Turbidity current?

Question

Congo Canyon

Answer 1

Turbidity currents are density driven currents in which sediment filled water (in most cases) moves faster.

Answer 2

It is like an underwater avalanche (actually an avalanche would be considered a turbidity current in a sense, now I think about it). Sediment accumulates near the top of a slope (in the ocean this is usually the rise at the edge of the continental shelf), and episodically the mass becomes unstable and slides down the slope. It is a density current because the mass per volume of a mix of solids and water is higher than the mass per volume of clear water, so the mass slides along the bottom of the ocean. You get submarine canyons forming from erosion during repeated passage of the turbidity currents (and thus these are usually near the mouth of major rivers where a lot of sediment is added to the shelf), and at the base of the slope you get a fan of sediments from the deposition of the material as it slows following its descent. The momentum of the turbidity current can tranfer a lot of material quite far from the slope, out onto the abyssal plain.