1. CONTINENTAL DRIFT
AND
PLATE TECTONICS

2. EARTH’S STRUCTURE DENSITY IS KEY TO UNDERSTANDING STRUCTURE OF EARTH
DENSITY = MASS PER UNIT VOLUME
DENSITY = MASS / VOLUME

3. EARTH'S LAYERS LIQUID LAYER, EXTREMELY HOT
SILICON, IRON, OXYGEN & MAGNESIUM
SOLID IRON, VERY DENSE AND HOT
EARTH'S LAYERS

4. Interior Structure of the Earth Based on Density and Strength
Greatest density and pressure

5. Layered Earth - Internal Heat
Heat from within Earth keeps the asthenosphere flowing. This allows the lithosphere to keep moving. The source of this heat is radioactive decay, given off when the nuclei of unstable forms of elements break apart.

6. HEAT DISPERSAL
The heat from within the Earth travels in convection currents in the mantle.

7. Mechanism of Seafloor Spreading Convection

8. Isostatic Displacement
The ship sinks until it displaces the same amount of water equal to the weight of the ship and its contents.

9. Sea Floor Spreading...
A Key Idea

10. Sea Floor Spreading Proposed in 1960 by Alfred Wegener
Explained the development of the Mid-Ocean Ridge
Convection currents were proposed to cause the ocean to grow and the continents to move.

12. Types of Plate Boundaries
Constructive or divergent boundaries- Formation of an Ocean
Figure 03-24

13. Mechanism of Seafloor Spreading - Convection
Figure 03-10

14. New Evidence Supports Wegener’s Theory of Continental Drift
Wegener’s theory of continental drift was out of favor with the scientific community until new technology provided evidence to support his ideas.
Seismographs revealed a pattern of volcanoes and earthquakes
Radiometric dating of rocks revealed a surprisingly young oceanic crust (younger at the mid-ocean ridges)
Echo sounders revealed the shape of the Mid-Atlantic Ridge

15. GLOBAL EARTHQUAKE DISTRIBUTION GLOBAL VOLCANIC DISTRIBUTION
Any connections between earthquake sites and plate boundaries?
Figure 03-14a

16. Iceland: The land of fire and ice where the mid ocean ridge splits the land

17. Plate Boundaries
Figure 03-14b

18. The Mid Ocean Ridges run around the globe like seams on a baseball

19. SEA FLOOR AGE
Figure 03-12

20. TYING IT ALL TOGETHER...
THE THEORY OF PLATE
TECTONICS

21. PLATE TECTONICS
Continental Drift and Sea Floor Spreading tied together in the Theory of Plate Tectonics
Outer Earth divided into 12 major lithospheric plates
Plates float on asthenosphere
Convection currents drive plate movement

22. Changing Paleogeography
Figure 03-38

23. Fossil Evidence for Continental Drift Distribution of Mesosaurus

24. EARTH'S MAGNETIC FIELD

25. ACTUAL MAGNETIC
FIELD IS SHIFTED
A BIT FROM
GEOGRAPHIC
NORTH

26. SHIFTS IN POLARITY SUPPORT THEORY OF PLATE TECTONICS

27. Seafloor Paleomagnetic Pattern suggests Seafloor Spreading
Figure (9th Edition)

28. Youngest
Oldest

29. FEATURES ON OCEAN FLOOR SUPPORT PLATE TECTONICS
Front piece of Book

30. Destructive (convergent)
Constructive (divergent)
New ocean floor formed
Types of Plate Boundaries
Destructive (convergent)
Ocean floor destroyed
Passive (Transform)
Slip/Strike

31. Diagram from USGS Education and Outreach web page
Divergent
Convergent
Transform
Diagram from USGS Education and Outreach web page

32. MID-ATLANTIC RIDGE
Constructive, Divergent Boundary OR Destructive, Convergent Boundary?

33. Types of Convergent Margin
Ocean-Continent
Ocean-Ocean
Continent-Continent
Figure 03-27

34. OCEAN-CONTINENT BOUNDARY
Convergent Margins
Figure 03-28b,c
OCEAN-CONTINENT BOUNDARY

35. Convergent Margins
Figure 03-29

36. PASSIVE OR TRANSFORM BOUNDARIES
Figure 03-30

37. Hot Spots and Island Chain Formation
Figure 03-32

38. A VOLCANIC ISLAND CHAIN FORMS WHEN PLATE MOVES ACROSS A HOT MANTLE PLUME

41. Hot Spots and Mantle Plumes
Figure 03-32

42. Reefs and Atolls
Figure 03-34