earth's structure and motion

Text Chapter - 8.4 Earth’s Layered

Structure

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Layers of the Earth

Earth’s interior consists of 3 major zones defined by its chemical

composition.

Earth’s layers are divided based on

physical properties.

Density

What causes materials to arrange

into layers?

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Crust- A thin outer layer of Earth (~ 7 km)

Divided into:a. Oceanic Crust – made of Basaltic

Rock- more dense than cont. crust

b. Continental Crust – made of Granitic Rock

(look at the ESRT pg 10)

Moho - (Mohorovicic Discontinuity)

- Separates the crust from the underlying mantle.

- Earthquake waves increase when they reach this layer.

The red line represents the

Moho.

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Look at the ESRT pg 10

Upper Mantle - Asthenosphere –- a soft, weak layer beneath the lithosphere.- rocks are close to their melting temps.- Convection currents move the soft hot rock towards the surface and the cooler rock further into the earth.

Convection Currents

** Plates move in the direction the

convection current is moving**

The Lithosphere is the Earth’s outermost layer

and consists of the crust and

asthenosphere.

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Look at the ESRT pg 10

Lower Mantle – Stiffer Mantle - A solid, rocky shell that extends to a

depth of 2890 km.

The Mantle composition was determined from

rocky meteorites.

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Look at the ESRT pg 10

Core

- The deepest layers of the Earth.- Composed of iron & nickel.

a. Outer Core – liquid, No S-Waves, P-Wave velocity decreases

b. Inner Core – solid iron and nickel,

P-Wave velocity increases

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Look at the ESRT pg 10

How do we know?

Scientists hypothesis that • The earth is similar in composition to

meteoroids.

• Since some seismic waves (S-Waves) do not make it through the earth that some of the layers must be liquid.

» This is known as the shadow zone

• Other seismic waves (P-Waves) change speed and direction when traveling through the earth which supports the changing densities between layers

Shadow Zone

The absence of P and S

waves from about 105o to 140o around the globe is

known as the Shadow

Zone

Closure:

• Layers of Earth WS• Brainpop – Earths Structure