68 THE OCEAN FLOOR 



Regarding the past history of the Mid-Atlantic Ridge, 

 Tolstoy and others believe that there have been two 

 major periods of activity in the history of both the 

 Azores and Iceland, one during early or middle Tertiary 

 and the other during late Tertiary to Recent. This sug- 

 gests that the origin of the ridge may be associated with 



Fig. 25. Model from CIoos' ex- 

 periment 



the Alpine orogenies. Gutenberg and Richter in 1949 

 even suggested that the Mid-Atlantic Ridge may be a 

 belt of Tertiary folds, the high degree of seismicity 

 characterizing it being due to block faulting, following a 

 redistribution of tectonic forces. This view of active 

 tectonic forces in great ocean depths I shall discuss 

 further in Chapter 6. 



