The Sailing Stones of Death Valley

Death Valley National Park is a strange place by any standard. Famously known for being the hottest place on earth, Death Valley also sits at the driest and lowest elevation in North America. Its strangest feature of all is the mysterious Racetrack Playa. Here, rocks drift across the flat desert landscape, seemingly propelled by no power other than their own!

Located on the border of California and Nevada, Death Valley National Park was designated in 1933, and is home to one of the world’s strangest phenomena: rocks that move along the desert ground with no gravitational cause. Known as “sailing stones,” the rocks vary in size from a few ounces to hundreds of pounds. Though no one has ever seen them actually move in person, the trails left behind the stones and periodic changes in their location make it clear that they do.

The rocks of Racetrack Playa are composed of dolomite and syenite, the same materials that make up the surrounding mountains. They tumble down due to the forces of erosion, coming to rest on the parched ground below. Once they reach the level surface of the playa, the rocks somehow move horizontally, leaving perfect tracks behind them to record their path.

Many of the largest rocks have left behind trails as long as 1,500 feet, suggesting that they’ve moved a long way indeed from their original location. Rocks with a rough-bottomed surface leave straight tracks, while smooth-bottomed rocks tend to wander. The sailing stones have been observed and studied since the early 1900s, and several theories have been suggested to explain their mysterious movements.

In 2014, scientists were able to capture the movement of the stones for the first time using time-lapse photography. The results strongly suggest that the sailing stones are the result of a perfect balance of ice, water, and wind. In the winter of 2014, rain formed a small pond that froze overnight and thawed the next day, creating a vast sheet of ice that was reduced by midday to only a few millimeters thick. Driven by a light wind, this sheet broke up and accumulated behind the stones, slowly pushing them forward.