2. Earth’s Interior
• Geologists have only been able to drill to 3.8
kilometers.
• The center of the Earth is more than 6,000
kilometers deep.
Since Geologists cannot observe the Earth’s
interior directly, they must rely on indirect
measures.
• Seismic Waves are recorded and study how they
travel through the medium of the Earth.
•This information has shown that the Earth has
several layers.

3. Crust
Crust: the layer of rock that
forms Earth’s outer skin.
• The crust includes rocks,
mountains, soil, and water.
• The outer rind of rock is
much thinner than what is
beneath it.
• The crust includes both dry land and the ocean floor.
• It is thinnest beneath the ocean and thickest under
mountains.
•The crust can range from 5-40 kilometers.
•Oceanic crust is made up of basalt.
•Continental crust is made up of granite.

4. Mantle
The mantle is a layer of hot rock that extends nearly 3,000
kilometers deep.
• The Lithosphere is the upper portion of the mantle and the
lower portion of the crust.
• It is approximately 100 kilometers deep and floats on top
of the Asthenosphere .
•The Asthenosphere is a soft layer of the mantle.
•This layer flows slowly.
•The Asthenosphere is approximately 350 kilometers deep.
•The Mesosphere is the solid lower part of the mantle
below the Asthenosphere .

5. Earth’s Magnetic Field
• Currents in the liquid outer core force
the solid inner core to spin. (planet
within another)
•The inner core spins slightly faster
than the rest of the planet.
•This movement creates the Earth’s
magnetic field.

8. Earth’s Interior

10. The theory that states that pieces
of Earth’s lithosphere are in
constant, slow motion, driven by
convection currents in the mantle.

11. • The theory of plate
tectonics explains the
formation,
movement, and
subduction of Earth’s
plates.

12. Forces that causes Earth’s
plates to move.
• The plates of the lithosphere float on top of the
Asthenosphere.
• Convection currents rise in the Asthenosphere and
spread out beneath the lithosphere.
• Convection current forces drag the overlying plates
along. The currents cool and sink deeper into the
mantle.
• Scientists think that the downward movement may
provide the force that causes the subduction of plates
carrying oceanic crust.

13. Forces that causes Earth’s
plates to move.

14. Slab Push Hypothesis
• Magma rising along the mid oceanic
ridge exerts a force that pushes an oceanic
plate away from the ridge.
• The force of gravity causes plate
movement by pulling cooler, denser
oceanic plates down toward the mantle.
• Slab push and pull work together with
convection currents to move the plates.

15. The earth’s surface is
made up of about nine
large plates and several
smaller plates.

17. Places where two plates meet.

19. There are three types of
plate boundaries.
1. Transform Boundary
2. Divergent Boundary
3. Convergent Boundary

20. Two plates slip past each
other, moving in opposite
directions.

21. Earthquakes occur frequently
along this boundary.

22. The San
Andreas Fault
in California
is an example
of a
transform
fault along a
transform
boundary.

23. Two plates move away from
each other.

24. • When divergent boundaries develop
on land, two of Earth’s plates slide
apart.
• A rift valley forms along the
divergent valley.
• Ex. The Great Rift Valley in east
Africa is about 3,000 kilometers long.
Divergent Boundary

26. Two plates move towards
each other.

27. • When plates converge, it
results in a collision.
• Collisions happen between:
1. Oceanic crust to oceanic crust
2. Oceanic crust to continental crust
3. Continental crust to continental crust

31. Plate Movement
• The plates move at about
1-10 centimeters per year.
• The North American and
Eurasian plates move at
about 2.5 cm/year.

32. Plate Movement
• Pangaea existed about 260
million years ago.
• Approximately 225 million
years ago Pangaea began to
break apart.

33. Plate Movement