1. Section 1 – Inside the Earth
Plate Tectonics
Section 1 – Inside the Earth

2. -Three main layers:
1. crust
2. mantle
3. core

3. Center of Earth
-Temperature:
starts cold warmer
hot in center
-Pressure:
deeper you go greater
pressure
-caused by weight of rocks

4. The Crust
-outer layer of rock
5-100 km thick
-thinnest under ocean
-thickest under mountains
Made mainly of oxygen, silicon, aluminum

5. -underneath ocean
Much denser minerals than continental crust
Rocks contain smaller crystals (basalt)
-crust on land
lighter, less dense
Rocks contain larger crystals (granite)
The Crust (cont.)
Oceanic Crust
Continental Crust

7. The Mantle
Lithosphere
-layer of hot rock
-between crust and core
-rigid layer of crust and upper mantle
-averages km thick

8. Asthenosphere
-soft layer of lower mantle below lithosphere
-can bend like plastic
-material flows slowly
Pieces of the lithosphere (tectonic plates) move on the asthenosphere.
-250 km thick

10. The Core
-Outer core:
-Inner core:
molten metal (iron & nickel)
behaves like thick liquid
dense ball of solid metal
such high pressure, can’t become liquid
6,380 km

12. Tectonic Plates
Pieces of lithosphere that move around on top of the asthenosphere.
Fit together like jigsaw
Consists of upper mantle, continental and/or oceanic crust
J Tuzo Wilson

13. How does scientists know so much about the depths of Earth without actually going?

14. Indirect Evidence: What’s inside Earth?
-can’t dig to center
-closest is a mine 3.8 km deep

15. Seismic Waves to study interior
Vibrations caused by earthquakes
Travel at different speeds through Earth depending on density and composition of material.
Earth’s is made of different layers

17. Continental Drift

18. Alfred Wegener Continental Drift
-1912, proposed the hypothesis of continental drift.
Hypothesis that states that continents once formed a single landmass, broke up, and drifted to their present locations.
This single landmass was called Pangaea “All Earth”

19. Pieces of Evidence to make continental drift hypothesis.
-1. continents seemed to fit
-2. fossils found on both sides of ocean were similar
-3. glacial activity in areas too warm for ice and mountains

20. Pangaea
Existed about 250 mya
Split into two continents – Laurasia and Gondwana about 180 mya
Split again to make present continents.

21. Pangaea
Laurasia
North America
Asia
Europe
Gondwanaland
South America
Africa
Australia
Antarctica
India

23. Sea-Floor Spreading

24. Sea-floor Spreading
Harry Hess
Tectonic plates move away from each other.
Seafloor spreads apart
Magma fills in the gap
New crust forms and older crusts gets pushed away from Mid ocean ridge (MOR).

25. mid-ocean ridge (MOR)
sonar
-chain of submerged mountains in ocean basins
Where sea floor spreading takes place
-mapped using sonar
-bounce sound waves off underwater objects
-records echoes of waves

27. Evidence for Sea-Floor Spreading Magnetic Reversals
Earth’s magnetic pole changes
Evidence of these reversals along the ocean floor as the crust moves away from the MOR.

28. Rift Valley
As mountains (MOR) build up a rift valley forms between then in the rift zone.

29. Plate tectonics
-pieces of lithosphere are in constant, slow motion
-plates driven by convection currents in mantle
-plates float on asthenosphere
-plates collide, pull apart, or grind
-forms features: volcanoes, mountains, trenches, etc…
-plates move 1 to 10 cm per year

30. Plate boundary
-a place where tectonic plates touch
-three boundaries: transform, divergent, convergent

31. Convergent boundaries
Subduction
-plates come together
-results in collision
oceanic-oceanic
Oceanic-continental
Subduction occurs
Continental-continental
Dense oceanic crust sinks below less dense continental crust.

34. Divergent boundaries
Two plates move apart-separate
Form mid ocean ridges
-also occur on land; forms rift valley

35. Transform boundaries
-crust neither created nor destroyed
-plates slide past each other
-example; San Andreas fault in Cali.
earthquakes

36. 3 types of Convergent boundaries
Continental-continental
Continental-oceanic
Oceanic-Oceanic
Makes mountains Makes trenches and volcanoes b/c of subduction Makes under water mountains

39. Plate Motion Convection Tracking motion
hot rock from deep within Earth rises, but cooler rock near surface sinks.
Causes lithosphere to move.
very slow
movement measured in cm/yr
global positioning system (gps)

40. Deforming the Earth’s Crust

41. Deformation
Process that causes a rock to change because of stress

42. Types of stress Compression Tension folding When an object is squeezed
Ex. Convergent
Forces act to stretch on object
Ex. Divergent
Rock layers bend due to stress

43. Faulting –rock break and slide past eachother
Normal
Reverse
-breaks in crust where rocks slip past each other

44. Mountain Formation From Convergent boundaries
They start as folds and faults
Ex. Folded mts
Fault block mts.
volcanic mts.

45. Vertical movement in the earth’s crust:
Uplift rising of regions of the
earth’s crust to higher
elevations.
Subsidence the sinking of regions of
the earth’s crust to
lower elevations.