The Ocean FloorThe Ocean Floor

Studying the Ocean FloorStudying the Ocean Floor

Scientists use Scientists use sonarsonar to to determine the oceans depthdetermine the oceans depth

The The sound movessound moves through through the water, bounces off the the water, bounces off the ocean floor, and returns to ocean floor, and returns to the shipthe ship

Ocean BasinsOcean Basins

Ocean basinsOcean basins are low areas are low areas of Earth that are filled with of Earth that are filled with waterwater

The The continental shelfcontinental shelf is the is the gradually sloping end of a gradually sloping end of a continent that extends under continent that extends under the ocean to 350 m deepthe ocean to 350 m deep

The Ocean FloorThe Ocean Floor

Beyond the shelf, the ocean Beyond the shelf, the ocean floor floor drops more steeplydrops more steeply, , forming the continental slope.forming the continental slope.

The The continental slopecontinental slope extends from the outer edge extends from the outer edge of the continental shelf down of the continental shelf down to the ocean floor.to the ocean floor.

Ocean BasinsOcean Basins

Beyond the continental Beyond the continental slope lie the slope lie the trenches, trenches, valleys, plains, valleys, plains, mountains,mountains, and ridges and ridges of the ocean basinof the ocean basin

Ocean BasinsOcean Basins

In the deep ocean, In the deep ocean, sedimentsediment, , derived mostly from land, derived mostly from land, settles constantly on the settles constantly on the ocean floor.ocean floor.

These deposits fill in valleys These deposits fill in valleys and create flat seafloor areas and create flat seafloor areas called called abyssal plainsabyssal plains..

The Ocean BasinsThe Ocean Basins

Some areas of Some areas of abyssal abyssal plainsplains have small hills have small hills and seamounts.and seamounts.

SeamountsSeamounts are are underwater, inactive underwater, inactive volcanic peaksvolcanic peaks

Ridges and TrenchesRidges and Trenches

Mid-ocean ridges can be Mid-ocean ridges can be found at the bottom of all found at the bottom of all ocean basins. ocean basins.

A A mid-ocean ridgemid-ocean ridge is the is the area in an ocean basin where area in an ocean basin where new ocean floor is formed.new ocean floor is formed.

Ridges and TrenchesRidges and Trenches

On the ocean floor, On the ocean floor, subduction zonessubduction zones are marked by deep are marked by deep ocean trenches.ocean trenches.

Trenches and RidgesTrenches and Ridges

A A trenchtrench is a long, is a long, narrow, steep-sided narrow, steep-sided depression where one depression where one plate sinks beneath plate sinks beneath another.another.

Question 1Question 1

What is the What is the continental shelf?continental shelf?

AnswerAnswer

The continental shelf is The continental shelf is the gradually sloping the gradually sloping end of a continent that end of a continent that extends under the extends under the ocean. ocean.

Question 2Question 2

Which structure extends from Which structure extends from the outer edge of the continental the outer edge of the continental shelf to the ocean floor?shelf to the ocean floor?

A. abyssal plainA. abyssal plain

B. continental slopeB. continental slope

C. oceanic trenchC. oceanic trench

D. seamountD. seamount

AnswerAnswer

The answer is B. The The answer is B. The other features lie other features lie beyond the beyond the continental slope. continental slope.

Question 3Question 3

What is the area in an What is the area in an ocean basin where ocean basin where new ocean floor is new ocean floor is forming?forming?

AnswerAnswer

New seafloor forms New seafloor forms at mid-ocean ridges at mid-ocean ridges as lava erupts as lava erupts through cracks in through cracks in Earth’s crust.Earth’s crust.