the ocean floor

traveling to the ocean floor

Only a specially designed vehicle can venture beneath the sea surface. But only very special vehicles can reach the ocean floor. Three are described here and pictured in Figure 14.21: In 1960, scientists used the submersible Trieste to travel into the Mariana Trench. They succeeded, but the trip was very risky. Making humans safe at such depths costs a lot of money. People have not traveled to this depth again. In 2012, the film director, James Cameron, dove to the bottom of the Mariana Trench by himself in a submersible that he had built for the purpose. The vehicle named Alvin was developed soon after Trieste. The submersible has made over 4,000 dives deep into the ocean. People can stay underwater for up to 9 hours. Alvin has been essential for developing a scientific understanding the worlds oceans. Today, remote-control vehicles, called remotely operated vehicles (ROVs) go to the deepest ocean floor. They dont have any people on board. However, they carry devices that record many measurements. They also collect sediments and take photos.

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features on the ocean floor

Scientists have learned a lot about the ocean floor. For example, they know that Earths tallest mountains and deepest canyons are on the ocean floor. The major features on the ocean floor are described below. They are also shown in Figure 14.22. The continental shelf is the ocean floor nearest the edges of continents. It has a a gentle slope. The water over the continental shelf is shallow. The continental slope lies between the continental shelf and the abyssal plain. It has a steep slope with a sharp drop to the deep ocean floor. The abyssal plain forms much of the floor under the open ocean. It lies from 3 to 6 kilometers (1.9 to 3.7 miles) below the surface. Much of it is flat. An oceanic trench is a deep canyon on the ocean floor. Trenches occur where one tectonic plate subducts under another. The deepest trench is the Mariana Trench in the Pacific Ocean. It plunges more than 11 kilometers (almost 7 miles) below sea level. A seamount is a volcanic mountain on the ocean floor. Seamounts that rise above the water surface are known as islands. There are many seamounts dotting the seafloor. The mid-ocean ridge is a mountain range that runs through all the worlds oceans. It is almost 64,000 kilometers (40,000 miles) long! It forms where tectonic plates pull apart. Magma erupts through the ocean floor to make new seafloor. The magma hardens to create the ridge.

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resources from the ocean floor

The ocean floor is rich in resources. The resources include both living and nonliving things.

living resources

The ocean floor is home to many species of living things. Some from shallow water are used by people for food. Clams and some fish are among the many foods we get from the ocean floor. Some living things on the ocean floor are sources of human medicines. For example, certain bacteria on the ocean floor produce chemicals that fight cancer.

studying the ocean floor

Scientists study the ocean floor in various ways. Scientists or their devices may actually travel to the ocean floor. Or they may study the ocean floor from the surface. One way is with a tool called sonar.

using sonar

Did you ever shout and hear an echo? If you did, thats because the sound waves bounced off a hard surface and back to you. The same principle explains how sonar works. A ship on the surface sends sound waves down to the ocean floor. The sound waves bounce off the ocean floor and return to the surface, like an echo. Figure 14.19 show how this happens. Sonar can be used to measure how deep the ocean is. A device records the time it takes sound waves to travel from the surface to the ocean floor and back again. Sound waves travel through water at a known speed. Once scientists know the travel time of the wave, they can calculate the distance to the ocean floor. They can then combine all of these distances to make a map of the ocean floor. Figure 14.20 shows an example of this type of map.

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nonliving resources

Oil and natural gas lie below some regions of the seafloor. Large drills on floating oil rigs must be used to reach them. This is risky for workers on the rigs. It is also risky for the ocean and its living things. An oil rig explosion caused a massive oil leak in the Gulf of Mexico in 2010. Oil poured into the water for several months. The oil caused great harm to habitats and living things, both in the water and on the coast. The oil spill also hurt the economy of Gulf Coast states. The effects of the oil spill are still being tallied. There are many minerals on the ocean floor. Some settle down from the water above. Some are released in hot water through vents, or cracks, in the seafloor. The minerals in hot water settle out and form metallic chimneys, as in Figure 14.23. These metals could be mined, but they are very deep in the sea and very far from land. This means that mining them would be too expensive and not worth the effort. Some types of minerals form balls called nodules. Nodules may be tiny or as big as basketballs. They contain manganese, iron, copper, and other useful minerals. As many as 500 billion tons of nodules lie on the ocean floor! However, mining them would be very costly and could be harmful to the ocean environment.

