Chapter 12 Section 3
Earth’s Interior
Chapter 12 Section 3 – What You’ll Learn - page 370
Before you read - write the reading’s objectives in this space:
1 – _____________________________________________
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2 – _____________________________________________
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Chapter 12 Section 3 – What You’ll Learn - page 363
Before you read - write the reading’s objectives in this space:
1 – Explain how geologists infer the structure of Earth’s deep
interior.
2 – Describe Earth’s internal structure and composition.
How do scientists learn about Earth’s interior?
Use seismic waves to gather data about Earth’s interior –
kind of like a sonogram on humans!
Label the diagram
to the right with
the general name
and thickness:
Earth’s Interior Video 1.5 min
1
How do scientists learn about Earth’s interior?
Use seismic waves to gather data about Earth’s interior –
kind of like a sonogram on humans!
Label the diagram
to the right with
the general name
and thickness:
Asthenoshphere
200 km
Mantle 2900 km
Outer core
2250 km
Earth’s Interior Video 1.5 min
Inner core 1220 km
Recall what is refraction?
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What is a discontinuity?
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Andrija Mohorovičić was the first in the world to establish, on the
basis of seismic waves, a surface of velocity discontinuity that
separates the crust of the Earth from the mantle and which was
named the Mohorovičić Discontinuity, also known as the Moho, in his
honor.
2
Recall what is refraction?
The bending of waves
due to a change in
density.
What is a discontinuity?
A boundary that marks a density change between Earth’s
layers. The Mohorovičić discontinuity separates Earth’s crust
from the mantel.
Andrija Mohorovičić was the first in the world to establish, on the
basis of seismic waves, a surface of velocity discontinuity that
separates the crust of the Earth from the mantle and which was
named the Mohorovičić Discontinuity, also known as the Moho, in his
honor.
What is the shadow zone?
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What is the shadow zone?
A dead zone between 105
and 140 degrees from the
focus of an earthquake,
little or no seismic waves
can be detected.
This is because primary
waves (P-waves) are
refracted by the Earth's
core and secondary waves
(S-waves) are stopped by
the core.
Earth’s Interior
3
Shadow Zones
Composition of Earth’s Layers describe the following:
The crust and uppermost mantle (The lithosphere) _______
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The asthenosphere _____________________________
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Mantle below the asthenosphere __________________
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The cores ___________________________________
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4
Composition of Earth’s Layers describe the following:
The crust and uppermost mantle (The lithosphere) are made
of rocky material—mostly silicates.
The asthenosphere is a weaker, plastic like layer upon which
Earth’s lithospheric plates move.
Mantle below the asthenosphere also is composed of silicates.
The cores are made mostly of metallic material iron and
nickel.
How do astronomers think the Earth
formed? ____________________
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5
How do astronomers think the Earth
formed?
From meteor-like material forced
together by gravity and melted. The
densest of this material settled
toward the core and the lower
density materials settled outward.
Section Check
Question 1
What is Earth’s core made
of?_____________________________________
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6
Section Check
Question 1
What is Earth’s core made of?
Answer
Earth’s core is primarily made of metallic
material such as iron and nickel.
Question 2
Section Check
Earth’s internal layers become _______
with depth.
A. cooler
B. darker
C. denser
D. lighter
7
Question 2
Section Check
Earth’s internal layers become _______
with depth.
A. cooler
B. darker
C. denser
D. lighter
Answer
The answer is C.
Section Check
Question 3
What can’t S-waves penetrate the liquid outer
core?
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8
Section Check
Question 3
What can’t S-waves penetrate the liquid
outer core?
Answer
S-waves only travel through solids. This
suggests that the outer core is in a liquid state.