134 



Sediments accumulating on a slope are unstable and the 

 stability of the deposit in general depends upon; (1) the size 

 and sorting of the sediment, (2) water content, (3) the degree 

 of compaction, and (4) the angle of the slope. Loose, fine- 

 grained sediment having a high water content and accumulating 

 on a steep slope is unstable and eventually slides off the 

 slope into deeper water, 



Shepard has shown that slumping and submarine landslides 

 are common, especially when the canyons are close to shore 

 vdiere there is an abundant supply of sediment. No quantitative 

 data exist on the periodicity of slumping, but it is likely 

 that the sediments are unstable on the slopes of submarine 

 canyons, and that slvimping takes place fairly often. A 

 detailed study of a slope off Palos Verdes Hills indicated 

 that appreciable quantities of sediments may accumulate on a 

 slope before slumping takes place, but evidence was presented 

 that indicated slumping very probably did occur (Emery and 

 Terry, 1956), Benest (1899) pointed out the difficulties that 

 resulted from placing telephone cables across submarine canyons, 

 and the difficulty was not remedied until the cables were placed 

 on the shelf well above the head of the submarine canyons. 



The cores taken in Santa Monica and Redondo canyons indi- 

 cate that slumping and sliding probably takes place, parti- 

 cularly in Santa Monica Canyon, 



