Earth’s Structure - formed 4.6 billion years ago
- James Hutton (1700’s) , believed that the earth was much older than thought to be, and
that the earth’s surface had changed over time
-Uniformitarianism – geologic processes occurring today are that same as in the past
The Science of Geology
- Study of the planet earth including its composition and structure
- 2 types of forces: 1. Constructive (shape earth by mountain building and other land
areas like islands)
2. Destructive ( slowly wear away land features)
A Cross Section of Earth
- Layers are divided based upon composition of materials
- Temperature and pressure increase with depth
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The Crust - rocky outer layer of crust
Majority of rocks are made of silicon and oxygen ( silicates )
Often contain metals of Al, Fe, Ca
Continental Crust – less dense rocks such as granite ( 8 – 75 Km thick )
Oceanic Crust – dense rocks like basalt ( @ 7 Km thick )
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The Mantle
Hot but solid rock, 2,850 Km to the core, composed of silicates rich in magnesium
3 layers: Lithosphere – cool, rigid rock, 100 Km, Asthenosphere soft weak rock,
flows, mesosphere strong rock
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The Core
Large sphere of metals ( mostly iron and nickel )
Outer core – 2,260 Km, liquid, creates earths’ magnetic field
Inner core – 1,220 Km, solid due to extreme pressure (3.6 million times the pressure
at earth surface ), 5,500 0C ( almost surface of sun temperature)