Physical Geology 101
The Earth's Interior


The Earth’s Interior

Interior structure is related to formation of Earth 4.6 billion years ago.
Differentiation:

Looking into the Earth's Interior

Surface samples.
Drilling - 8-9 km deep
- deepest drill hole - 12 km
Ophiolite Sequences - 7-10 km deep
Xenoliths - 0-100 km deep
Kimberlites - 200 km deep

How do we get information from deeper than 200 km?
Seismic Waves - (waves of energy) reflect or refract off of materials in interior.

Reflection and Refraction


Reflection and refraction are affected by:
1.
2.
3.
4.

Looking into the Earth's Interior


Sources of seismic waves?
1.
2.
3.
4.

The Earth's Interior Least Dense to Most Dense

Atmosphere

- 0-500 km above solid and liquid surface

Oceans

- 0-11 km above solid surface

Crust

Continental Crust & Oceanic Crust
Continental Crust
- average composition = granite
- density = 2.6-2.7 g/cc
- 10-70 km thick (average 33 km)
Oceanic Crust
- average composition = basalt
- density = 2.6-2.8 g/cc
- 6-10 km thick

Lithosphere

- contains the Crust and the Upper Mantle
- average composition = gabbro
- 100 km

Asthenosphere

- partially molten - 1-2 %
- capable of flow
- average composition = peridotite
-100-350 km

Upper Mantle

- partly solid - partly molten
- peridotite
- includes lowest portion of the Lithosphere and all of Asthenosphere
-~33-670 km

Crust - less dense
Mantle - more dense

Lithosphere - more rigid
Asthenosphere - less rigid

Lower Mantle

- average composition = peridotite*
* increased pressure has changed minerals
- 670-2900 km

Outer Core

- liquid iron and nickel
- 2900-5150 km

Inner Core

- solid iron and nickel
- 5150-6370 km

Comparison of Earth's core with the cores of the Inner Planets.

Seismic Tomography

"Onion Layer" interior structure
Seismic Tomography allows for more detailed images of Earth's interior.
Boundaries between layers are not smooth but have bulges and basins.
Formed by hot material rising and cool material sinking.