150 THE OCEAN FLOOR 



berg finds the hypothesis that turbidity currents caused 

 the breaks incompatible with the fact that the direction 

 of flow would have carried the current over obstruc- 

 tions in its path. In particular, Kuenen's endorsement 

 of the American authors' belief that some of the breaks 

 may be attributed to individual fast arms of the hypo- 

 thetical current is rejected. Summing up Kullenberg's 

 different arguments, one may say that postulating a 

 turbidity current solely on the ad hoc evidence of its 

 effects on submarine cables appears to be a highly 

 dubious proceeding, quite apart from the fact that an 

 exorbitant velocity must in that event be ascribed to it. 

 The present evidence, we may conclude, hardly 

 affords clear proof that turbidity currents have played 

 any dominant part in sculpturing the ocean floor. Both 

 their extension over the deep ocean bottom and their 

 velocities on steep slopes appear to have been over- 

 estimated by Heezen and Ewing. 



