Death Valley National Park officials are investigating the theft of several of the rocks that mysteriously roam across a remote ancient lake bed known as the Racetrack Playa.
Rocks of various sizes -- from baseball to basketball -- scoot across the 2.5-mile-long, oval-shaped mudflat on the north end of the park, leaving tracks that are straight, curved and even looped. Some tracks extend up to 600 feet.
Geologists theorize that the rocks slide after rain moistens the top few centimeters of the lake bed and a high wind pushes them around.
"We've had more instances of folks taking the rocks," Death Valley spokesman Terry Baldino said. "They don't seem to understand that outside of the Racetrack, these marvelous rocks have no value."