The dune field migrated eastward with the prevailing wind, one column at a time, burying whatever lay in its path. By the fourth survey the sand covered the entire grid. Then the storm reversed — a westerly gale that scoured the leading edge clean. The newest column of sand, the easternmost strip with the loosest grains, blew back to bare rock overnight. The older dunes behind it held firm. The next season's wind pushed the sand east again as though the storm had been a rumor.