CONTINENTAL AND DEEP SEA PLATEAUS. 



181 



tain contours, fourteen in number * and from his figures I have con- 

 structed the profile. Vertical distances represent heights, and horizontal 

 distances represent terrestrial areas. The full width of the diagram from 

 side to side stands for the entire surface of the earth. The striking feat- 

 ures of the profile are its two terraces or horizontal elements. Two-fifths 

 of the earth's area lies between 11,000 and 16,000 feet beneath the ocean, 

 constituting a vast submerged plateau, whose mean altitude is — 14,000 

 feet. This is the plateau of the deep sea. One-fourth of the earth's area 

 falls between the contour 5,000 feet above tbe ocean and the contour 

 1,000 feet below, and has a mean altitude of + 1,000 feet. This is the 

 continental plateau. The two plateaus together comprise two-thirds of 

 the earth's surface, the remaining third including the intermediate slopes, 

 the areas of extreme and exceptional depth, and the areas of extreme and 

 exceptional height. Thus in the broadest possible way, and in a manner 



s s 



Figure 2.— The continental Plateau as related to the Western and Eastern Hemispheres. 



practically independent of the distribution of land and water, we have 

 the ocean floor clearly differentiated from the continental plateau. It is 

 at once evident that for the discussion of the greater terrestrial problems 

 connected with the configuration of the surface, and especially of the 

 problems of terrestrial mechanics, we must substitute for the continents, 

 as limited by coasts, the continental plateau, as limited by the margins of 

 the continental shoals. 



It does not follow from the profile, which, as I have said, represents 

 only the relation of extent to altitude, that all districts of continental 

 plateau are united in a single body, and in point of fact they are net 

 completely united; but the greater bodies are brought together, and the 

 only outlying district is that of the Antarctic continent. Running a line 



* John Murray: On the height of the land and the depth of the ocean. Scottish Geographical 

 Mag., vol. iv, 1888, p. 1. 



