Lesson 2 - Continental Drift and Plate Tectonics

Question 1

What is continental drift?

Answer 1

The movement of the Earth’s continents relative to each other

Question 2

What is the thickness of the lithosphere on the continents?

Answer 2

Up to 250km thick

Question 3

What is the thickness of the lithosphere beneath the oceans?

Answer 3

Just 100km thick

Question 4

What type of rock largely makes up the lithosphere?

Answer 4

Peridotite

Question 5

What is the thickness of the Earth’s crust?

Answer 5

Around 35km thick

Question 6

What type of rock composes the continental crust?

Answer 6

Granitic rock

Question 7

What is the thickness of the ocean crust?

Answer 7

Around 7-8km thick

Question 8

What type of rock is the ocean crust made of?

Answer 8

Basaltic rock

Question 9

What layer does the lithosphere float on?

Answer 9

Asthenosphere

Question 10

What is the asthenosphere?

Answer 10

A viscous lower layer that forms the upper part of the mantle

Question 11

What is the process called that describes the movement of lithospheric plates?

Answer 11

Plate tectonics

Question 12

How many major lithospheric plates are there?

Answer 12

Seven major lithospheric plates

Question 13

What are the three types of plate margins?

Answer 13

• Conservative
• Constructive
• Destructive

Question 14

What happens at conservative margins?

Answer 14

Plates slide alongside one another

Question 15

At which type of margin does mantle material rise to form new oceanic crust?

Answer 15

Constructive margins

Question 16

What occurs at destructive margins?

Answer 16

Lithosphere descends into the mantle and is destroyed

Question 17

What is the role of ocean trenches in plate tectonics?

Answer 17

They are sites where lithosphere is destroyed

Question 18

List two mechanisms that drive tectonic plate movement.

Answer 18

• Volcanic activity
• Convection of hot magma

Question 19

What is the significance of plate tectonics in geology?

Answer 19

It is responsible for the configurations of continents and the creation and destruction of ocean basins

Question 20

What happens to the ocean floor when it meets the continent at destructive plate boundaries?

Answer 20

The ocean floor is subducted as it is denser and thinner than continental rock

Question 21

What occurs when two continents meet at a subduction zone?

Answer 21

The continental crust is too buoyant to be subducted and buckles, forming mountain chains

Question 22

What are ophiolites?

Answer 22

Thin slivers of ocean crust that remain after the ocean plate is completely subducted

Question 23

What is the suture zone?

Answer 23

The area where two continents joined

Question 24

What is an example of continent-continent collision?

Answer 24

The formation of the Himalayas

Question 25

How long ago did India crash into Asia, leading to the formation of the Himalayas?

Answer 25

Around 30 million years ago

Question 26

What do constructive plate boundaries create?

Answer 26

Ocean crust

Question 27

What do cooling and sinking oceanic crust form?

Answer 27

Abyssal plains

Question 28

How often has the direction of the Earth's magnetic field flipped?

Answer 28

At intervals of a few hundred thousand to a few million years

Question 29

What is the maximum age of ocean floor observed?

Answer 29

About 160 million years

Question 30

What forms on the ocean floor when magma cools and moves away from the axial ridge?

Answer 30

Magnetic anomaly stripes

Question 31

What do transform faults do?

Answer 31

Offset the line of the boundary between two plates

Question 32

What occurs around transform faults?

Answer 32

A narrow zone of shallow earthquakes

Question 33

What is the area beyond the transform fault on either side known as?

Answer 33

The fracture zone