Plate Tectonics

Question 1

Earths structure

Answer 1

Inner core
Outer core
Mantle
Crust

Question 2

Types of crust

Answer 2

Oceanic crust - is typically found beneath the world’s oceans and is formed at spreading centres on oceanic ridges at constructive plate margins.
Continental crust - is thicker (35km) and older. It is also less dense than the oceanic crust and is mainly composed of granite.

Question 3

Alfred wegemers evidence

Answer 3

Continental fit
Geological evidence
Climatological evidence
Biological evidence

Question 4

Ridge pull

Answer 4

occurs at mid-oceanic ridges at constructive plate margins
magma that rises to the surface is very hot and heats the surrounding rocks.
These expand and become elevated above the sea floor forming a slope
Gravity then causes it to slide down the slope, away from the mid-ocean ridge. This results in sea-floor spreading, where new crust is formed

Question 5

Slab pull

Answer 5

At a destructive plate margin, the subducting ocean plate, usually composed of basalt, is denser than the surrounding material. As the plate begins to sink into the mantle it pulls the rest of the plate behind it.

Question 6

Main types of plate margin

Answer 6

Constructive
Conservative
Destructive subduction
Destruction collision

Question 7

Constructive margins

Answer 7

Plates move away from each other and new crust is formed
produces mid- ocean ridges such as the mid-Atlantic ridge. Submarine volcanoes may also form.

Question 8

Collision and destructive plate margins

Answer 8

are both examples of convergence (when plates move towards each other)
Where continental crust meets continental crust, this is known as a collision margin.
Where oceanic and continental crust meets is a destructive subduction

Question 9

Conservative plate margins

Answer 9

are found where plates rub past each other, either in the same direction or in the opposite direction.
When the pressure is released then shallow focus earthquakes usually occur

Question 10

Landforms associated with constructive plate margins

Answer 10

Oceanic ridges
Rift valleys

Question 11

Types of convergent margins

Answer 11

Oceanic / continental
Continental / continental
Oceanic / oceanic

Question 12

Landforms from oceanic / continental plate margins

Answer 12

Deep trenches
Fold mountains
Earthquakes
Volcanoes
Island arcs

Question 13

Oceanic / oceanic plate convergence landforms

Answer 13

Ocean trenches
Island arcs

Question 14

Continental / continental convergence landforms

Answer 14

Fold mountains
Earthquakes

Question 15

Magma plumes (hotspot)

Answer 15

A concentration of radioactive elements inside the mantle may cause such a hot spot to develop.

Question 16

Lithosphere

Answer 16

The crust and rigid upper layer of mantle

Question 17

Asthenosphere

Answer 17

Most of the mantle as semi molten rock

Question 18

Processes related to high temps in earths core

Answer 18

Primordial heat - left over from earths formation
Radiogenic heat - radioactive decay of isotopes
Without these two heat sources the earth would be classed as a “dead planet”

Question 19

Convection currents

Answer 19

Circular motion of asthenosphere that causes plates to move

Question 20

How many major plates on earth

Answer 20

7

Question 21

How fast do plates move a year

Answer 21

Average - 5-10cm/year
Some up to 18cm/yr

Question 22

Oceanic ridges

Answer 22

Occur at constructive
Two plates move apart there is a weaker zone in the crust and an increase in heat near surface

Question 23

Volcanic islands

Answer 23

A series of submarine volcanoe eruptions cause them to appear out of the surface of the ocean

Question 24

Rift valleys

Answer 24

Constructive margins in continental areas
As crust moves apart, areas of crust drop down between parallel faults to form rift valleys
Example is East African rift valley

Question 25

Deep ocean trenches

Answer 25

Occur at destructive subduction between oceanic and continental crust

Question 26

Benioff zone

Answer 26

The further the rock descends at a subduction boundary the hotter the surroundings become
Oceanic plates melt into magma