Structures of the Earth - Evidence

Structures of the Earth:

Objective: Geophysical Methods scientists use such as seismic wave analysis, gravity, and magnetism to interpret Earth's Structure.

How did scientists determine what the layers of the earth were made of?

Earth's magnetic field

• Exists because of an iron, liquid outer core that functions like an electromagnet.

• Historical changes in magnetic field orientation confirm the liquid outer core model.

Chemical composition of rocks on Earth's surface

• Mantle rock is ejected as magma from volcanoes.

• Kimberlites are mantle rock that was injected into cracks and lifted to the surface.

• Stony and iron meteorites reveal mantle and core materials.

High-pressure laboratory experiments

• Show how minerals change under pressure.

• Along with rock evidence, these inform us about pressures inside Earth.

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P waves and Seismic Waves...........

Seismic waves are waves that travel through the Earth after an earthquake.

• S-waves do not go through liquids. Since they do not go into the outer core, they reveal that the outer core is liquid. S-waves stop there.

• P-waves refract when density and state (solid to liquid) change, creating "shadow zones" on Earth's surface where no seismic waves appear.