The deep sea begins where the continental slope ends. Areas of the ocean with depths of 1800 m or more, or areas of the seabed on the oceanic crust, are often called the deep sea. Even though the continental slope is not so steep, often only 2-10°, its transition to the abyssal plain may often be viewed on a detailed bathymetric chart. The abyssal plains tend to contain more fine-grained sediments than the shelf or slope. However, in the deep sea areas of the Norwegian Sea, coarse material such as pebbles, gravel and boulders may be found which were deposited by icebergs during the ice age.
Landslide material originating from the shelf and/or slope may be found on the abyssal plain, often containing large blocks. Deposits from turbidity currents (currents with high sediment content flowing along the sea floor) may extend hundreds of kilometres across the abyssal plain.
Hot springs can be found in some places along the mid-Atlantic Ridge. Associated with these hot springs are mineral deposits, rich in species of life that thrives in heated water. At the time of writing, deep sea mining is being planned on such deposits offshore of Papua New Guinea.