DEPTH OF THE OCEAN 



31 



fathoms, covering an area of about 10 millions 

 of square miles; many deep submerged 

 gullies which cross this shelf appear to be 

 the continuations of existing river-channels, 

 and are regarded as evidence that the con- 

 tinental shelf represents a former extension 



4500 

 4000 

 J500 

 3000 

 2S00 

 2000 

 1500 

 1000 

 500 

 



soo 



1000 

 1500 



2000 

 2500 

 3000 

 3500 

 4000 

 4500 

 5000 

 5500 



Fia. 



Area Percentage 



OtolOOfms. ISmiU.saail«. 8 

 100 -SCO 

 500-1000 • 10 

 I000-20OO- 4 

 OW-2000- _2, 

 57 



Area Percentage 



OtolOOfms. lOBMH.Kjrote- 5n 



I0O-5OO - 7 - 

 SOO-IOOO- 5 • 

 I00O-2000- 27 . 

 2000-100O- 81 ■ 

 3000- JO.- 

 140- 



"wl etf 



30Z 



wz 



6QX 



702 so;; 9qz looz 



1. — Diagrammatic section showing the average contour of the 

 lithosphere, based upon the percentages of the areas between the 

 contour- lines above and below sea-level. 



of the continents. The connecting con- 

 tinental slope, between the 100-fathoms line 

 and the depth of the mean sphere level, 

 covers an area of about 30 millions of square 

 miles, or only three times that occupied by 

 the continental shelf, although the interval 

 of depth is 1600 fathoms as compared 

 with 100 fathoms. The junction between the 



