Racetrack Playa

Racetrack Playa is a dry lakebed in Death Valley National Park, Inyo County, California, about 2.8 miles long and 1.3 miles wide at an elevation of 3,714 feet within a closed drainage basin ringed by mountains. Its surface is dried clay, packed into a hard, smooth, remarkably level pavement that varies by only about 1.5 inches in elevation from one end to the other, and it develops a mosaic of hexagonal mud cracks when wet. A few times a year, light rain running off the surrounding mountains forms a shallow temporary lake on the playa; as the water evaporates in the desert heat it leaves behind a thin layer of slick mud that shrinks and cracks into interlocking polygons as it dries fully. The playa is best known for its sailing stones, rocks weighing up to 320 kilograms that leave long tracks as they slide across the surface; research has shown the rocks move when thin sheets of ice, just a few millimeters thick, begin to melt during light wind, an ice-shove mechanism that can push them along at speeds up to five meters a minute, resolving a mystery documented since 1948. This entity documents Racetrack Playa specifically as a geological formation.