Yardangs are normally defined as spectacular streamlined, sharp and sinuous ridges that extend parallel to the wind, and are separated by parallel depressions. They are sometimes said to resemble upturned
ships’ hulls. Yet the form of yardangs varies. Two size classes are distinguished – mega-yardangs and yardangs. Mega-yardangs, which are over 100 m long and up to 1,000 m wide, are reported only from the central Sahara and Egypt, some good examples occurring in the Boukou area near the Tibesti Mountains of Chad.
IT IS AN EROSIONAL LANDFORMS FORMED BY WIND ACTION DUE TO DIFFERENTIAL EROSION.