OCEANS AND THEIR HISTORY 17 



two continental blocks, Europe-Africa and the two 

 Americas, which began to open up in Cretaceous time 

 and is still widening through a progressive westward 

 drift of the two Americas. The Atlantic Ocean would 

 thus have a maximum age in its central parts of less 

 than 100 million years, perhaps only 70 million years. 

 A great variety of arguments geographical, geologi- 



Fig. 8. Birth of the Atlantic Ocean 



cal, biological, paleontological, etc. have been brought 

 forward in support of this ingenious theory. Since its 

 vogue in the twenties, adverse criticism has been over- 

 whelming and very few leading scientists of our 

 skeptical age have remained faithful "Wegenerians." 

 One main objection to the theory is that enormous 

 energy would be required to move the vast continental 



