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narrow gaping fracture, which opened to the present Atlantic Ocean 

 by horizontal movements of continental areas. 



In either view regarding the origin of the ridge the movements 

 can take place with velocity-differences in a horizontal direction. 

 Other explanations, such as the ridge being of volcanic origin or 

 the highest parts of a subsided continent (horst), do not consider 

 horizontal movements. Vertical movements may occur and may have 

 occurred in some places perhaps in an upward, in other places in 

 a downward direction, and varying at different periods, because no 

 movement of the earth's crust will have exactly a horizontal direction 

 for a long time, just as it will never have exactly a vertical direction. 



The comparative method does not enable us to trace out the 

 movement of the Central Atlantic Ridge down from its earliest 

 development. It proves, however, that the simple explanations by 

 upward and downward vertical movements, which have been 

 suggested, cannot be maintained. 



