SAND DUNES 557 



Types of Sand Dunes. 



Three types of sand dunes are recognized, their characters being 

 largely determined by their location. These are: ist, shore dunes, 

 or those formed from the sands left to dry on the retreat of the 

 water; 2nd, river-bed dunes, and, 3rd, inland or desert dunes. 

 While all of these have fundamental features in common, they, 

 nevertheless, show individual characteristics due to the topographic 

 diversity and structural peculiarities- of the respective regions in 

 which they occur. 



(i) Strand Dunes. These are a common feature of the coasts, 

 being found on the shores of the sea and of the larger lakes. Typi- 

 cal and well-known examples of seashore dunes are found in the 

 Provincetown region of Cape Cod, Massachusetts, and from there 

 southward along Long Island coast and the sandy coast from New 

 Jersey to Florida. They are further found on the shores of the 

 Baltic, especially on the narrow sand bars which separate off the 

 Kurische and Frische Haff on the east Prussian coast, and on the 

 west coast of Kurland and the Gulf of Riga in Russia. (Berendt- 

 4.) Extensive dune areas are also found on the east and south 

 coast of the North Sea, especially in Denmark, and the coast of the 

 Netherlands and Flanders from the mouth of the Elbe to Pas-de- 

 Calais, while the French coast of the Bay of Biscay bears the most 

 extensive dune accumulations of all. Finally, extensive shore dunes 

 are developed on the eastern and southern coast of Lake Michigan, 

 and to a lesser extent on the shores of the other Great Lakes of 

 North America. Shore dunes are most typically developed where 

 a broad flat zone of sand fronts a low country, as in the examples 

 cited, but they may also occur where such a sand zone lies at the 

 foot of rocky cliffs. In such cases the dunes will accumulate on 

 the summit of the cliff, as on the Normandy coast of France, the 

 west coast of Jutland and the West Schleswig-Holstein coast, far- 

 ther south, where the height of the cliff in one case. (Island of Sylt 

 among the north Friesian islands) was 34 meters and that of the 

 dunes upon it reached a height of 28 meters. They are, however, 

 never found where rocky coasts descend directly into the waters, 

 as on the northern New England coast and the rocky coast of the 

 maritime provinces of Canada, the rocky coasts of Great Britain 

 and of Scandinavia and Finland. The best development of coastal 

 dunes seems to be on a sinking coast, over 90% of the coast dunes 

 of Europe being thus located, according to Sokolow. 



The most important coastal dunes of Europe (Sokolow), if 

 not of the world, are found on the French coast of the Gulf of Bis- 



