ORIGIN OF PLAYA STONE TRACKS, RACETRACK PLAYA, INYO COUNTY, CALIFORNIA

Abstract

Curious tracks on playas, obviously made by moving stones, have been interpreted as caused by wind blowing stones over wet level clay. The stones weigh from ounces to several hundred pounds. Among hundreds of tracks on Racetrack Playa, Inyo County, California, certain ones exhibit near parallelism which implies unit movement; precise measurements and plots confirm this. Certain bends and cusps in these irregular tracks are comparable in all tracks of the same “signature”. A transparency plot of analogous points (one for each track in same signature group), when moved along plotted tracks, matches repeatedly at other analogous points. Rotation precluded true parallelism of tracks and identity of lengths and shapes. Distance of unit movement exceeded 300 feet, and maximum spread of stones in unit is 480 feet. Unit movement over so great a span scarcely allows any reasonable conclusion as to cause other than wind-blown ice floes dragging protruding stones. Ice ramparts and other evidence indicate longshore shearing motion, feasible for ice floes but impossible for ice shove by thermal expansion. The writer finds no evidence that stones, freely wind blown, have made tracks. Though not disproved, this idea meets serious objections in many other small object tracks than those surveyed and is unfeasible for tracks inscribed by 300 pound stones.