BOTTOM WATERS 149 



too Steep for an angle of repose or where disturbances 

 by tectonic or volcanic forces occur, so that conditions 

 for the setting up of turbidity currents as defined by 

 Kuenen may be fulfilled locally. Many geologists, how- 

 ever, incline to the view that such turbidity currents are 

 rather exceptional occurrences. So far they have not 

 been directly observed in the open ocean, and their 

 importance in eroding the consolidated material in 

 submarine canyons is doubtful since the water they 

 carry is already overloaded with sediment. This view 

 is shared by Shepard, the American authority on sub- 

 marine canyons. Attempts to set up artificial turbidity 

 currents along submarine canyons through explosions 

 have so far failed. Recent observations carried out in 

 moderate depths within a Swedish fjord where great 

 quantities of sediment were dumped failed to give any 

 evidence for turbidity currents of any notable velocity. 



However, in echograms from the equatorial Indian 

 Ocean to the south of Ceylon, obtained during the 

 "Albatross" cruise, Koczy has found indications of 

 shallow submarine values in great depths, which may 

 possibly be due to turbidity currents. This view has 

 been further expounded in a recent paper by Dietz." 



Recently, KuUenberg published a criticism of the 

 paper in which Heezen and Ewing attribute the breaks 

 of the submarine cables over the Grand Banks after an 

 earthquake in 1929 to turbidity currents set up by the 

 quake (see Chap. 5, n. 1 ) . Studying in detail the topog- 

 raphy of the area where the breaks occurred, Kullen- 



