1. Plate Tectonics
Earth Science

2. Continental Drift
The theory of Continental Drift was created by Alfred Wegener in ~ 1915
His theory stated that the continents were one large land mass called Pangea and drifted to their present locations

3. Evidence For Pangea Jig-Saw Puzzle Fit Of Continents
PANGAEA
Jig-Saw Puzzle Fit
Of Continents
B) Similar Rocks and Fossils
C) Glacial evidence
D) Coal Deposits
E) Mountain Ranges
225 million years ago
135 million years ago
65 million years ago
Present

4. Theory of Plate Tectonics
The Theory of Plate Tectonics states that Earth’s crust is made up of a number of solid pieces called plates, and these plates move in relation to each other.
The term tectonics refers to the forces that deform Earth’s Crust.

5. INDIAN-AUSTRLIAN PLATE
Reykjanes
Ridge
EURASIAN
PLATE
EURASIAN PLATE
Mid-
Atlantic
Ocean
Ridge
ANATOLIAN
PLATE
JUAN DE
FUCA PLATE
NORTH
AMERICAN
PLATE
CHINA
SUBPLATE
CARIBBEAN
PLATE
Transform
fault
PHILIPPINE
PLATE
ARABIAN
PLATE
PACIFIC
PLATE
COCOS
PLATE
AFRICAN
PLATE
Mid-
Indian
Ocean
Ridge
Transform
fault
SOUTH
AMERICAN
PLATE
Carlsberg
Ridge
East Pacific
Rise
SOMALIAN
SUBPLATE
INDIAN-AUSTRLIAN PLATE
Southeast Indian
Ocean Ridge
Transform
fault
Southwest Indian
Ocean Ridge
ANTARCTIC PLATE
Plate motion
at convergent
plate boundaries
Divergent ( ) and
transform fault ( )
boundaries
Plate motion
at divergent
plate boundaries
Convergent
plate boundaries

6. Oceanic vs. Continental Crust
Oceanic Crust (predominately igneous basalt)
Mafic – rich in iron
High density, thin
Continental crust (predominately granite)
Felsic – rich in feldspars and Al
Low density, thick

7. What is the Driving Force?
The driving force to move the plates comes from convection cells in the mantle

8. Spreading
center
Oceanic tectonic
plate
Oceanic tectonic
plate
Ocean trench
Collision between
two continents
Plate movement
Plate movement
Tectonic plate
Oceanic
crust
Oceanic
crust
Subduction
zone
Continental
crust
Continental
crust
Material cools
as it reaches
the outer
mantle
Cold dense
material falls
back through
mantle
Mantle
convection
cell
Hot material
rising
through
the mantle
Two plates move
towards each other.
One is subducted
back into the mantle
on falling convection
current.
Mantle
Hot outer
core
Inner
core

9. Divergent Boundary 2 plates separate Example: Mid-Atlantic Ridge
Features Formed:
Mountains
Volcanoes
Ridges
Rift Valleys

10. Convergent Boundary 2 plates come together
Example: land/land (Collisional Boundary)
India/Asia
Features Formed: Mountains - Himalayas

11. Convergent Boundary 2 plates come together Features Formed:
Example: ocean/land
Nazca plate/S. American plate
Features Formed:
Subduction Zones
Ocean Trenches
Mountains
Volcanoes

12. Transform (lateral) Boundary
2 plates slide past each other
Example:
San Andreas Fault
Features Formed
Fault Line

13. San Andreas Fault

14. Plate Tectonics

15. Evidence for Sea Floor Spreading
Igneous Ocean Rock – evidence shows that igneous material along the center of the mid-ocean ridge is younger (it formed most recently) than the igneous material farther from the ridges.
As new crust is generated at the mid-ocean ridges, the ocean floor widens.

16. Sea Floor Spreading

18. Reversal of Magnetic Polarity
The strips of basaltic igneous rock which lie parallel to the mid-ocean ridges show matched patterns of magnetic reversals
Over thousands of years, the magnetic poles of Earth reverse their polarities, the north magnetic pole becomes the south magnetic pole and vice versa

19. Magnetic Polarity Cont.
When basaltic magma flows up into the ridge and cools, crystals of magnetic minerals align themselves with Earth’s magnetic field like tiny compass needles, thus recording the magnetic polarity at the time of formation.

20. Magnetic Reversals

21. Hot Spots

22. Hot Spots

23. Hot Spots Hot Spots: Places on Earth’s surface found
within the plates, with unusually high heat
flow.
The cause of these hot spots are plumes of
magma rising up from the mantle producing
active volcanoes.

24. Hot Spots Continued As the plate passes over a hot spot, a chain of
volcanic mountains form. The only mountain that
remains active is the mountain located directly
over the hot spot.

25. Hot Spots

26. Crustal Activity Normal Deposition of Rock Layers (Strata):
Horizontal layers show
no movement (crustal
activity)
Sedimentary Rock
Lava Flows

27. Folding Caused by strata (layers) bending due to mountain building.
Example: Appalachian Mountains

29. Tilting Layers of rock that have moved from a horizontal position to
an angular position
Example: Any fault
or an area uplifted
by an intrusion

31. Faulting A zone of weakness or a crack in the crust
along which rocks have
moved. If there is no
movement it is called a
fracture.
Examples:
Teton Mountains
San Andreas Fault

32. Fault-block Mountains

33. Evidence of Crustal Activity
Displaced Fossils:
Marine fossils found in
layers of sedimentary
rock thousands of feet
above sea level
Suggests that layers
rock (strata), have been
uplifted.

34. Evidence of Crustal Activity
Subsidence:
The sinking of rock
strata. Shallow water
organisms have been
found as fossils deep
within the ocean,
indicating the land is
sinking