BOTTOM WATERS 147 



It should be noted here that if, through volcanic 

 action, lime is removed over large areas of the sediment 

 carpet, the carbon dioxide set free will, because of 

 the high water pressure, remain in solution and increase 

 the capacity of the bottom water for removing more 

 quantities of lime. 



If this view is correct, a study of the lime content 

 in stratified cores, especially near volcanic islands or 

 peninsulas, should afford an index of variations in 

 volcanic activity in the past, at least where cores of 

 sufficient length can be obtained. 



I have now to take up a highly controversial point 

 regarding the bottom currents and their effect on the 

 sediment. Forty years ago the great American geologist 

 Reginald Daly suggested that the remarkable sub- 

 marine canyons which cut deep into the coastal shelf 

 and adjoining continental slope (and which sometimes 

 are discernible down to depths of 10,000 feet or even 

 more) may have been excavated by submarine erosion.^ 

 Water heavily laden with sediment will have its specific 

 weight increased, and sliding down a submarine slope 

 it may acquire sufficient energy to cut deep furrows 

 in unconsolidated, perhaps even consohdated, sediment 

 layers, producing a kind of river bed. This hypothesis 

 of sediment-laden or "turbidity" currents has in recent 

 times been taken up by Kuenen of Groningen who 

 through beautiful experiments in the laboratory has 

 demonstrated both the velocity and the eroding power 

 of turbidity currents artificially produced.^ 



