Earth's Internal Structure: How Do We Look Inside Earth (2.2.1)

Question 1

Is evidence from meteorites direct or indirect?

Answer 1

Indirect.

Question 2

Where does rare direct evidence for what Earth’s mantle is made of come from?

Answer 2

Rare xenoliths brought up by lava flows.

Question 3

What are most xenoliths made up of?

Answer 3

Peridotite rock. Nothing deeper than few hundred km, most <100km.

Question 4

What are kimberlites?

Answer 4

Volcanic rock containing diamonds and other rock/mineral fragments, deep in mantle.

Question 5

What is peridotite?

Answer 5

• Utlramafic rock made mostly of olivine.
• Olivine has simple crystal structure.
• High density/melting point.
• Very strong, flows as ductile solid.

Question 6

How do we (think we) know the model for Earth’s internal structure?

Answer 6

Using remote methods (geophysics!):
- Seismology: propagation of elastic waves through Earth.
- Gravity: small-scale variations in Earth’s gravity.
- Heat: Earth’s heat budget and thermal properties.
- Magnetism: Locked in rocks.