CONTINENTAL TERRACES AND SUBMARINE VALLEYS III 



Louisiana and Texas coast that unconsolidated sediments rule 

 down to the depth of at least 10,000 feet. See Figure 60. 



s 



CAUOU 

 ISLAND 



■'o 





Vi 



FIGURE 60. NORTH-SOUTH SECTION ACROSS LOUISIANA, SHOWING LOCATION 

 OF DEEP BORE-HOLES. GREAT EXAGGERATION OF THE VERTICAL SCALE MUCH 

 OVER-STEEPENS THE INCLINATION OF THE BEDS OF SEDIMENTARY ROCK. 



Valley Systems of the Continental Slope 



The scientific imagination must be stretched as we plunge 

 into the black dark under the waves, to see what the conti- 

 nental slopes are really like. 



Before the development of echo-sounding, geologists as- 

 sumed that in general the continental slope is essentially as 

 smooth and monotonous as the shelf. The smoothness was 

 thought to be a necessary result of the mode of upbuilding of 

 the continental terrace as a whole. Great was the astonishment 

 of geologist and oceanographer at the discovery of the closely 

 set series of valleys and ridges. Further, it already appears 

 highly probable that the submerged flanks of the continents are 

 so trenched, dissected, through a total length of 50,000 miles or 

 twice the circumference of the earth. The phenomenon is 



