding, hurricane-strength winds, and even UFOs have been offered, but the mystery was finally solved when researchers caught the rocks in the act!

Check out the National Geographic article and watch the video below.