Siliciclastic Slopes and Submarine Fans

3 Continental Slope and Continental Rise 2.5.3.1 Siliciclastic Slopes and Submarine Fans 

The continental slope is the relatively steep (usually 3-6°) portion of the seafloor which lies at the seaward border of the continental shelf (Heezen et al., 1959) in water depths ranging from 100-200 m to 1,400-3,200 m, and locally to much greater depths (Bouma, 1979). This area is located just above the transition between continental and oceanic crust. The continental slopes are narrow (20-100 km), covering an area approximately 2.87 X 10E6 km, 5.6% of the Earth s surface (Drake and Burke, 1974). About half of the world s continental slopes terminate in deep-water trenches or shallower depressions, the rest gradually merging with slopes of 1 100 to 1 700 into continental rises and their deep-sea fans (Curray, 1966). 

Based on their geological evolution, structure, and morphology, Emery (1977, 1980) distinguished six distinct types of continental slopes  

A seaward downwarping, thickly accumulating sediment wedge over old, irregular terrain (2°-6°, e.g., eastern United States [Schlee et al., 1979]). 

A subsiding, very steep (up to 45°) continental slope supported by the growth of thick, massive calcareous reefs (e.g., Bahamas-Cuba, southwest Africa [Fairbridge, 1966]). 

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