Hazards: Plate Tectonics

Question 1

What are the 4 layers of the Earth’s interior?

Answer 1

Inner core
Outer core
Mantle
Crust

Question 2

What is the Earth’s core made of?

Answer 2

Dense rocks containing iron and nickel alloys

Question 3

What is the difference between the inner and outer core?

Answer 3

Inner is solid, outer is molten

Question 4

What is the temperature of the Earth’s core?

Answer 4

5000 C

Question 5

Which 2 processes heat the Earth’s core?

Answer 5

Primordial heat

Radiogenic heat

Question 6

Whats primordial heat?

Answer 6

Heat left over from the Earth’s formation

Question 7

WHat’s radiogenic heat?

Answer 7

Heat produced by the radioactive decay of isotopes

Question 8

What is the mantle made up of?

Answer 8

Molten and semi-molten rocks containing lighter elements such as silicon and oxygen

Question 9

What makes the crust so light?

Answer 9

The elements it contains - silicon, oxygen, aluminium, potassium, sodium

Question 10

What is the lithosphere?

Answer 10

The crust and the rigid upper section of the mantle

Question 11

How thick is the lithosphere?

Answer 11

80-90km

Question 12

Which section of the Earth is divided into plates?

Answer 12

The lithosphere

Question 13

What is the asthenosphere?

Answer 13

The semi-molten layer beneath the lithosphere on which plates float and move

Question 14

What are the 2 different types of crust?

Answer 14

Oceanic and continental

Question 15

How thick is continental crust?

Answer 15

30-70km

Question 16

How thick is oceanic crust?

Answer 16

6-10km

Question 17

How old is continental crust?

Answer 17

Over 1,500 million years

Question 18

How old is oceanic crust?

Answer 18

Less than 200 million years

Question 19

Which is denser, oceanic or continental crust?

Answer 19

Oceanic

Question 20

What is continental crust composed of?

Answer 20

Granite: SIAL and oxygen

Question 21

What is oceanic crust composed of?

Answer 21

Basalt: SIMA and oxygen

Question 22

Who noticed the jigsaw fit in the 17th century?

Answer 22

Francis Bacon

Question 23

Why did Francis Bacon’s findings not attract any attention?

Answer 23

No one thought continents could move

Question 24

What is the jigsaw fit?

Answer 24

A description of how continents’ coastlines fit together

Question 25

Who published the theory of continental drift?

Answer 25

Alfred Wegner

Question 26

When was the theory of continental drift published?

Answer 26

1912

Question 27

What supercontinents did Pangea split into?

Answer 27

Laurasia and Gondwanaland

Question 28

What is the theory of continental drift?

Answer 28

The theory that continents are moving, and splitting from each other to form new continents

Question 29

What were the 3 pieces of evidence for the theory of continental drift?

Answer 29

Similar fossil remains Pattern of rocks Jigsaw fit

Question 30

Give an example of fossil remains that provide evidence for continental drift.

Answer 30

Mesosaurus remains found in South America and Southern Africa - freshwater and land reptile

Question 31

What other explanations could there be for the mesosaurus fossils?

Answer 31

Land bridge, ice bridge, separate evolution

Question 32

Give an example of how rock patterns provide evidence for continental drift.

Answer 32

There is a similar pattern of rock layers on the coasts of Scotland and Canada, suggesting they were once close together or joined

Question 33

Give evidence for palaeolatitude and palaeoenvironment.

Answer 33

Limestone is formed in shallow, marine environments in the tropics yet is abundant in the UK, suggesting the UK used to be more southernly and tropical

Question 34

What further evidence developed the theory of plate tectonics?

Answer 34

Sea floor spreading

Question 35

WHat was the evidence for sea floor spreading?

Answer 35

Identical bands of alternating polarity on either side of the mid-atlantic ridge Younger rock in the centre

Question 36

Why are there bands of alternating polarity either side of the mid atlantic ridge?

Answer 36

Iron particles in lava erupted from the ocean floor are aligned with the Earth's magnetic field. As they solidify they provide a permanent record of the Earth's polarity at the time of the eruption. The Earth's polairty reverses at regular intervals forming bands of rock

Question 37

How often does the Earth's magnetic field flip?

Answer 37

Every 450,000 years on average

Question 38

Why does sea floor spreading provide evidence for tectonic plate theory?

Answer 38

Sea floor spreading implies the Earth must be getting bigger but this is not the case, so plates must be being destroyed somewhere else to accomodate the increase in size at ocean ridges

Question 39

How to tectonic plates move?

Answer 39

Convection currents of magma within the asthenosphere

Question 40

What is gravitational sliding?

Answer 40

Where the upwelling of magma from ocean ridges forms a higher elevation of the oecan ridge, causing gravity to act down the slope of the ridge

Question 41

What is slap pull?

Answer 41

The gravity-generated force downwards of oceanic plates as they sink into the mantle

Question 42

What type of plate boundaries does gravitational sliding occur at?

Answer 42

Constructive

Question 43

What type of plate boundaries does slab pull occur at?

Answer 43

Destructive

Question 44

What are the 4 different types of plate boundary?

Answer 44

Constructive Destructive Colission Conservative

Question 45

What landforms form at constructive plate boundaries?

Answer 45

Ocean ridges, rift valleys and volcanic islands

Question 46

What landforms form at destructive plate boundaries?

Answer 46

Fold mountains and oceanic trenhces

Question 47

What are conservative plate boundaries?

Answer 47

Where 2 plates slide past each other parallel to the plate margin

Question 48

Why is there no volcanic activity at conservative plate margins?

Answer 48

There is no subduction

Question 49

Example of fold mountains and ocean trench. what are the plates?

Answer 49

Andes Peru Chile trench Nazca and South American plates

Question 50

What are collision boundaries?

Answer 50

Convergent boundary between 2 continental crusts

Question 51

How are ocean ridges formed?

Answer 51

Oceanic plates move apart | Balsatic lava upwells between plates to form a ridge.

Question 52

How are rift valleys formed?

Answer 52

Continental plates move apart by convection. Areas of crust drop down between parallel faults to form a valley called a graben. The upstanding blocks on either side are horsts.

Question 53

Give an example a rift valley? What has formed here?

Answer 53

East African Rift Valley | The volcano Mount Kenya

Question 54

How do deep sea trenches form?

Answer 54

Where oceanic and continental plates meet, the denser oceanic plate subducts underneath the continental one. The downwarping of the oceanic plate forms a very deep part of the ocean known as a trench.

Question 55

Why does oceanic crust subduct under continental crust?

Answer 55

Oceanic crust is denser

Question 56

Why is oceanic crust denser than continental crust?

Answer 56

It contains sima

Question 57

How to island arcs form?

Answer 57

During subduction the descending plate encounters hotter surroundings and melts. As the material is less dense than the asthenosphere it rises towards the surface as magma plumes. When these reach the surface they form composite volcanoes. If eruptions take place offshore a line of volcanic islands forms.

Question 58

How do young fold mountains form?

Answer 58

As 2 continental plates converge, little subduction occurs so their edges and sediments between them are forced upwards into fold mountains.

Question 59

Why is there little subduction between continental plates?

Answer 59

They have much lower density than the underlying layers