deflation

The removal of fine, loose material from a surface by wind, leaving behind the coarser particles that the wind cannot lift. Deflation is how desert pavement forms — the sand and silt blow away, and the pebbles and stones settle into a tight mosaic. It is also how desert basins deepen: the wind excavates them grain by grain, sometimes creating depressions that lie below sea level. The Qattara Depression in Egypt, 440 feet below sea level, was carved largely by deflation.