170 



WORK OF THE OCEAN 



PROCESSES IN OPERATION IN THE SEA 



Diastrophism. So far as the lithosphere is concerned, the sea- 

 level is the critical level. At this level and above, many processes 

 are in operation which are not effective below, while below sea-level 

 some processes are effective which find no counterpart above. 

 Warpings of the surface which do not involve the submergence of 

 land or the emergence of sea bottom, are relatively unimportant 

 compared with those which do. The rise of the bottom of the sea 

 from a depth of 400 fathoms to a depth of 200 fathoms would not 

 have important results, so far as the area itself is concerned, while 

 an equal rise of the bottom beneath 100 fathoms of water, or an 

 equal sinking of land 500 feet high, would be much more important. 



Fig. 174. Map showing the early stages in the simplification of a shoreline 

 by deposition, and showing that at this stage the irregularities are increased. 

 If the land rose or the sea sank 100 fathoms, the coast-line would be regular. 



