294 



GEOLOGY 



of the sea-level) tends to the opposite results, for in this case the 

 sea advances on a surface which has relief, and the water enters 

 every depression brought to its level. Thus the numerous bays at 

 the lower ends of the streams along the Atlantic coast from Long 

 Island Sound to Carolina are the results of recent sinking. From 

 the present configuration of coast-lines it has been inferred that the 



Fig. 241. The submerged valley which has been interpreted as the con- 

 tinuation of the Hudson Valley. The position of the valley is indicated 

 by contours. (Data from C. and G. Survey.) 



present is, on the whole, an era of continental depression. 1 River 

 valleys, the lower ends of which are embayed, are sometimes found 

 to be continuous with submerged valleys beyond the coast-line 

 (Fig. 241). Submerged river valleys show that the surface in 

 which they lie was once land. 



The effects of diastrophism in the ocean and about its borders, 

 may (1) make the water of any ocean, or of any part of it, shallower 

 or deeper; (2) cause the emergence or submergence of land; (3) 

 make coast-lines regular or irregular; (4) shift the habitat of many 



1 J. Geikie, Earth Sculpture, p. 329. 