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instructional diagrams

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This diagram shows an abbreviated version of underwater landscape. The ground under an ocean gets slowly deeper shortly after passing the beach, which is called the continental shelf. After this it slopes down steadily in the continental slope. After the slop is an abyssal plain, which is significantly deeper but not as deep as a trench-here, there is no sunlight. A volcanic arc comes before an underwater volcano, which forms a volcanic island that may or may not be dormant. A continental slope can also be considered a continental rise if it is seen from the opposite direction.

description_image

The following diagram is that of an ocean floor. The major features on the ocean floor are continental shelf, continental slope, continental rise and the coast. The continental shelf in the ocean floor is nearest to the edges of continents. It has a gentle slope. The continental slope lies between the continental shelf and the abyssal plain. It has a steep slope with a sharp drop to the deep ocean floor. The abyssal plain forms much of the floor under the open ocean. Magma erupts through the ocean floor to make new seafloor. The magma hardens to create the ridge.

questions

Only a tiny fraction of the ocean floor has ever been studied.

-->  a. true

b. false

The tallest mountains on Earth are located on the ocean floor.

-->  a. true

b. false

Earths deepest canyon is the Grand Canyon in the American Southwest.

a. true

-->  b. false

Ocean water over the abyssal plain is shallow and warm.

a. true

-->  b. false

The deepest ocean trench is 3 kilometers below sea level.

a. true

-->  b. false

The mid-ocean ridge is created by magma that cools and hardens.

-->  a. true

b. false

Most of the ocean floor is too deep for organisms to live there.

a. true

-->  b. false

The only resources on or below the ocean floor are minerals such as manganese.

a. true

-->  b. false

Oil rigs floating on the ocean extract petroleum from sea water.

a. true

-->  b. false

Hot water escapes through vents in the ocean floor.

-->  a. true

b. false

volcanic mountain on the ocean floor

a. abyssal plain

b. continental shelf

c. continental slope

d. mid-ocean ridge

e. oceanic trench

-->  f. seamount

g. metallic chimney

mostly flat part of the ocean floor under the open ocean

-->  a. abyssal plain

b. continental shelf

c. continental slope

d. mid-ocean ridge

e. oceanic trench

f. seamount

g. metallic chimney

deep canyon on the ocean floor

a. abyssal plain

b. continental shelf

c. continental slope

d. mid-ocean ridge

-->  e. oceanic trench

f. seamount

g. metallic chimney

part of the ocean floor that lies between the continental shelf and abyssal plain

a. abyssal plain

b. continental shelf

-->  c. continental slope

d. mid-ocean ridge

e. oceanic trench

f. seamount

g. metallic chimney

mountain range that runs through all the worlds oceans

a. abyssal plain

b. continental shelf

c. continental slope

-->  d. mid-ocean ridge

e. oceanic trench

f. seamount

g. metallic chimney

structure on the ocean floor formed by minerals from hot water

a. abyssal plain

b. continental shelf

c. continental slope

d. mid-ocean ridge

e. oceanic trench

f. seamount

-->  g. metallic chimney

ocean floor near the edge of a continent

a. abyssal plain

-->  b. continental shelf

c. continental slope

d. mid-ocean ridge

e. oceanic trench

f. seamount

g. metallic chimney

The main reason it is difficult to directly study the deep ocean floor is that the

a. ocean floor has not been mapped.

-->  b. pressure is too high.

c. distance is too far.

d. water is too hot.

The ocean floor can be studied by scientists at the waters surface with

a. submersibles.

b. sonar devices.

c. remote-control vehicles.

-->  d. two of the above

When using sonar, the distance to the ocean floor is calculated from the

a. time it takes sound waves to travel to the ocean floor.

b. pressure ocean water exerts on the ocean floor.

c. speed of sound waves through ocean water.

-->  d. two of the above

The deepest oceanic trench occurs in the

a. Atlantic Ocean.

-->  b. Pacific Ocean.

c. Arctic Ocean.

d. Indian Ocean.

The mid-ocean ridge forms where tectonic plates

a. slide past one another.

b. push together.

-->  c. pull apart.

d. subduct.

Examples of minerals on the ocean floor include

a. iron.

b. copper.

c. manganese.

-->  d. all of the above

Nodules on the ocean floor are

a. deposits of petroleum.

b. pockets of natural gas.

c. fossils of organisms.

-->  d. balls of minerals.

diagram questions

question_image

Which label shows the seamount?

a. X

b. E

-->  c. L

d. K

question_image

Which of the labeled elements shows an oceanic abyss?

