Remember those crazy rocks that were mysteriously sliding along the Death Valley floor when no one was watching? Someone finally caught the stones in action and we finally know what is making them move. Three scientists slapped 15 GPS-loaded rocks onto the Racetrack Playa and after a lot of patience, they discovered that a little bit of water, ice, wind, and a very precise set of circumstances is all it takes to get the stones moving.
Every so often, water floods the Racetrack Playa in Death Valley, filling the area with a couple inches of water. When that water freezes, it creates thin sheets of ice underneath the rocks. If the sun shines the next day, it cracks the ice. Add to that some wind gusts of at least 10 MPH and off the rocks go.
The scientists finally caught the rocks in action in 2013 when about 60 stones started scuttling across the valley over a few days. Some of the rocks traveled up to 200 feet, though it was usually only for a few seconds at a time. One adventurous stone, however, kept traveling for 16 minutes. You can watch the whole event unfold in a video from Jim Norris here.
Images via NASA