1. Plate Tectonics

2. The Theory of Plate Tectonics
Earth’s crust is made of many plates
These plates move as a result of convection in the mantle
Earth’s surface is constantly being reshaped by these movements
Earthquakes, volcanoes, rifting and mountain building all result from the process of plate tectonics.

3. “ Continental Drift” Alfred Wegner – German scientist
Continents have not always been in their present locations
All continents were once part of a super-continent called Pangea
Also only one great ocean called Panthalassa

4. EVIDENCE TO SUPPORT CONTINENTAL DRIFT
Puzzle-Like fit of the continents
Fossil Evidence
Matching Geologic Features
Evidence of Climate Change

5. Wegener’s evidence for Continental drift
Fossils of ferns and reptiles are the sameon many different continents.
Evidence of Glaciers in areas that are now tropical.
Same types of rocks layers are the same on continents that are separated by an ocean.
The coastlines of Africa and South America fit together like puzzle pieces.

10. EVIDENCE TO SUPPORT CONTINENTAL DRIFT
Puzzle-Like fit of the continents
Fossil Evidence
Matching Geologic Features
Evidence of Climate Change
So….. If Alfred Wegner had all of this evidence to support his theory of Continental Drift, why did many scientists not accept his idea? What was he missing?

11. Convection Currents

12. The Movement of Plates

13. CONVECTION
Convection is overturning motion and the transfer of heat resulting from heating and density differences
Lithospheric plates move as a result of convection in the mantle
Convections cells in the asthenosphere rotate slowly over millions of years.
Because the convections cells rotate in different directions, the plates move in different directions also
Convection can also be used to explain the cause of wind and ocean currents

14. Early Earth and Plate Tectonics
Convection in the Mantle
Earth's Future
Earth 100 Million Years From Now

15. Plate Boundaries Where two plates meet a plate boundary is formed.
What happens at a plate boundary depends on the direction each plate is moving and the density of each plate
Earth’s surface is constantly being reshaped by these movements
Earthquakes, volcanoes, rifting and mountain building occur at or near plate boundaries.
Plate movements also cause forces that affect areas along the boundary and within the plate itself.

16. Type of Plate Boundaries
Plate boundaries are classified into three main groups based upon the relative direction of movement
Convergent Plate Boundary: plate move towards each other
Divergent Plate Boundary: plate move apart
Transform Boundaries: plate slide past each other (side by side)

17. Convergent Boundaries
There are three types of convergent boundaries classified the type of crust involved:
Continent to continent convergence
Ocean to continent convergence
Ocean to ocean convergence

18. Continental-Continental boundaries
The Himalayan Mountains, Including Mt. Everest, formed as a result of the convergence of the Indian and Asian Plates

19. Oceanic-Oceanic boundaries:
Island arc volcanoes and deep ocean trenches form at ocean crust to ocean crust convergent boundaries

20. Continental-Oceanic boundaries:
Ocean crust to continental crust convergent boundary. Because oceanic crust is more dense than continental crust, the ocean crust is subducted

21. Subduction Zones
When two plates of different densities collide at a convergent boundary, the denser plate is driven under the less dense plate forming a subduction zone
Magma is generated in the subduction zone resulting in the formation of volcanic arcs.

23. Transform Boundaries
When two plates slide past each other a transform boundary is formed.
Earthquakes are common along transform boundaries because the plate do not slide smoothly past each other

25. The San Andreas fault is an example of a Transform Boundary

26. Divergent Boundaries
When two plates move apart a divergent boundary is formed.
Mid-Ocean Ridges and Rift Valleys form at divergent boundaries

29. New ocean crust is created at mid-ocean ridges.
These are also referred to as spreading centers

30. Iceland is a volcanic island that has formed on top of a Mid- Atlantic ridge

39. Identify the types of boundary and geologic landforms2 3 1 D E K J F G B A H C

40. A B
Convection Current B
Convection Current A
Convection Current A

42. December 26, 2004 -An Earthquake 9
December 26, An Earthquake 9.0 on the Richter hit Indonesia creating a massive tsunami that killed over a quarter of a million people

44. A B
Convection Current B
Convection Current A
Convection Current A