12.2 Features of Tectonic Plates

Question 1

What does the existence of mountains, volcanoes, and earthquakes suggests?

Answer 1

It suggests that Earth’s interior is not simply a solid ball of rock.

Question 2

What did scientists think Earth begin as? When did it start?

Answer 2

They think that Earth began as a molten ball, over 4.5 billion years ago.

Question 3

What is 3/4 of Earth’s crust made of?

Answer 3

Elements silicon and oxygen, which combine to form group of rocks called silicates.

Question 4

How many layers is Earth made of?

Answer 4

4

Question 5

Fill in the blank:

Earth’s outer layer is composed of several large, rigid but mobile chunks of rock known as _______ _______.

Answer 5

Tectonic Plates.

Question 6

What is the lithosphere made of?

Answer 6

The uppermost mantle, crust, and tectonic plates.

Question 7

How many tectonic plates are there?

Answer 7

12 major ones, many smaller ones.

Question 8

What do oceanic plates contain?

Answer 8

It contains the dense rock basalt.

Question 9

What does the continental plate contain?

Answer 9

Large amounts of granite.

Question 10

What is the crust made of?

Answer 10

Solid, brittle rock.

Question 11

What is Earth’s thickest layer?

Answer 11

The mantle.

Question 12

What is the upper mantle composed of?

Answer 12

Partly molten rock containing iron and magnesium.

Question 13

What is the lower mantle made of?

Answer 13

Solid, dense material that contains the elements magnesium and iron.

Question 14

Is the outer core solid or liquid?

Answer 14

Liquid.

Question 15

What keeps the inner core solid?

Answer 15

The incredible pressure.

Question 16

What elements are in the core?

Answer 16

Iron and nickel.

Question 17

What is below the lithosphere?

Answer 17

Asthenosphere

Question 18

What is the asthenophere?

Answer 18

A partly molten layer in the upper mantle.

Question 19

Why does the temperature of the asthenosphere vary throughout?

Answer 19

Because of large quantities of radioactive elements such as uranium occur in some areas.Radioactive decay heats up the mantle in these spots.

Question 20

What’s the result of the radioactive decay?

Answer 20

A convection current results as the hotter, less dense material in the mantle. It rises, cools and sinks again, only to be reheated.

Question 21

What is the process I just described call? (The process when the material gets hot in the mantle by radioactivity, rises, cools, than gets reheated again.)

Answer 21

Mantle Convection.

Question 22

What do scientists hypothesize about the mantle convection?

Answer 22

That it is one of the driving forces behind plate movement.

Question 23

Where do rising currents of magma reach Earth’s surface?

Answer 23

At a spreading centre.

Question 24

What is a spreading centre in a ocean called?

Answer 24

It’s called a spreading ridge or oceanic ridge.

Question 25

What is a spreading centre on land called?

Answer 25

A rift valley.

Question 26

What happens when magma reaches the surface?

Answer 26

It becomes new rock.

Question 27

What happens as new material at a ridge or rift valley pushes older material aside? What is this process called?

Answer 27

The tectonic plates move away from the ridge. The process is called ridge push.

Question 28

If two plates collide, which one will pushed down?

Answer 28

The older and denser one.

Question 29

Define subduction.

Answer 29

The action of one plate pushing below another.

Question 30

What are areas of subduction called?

Answer 30

Subduction zones

Question 31

What happens at a subduction zone?

Answer 31

Large earthquakes and volcanic eruptions.

Question 32

Define slab pull.

Answer 32

The pulling of a tectonic plate as its edge subducts deep into the mantle.