L1 - Earth Structure

Question 1

What are the 4 basic layers of they Earth?

Answer 1

Inner core
Outer core
Mantle
Crust

Question 2

What form the crust?

Answer 2

Oceanic (under seas) and continental (under land) lithosphere

Question 3

Describe the characteristics of the oceanic lithosphere.

Answer 3

Thin - 5-8km
Made of balsatic rock
Denser than continental crust 3.0g/cm3

Question 4

Describe the characteristics of the continental lithosphere.

Answer 4

Thick - 30-40km

Lighter than oceanic, made of granitic rock, 2/7g/cm3

Question 5

What are the general features of the crust?

Answer 5

Lays above semi-fluid mantle
Heats quickly with depth. 200-400degrees C
Continually stressed due to plate tectonic movement and convection current
When plates pull apart there are deep cracks and magma rises
Rock melts as pressure is released (boiling point hit)

Question 6

Describe the structure of the mantle.

Answer 6

Upper mantle is solid - melting at hotspots and plate boundaries
Asthenosphere below - sticky, viscous and dense moved rock - due to convection currents
2900km thick
1000degrees C
Mantle temperature and pressure increases so lower mantle is solid

Question 7

Describe the structure ad characteristics of the core.

Answer 7

Hot - outer-core (4500-5500 degrees C), inner (6000 degrees C)
Inner core - dense solid ball of iron and nickel due to pressure.
Radioactivity due to radioactive decay of uranium and thorium.

Question 8

What is the upper mantle split into?

Answer 8

Lithosphere

Asthenosphere

Question 9

Describe the structure and characteristics of the lithosphere.

Answer 9

• Crust and top layer of upper mantle
• Made of peridotite
• 80-100 km thick; thinner under the oceans and in volcanic-ally active areas
• Broken up into tectonic plates (lithospheric plates) of varying sizes which float on the asthenosphere

Question 10

Describe the structure and characteristics of the asthenosphere.

Answer 10

Dense. mobile layer of upper mantley
100-300km thick
1300 degrees C
High pressure but low enough so rocks can flow

Question 11

What are convection currents, what do they do and how do they work?

Answer 11

They move tectonic plates
Rock is heated at the lower mantle, rises and then cools by losing energy, it is forced sideways as it is blocked by the asthenosphere
The rock then falls, hits the outer core and process is repeated.

Question 12

Where do convection currents get their energy from?

Answer 12

They need a source of heat, radioactive decay and residual heat (heat left over from when the Earth formed)