Final answer:
Underwater avalanches of suspended sediments are known as turbidity currents. They lead to turbidite deposits on the sea-bottom with a distinct graded bedding pattern.
Step-by-step explanation:
Underwater avalanches of suspended sediments are called turbidity currents. These currents are underwater flows of water mixed with sediment that move downhill, due to gravity, carrying grains sorted by density. Turbidity currents can start at the edge of the continental shelf and progress down the continental slope.
They are capable of creating turbidite sedimentary deposits on the sea floor, which are formed by massive slope failures. This process results in sediment sorted by size with the coarsest particles settling at the bottom and progressively finer ones towards the top, a phenomenon known as graded bedding.