Ocean Regions: Ocean Floor - Continental
Margin & Rise
Surrounding nearly all continents is a shallow extension of that
landmass known as the continental shelf.
This shelf is relatively shallow, tens of meters deep compared to
the thousands of meters deep in the open ocean, and extends outward
to the continental slope where the
deep ocean truly begins.
Sediment from the erosion of land
surfaces, washed into the sea by rivers and waves, nourishes microscopic
plants and animals. Larger animals then feed upon them. These larger
animals include the great schools of fish, such as tuna, menhaden,
cod and mackerel, which we catch for food.
The continental shelf regions also contain the highest amount of
benthic life (plants and animals that
live on the ocean floor).
The continental slope connects the
continental shelf and the oceanic crust. It begins at the
continental shelf break, or where the bottom sharply drops
off into a steep slope. It usually begins at 430 feet (130 meters)
depth and can be up to 20 km wide. The continental slope, which
is still considered part of the continent, together with the continental
shelf is called the continental margin.
Submarine canyons cut through many of the continental margins.
Some of these have been carved by turbidity currents,
which are bottom currents that carry lots of sediment.
Past the continental slope, we find the continental
rise. As currents flow along the continental shelf and down
the continental slope, they pick up and carry sediments along and
deposit them just below the continental slope. These sediments accumulate
(gather) to form the large, gentle slope of the continental rise.