Answer:
Dense mixtures of sand, mud, and other debris that move at high speeds down submarine canyons.
Explanation:
They form by the the high amount of sediment in the upper level of the canyons, and because gravity force this big amount of soil need to be localize in another lower part of the canyon. By going down, they grow like an avalanche and the speed and force increases. So, they can modify the physical shape of the sea floor.
They can appear as a product of an Earthquake, collapsing slopes, and other geological phenomena.