166 



A YEAR IN SCIENCE 



CopyrigJit "by Underwood & Underwood, N. Y. 



FIG. 62. A forest on Cape Cod planted as a windbreak is being 

 buried by drifting- sand. 



Lake Michigan are other sand dune regions. Dunes 

 vary much in size. Very large ones occur in central 

 Wyoming. The largest ones are found in the Sahara 

 Desert where they reach a height of several hundred 

 feet. 



The growth of a dune begins when the sand is 

 stopped by some object on the earth's surface. Once 

 started, the dune increases by the addition of more 



