5.3 Plate Tectonic Theory

Question 1

Define Seismic

Answer 1

Types, frequency & size of earthquakes that happen over a period in an area

Question 2

Define Paelaeomagnetism

Answer 2

Geophysics - magnetism in rocks induced by Earth’s magnetic field

Question 3

Define Polarity

Answer 3

Orientation of poles - direction of a magnetic/electric field

Question 4

Define Subduction

Answer 4

When a denser plate slides under a lighter plate into the mantle

Question 5

Define Lithosphere

Answer 5

Outer part of the Earth - crust + upper mantle

Question 6

Define Convection Current

Answer 6

Fluid stream propelled by thermal convection

Question 7

Define Asthenosphere

Answer 7

Upper layer of Earth mantle - low resistance to plastic flow - convection occurs here

Question 8

Define Plate Tectonic Theory

Answer 8

Theory of formation & distribution of Earth structural features of plate movement

Question 9

How and when did Alfred Wegner contribute to Plate Tectonic Theory?

Answer 9

Made theory of Continental Drift (1912)

Question 10

Outline Alfred Wegner’s theory

Answer 10

300m years ago - single continent (Pangaea) split into 2 continents (Laurasia & Gondwanaland) which split into today’s continents

Question 11

Outline geological evidence Alfred Wegner had for his theory

Answer 11

Jig-saw appearance of continents (e.g South America & West Africa fitting)

Question 12

Define Sea Floor Spreading and outline the distance it annually spreads

Answer 12

Atlantic Ocean spreading outwards from the centre
5cm per year

Question 13

Outline the process that occurs every 40,000 years and what is measured

Answer 13

Earth’s magnetic field switches polarity - Iron Oxide erupted onto sea floor measures polarity at that time

Question 14

What else must be done in order to counter sea floor spreading and keep balance?

Answer 14

Subduction (plate destruction seen at oceanic trenches)

Question 15

Outline 3 features of Continental Plates

Answer 15

1. Thinner, lighter - not subducted
2. Permanent can’t be destroyed
3. Old age

Question 16

Outline the 3 features of Oceanic Plates

Answer 16

1. Denser - are subducted
2. Not permanent - formed & destroyed at mid-ocean ridges
3. Young Age

Question 17

What 3 processes help create Mid-oceanic ridges?

Answer 17

Ridge push , Slab Pull, Convection Currents

Question 18

Define Ridge Push

Answer 18

Mid-ocean ridges - magma rises and heats rocks around - creates slope and gravity effect. Causes sea floor spreading

Question 19

Define Slab Pull

Answer 19

Subducting plates sink - mantle pulls the rest behind it due to gravity
Subducting plate and plate above cause friction = earthquakes in subduction zone