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Internal Structure of EarthUnit 1, Section 3

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Essential Questions What are the layers of the Earth? How do Earth’s internal forces

change its surface?

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Layers of the Earth

1. What is inside the Earth?• Cannot dig a hole to the center of the Earth• There are extreme conditions in Earth’s

interior

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Finding Indirect Evidence

1. Cannot observe Earth’s interior directly

2. Seismic Waves – results of Earthquakes

3. Geologist study how the waves travel through the Earth

4. Speed of seismic waves and paths they take reveal how the planet is put together

5. Inside the Earth's Interior

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Seismic Waves and Earth’s Structure

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Seismic Waves and Earth’s Structure

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Earth’s Interior1. Earth’s interior is made up of layers 2. Each layer surrounds the layers

beneath it (like an onion)

Q – What kind of indirect evidence do geologist use to study the structure of the Earth?

A) Seismic Waves

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Temperature

0 M

20 M

Several Km

Cool

Every 40 m = 1°C IncreaseRapid Increase in Temperature

Increases more slowly, but steadily

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Pressure

1. The deeper you go, the greater the pressure

Pressure – the force pushing on a surface or area

2. Because of the weight of the rock above, the pressure inside the Earth increases as you go deeper

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The Layers of the Earth

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The Layers of the Earth

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CrustCrust – a layer of rock that forms Earth’s

outer layer1. Includes rocks, mountains, soil, water

that covers the surface of the Earth2. Relatively thin3. Includes both dry land and ocean floor4. Thinnest beneath the ocean 5. Thickest under high mountains6. Ranges from 5 to 40 km thick

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Ocean Crust – crust beneath the ocean floor and consist mostly of dense rock like basalt

Continental Crust – crust that forms continents and consist mostly of less dense rocks like granite

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CrustBasal

tGranite

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The Mantle

1. A layer of hot rock, similar to the Crust

Lithosphere – uppermost part of the mantle and the crust together form a rigid layer that averages 100 km thick

2. Temperature and pressure increases with depth

3. Making under the lithosphere less rigid than rock above (somewhat like plastic)

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The MantleAsthenosphere – ‘asthenes’ means weak1. Material is soft and can flow slowly2. Lithosphere floats on top of the

asthenosphere3. Mantle is 300 km thick

Q – How does the material of the asthenosphere differ from materials of the lithosphere?

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The Mantle

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The Core1. Consist of

two parts1. Liquid

Outer Core2. Solid Inner

Core

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The Core1. The core makes

up one-third (1/3) of the Earth’s mass but only 15% of its volume

2. The core is just slightly smaller than the moon

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The CoreOuter Core – a layer

of molten metal that surrounds the inner core

1. In spite of enormous pressure, the outer core behaves like a thick liquid

Inner Core – A dense ball of solid metal

1. Extreme pressure squeezes the atoms of iron and nickel so much that they cannot spread out and become liquid