What causes the bizarre “Sailing Stones” of Death Valley to move?

Located in the United States on the California-Nevada border, Death Valley National Park features a narrow stretch of dried-up, flat, cracked lakebed nicknamed Racetrack Playa (Beach). It's not a racetrack for vehicles; it's a racetrack for large rocks.

The stones, weighing up to 700 lbs (317 kg), sail mysteriously on their own across the desert floor, leaving trails behind in the sand. The phenomenon left researchers puzzled for decades, but geologists believe they have finally solved the mystery.

The “sailing” stones have been observed and studied since the early 1900s; several theories have been suggested to explain their mysterious movement, ranging from strong winds to extraterrestrials. The most likely culprit was strong wind gusts (the region is flat and strong winds are common) but that theory was debunked due to the massive size of some of the rocks and the curved trails often left behind.

In the winter, it’s rare for Death Valley to experience below-freezing temperatures, but not impossible. Researchers placed stones equipped with GPS on the “racetrack”, then waited and watched via time-lapse photography. In the winter of 2014 cameras captured rain forming a small pond that froze overnight; it began to thaw the next day, creating a thin sheet of ice under the stones. As anticipated, winds then sent the rocks sailing across the icy-wet surface at speeds up to 16 feet (5 m) per minute.

Some visitors to Death Valley still seem to prefer more occult explanations.