1. CHAPTER 4 Created by Miss McDevitt
PLATE TECTONICS
CHAPTER 4
Created by Miss McDevitt

2. FORMATION OF EARTH AGE OF EARTH -4.6 BILLION YEARS
BIG BANG THEORY – 15 BILLION YEARS AGO
BIG BANG ANIMATION
formed from cloud or clouds of dust which was debris from huge explosion
3 theories evolved form how Earth formed
Earth was very hot:
1. from colliding particles
2. compression of layers
3. radioactive materials

3. HOW DO WE KNOW EARTH IS LAYERED?
Seismic Waves speed & path of the 3
types of waves
created by earthquakes
Rock Samples
- scientists can make
inferences about the
conditions inside Earth

4. FEATURES OF LAYERS
Temperature surface to 20m is rock which is cool below 20m the deeper you go the warmer it gets (every 20m = 1° C increase)
Pressure deeper you go the greater the pressure inner core is 2 million X greater than the atmosphere’s pressure

5. LAYERS OF EARTH

6. THE CORE
INNER CORE solid due to high pressure °C made mostly of iron (Fe) also composed of Ni (nickel), Si, Al
OUTER CORE molten, liquid °C Fe & Ni creates Earth’s magnetic field

7. MANTLE AS A WHOLE Molten Rock Mg, Si, O, Al, Fe, Ca ASTHENOSPHERE
Upper Part of Mantle
Semi-solid/semi-liquid rock (tar-like)
Convection current occur here
This layer flows
LITHOSPHERE
Crust & upper part of mantle
Solid rock
AKA “the plates”
Floats on the asthenosphere

8. CRUST Outermost layer Made of solid rock Brittle layer
Under oceans  3-6 miles thick , mostly made of basalt
Under continents  miles thick, mostly made of granite

9. LAYERS COMPARED

10. HEAT TRANSFER Radiation – heat transfer through empty space
Conduction – heat transfer through solids
Convection – heat transfer through liquids & gases

11. CONTINENTAL DRIFT THEORY
Introduced in 1912 by German meteorologist Alfred Wegener
The Origin of the Continents and Oceans
Evidence that the continents had moved across Earth’s surface and formed the supercontinent of Pangaea
Pangaea eventually broke up over tens of millions of years

12. WEGENER’S EVIDENCE
Landforms
Fossils
Climate

13. LANDFORMS
Continental Animation

14. FOSSILS

15. PANGAEA
N.A.
Africa
S.A.
India
Australia
Antarctica

16. FAILURE TO LAUNCH Wegener’s Problem
Could not provide a mechanism to help prove this movement

17. SEA-FLOOR SPREADING 1960 – Harry Hess (American geologist)
Discovered an undersea mountain range (Mid-Atlantic Ridge)
He discovered the ocean floor moved like a conveyor belt
He also found that magma erupts from the middle of ridge

18. WHAT IT LOOKS LIKE!
Sea-floor spreading

19. EVIDENCE Alvin- found magma at bottom of sea floor
Alvin – took drilling samples (discovered ages of rocks)
Magnetic stripes on the ocean floor
Warmer in the center of ridge due to magma erupting

20. MAGNETIC STRIPES
Magnetic reversals

21. PLATE TECTONICS THEORY
Developed by J. Tuzo Wilson
Earth’s plates (lithosphere) are in constant motion due to convection currents

22. PLATE BOUNDARIES Extend deep into lithosphere
Faults (breaks in Earth’s crust) form along these boundaries
3 types

23. DIVERGENT
CONVERGENT
TRANSFORM

24. TRANSFORM Plates slip past each other
Move in opposite directions of one another
Ex: North American - Pacific

25. DIVERGENT Plates move away from each other
Most occur at the Mid-ocean ridge
2 Types:
1. ocean-ocean (ridge forms)
2. continent-continent (rift valley forms)

26. TYPES OF DIVERGENT BOUNDARIES

27. CONVERGENT Plates move toward each other
Density determines which plate comes out on top
3 types:
1. ocean-ocean (trench forms)
2. continent-continent (folded mtns. form)
3. ocean-continent (volcano forms)

28. TYPES OF CONVERGENT BOUNDARIES

30. MAJOR PLATES North American South American Pacific Indian
Indo-Australian
Antarctic
African
Eurasian
Nazca

31. MINOR PLATES Somali Phillipine Scotia Cocos Caribbean Juan de Fuca
Arabian