Transcript Interior of the Earth

How do we know about
layers deep within the
Earth?
Key Points
1.
There are many layers of the Earth:
A.
B.
C.
2.
Core—inner and outer
Mantle
Crust—oceanic and continental
The uppermost layers are divided into two
regions:
A.
B.
Lithosphere
Asthenosphere
Key Points Continued
3.
Earthquakes generate two types of waves:
a.
b.
P Waves
S Waves
The Structure of the Earth

1.
Earth is composed of several layers.
CORE:
 Inner core
 Densest
 Iron and nickel
 Solid- high pressure
 Hot
 Outer core
 Iron and nickel
 Liquid-lower pressure
 Heat within the core generates convection
currents in the mantle
2. MANTLE:
 Dense rocky material near the core
 “Squidgy” near the crust
 Less dense than the core, more dense than
crust
 Convection currents take place here

This is where magma heats up, rises, cools and sinks back
down again to heat and start the process over again.
3. CRUST: the outermost and thinnest layer of
the Earth. Crust is the thickest at mountain
ranges and most thin at the ocean bottoms.
 Continental Crust: About 22 miles deep under
the continents
 Oceanic Crust: About 6 miles deep under the
oceans
Lithosphere/Asthenosphere


Lithosphere: Includes oceanic/continental
crust and the uppermost layer of the mantle up
to 100 km below the surface of the Earth.
Asthenosphere: Includes the area of the
mantle below the Lithosphere.
Earth’s Magnetic Field


Currently, the Earth’s magnetic pole is located
near Earth’s North Pole. This is a condition
called normal polarity.
Periods when the north magnetic pole is located
near Earth’s South Pole are called reverse
polarity.


When molten lava solidifies at mid-ocean ridges,
iron-containing minerals in the lava align
themselves with Earth’s active magnetic field.
These minerals record the orientation of the
magnetic field at the time they solidified.
Click here to see a demonstration of Earth’s
alternating magnetic polarity.
P and S Waves


1.
2.

Scientists analyze seismic data (information from
eirthquakes) to infer processes that occur inside
the planet.
Every earthquake generates 2 types of waves:
Primary waves (P waves)
Secondary waves (S waves)
Click here for an example of p and s wave
movements.

After watching the demo, what do you notice
about the speed of the P waves in the land vs.
the speed of the S waves in the land?


What do you notice about the speed of the P
waves in the water?


P waves travel faster through the land
P waves slow down
What do you notice about the speed of the S
waves in the water?

They can’t travel in liquids
Continental Crust vs.
Oceanic Crust
Continental (40%)
 Composition




Less dense


35-40 km
Oldest of the rocks





“Floats” on top of mantle
Thicker


Granite
Sedimentary
Metamorphic
Oceanic (60%)
 Composition
Because of low density it is
rarely subducted (recycled)
back into the mantle
More dense
Thinner


Mafic rocks
Sima
7-10 km
Age doesn’t exceed 200 million
years

Always subducts between oceanic
and continental plate boundaries.
(recycled back into the mantle)
Summary





The Earth is made up of several layers—inner and
outer core, the mantle, and the crust.
The crust is made up of oceanic and continental
crust.
The lithosphere includes the crust and uppermost
layer of the mantle.
The aesthenosphere includes the mantle below
the lithosphere.
The Earth’s magnetic north reverses over time.
Summary Continues

Scientists study P and S waves to determine the
layers of the Earth—s waves travel through
solids only, p waves travel through solids and
liquids.
Since it is not possible to journey to the center
of Earth. What must scientists do to infer
processes that occur inside the planet?
1.
2.
3.
Use drills to drill
deep into the layers
Study seismic data
from earthquakes
Use satellites to view
images of the layers
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What are the two types of waves
that earthquakes generate?
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1.
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2.
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3.
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4.
S waves and P waves
A waves and B waves
R waves and S waves
Y waves and X waves
20 Seconds
Remaining
P waves can…
1.
2.
3.
Travel through solids
only
Travel through
liquids only
Travel through both
solids and liquids
20
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S waves can…
1.
2.
3.
Travel through solids
only
Travel through
liquids only
Travel through both
solids and liquids
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2
3
Which statement is true?
1.
2.
3.
P waves travel faster
through solids than S
waves
S waves travel faster
through solids than P
waves
P and S waves travel
through solids at the
same speed
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33%
2
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25
How do scientists use P and S
waves?
1.
2.
3.
To measure the
strength of an
earthquake
To see what layers
are solid and what
layers are liquid
To measure the
strength of the core
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