Ocean Floor Features 14.2

Continental Margin • That portion of the seafloor adjacent to the

continents; it may include the continental shelf, continental slope, and continental rise.

Continental Shelf

• The gently sloping surface at the base of the continental slope.

Continental Slope• The steep gradient that leads to the deep-

ocean floor and marks the seaward edge of the continental shelf.

Submarine Canyon • A seaward extension of a valley that was cut

on the continental shelf during a time when sea level was lower; a canyon carved into the outer continental shelf, slope, and rise by turbidity currents.

Turbidity Current • A downslope

movement of dense, sediment-laden water created when sand and mud on the continental shelf and slope are dislodged and thrown into suspension.

Continental Rise • The gently sloping surface at the base of the

continental slope.

Ocean Basin Floor

• Area of the deep-ocean floor between the continental margin and the oceanic ridge.

Abyssal Plains• Very level area of the deep-ocean floor,

usually lying at the foot of the continental rise.

Seamounts

• An isolated volcanic peak that rises at least 1000 meters above the deep-ocean floor.

Mid-Ocean Ridge

• A continuous elevated zone on the floor of all the major ocean basins and varying in width from 1000 to 4000 kilometers.

Seafloor Spreading

• The process by which plate tectonics produces new oceanic lithosphere at ocean ridges.

Key Concept

• What are the three main regions of the ocean floor?–The floor regions are: continental

margins, ocean basin floor, and mid-ocean ridge.

Key Concept• How do continental margins in the

Atlantic Ocean differ from those in the Pacific Ocean?–The Atlantic Ocean has thick layers of

undisturbed sediment cover with very little volcanic or earthquake activity. –The Pacific Ocean crust is plunging beneath

continental crust and experiences both volcanic and earthquake activity.

Key Concept

• How are deep-ocean trenches formed?–Trenches are formed at sites of plate

convergence where one moving plate descends beneath another and plunges back into the mantle.

Key Concept

• How are abyssal plains formed?–The sediments that make up abyssal

plains are carried there by turbidity currents or deposited as a result of suspended sediments settling.

Key Concept

• What is formed at mid-ocean ridges?–New ocean floor is formed at mid-

ocean ridges as magma rises between the diverging plates and cools.