1.2a - Conveyer Belts

Question 1

How is convection created?

Answer 1

Convection is created in the mantle by heat radiating outwards from the inner core.

Question 2

What are destructive plate boundaries and where do they occur?

Answer 2

Destructive plate boundaries either form at subduction zones or a continental collision, depending on the type of plate.
When a dense oceanic plate collides with a less dense continental plate, the oceanic plate is thrust underneath, forming a subduction zone.
During collisions between two continental plates, large mountain ranges are formed.

Question 3

What is the theory of plate tectonics?

Answer 3

The theory of plate tectonics is a theory that was developed over 60 years ago to explain the large-scale movements of the lithosphere. It was based around the evidence for sea-floor spreading and ocean topography, paleomagnetism, etc.

Question 4

What is the earth’s structure comprised of?

Answer 4

It is made up of the inner and outer cores, mantle, and the outer crust, due to the gravity acting on materials of different densities.
The crust is on the outside, followed by the mantle, then the outer core and finally the inner core.

Question 5

What is paleomagnetism?

Answer 5

Paleomagnetism results from the zone of magma ‘striking’ the Earth’s magnetic polarity when it cools. When magmas and lavas solidify, the iron minerals in the rock align with the Earth’s magnetic field, permanently recording the direction.

Question 6

What is mantle convection?

Answer 6

The movement of mantle materials in cells when heated by radiation from the Earth’s core. It is thought that there may be several layers of convection.

Question 7

What is sea floor spreading?

Answer 7

Sea floor spreading is the movement of the oceanic crust away from a constructive plate boundary, as recorded by the stripes in the basaltic rock (paleomagnetism)

Question 8

What is subduction?

Answer 8

Subduction is the process involving the decent of an oceanic plate into the upper mantle beneath a continental plate

Question 9

What is slab pull?

Answer 9

At a subduction zone the descending part of the oceanic tectonic plate pulls the rest of the plate with it

Question 10

What is the composition and temperature of the crust?

Answer 10

Surface temperature to about 400 ° C

Granite (continental) and basalt (oceanic)

Question 11

What is the composition and temperature of the mantle?

Answer 11

870 ° C
Peridotite
Upper = olivine
Lower = magnesium silicate

Question 12

What is the composition and temperature of the outer core?

Answer 12

4400 to 6100 ° C
12% sulphur
88% iron

Question 13

What is the composition and temperature of the inner core?

Answer 13

7000 ° C (radioactive decay)
20% nickel
80% iron