210 



EARTH FEATURES AND THEIR MEANING 



the windward side and -carrying it over the crest, from where it 

 slides down the leeward slope and assumes a surface which is 

 the angle of repose of the material. In contrast with this the 



windward slope is 

 notably gradual, be- 

 ing shaped in con- 

 formity to the wind 

 currents. 



The dunes which 

 are raised upon sea- 

 shores, like those of 

 the desert, are con- 



Fio. 219. Sand accumulating both to windward and stantly migrating, 

 to leeward of a firm and impenetrable obstruction, those Upon the shores 



of the North Sea at 

 the average rate of 

 about twenty feet per year. Relentlessly they advance, and de- 

 spite all attempts to halt them, have many times overwhelmed 

 the villages along the coast. Upon the great barrier beach known 

 as the Kurische Nehrung, on the southeastern shore of the Baltic 

 Sea, such a burial of villages has more than once occurred, but 

 as in the course of time further migration of the dune has pro- 

 ceeded, the ruins of the buried villages have been exhumed by 

 this natural excavating process (Fig. 220). 



The wind comes from the left (after a photograph 

 by Bastin). 



/a es 



Sca/e of Miles. 



FIG. 220. Successive diagrams to show how the town of Kunzen was buried, and 

 subsequently exhumed in the continued migration of a great dune upon the 

 Kurische Nehrung (after Behrendt). 



The forms of dunes. The forms assumed by dunes are de- 

 pendent to a very large extent upon the strength of the wind 

 and the available supply of sand. With small quantities of 



