seif
SAFE
A long, narrow, sharp-crested sand dune aligned parallel to the prevailing wind direction — a sand ridge that can run unbroken for miles. Seif dunes form in areas of consistent wind direction with abundant sand, and they dominate the great ergs of the Sahara and the Arabian Peninsula. Seen from the air, a field of seif dunes looks like a plowed field at continental scale.
Etymology
Arabic sayf, meaning sword. The dune's crest is the blade — sharp, straight, and cutting across the desert.
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