1. Text Chapter - 8.4
Earth’s Layered
Structure
Do Now:
Label a new sheet of paper with
UNIT 6
2. 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.
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What causes materials
to arrange into
layers?
Density
4. 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)
5. Moho - (Mohorovicic Discontinuity)
- Separates the crust from the
underlying mantle.
- Earthquake waves increase when they
reach this layer.
The red line
represents the Moho.
6. Do Not Copy
Look at the ESRT pg 10
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7. 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.
** Plates move in
the direction the Convection
convection current Currents
is moving**
8. 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
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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
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12. 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
13. Do Not Copy
Look at the ESRT pg 10
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14. 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
15. Shadow Zone
The absence of
P and S waves
from about 105o
to 140o around
the globe is
known as the
Shadow Zone
