134 ELEMENTARY GEOLOGY 
Where the conditions are especially favorable, the 
blown sand may move inland. The removal of a for- 
est will often allow the wind to blow the sand inland 
so that not only is the site of the forest covered by 
sand dunes, but fertile farms, formerly protected, are 
submerged beneath the accumulation (Fig. 61). On 
the coast of France, the sand dunes have moved in- 
Fic. 63. 
Hills in Bermuda Islands formed of blown coral sand now cemented into a hard 
coral rock. 
ward, not only covering farms, but destroying villages. 
Likewise on the shore of Lake Michigan, there is a 
sand dune region that is even now destroying forests 
(Fig. 64). The French government is preventing the 
inland march of the sand by planting trees which 
check the action of the wind. 
When blown by the wind the sand is assorted into 
layers of varying coarseness. This results from the 
