I 



4 THE OCEAN FLOOR 



planets, our earth with its glittering oceans would no 

 doubt be an object of admiration and envy, and would 

 probably be called "the water planet." It certainly forms 

 a striking contrast to its next neighbors in space. Venus, 

 "the cloud planet," coyly hides her charms behind an 

 impenetrable veil of dazzling white clouds. (Spectro- 

 scopic analyses indicate these clouds do not contain 

 water but are largely built up from carbon dioxide.) 

 Her old admirer Mars, "the desert planet," is also 

 deficient in water. Venus is possibly still in a pre-oceanic 

 stage, but Mars is strongly suspected of having con- 

 sumed his original supply, either drinking it into his 

 crust or perhaps squandering it into interplanetary 

 space. This contrast inevitably suggests that our present 

 oceanic splendor represents a transient stage in the 

 development of earth, which may be on its way toward 

 the Martian state of complete desiccation. According 

 to some pessimists, in another few thousand million 

 years or so oceanographers will have to learn a new 

 profession. 



Let us, for a moment, anticipate such a future devel- 

 opment of ocean shrinkage and assume our earth to 

 have become half dry, so that the sea surface has fallen 

 below its present level by 4,000 meters, that is, some 

 13,000 feet. Figure 2 gives an idea of how the Atlantic 

 Ocean will then look. The present continents are gray, 

 the remaining ocean is black, and the parts of the sea 

 bottom uncovered by the retreating ocean are white. 



One easily recognizes the characteristic S-shape of 



