The Earth's Interior
PHYSICAL GEOLOGY 101

Formation of the Earth

Differentiation
Most dense material sinks to center.
Least dense material floats on top.

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

Looking into the Earth's Interior

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 are affected by:
Sources of seismic waves?

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

Crust - less dense
Mantle - more dense

Lithosphere - more rigid
Asthenosphere - less rigid

Upper Mantle

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

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 the Earth's interior.
The boundaries between the layers are not smooth but have bulges and basins.
Formed by hot material rising and cool material sinking.

Study Guide

Earth's Interior Study Guide

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Notice: The material contained within these web pages only applies to those courses and sections taught by Richard Harwood. Unless otherwise noted, all images and graphics contained within are the property of Richard Harwood and may only be reproduced with permission from the author.