Floor of the Sea 



ROCKY MOUNTAINS 



N. lAT. W V 

 W. LONG, 7f Ir ,, 



Elevations m feet 

 Horizontal scale in 



nautical miles 



S, lAT 22* a 



L LONC \rjt sea level 



Comparative Profiles 



Tliese diagrams compare tiie profile 

 across the United States witii those 

 of the Atlantic and eastern Pacific. 

 The exaggerated vertical scale of 

 100:1 distorts the actual slope, 

 which seldom exceeds 20°. The 

 Atlantic section shows the mid- 

 Atlantic Ridge to be comparable to, 

 if not greater than, the western 

 mountains of North America. 



The Formation of Guyots 



These diagrams show the formation 

 of atolls and the flat-topped 

 seamounts called "guyots." Their 

 similarity to atolls gives a strong 

 indication of how they are formed : 

 1. A volcano forms a seamount. 2. A 

 volcanic island is built up. 3. The 

 extra mass of the volcano depresses 

 the Earth's crust and the volcano 

 begins to sink. 4. Waves cut off 

 the top of the island. 5. Coral 

 growing on the fringes builds up as 

 the volcano sinks, forming a barrier 

 reef and lagoon. 6. In time nothing 

 is seen of the volcano, which 

 becomes covered with limestone. 



7. If the sinking rate exceeds the 

 rate of coral growth, the coral is 

 dragged down and stops growing. 



8. The guyot reaches equilibrium 

 depth when its mass is supported by 

 the displaced mantle material 

 beneath the oceanic crust. 





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