1. WORLD GEOGRAPHY 3202 INTRODUCTION
The Size of the World

2. The Earth’s Interior
Crust (Lithosphere)
Mantle
Outer Core
Inner Core

3. Inner Core
The deepest part of the earth (1512 miles deep) is a solid that contains both iron and nickel.
It is because of this that the center of the earth is a magnet - a compass.
It generates a magnetic field that protects the earth from flying out of orbit.

4. Outer Core
Outside of the inner core lies the outer core ( miles deep).
This is much like the inner core with the exception that it is a liquid that contains sulphur and oxygen (which lowers the melting point).

5. Mantle
Occupying 1789 miles of the earth is the magma (iron and magnesium) that makes up the mantle.
Upper and lower
It is extremely hot!!
The upper mantle is goopy and very plastic- like.
The lower mantle is mostly solid.

6. Crust Also called lithosphere
This is the top layer of the earth, which is basically hardened mantle (magma).
It contains two segments, the oceanic and continental crusts.
Note: this is the same crust, it just depends how thick it is to determine if it is part of the Oceanic or Continental Crust.

7. Read About Earth’s interior
Our Text p. 4-6

8. Theory Of Continental Drift
Alfred Wegener
It is this German man to whom we credit with the proposal of the theory of Continental Drift. (1912)

9. While pondering the similarities between the coastlines of South America and Africa, Wegener came up with an idea:
What if the continents were once all connected and just drifted over the years?

10. Wegener’s Proof

11. Wegener’s Proof

12. Wegener’s Proof

13. The Flaw in Wegener’s Theory
He thought that each of the continents were a separate plate. They were just drifting on a never- changing ocean. Like styro-foam floating on a pool of water!!

14. Missing Proof
Wegener could not explain what mechanism was powerful enough to move huge continents
Scientist’s never believed him

15. Canadian Correction J. Tuzo Wilson
He is the 1960’s Canadian scientist who resurrected Wegener’s theory after years of disbelief by the science community.
Today, we know that Wegener’s Theory was false, thanks to the discovery of crustal plates.
The plates of the earth are not composed of just land. They're composed of ocean too.

16. Canadian Correction – cont’d
In some cases, the plates are just land, in others they're just ocean, and, in still other cases, they consist of land and ocean.
They each have different boundaries and move in all different directions.

17. Plates of the earth p. 12

19. Continental Drift Animation

20. Continental Drift
refers to the movement of the more than 20 plates (9 major) due to convergent, divergent, and transform boundaries.
the continents drift at a rate of 2 inches a year.
started 200 million years ago
Pangea (land) & Panthalasa (sea)

21. Plate Tectonics
Tectonic plates move or float on top of the upper mantle.
However they do not float freely.
The plates are forced in specific directions by the flow of magma beneath.

22. Plate Tectonics – cont’d
Plates move with the flow of magma.
The magma closer to the core heats and then rises towards the surface as its density decreases.
Once the rising magma reaches the lithosphere it moves in opposite directions.
The magma forms convectional currents.

23. Convection Currents

24. Plate Tectonics – Convection Currents

25. Divergent Boundaries
Tensional Forces occur where two tectonic plates are pushed apart. The tension is created as the plates move away from each other.
Ridge Zones sometimes occur where two plates move apart. The magma rises between the plates and forms a ridge.
Again caused by convectional currents in the magma

26. Tensional Forces – Ridge Zones
This diagram above shows “Sea Floor Spreading”

27. Where’s the TENSION?

28. Convergent Boundaries
Compressional Forces occur where two tectonic plates come together. They compress against each other.
Subduction Zones sometimes occur where compressional forces result from two plates colliding and one plate slips under the other.
Again caused by convectional currents in the magma

29. Compressional Forces – Subduction

30. Where’s the Subduction / Compression?