CHAPTER III 



CONTINENTAL TERRACES AND 

 SUBMARINE VALLEYS 



Introduction 



Men of science, like fishermen and navigators, have long had 

 lively interest in the continental terrace, but its scientific appeal 

 has recently become more than ever eloquent. For it has been 

 discovered that the long outer slope of the terrace is wonder- 

 fully dissected into a maze of deep valleys, separated by high 

 ridges. The cause of this systematic ruggedness, quite unsus- 

 pected ten years ago, when echo-sounding was not yet applied 

 in the delineation of the continental slope, is the principal 

 theme of this chapter. Before entering on its discussion, note 

 will be taken of a few instances where the dry-land topography 

 of the continents reflects the process of terrace-building. Then 

 account will be given of a new method for detecting the nature 

 of the invisible mass composing the terrace. Already it has 

 been proved that the normal thickness of the terrace deposits 

 is measurable in thousands of feet; also that, in general, the 

 deposits are but loosely consolidated, if at all. With these two 

 facts in mind, we shall be prepared to discuss the valley systems 

 sunk in the deeply submerged flanks of the continents. 



The Terraces 



From the first chapter we recall some facts and definitions. 

 The widths of the terraces vary from a few miles to 200 miles. 



