The Sliding Rocks of Racetrack Playa

The sliding rocks at Racetrack Playa (A Playa is a dry river bed) may be considered one of the most interesting mysteries of Death Valley National Park. These sliding rocks can be found on the floor of the playa with a long trail behind them. Somehow these rocks slide across the playa even though weighing several hundred pounds. This raises a very changeling question: How do they move? No one exactly knows how they move, but some have come up with a couple of ideas. The strange thing is that no one has ever seen them in motion. The Racetrack Playa is almost completely flat. It is about 4 kilometers long (2.5 miles - north to south) and about 2 kilometers wide (1.25 miles - east to west). The surface is covered with mud cracks and the sediment is made up mainly of silt and clay. The climate in Death Valley National Park is very dry; it only rains a couple of inches per year. When it actually rains the steep mountains which surround Racetrack Playa produce a large amount of runoff that converts the playa floor into a broad shallow lake. When the surface of the playa is wet it can be turned in a very slippery, soft mud. The shape of the trails behind the heavy rocks suggests that they moved during times when the mud was soft and wet. Since there is no disruption around the rocks or trails, this tells us that there is no human or animal assisting the movement of the rocks. Some people believe that the rocks are moved by ice. The idea is that the water freezes around the rocks and then the wind blows across the top of the ice; dragging the ice sheet with its embedded rocks across the surface of the playa. Although the ice was a good theory, scientists preformed experiments to prove the ice theory inconsistent. The wind is the favored mover of the rocks. The question remains is do they slide while encased in an ice sheet or do they simply side over the surface of the mud? This story will remain a mystery until the real answer is discovered.