Earth's Interior

1. Geologists have used two main types of
evidence to learn about Earth’s interior:
1. Direct evidence from rock samples
2. Indirect evidence from seismic
waves.

3. • Rocks from inside Earth give geologists clues
about Earth’s structure.
Evidence From Rock Samples
• Geologists have drilled holes, or blasted rock to bring up
samples and make inferences about conditions deep inside
the Earth.
• These rocks provide more information about the interior.
• But we can only drill and blast rock to a certain depth, which
is not nearly deep enough to gain more perspective about
the Earth’s interior.

5. Evidence From Seismic Waves
 Geologists cannot look inside Earth.
 Instead, they must rely on indirect methods of
observation, they use seismic waves.
 When earthquakes occur, they produce
seismic waves .
 Geologists record the seismic waves and
study how they travel through Earth.
 The speed of seismic waves and the paths
they take reveal the structure of the planet.

9. The three main layers of Earth are the crust, the
mantle, and the core.
These layers vary greatly in size, composition,
temperature, and pressure.
 Temperature
 After about 20m of depth the temp. of the rock
begins to gradually rise toward the center of the
earth.
 Pressure
 As you move closer to the center of the earth
pressure will gradually increase because the
amount of rock above you increases.
 On the surface, the Earth resembles more of a
cracked hardboiled egg prior to peeling the shell.
EARTH’s INTERIOR

10. Earth is like a cracked
hardboiled egg!

11. Lithospheric Plates
 The surface of Earth is made up of rigid plates that
move relative to each other.
Move together
Move apart
Slide past

12. Lithospheric Plates
1. Why is the Earth broken up into
different pieces on the surface?
2. What is making the plates move
relative to one another?

13. Convection Currents
Heat from the Interior creates convection currents slowly
moving rock due to density differences.