-->  a. W

b. E

c. F

d. J

question_image

What is the deepest oceanic trench currently known?

-->  a. Mariana Trench

b. Sea Mount

c. Mount Everest

d. Abyssal Plain

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What is the deepest point in the ocean?

a. Continental Slope

b. Abyssal Plain

-->  c. Mariana Trench

d. Sea Mount

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What is the depth difference between continental shelf to continental rise?

a. 5700 meters

b. 2700 meters

-->  c. 3700 meters

d. 100 meters

question_image

What's the lowest surface?

a. abyssal plain

b. sea mount

c. continental shelf

-->  d. marina trench

question_image

Among the ocean features, how many is known to occur when one tectonic plate subducts under another?

-->  a. 1

b. 3

c. 4

d. 2

question_image

How many ocean features are depicted?

a. 3

b. 2

c. 1

-->  d. 6

question_image

What is the level below the Continental Shelf?

-->  a. Continental Slope

b. Continental Rise

c. Sea Mount

d. Mount Everest

question_image

Which is deeper in the diagram?

a. abyss

b. guyot

-->  c. ocean trench

d. continental slope

question_image

What is the lowest lying feature or the ocean floor?

-->  a. Ocean trench

b. abyssal plain

c. abyss

d. continental slope

question_image

How many features does the ocean floor have?

-->  a. 9

b. 10

c. 8

d. 7

question_image

How many trenches shown?

a. 4

-->  b. 1

c. 2

d. 3

question_image

Where does the seamount lie with respect to guyot?

-->  a. Right of it

b. Exactly below it.

c. Left of it.

d. Exactly above it.

question_image

Which landform connects the continental shelf to the continental rise?

a. transform fault

b. seamount

c. guyot

-->  d. continental slope

question_image

What do you call a seamount with a flat top?

a. Seamount

-->  b. Guyot

c. Abyssal Plain

d. Trench

question_image

What is the lowest point?

a. Continental Slope

-->  b. Trench

c. Continental Rise

d. Transform Fault

question_image

How many continental parts does the seafloor have?

-->  a. 3

b. 1

c. 4

d. 2

question_image

How many items are depicted in the diagram?

a. 9

b. 4

c. 7

-->  d. 10

question_image

What connects the continental shelf to the continental rise?

a. abyssal plain

b. guyot

c. seamount

-->  d. continental slope

question_image

It is formed by deposited layers of sediment decreasing the steepness of the slope at the base.

a. abyssal plain

b. continental shelf

c. submarine canyon

-->  d. continental rise

question_image

What is the continental shelf?

a. The coastal plain

b. The shore

-->  c. The ocean floor nearest the edges of continents

d. The continental edge

question_image

What connects the continental slope to the abyssal plain?

a. shoreline

b. submarine canyon

-->  c. continental rise

d. coastal plain

question_image

What type of crust makes up the coast?

a. Deep sea fan

b. Oceanic crust

c. Continental shelf

-->  d. Continental crust

question_image

What is the area between coast and deep ocean basin called?

a. Deep sea fan

-->  b. Continental margin

c. Volcanic island

d. Ridge

question_image

What is the lowest point?

a. Oceanic Crust

b. Continental Slope

c. Continental Rise

-->  d. Continental Crust

question_image

How many crusts are there?

a. 5

b. 4

-->  c. 2

d. 3

question_image

What lies between the coast and deep ocean basin?

-->  a. Continental margin

b. Deep sea fan

c. Oceanic crust

d. Ridge

question_image

What is the bottom of the ocean called?

-->  a. Ocean floor

b. Continental rise

c. Continental shelf

d. Continental slope

question_image

What part is the ocean floor nearest the edges of continents?

-->  a. Continental Shelf

b. Continental Crust

c. Continental Rise

d. Continental Slope

question_image

How many times the continental crust appears in the diagram?

a. 3

-->  b. 1

c. 9

d. 2

question_image

Which layer is below the ocean floor?

a. Continental Shelf

-->  b. Oceanic Crust

c. Continental Slope

d. Continental Rise

question_image

How many types of crust are shown in below image?

-->  a. 2

b. 4

c. 5

d. 3

question_image

How many types of crust are shown in diagram?

a. 1

b. 4

-->  c. 2

d. 3

question_image

Where would a volcanic island form?

a. deep sea fan

b. Continental crust

-->  c. ridge

d. continental shelf