1. Continental Drift 1912 – German Scientist Alfred Wegener
Proposed that the world’s landmasses were once joined together
There was once a supercontinent he named Pangaea

2. Theory of Plate Tectonics
Lithosphere divided into plates & their movement
produces changes in Earth’s surface
Evidence to support the theory of Continental
Drift
Shape of the continents
Mountain ranges
Similarity of rocks
Similarity of fossils

3. World Plates

4. What are tectonic plates made of?
Plates are made up of the rigid lithosphere

5. What lies beneath the tectonic plates?
The asthenosphere – liquid part of the mantle

6. Plate Movement
Plates moved around by convection cells in the underlying hot mantle

7. Plate Boundaries The interface at which the plates interact
The site of most of the major events involving Earth’s crust
Mt. Building, Earthquakes, Volcanic Eruptions
3 major types:
Convergent
Divergent
Transform

8. Plate boundaries

9. Convergent Plate Boundaries
Plates come together
Subduction
The more dense plate goes under the less dense plate
Trenches – deepest parts of the ocean
Collision
Two low density plates collide

10. Himalayas

11. Divergent Plate Boundaries
Plates spread apart
As plates move apart new material is erupted to fill the gap
Occurs at mid-ocean ridges – Rift Valleys
Sea Floor Spreading

12. Iceland
Iceland has a divergent plate boundary running through its middle

13. Divergent Boundaries

14. Transform Plate Boundaries
Plates slide past one another
Ex. San Andreas Fault

15. Ocean Evidence Discovered in the 1950’s Oceanic crust age Heat Flow
Increases as you move away from the ridges
Rocks equidistant from the mid-ocean ridge in opposite directions are the same age
Heat Flow
Heat decreases as distance from ridges increases

16. Magnetic Reversals Earth has a magnetic field
The field has a North & South Pole
The position of these poles has reversed many times in the past

17. Magnetic Reversals

18. Visible Effects of Plate Tectonics
Earthquakes
Mountain Building
Hot Spots
Tsunamis
Volcanoes

19. Hot Spots A location where hot plumes of magma flow out of the crust
Located in the interior parts of plates
Due to plate movement, this can create island chains
Hawaii

20. Tsunami Large ocean wave Caused by a disruption of the ocean floor
Earthquake
Underwater volcano
Underwater landslide

21. 2004 Tsunami

22. Volcanoes
Mountains composed of extrusive igneous rocks

23. Ring of Fire
Region surrounding the Pacific Ocean