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Text Chapter - 8.4 Earth’s Layered
Structure
Do Now:Label a new sheet of paper
withUNIT 6
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
