Plate Tectonics

Question 1

Crust

Answer 1

Earths outer shell
Made of 14 plates
Oceanic (5km thick)
Continental crust (30 to 70km thick)

Question 2

Mantle

Answer 2

Essentially a solid but behaves like a liquid 
(semi-molten layer of rock) 
1000C
2885km
Magma here

Question 3

Outer Core

Answer 3

Liquid metal is in motion
Mainly iron
2270km thick
4000C

Question 4

Inner Core

Answer 4

Solid Metal
Iron/Nickel
1216km 
5000C - 7000C
Heat source that drives convection

Question 5

Asthenosphere

Answer 5

Soft plastic like rock

The upper mantle, just below the lithosphere

Question 6

Lithosphere

Answer 6

The solid top layer of crust in which plates are formed

Consists of crust and upper mantle

Question 7

Oceanic Crust Thickness

Answer 7

6-10km thick

Question 8

Oceanic Crust Age

Answer 8

<200million years old

Question 9

Oceanic Crust Density

Answer 9

Very Dense

3g/cm3

Question 10

Oceanic Crust Mineral Content and Rock Type

Answer 10

Si Mg

Basalt

Question 11

Which is denser oceanic or continental crust?

Answer 11

Oceanic

Question 12

Continental Crust Thickness

Answer 12

30-70km

Question 13

Continental Crust Age

Answer 13

1500 million - 3.8 billion years old

Question 14

Continental Crust Density

Answer 14

Less dense than oceanic crust

2.7g/cm3

Question 15

Continental Crust Mineral Content and Rock type

Answer 15

Si Al

Various Rocks, e.g granite

Question 16

Convection currents

Answer 16

Draw and label a convection current’s diagram with arrows

Question 17

Explain Earths heat source.

Answer 17

Heat is being produced through radioactive decay of naturally radioactive elements, eg uranium.

Subatomic particles are produced and collide with surrounding material inside Earth, motion equals heat

Question 18

List 5 pieces of evidence supporting continental drift.

Answer 18

Fossil Fit
Geological Fit
Tectonic Fit
Jigsaw Fit
Paleomagnetism

Question 19

Jigsaw fit example

Answer 19

Eastern South America and west Africa

Coastlines are matched at a depth of 1000m below sea level

Question 20

How can gaps and overlaps in jigsaw fit be explained?

Answer 20

• Sea level rise
• coastal erosion
• Coastal deposition
• Land level changes

Question 21

Geological Fit Example

Answer 21

Geology of eastern South America and west Africa were mapped and that ancient rock (2,000 million years old) were continuous from 1 continent to another

Question 22

Tectonic Fit example

Answer 22

Fragments of an old fold mountain belt between 400 and 450 million years ago are found in a variety of continents

Caledonian Mountain In Greenland, England, Canada etc

Question 23

Fossil Evidence

Answer 23

Fossils found on separate continents, (once connected)

They cannot swim or fly

Question 24

How are paleomagnetism and continental drift linked?

Answer 24

New material @ mid oceanic ridge
Earths magnetism randomly flips
Striped pattern in magnetism and match it to age
Due to sea floor spreading

Question 25

Slab Pull

Answer 25

@ subduction zones, gravity “pulls” the oceanic plate down into the mantle. This destroys crust material

Question 26

Ridge push

Answer 26

Material pushing out from the ridge

Question 28

Sea Floor Spreading

Answer 28

Movement of oceanic crust away from constructive plate margins at mid-ocean ridges

Question 29

Benioff Zone

Answer 29

Where plates melt in the mantle due to friction and heat

Question 30

Constructive Margin

Answer 30

2 plates move apart leaving a gap in the middle or magma to rise from the asthenosphere and fill the gap

Question 31

Constructive Margin Features

Answer 31

Shield Volcanoes - Eyjafallajokull Earthquakes Rift Valleys -East African Rift Valley Mid-ocean Ridges - Mid-Atlantic Ridge

Question 32

Destructive Margin

Answer 32

Dense oceanic plate descends beneath less dense continental plate SUBDUCTION Magma can rise through cracks in the continental plate and form volcanoes upon reaching the surface

Question 33

Destructive Margin Features

Answer 33

Earthquakes Volcanoes Fold Mountains Ocean Trenches

Question 34

Conservative Margin

Answer 34

2 plates slide past each other along a fault line

Question 35

Conservative Margin Features

Answer 35

Shallow Earthquakes | Fault line - San Andreas

Question 36

Collision Boundary

Answer 36

2 plates of similar densities move towards each other causing the material between them to buckle upwards and form fold mountains.

Question 37

Collision Boundary Examples

Answer 37

The Himalayas, (fold mountains)

Question 38

Oceanic - Oceanic Margin

Answer 38

2 oceanic plates move towards each other Faster/denser is subducted Melts in Benioff zone Less dense molten material arises

Question 39

Oceanic - oceanic Margin Features

Answer 39

``` Ocean trenches - Mariana Trench Island arcs - West Indies Earthquakes Composite volcanoes - Montserrat Tsunamis ```

Question 40

Oceanic - Continental Margin

Answer 40

Oceanic and continental Move towards each other Denser oceanic subducts Melts in Benioff Zone Less dense molten material rises

Question 41

Oceanic - continental Margin Features

Answer 41

Ocean trenches - Peru/Chile Trench Composite volcanoes - Cotopaxi Fold mountains – Himalayas

Question 42

Continental- continental Margin

Answer 42

Continental plates move towards each other Both plates have a lower density than asthenosphere Can’t subduct Collide and rise upwards

Question 43

Continental - continental Margin Features

Answer 43

Earthquakes | Fold mountains – Himalayas

Question 44

Hotspots

Answer 44

Small area with unusually high concentration of radioactive elements below the surface

Question 45

Hotspot features

Answer 45

Shield volcanoes - Mauna Loa, Hawaii

Question 46

Magma plume

Answer 46

Rising column of hot rock at plate margin or through a plate