CLIMATIC FACTORS : THE AIR 



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FlG. 55. Extensive active sand dunes on the coast of Oregon showing 

 transverse ridges that have typical form with gradual slope to windward and 

 an abrupt drop to leeward.— Photo by W. S. Cooper. 



FlG. 56. Blowout in Oregon coastal dune that was once completely stab- 

 ilized by vegetation. This is a compound blowout as indicated by the partial- 

 ly stabilized surface of an earlier blowout (lower right), which was again 

 excavated to a lower level by later blowout.— Photo by W. S. Cooper. 



