tectonics L2 theory & plate movement

Question 1

Plate Tectonic Theory

Answer 1

scientific theory that attempts to explain why the Earths crusts acts the way it does & produces the landforms and hazards we can see on the Earths Surface

Question 2

How do Convection Currents work?

Answer 2

radioactive decay & pressure in the core heat the mesosphere.
heat causes that part of the mantle to rise as it becomes less dense (semi-molten)
as it reaches the lithosphere it cools down because it’s further from the heat source — density and increases and starts to sink

Question 3

How do convection currents relate to plate tectonic theory?

Answer 3

provides an explanation for plate movement
does NOT provide evidence of plate movement

Question 4

What is Paleomagnetism?

Answer 4

(Hess)
magnetic strips on the ocean floor (containing magnetite in the basalt) preserve a record of the polarity of the Earths magnetic field which switches over time.
(Constructive boundary)
(Vine & Matthews)
either side of the ocean ridge has a symmetrical pattern of normal polarity to magnetic polarity stripes

Question 5

How does Paleomagnetism link to Plate Tectonic Theory

Answer 5

provides evidence of plate movement as the change over time is recorded BUT does NOT provide an explanation for plate movement

Question 6

What is Sea Floor Spreading?

Answer 6

(Hess)
Discovered the oceans were shallower in the middle and identified the mid ocean ridges

he envisaged that oceans grew from their centres (constructive boundaries)

Question 7

How does Sea Floor Spreading relate to Plate Tectonic Theory?

Answer 7

Provides evidence for the movement and explanation for how the move but not the CAUSE

Question 8

What is Continental Drift?

Answer 8

Theory that the continental landmasses have changed position over time from a single landmass (Pangea)

Question 9

What is Ridge Push?

Answer 9

Upwelling mantle at mid ocean ridges — newly formed plates oceanic ridges are warm — so have a higher elevation
- gravity causes the higher plate at the ridge to push away the lithosphere that lies further from the ridge

Question 10

What is Slab Pull?

Answer 10

• colder plates sink at subduction zones because they become more dense than the underlying mantle
• the plate pulls the rest of the warmer plate along behind it

Question 11

What is Seismic Topography?

Answer 11

• image of the Earths interior in 3 dimensions using seismic waves
• helps to build an image of mantle upwelling & subduction

Question 12

How is GPS Tracking useful for Plate Tectonic Theory?

Answer 12

can track speed & direction of plate movement