THE OCEAN AND ITS WORK 



225 



the Piedmont Plateau (p. 91). The name indicates that the streams 

 flow over falls or rapids where they pass from the hard rocks of the 

 old land to the easily eroded sediments of the Coastal Plain. 



The greatest coastal plain in the world forms the north and west 

 parts of Siberia and has a maximum width of more than 1000 miles. 

 The plain is low and poorly drained. 



If England, eastern Europe, and the intervening sea floors were 

 raised 300 feet, England would be united to the mainland, the Baltic 

 would be changed to a chain of lakes, and the North Sea would be 

 reduced to a gulf. If this should happen, the ancient shores could be 

 readily determined by the elevated sea cliffs, sea beaches, wave-cut 

 terraces, and sand spits ; while the raised sea bottoms would consti- 

 tute coastal plains. The new shores would be smooth with few in- 

 dentations. 



Cuestas. — The material of land newly raised from the sea has a dip seaward, 

 due both to the original inclination of the sediments and also to that which was brought 

 about during the process of uplift. If the beds of recently raised coastal plains differ 

 somewhat in resistance, the streams will in time give a zonal character to the topog- 

 raphy, the harder beds standing higher than the softer ones. There will thus result 



3* 





B 



Fig. 217. — Diagrams A and B illustrate the development of cuestas. As the weak 

 stratum of the coastal plain was cut away more rapidly than the firm, the latter 

 formed rather steep slopes facing inward, and long, gentle slopes towards the coast. 



