Option D.1.1

Question 1

What is internal heating

Answer 1

The flow of heat from the Earth’s interior to the earth’s surface

Question 2

Sources of internal heating - Radiogenic

Answer 2

Radioactive decay of materials in the earth’s mantle and crust

Question 3

Sources of internal heating - Primordial

Answer 3

The heat lost as the earth continues to cool from its original formation

Question 4

Convection currents process

Answer 4

1. Hot magma rises to the surface
2. it then spreads out at mid ocean ridges
3. The cold solidified crust sinks back into the Earth’s interior because it is heavier and denser than the surrounding materials

Question 5

What is the cause of convection currents movement

Answer 5

The radioactive decay of Uranium and Potassium in the mantle.

Question 6

What are plumes?

Answer 6

A small area of unusually high heat flow

Question 7

How can plumes cause movement?

Answer 7

The outward flow of viscous rock from the centre may create drag force on the planes and force them to move.

Question 8

Where are most plumes found?

Answer 8

Near plate margins.

Question 9

What is subduction?

Answer 9

The plunging of one plate beneath the another

Question 10

Where do subduction zones form?

Answer 10

Where an oceanic lithosphere collides with another plate whether oceanic or continental.

Question 11

How does subduction happen?

Answer 11

• The density of the oceanic plate is high similar to that of the asthenosphere so it can easily be pushed down into the upper mantle
• Subducted oceanic crust remains cooler and denser for millions of years so once initiated subsuction continues driven in part by the weight of the subducting crust.
• The subducting plate drags the rest of the plate behind it
• The plate is heated up by surrounding mantle
• Eventually melts releasing gases which rise to surface as liquid rock

Question 12

Where does rifting occur?

Answer 12

Constructive/Divergent plate boundaries

Question 13

Examples of rifting

Answer 13

East Africa rift valley, rift at Thingvellir, Iceland ( North America and Eurasion plate moving away from eachother)

Question 14

What is believed to be the main cause of rifting

Answer 14

Hotspot activity

Question 15

Process of rifting

Answer 15

1. Upweling convection in mantle causes the oceanic crust to form a ridge
2. Lateral tension develops, causing rift faulting and downward movement of the central block; magma intrudes along faults giving surface area
3. Lateral movement continues with further intrusions parellel to original rift faults
4. Main rifting sequence is repeated periodically as upwelling continues.