Tectonics: 1.4 - Earth's Conveyer Belt

Question 1

Earth’s structure

Answer 1

Inner core: solid steel

Outer core: 2,300 km of molten liquid metal -> flows because of Earth’s rotation -> creating a magnetic due to metal in outer core -> but it’s unstable so polarity swaps every 200,000 years

Mantle: peridotite (rock with high concentration of magnesium, and also iron and silica)

Crust: igneous, metamorphic and sedimentary rock

Question 2

Lithosphere

Answer 2

Crust and upper mantle

Question 3

Asthenosphere

Answer 3

Layer of mantle below lithosphere

Question 4

90% of heat at depth comes from…

Answer 4

Radioactive decay, as well as some latent heat from core

Question 5

Decompression melting

Answer 5

As the pressure decreases the melting point of substances decreases

This means rock in the mantle melts as it rises, creating magma

This is why the asthenosphere acts like soft toffee

Question 6

Mid-ocean Ridge

Answer 6

Formed when magma collects in chambers, rises to the surface, and cools

This buildup of material creates a ridge

Question 7

Sea floor spreading

Answer 7

Combination of ridge push and slab pull

Question 8

Ridge push

Answer 8

When a ridge collapses under its own weight, pushing tectonics plates away

Question 9

Slab pull

Answer 9

When a tectonic plate subducts into the mantle under its own weight, pulling the whole plate down

Question 10

Palaeomagnetism

Answer 10

Lava on surface contains magnetic material. When lava cools these materials align with the Earth’s North and South Poles at the time

Ridge push causes materials to split, both facing ‘North’. When polarity swaps, materials align with the new ‘North’ (old South), facing the opposite direction. Ridge push causes material to split, etc.

Question 11

Evidence for sea floor spreading

Answer 11

Palaeomagnetism