1. Features on Earth’s Surface
Earth’s Dynamic Surface
Features on Earth’s Surface

2. Watch Constructive Forces earthquakes crustal deformations
volcanic eruptions
sediment deposition
Watch

3. Destructive Forces Wear down landforms
carry bits and pieces of land to other places like the sea
weathering
erosion

4. Divergent Plate boundaries
Make new crusts
two plates moving apart in opposite directions

5. Alfred Wegener

6. Aim: How does the Theory of Plate Tectonics influence the way the Earth is today?
I. Plate Tectonics
A. Theory of Plate Tectonics
1. The surface of the Earth is composed of about a dozen major rigid, moving crustal plates and several smaller plates

8. Plates
a. Slabs of Earth’s lithosphere (crust and upper mantle)
b. Average thickness is 100 km (62 miles)
c. Most plates support both continent and ocean
B. Continental Drift – states that the continents have drifted and still are drifting apart.

10. C. Why do the plates move?
Due to tremendous heat, rock in the asthenosphere is like hot taffy
This allows plates to ride on top of hot, flowing rock.
3. Plates move because heat is being released from deep inside the earth.
4. Convection currents causes hot material to rise and expand (plates diverge) and cooler material to sink and contract (plates converge).

12. D. Alfred Wegener – proposed that in the distant past, the Earth’s continents were all joined as a single landmass.
1. Evidence for his theory
South America and Africa would fit remarkably well, shoreline to shoreline.
If the Americas were moved next to Africa and Europe, there would be a match of ancient continental rocks and tectonic (fold and fault) structures.
c. Pangaea – when Wegener placed all the continents together like a puzzle, it formed a large landmass which he called Pangaea.

13. Fossil Evidence

15. Seafloor Spreading
the seafloor actually spreads apart where the plates pull away
the lava reaches earths surface then solidifies
this makes new ocean crust
The new crust forms a mid ocean ridge

16. Lava cooling under ocean
Most lava is found at divergent boundaries in the ocean

17. Convergent Plate Boundaries
Destroy crust!
Plates converge or push into each other
deep ocean trenches
continental mountain chains
volcanic island chains

18. Continental Mtn. Range
Convergent continental plates

19. Transform Fault Boundaries
two plates grind past each other
San Andreas Fault

20. Thrust Fault
forms when compression makes a fracture form through the rock layers

21. The force actually pushed one set of rock layers up and on top of the nearby rock layers

22. Fold forms when rock layers bend without breaking
the rocks actually act like silly putty in slow motion

23. Hot Spots
Rock will continually rise through the mantle and melt through the plate
As the magma rises through the crust it actually makes new rock

24. Hawaiian Island in Pacific Ocean

25. Formation of island chains…

26. Lithosphere A rigid shell broken into piece (tectonic plates)
Its important because it proves that tectonic plates can move and the Earth is constantly changing

27. Convection Currents

28. Convection currents….
These currents occur in the asthenosphere (where it is hotter & can bend more easily)
they drag the plates along with them as they move

29. Theory of Plate Tectonics
Why is it important?

30. Watch we learn how features on Earth form
we learn to predict things to keep people safe
we know that Earth will continue to change
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