SECT. 3] TURBIDITY CURRENTS 743 



for it is difficult to believe that halting flows of muddy water could cut rock- 

 walled, giant canyons into the continental slope. 



Stetson and Smith (1937) believed that the density contrast between tur- 

 bidity currents and the superadjacent water was so small that a marine 

 turbidity flow would leave the bottom and flow as a turbid interflow when it 

 reached a depth where the density of the water exceeded that of the turbidity 

 current. However, later experiments by Kuenen, in which he used higher 

 density mixtures, yielded much greater velocities and suggested that erosion 

 could be accomplished by turbidity currents. 



Although high density turbidity currents had been effectively demonstrated 

 in Kuenen's later experiments, scepticism and lack of confidence in scale factors 

 prevented a general acceptance of the process when projected to full scale. The 

 concept of low-density turbidity currents which leave the bottom to form 

 interflows was also adopted by Menard and Ludwick (1951). Although they 

 concluded that submarine landslides "are the only likely sources of dense 

 turbidity currents thus far suggested", they had serious reservations, and felt 

 that such turbidity currents resulting from slides "may be tenuous rather than 

 dense". They also concluded that "turbidity currents resulting from suspended 

 sediment in rivers must be rare". Concerning the generation of turbidity 

 currents along the shore they concluded: 



"If they exist, marine turbidity currents produced by wave agitations, or any 

 other stirring agent, probably do not have high effective density. . . . 



"No means exist for holding the current in j^lace until the suspended sedi- 

 ment becomes very concentrated; therefore, it is unlikely that very dense 

 turbidity currents can be generated even by violent wave and current agita- 

 tion. ... 



"... turbidity currents may flow on the ocean surface or within the ocean 

 due to marine density stratification. . . . Surface flows and interflows may be 

 important geologically because they can spread sediment over wide areas." 



For this reason they conclude that "marine turbidity current deposits may 

 be difficult to identify". 



The concejDt thus projected was not appealing and most oceanographers and 

 geologists could not believe that turbidity currents were an important process 

 in oceans, and many comj^letely rejected the concej)t. 



2. Full- Scale Experiment 



The case for modern high-density, high-velocity turbidity currents was finally 

 proved by a study involving the explanation of both the breakage of submarine 

 cables and the origin of deep-sea sands. 



A . Grand Banks Turbidity Current 



In 1952 Heezen and Ewing concluded that the "... events associated with 

 the Grand Banks earthquake of 1929 November 18 may be considered as a 



y 



