The Sliding Rocks of Racetrack Playa

Paula Messina

The Racetrack Basin lies within the boundary of Death Valley National Park. 
Within the basin lies an almost perfectly flat dry lake, known as the Racetrack Playa.
Resting on its flat dry lakebed are pebble- to boulder-sized rocks, with masses estimated at up to 320 kilograms (Sharp and Carey, 1976). 

This in itself could be explained by simple mass wasting processes, yet the position of the rocks, often hundreds of meters from a source area, and the presence of furrows in the clay playa surface leading toward the rocks suggests that the rocks are moving by traction. 
Trails created by the rocks vary in length and direction.  Some trails show gradual (curving) or abrupt (angular) changes in direction; most trails indicate a general south/southwest to north/northeast motion (Kirk, 1952; Sharp and Carey, 1976).  Distances traveled of as much as 3.2 kilometers are inferred by the presence of distinctive lithologies far from possible areas of origin.  Many rocks appear to break off dolomite cliffs at the south end of the playa, and are ultimately "deposited" where the playa meets an alluvial fan, about 2 kilometers to the north (Sharp and Carey, 1976; Messina, Stoffer and Clarke, 1997).  Some trails are parallel to others that are in close proximity and generally strike from south to north, consistent with prevailing wind patterns, thereby suggesting wind as the motive force.

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