5.2 - Plate tectonics

Question 1

Define convection currents

Answer 1

Heated magma spreads out under plates and cools, causing plates to become dense and sink

Question 2

Define slab pull

Answer 2

At a destructive plate boundary - subducting oceanic plate is denser than surrounding material so pulls rest of plate in

Question 3

Define ridge push

Answer 3

Happens in constructive plate boundary at mid-ocean ridges
Hot magma rises to surface and cools and heats surrounding rocks
Those rocks then expand and elevate above sea floor to cause a slope
Sea floor spreads so new oceanic crust is formed

Question 4

Give 3 differences between oceanic and continental crust

Answer 4

Oceanic Continental
200 million yrs 3.8 billion yrs
Regularly subducted and destroyed Never destroyed
High density (subducts the plate) Low density

Question 5

Define intraplate

Answer 5

Middle of plate but can be thin

Question 6

Describe a constructive plate

Answer 6

/  \\_\_              \_\_/ \
    /      \   \\_\_   _/ /       \
  /          \   \   \/   / /        \
/              \     \   \/            \
Causes a rift valley to form
Tensional forces move plates

Question 7

Describe the crust

Answer 7

5-30km thick
Continental and oceanic
Iron rich

Question 8

Describe the mantle

Answer 8

2900km thick
3000 oc
Viscous solid
High pressure

Question 9

Describe the outer core

Answer 9

2200km thick
4000 - 5000 oc
Spins when Earth rotates to crease magnetic field

Question 10

Describe the inner core

Answer 10

1250km thick
6000 oc
Solid (high density)

Question 11

Name the discontinuity between crust and mantle

Answer 11

Moho’s discontinuity

Question 12

Name the discontinuity between mantle and asthenosphere

Answer 12

Repetti’s discontinuity

Question 13

Name the discontinuity between asthenosphere and outer crust

Answer 13

Gutenberg’s discontinuity

Question 14

Name the discontinuity between outer crust and inner crust

Answer 14

Leham’s discontinuity

Question 15

What is the asthenosphere?

Answer 15

Lower mantle where convection currents happen