Racetrack Playa

The Racetrack Playa is a scenic dry lake feature with "sailing stones" that inscribe linear "racetrack" imprints. It is dry for almost the entire year and has no vegetation. When dry, its surface is covered with small but firm hexagonal mud crack polygons. The sailing stones are a geological phenomenon found in the Racetrack. Slabs of dolomite and syenite ranging from a few hundred grams to hundreds of kilograms inscribe visible tracks as they slide across the playa surface, without human or animal intervention. Instead, rocks move when ice sheets just a few mm thick start to melt during periods of light wind. These thin floating ice panels create an ice shove that moves the rocks at up to five meters per minute. -from Wikipedia