Plate tectonics

Question 1

Why do plates move?

Answer 1

Convection currents
Slab pull
Ridge push

Question 2

What landforms are created at convergent plate boundaries?

Answer 2

Deep ocean trenches 
Island arcs 
Submerged mountain ranges 
Volcanoes 
Fault lines

Question 3

What landforms are created at divergent plate boundaries?

Answer 3

Ocean ridges
Rift valleys
Volcanoes

Question 4

What landforms are created at conservative plate boundaries?

Answer 4

No landforms made

Question 5

Name the 3 types of plate boundaries

Answer 5

Constructive - Constructive
Destructive - Constructive
Destructive - Destructive

Question 6

Describe where and how magma plumes are made

Answer 6

Radioactive decay in the core is concentrated, creating hot spots. These temperatures heat the magma, causing it to rise vertically and ‘burn’ through the crust

Question 7

Describe the structure of the earth

Answer 7

Crust:
- lithosphere, oceanic and continental
- asthenosphere, semi-molten allowing the plates to move
Mantle, molten and semi-molten rock
Core, dense rock (iron and nickel)

Question 8

Explain the development of the plate tectonic theory

Answer 8

• 17th Century, Francis Bacon noticed the land masses ‘fit’ together
• 1912, Alfred Wegener publish his theory of a super-continent named Pangea as well as his theory of continental drift
• 1940+, Sea floor spreading discovered: the Mid-Atlantic Ridge was discovered and scientists noticed alternating polarity of the rock, iron particles in lava aligned with the earths magnetic fields leaving evidence that the oceanic crust is slowly spreading

Question 9

Sea floor spreading implied …

Answer 9

That the earth was getting bigger, as this is not the case, plates must be been destroyed elsewhere. This was proven by the discovered of ocean trenches where the oceanic crust was being sub-ducted

Question 10

Explain the process of ridge push

Answer 10

This occurs at mid-ocean ridges when magma rises to the surface and heats the surrounding rock causing it to expand and raise to form a slope. As the new rock cools it becomes denser and slides down the slope resulting in sea floor spreading. Can cause shallow focus earthquakes due to friction.

Question 11

Explain the process of slab pull

Answer 11

This occurs at destructive plate boundaries when the denser oceanic plate begins to subduct gravity pulls the rest of the plate down with it. Can cause shallow and deep focus earthquakes due to friction.

Question 12

What are the 3 situations seen at convergent plate boundaries?

Answer 12

Oceanic to continental
Oceanic to oceanic
Continental to continental

Question 13

Describe the process of an oceanic to continental meeting:

Answer 13

Oceanic plate is denser so subduct under the continental
The bending of the oceanic plate forms an ocean trench
The continental land is uplifted and compresses to form a series of fold mountains
Sub-ducted crust melts and releases magma which rises to form volcanic eruptions

Question 14

Describe the process of an oceanic to oceanic meeting:

Answer 14

Subduction forms an ocean trench

Sub-ducted crust melts and releases magma forming submarine volcanoes

Question 15

Describe the process of a continental to continental meeting:

Answer 15

Plates uplift and buckle to form high fold mountains
May cause shallow focus earthquakes
No volcanic activity due to no subduction

Question 16

Describe what happens at a conservative plate boundary:

Answer 16

Two plates slide past each other
No volcanic activity
Friction between the plates can trigger shallow focus earthquakes

Question 17

How are mid-ocean ridges formed?

Answer 17

Transform faults form on submarine mountain ridges
Faults may widen at different rates, building stress, which can trigger shallow-focus earthquakes
Eruptions along the ridges can form submarine volcanoes - may rise to create volcanic islands

Question 18

How are rift valleys formed?

Answer 18

Crust stretches and fractures, producing parallel faults

Land between fault lines collapses to form a valley