Sailing stone in Racetrack Playa
Death Valley National Park in California is home to a place called The Racetrack Playa. The Racetrack is a dry lake situated 1130m above sea level, and even though it is 4.5km long, the ground is surprisingly flat, with only a 4cm height differential between the north and south ends. The mountains surrounding the Racetrack, comprised primarily of dark dolomite, reach as high as 1731m above the lake bed. When the heavy rains come, water rushes down the mountains and onto the lake bed, forming a shallow endorheic lake. Due to the hot temperatures of the region, the water evaporates, leaving behind a layer of soft mud. When the liquid fully evaporates, the ground cracks and leaves a mosaic pattern behind. While all of this is interesting, the feature that makes this area truly unique is something that has yet to be fully understood by the scientific community.
Image: Dan Mayer
Sailing Stones in Racetrack Playa
Over time, stones have fallen from the mountainsides onto the lake bed. Some of the stones are small, though others weigh as much as 700 pounds. Once they are situated on the incredibly flat surface, one might be inclined to think that they would sit undisturbed for thousands of years. This, however, is not the case. These gigantic rocks and boulders (known as Sailing Stones, Sliding Rocks, or Moving Rocks) are found all over the dry lake bed with long trails, or racetracks, having formed behind them, extending for hundreds of meters. Since there is no evidence of human or animal intervention in the movement of these stones, one has to wonder how the phenomenon is happening.
Large sailing stone
Not only to the stones move, but they move in completely different directions. Two stones could start next to one another, and start moving at approximately the same speed, but one will suddenly stop or change directions. Sometimes the sailing stones will turn around completely, moving back towards their point of origin. The tracks left behind are generally no wider that 30 cm, and less than 2.5cm deep. The longest tracks have been forming for numerous years, though to date, nobody has ever witnessed the event.
Sailing Stones in Racetrack Playa
In 1972 Bob Sharp and Dwight Carey began a seven year study, when thirty stones were named and movements monitored with stakes. During that time two stones of similar size were placed in a corral with a diameter of 1.7m, surrounded by rebar placed 64 to 76cm apart. Over the study period one of the stones moved, though the other did not. By the end of the study 28 out of the 30 selected stones had moved, and only seemed to do so in the winter. The smallest of the stones monitored was 6.5 cm in diameter, and had the longest single movement of 201m, while the largest stone to move weighed 36kg. The largest stone was approximately 320kg, though it was one of the two not to move during the seven year period. This stone had disappeared sometime before 1994, and was discovered in 1996 about 800m away.
Image: Dan Duriscoe
Night sky over the Sailing Stones
Another study was done in the mid ’90s and concluded that the trails left in the 1980s were formed by a large ice floe, possibly up to 800 meters wide in conjunction with strong winds, upwards of 145km/h in the area. While the movement during the 80s has a strong hypothesis, until someone actually witnesses the event, we won’t know for certain how these gigantic stones sail around the lake bed in Death valley National Park.