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

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

4. 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.

5. Forces that causes Earth’s
plates to move (continued).
•Convection current forces drag the
overlying plates along. The currents cool
and sink deeper into the mantle.
• Scientist think that the downward
movement may provide the force that
causes the subduction of plates carrying
oceanic crust.

6. QuickTime™ and a
decompressor
are needed to see this picture.

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

8. 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.

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

11. Places where two plates meet.

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

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

15. Earthquakes occur frequently
along transform boundary.

16. The San
Andreas
fault in
California is
an example
of a
transform
boundary.

17. Two plates move away from
each other.

18. • When a divergent boundary
develops 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.

20. Two plates move towards
each other.

21. • 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

22. This can happen where oceanic crust
meets oceanic crust.

23. This can happen where oceanic crust
meets continental crust.

24. This can happen where continental
crust meets continental crust.

25. 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.

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

27. Plate Movement
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