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Continental Terrace Continental Rise ' Deep sea bed 

 -I- 



Continental Margin 



Figure 1. — Sketch profile showing the components and average depths of the 

 continental margin. Not to scale. 



Where this break occurs, the average depth throughout the world is 

 about 72 fathoms, though for convenience the 100-fathom depth has 

 been adopted. 



The width of the continental shelf varies widely from a very narrow 

 shelf off the west coasts of North and South America, to hundreds of 

 miles along Arctic Europe and the Far East. It ranges from a mini- 

 mum of less than one mile to a maximum of 800 miles. Although the 

 depth of the shelf has been used as an international limit, it is the 

 width that determines the area of the shelf and, hence, its significance 

 for the exploitation of its resources. 



Continental Shelf of the United States 



The United States of America has a coastline approximately 12,000 

 miles long, with a continental shelf of 650,000 square miles at the 

 100-fathom depth, including the East Coast, West Coast, and Alaska. 



Off Newfoundland, the shelf width increases greatly, averaging 

 over 200 miles. To the south and east are the Grand Banks, which aver- 

 age only about 30 fathoms in depth and stretch eastward for more 

 than 450 miles. If the shelf were limited to 100 fathoms, the width 

 would be only about 200 miles. 



Between Newfoundland and Cape Hatteras, the shelf decreases in 

 depth from 80 to 30 fathoms. The channel into the Gulf of St. Law- 

 rence is more than 30 miles wide, and the shelf width varies from 

 about 120 miles off Nova Scotia to less than 20 miles off Cape Hatteras. 



From Cape Hatteras south, the shelf gradually widens from less 

 than 20 miles to a maximum of 70 miles off Georgia, then virtually 

 disappears off south Florida. If the Blake Plateau is considered as 

 a portion of the shelf, the maximum width would increase to about 



