Medano is a Spanish word meaning “a sand dune that exists along a seashore.” To American geologists, however, this term has come to signify a bare dune of immense proportions that migrates in the wind, consuming everything in its path. Just downwind (east-northeast) from Great Sand Dunes National Park in Colorado’s Sangre de Cristo Range is Medano Pass. Medanos ranging in height from twenty-ﬁve to one hundred feet once dotted the mid-Atlantic coast south of the Chesapeake Bay, but since the early twentieth century they have tended to ﬂatten out, a trend hastened by coastal development. Once common, ﬁelds of open sand have been replaced by houses with grassy yards, leaving scant loose sediment to nourish the great dunes. In the 1970s Jockey Ridge, a well-known medano on the North Carolina Outer Banks, stood at 110 feet, the highest dune on the East Coast. It now measures less than eighty feet. Nonetheless, the dune has shown itself to be indomitable. Blown by the wind, it is migrating quickly southwest, covering houses and roadways as it moves.