134 



lud-li 



DEPTHS OF THE OCEAN 



inciding generally with what we have designated the 



Area of the 

 Atlantic 

 sea-floor at 

 different 

 depths. 



Continental 

 shelf and 

 slope in the 

 Atlantic. 



Let us now consider the distribution of depth in the three 

 great oceans (the Atlantic, the Pacific, and the Indian Oceans), 

 regarding them as extending in each case as far south as 

 the shores of the Antarctic continent. 



Atlantic Ocean. — The Atlantic may be looked upon as 

 including the Arctic Ocean and Norwegian Sea, the 

 Mediterranean, Caribbean, and Gulf of Mexico, and as being 

 separated from the Pacific in the south at the meridian of Cape 

 Horn (long. 70° W.) and from the Indian Ocean at the meridian 

 of the Cape of Good Hope (long. 20' E.). As thus defined 

 the Atlantic Ocean covers an area of about 41,321,000 square 

 English miles, the distribution of depth being shown in the 

 following table : — 



These figures show that nearly three-fourths of the Atlantic 

 sea -floor are covered by water exceeding 1000 fathoms in 

 depth, and over one-half by water exceeding 2000 fathoms in 

 depth, but the most characteristic feature of this ocean when 

 compared with the Pacific and Indian Oceans is the large 

 proportion covered by water less than 1000 fathoms in depth. 

 The table shows that this shallowest zone (from o-iooo fathoms, 

 which includes both the continental shelf and the continental 

 slope) covers about i\\ million square miles, while the succeed- 

 ing zone (1000-2000 fathoms) covers only 7^ million square 

 miles. If again we divide the shallowest zone into two portions 

 by the 500-fathoms line, the predominance of the area covered 

 by shallow water is still more pronounced, the area less than 

 500 fathoms being nearly 10 million square miles as compared 



1 Murray and Renard, Deep-Sea Deposits Chall. Exp. p. 1S5, 1891 ; Murray, Summary 

 of Results Chall. Exp. p. 1433, 1895. 



