Chapter 14.2 Ocean Floor Features. The ocean floor has 3 major regions – the continental margins, the ocean basin floor, and the mid- ocean ridge.

Chapter 14.2Ocean Floor Features

• The ocean floor has 3 major regions – the continental margins, the ocean basin floor, and the mid-ocean ridge.

Continental Margins

• A continental margin is a zone of transition between a continent and the ocean basin floor.

• In the Atlantic Ocean, a thick layer of undisturbed sediment cover the continental margin. This area have very little volcanic or earthquake activity.

• In the Pacific Ocean the oceanic crust is moving below the continental crust. This make a very narrow continental margin that has volcanic activity and earthquakes.

Continental Shelf

• The continental shelf is a gently sloping submerged surface that extends from the shoreline.

• Some areas have very small continental shelves and some have very large shelves.

• Many continental shelves have mineral deposits, large reservoirs of oil and natural gas, and huge sand and gravel deposits.

• They can also be important fishing grounds.

Continental Slope

• The continental slope is at the edge of the continental shelf (seaward). This is an area that is steeper than the shelf.

• Some slopes have submarine canyons – these may go into the ocean basin floor.

• Turbidity currents are movements of dense, sediment-rich water down the continental slope.

Continental Rise

• Where trenches do not exist and the continental slope moves into a more gradual incline this is called the continental rise.

Ocean Basin Floor

• Ocean basin floor is between the continental margin and a mid-ocean ridge. This area makes up 30% of the Earth’s surface. This area has deep-ocean trenches, abyssal plains, and volcanic peaks called seamounts and guyots.

Deep-Ocean Trenches

• These are long, narrow creases in the ocean floor that form the deepest parts of the ocean.

• The deepest place on Earth is part of the Mariana Trench called the Challenger Deep.

• Trenches form where plates converge and one plate moves under another.

• There are many earthquakes and volcanoes in these areas – like the Ring of Fire.

Abyssal Plains

• These are deep, extremely flat parts of the ocean. They have a lot of fine sediment.

• These sediments are carried by turbidity currents or deposited as a result of sediments that were suspended settling.

• The Atlantic Ocean has the most extensive abyssal plains with few trenches.

Seamount and Guyots

• Seamounts are submerged volcanic peaks on the ocean floor. They are volcanoes that have not reached the ocean surface.

• There are seamounts everywhere but the Pacific Ocean has the most.

• Guyots are once-active, now-submerged, flat-topped structures. They were volcanic islands that have been eroded away.

Mid-Ocean Ridges

• This is found near the center of most ocean basins. It is underwater mountains that have developed on newly formed ocean crust.

Seafloor Spreading

• Seafloor spreading is where divergent plates are moving apart. New ocean floor is formed at this point.

Hydrothermal Vents

• Hydrothermal vents also form along mid-ocean ridges. They have mineral-rich water that is very hot. This area will have a lot of minerals and metals like sulfur, iron, copper, and zinc to precipitate (become solid) out of the water.