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1.3.3 Barchan Dune

Barchans are sand dunes of crecentric shape with the tips pointing downwind. Barchans develop best where the sand supply is limited and a unidirectional wind drives the migrating dunes across a nonsand floor. These dunes display many shapes and arrangements, and may be linked in echelon. The dunes become more separated as they migrate farther from the source. The smaller-sized barchans move much faster and are often assimilated into the larger ones which move much slower. The barchan is actually a type of transverse dune where the limited sand supply allows the wind to form the crecentric shape. The foreset beds (leeside) are much steeper than the backset beds on the windward side.


Images
Tule Wash Barchan:1958
Tule Wash Barchan:1958
Earth Science Slides by John S. Shelton
Barchan Dune  Tule Wash Barchan:1958  Aerial view of a large barchan in Northen Peru. 

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