The Structure of the Atlantic : 29 



Romantically inclined people hearing of the Atlantic Ridge have 

 suggested that this may be the remains of the lost and mythical con- 

 tinent or island of Atlantis now sunk beneath the waves. The scien- 

 tific evidence seems to be the other way about: that the ridge is not 

 old land that has sunk but new land that is rising. 



Incidentally this was the view of Wegener. Not much was known 

 about an Atlantic Ridge when Wegener propounded his ideas but he 

 argued that it was natural that the eastern and western continents 

 would part along a line of basic weakness in the earth's crust. Along 

 that line of weakness vulcanism would take place and new materials 

 would be thrust up. He argued that the volcanic character of the 

 Atlantic islands such as Iceland, Azores, Canaries, St. Paul's Rocks, 

 etc. was evidence in favor of his theories. At least in some quarters the 

 emergence of the Mid-Atlantic Ridge has aroused a new interest in 

 Wegener's ideas. 



The conventional view, of course, is that the heavy blocks of rock 

 that compose the base of the seas and the light blocks of the conti- 

 nents sorted themselves out in the basic formulation of the earth's 

 crust and have remained more or less fixed. Even the conventional 

 view admits vertical movement — balancing movements away from or 

 toward the center of the earth, which have changed the relations of 

 the sea to the land — but Wegener was arguing for floating and slid- 

 ing movement. 



The Atlantic Ridge though it is the most extensive is not the only 

 ridge by any means. Minor ridges of lesser height or greater depth, 

 whichever way you wish to put it, branch off from the Atlantic Ridge 

 and serve to separate the Atlantic into a series of basins and depres- 

 sions. Also there are independent ridges such as Bermuda to which 

 we have already referred and sharp spurs at Madeira, the Canaries, 

 the Cape Verdes. 



The deep waters of the Atlantic are then divided by the great Mid- 

 Atlantic Ridge and on either side of the ridge there are spurs or lesser 

 ridges running east and west which serve to mark off a number of 

 ocean basins, each of which has a special name. The names used are 

 those of some nearby land or of some important island group. Thus 

 there is an Iberia basin, a Canaries basin, etc. The basins all vary in 

 size and shape and many of them have special features which create 

 very dramatic underwater scenery; thus the Sierra Leone basin is rela- 

 tively small, a sort of Rhode Island among the basins and on the 

 other extreme, the North American basin which is vast enough to 

 embarrass a Texan. In the eastern Atlantic there are ten basins that 



