Since the report by McAllister and Agnew in 1948 of trails left by rocks on the Racetrack Playa, there has been much speculation as to their origin. Those authors attributed the movement of the rocks to the wind. However, since the Racetrack is at a high elevation, where freezing occurs during the winter, the aid of ice could not be ruled out. The finding of similar trails on Little Bonnie Claire Playa, recently reported by the present writer did not completely eliminate ice as a possible aid since it, too, is at a relatively high elevation.

The same phenomenon has since been observed on a playa at 1,600 feet elevation, and somewhat farther south than either of the previously mentioned ones. The aid of ice seems to be definitely ruled out, as well as possible pushing about by human beings. This leaves the wind as the most likely agent causing the movement of the rocks, as first suggested by McAllister and Agnew.

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