40 HISTORY OF THE OCEANS 



tentative review of the processes behind the facts may be useful. 

 The purpose of such a review is not primarily to arrive at a correct 

 account ot what takes place. Many of the observations are sus- 

 ceptible of more than one explanation, and there is no great virtue 

 in guessing which is correct and plumping for it. The important 

 thing seems to be to define the range of possible processes and to 

 suggest further observations and experiments that may distinguish 

 between them. 



I am suspicious of wide generalizations. To write down the 

 equations of motion and of the theory of the solid state and solve 

 them will tell little about what has happened on the ocean floor. 

 The line of progress seems to be to examine the individual happen- 

 ings and processes in the light of the principles of physics and 

 chemistry and to hope that the pieces will fit into a wider synthesis. 

 We must avoid forcing dubious or ill-digested details into some 

 preconceived grand theoretical scheme of geological development. 

 The major problems of geology have been with us for a long time 

 and we are not likely to solve them this year or next; but we can 

 use the new knowledge about the ocean floor to see what is the 

 real nature of the problems and we may hope gradually to approach 

 a correct account of present and past processes. 



Sedimentation 



The 1950's have seen the overthrow of most of the views held 

 on sedimentation in the abyssal plains. There is now no doubt 

 that a large part of the material in these plains is derived from 

 sediment originally accumulated in shallow water, and it is difficult 

 to suggest an alternative to Kuenen's "turbidity currents" as a 

 method of transport. The theory of these currents is in a very 

 poor state. The Reynolds number of a current 10 km long traveling 

 at 10 m/sec is 10^\ which is much above that experienced in the 

 largest wind tunnels. The extreme turbulence resulting from such 

 a Reynolds number will assist in keeping material in suspension, 

 but will dissipate energy and makes the long distances traveled 

 over a flat bottom even more surprising. There is no detailed 

 picture of how a turbidity current behaves. From the distribution 



