1. Plate Tectonics and Seafloor Spreading

2. Discovery of Subsea mountain ranges
led to theories of:
Plate Tectonics
and
Seafloor
Spreading

4. Development of Plate Tectonics Theory
Francois Placet: showed how the
continental coastlines matched
Antonio Snider showed how similar
fossils appear on different continents

5. continents broke apart along plate boundaries
Alfred Wegener
Developed the theory of
Plate tectonics or Continental
Drift
Proposed that the
continents broke apart
along plate boundaries

6. Permian
225 mya
See Fig. 3-1b
Triassic
200 mya

7. Jurassic
135 mya
Cretaceous
65 mya
See Fig 3-1b
Present Day

9. Plate Movement
See Fig. 3-7a

10. See Fig 3- 6a

11. Types of Plate Boundaries
• Divergent (moving apart)
• Convergent (moving together)
• Transform (sliding past )

12. 1.Characteristics of Divergent or Spreading Zones
• New oceanic crust is being made
• This creates undersea mountain chains
• Spreading rates:
1-2 cm/yr (slow)
6-15 cm/yr (fast)

14. Arabian Plate
African Plate
See Fig B3-4a

15. 2.Convergent Boundary Types:
• Type I: Subduction- Ocean Crust slips below Continental Crust
• Type II: Collision: 2 areas of continental
crust meet each other and push together

16. Convergent Plate Boundaries

18. Island Arc: Mariana Islands
See Fig. 3-6b

19. Oceanic- Continental
Peru-Chili
Nazca
See Fig.
3-6a

20. Characteristics of Subduction Zones
• Crust destroyed or deformed
• Frequent earthquakes
• Deep trenches
Major source of oil

21. Occurs when 2 continental plates meet-
Convergent Boundary Types
• Type II: Collision
Occurs when 2 continental plates meet-
Mountains formed

22. Eurasian and Indian Plates Crunch
Collision = 62 mya

23. Himalayan Mountain Formation
See Fig 3-11b
India
China

24. Type II: Continental-Continental Convergent Zone

25. Himalayan Mountains
See Fig. 3-11c

26. 3. Transform Plate Boundaries
Plates Sliding past each other
Transform boundary zones have many earthquakes both on land and under the ocean as well as volcanic islands .
This part of the Plate Tectonics Theory was
developed by John Tuzo Wilson, a Canadian
scientist

27. Transform Plate Boundary

28. San
Andreas
Fault:
See
Fig.
B3-2a

29. See Fig. 3-9a

30. See Fig. 3-9b

31. Hawaiian Island Chain

32. Continental Margins
These are the areas where the continents meet the oceans
There are two types:
Active: where 2 plates meet
Passive: where one plate continues out under the water to form a continental shelf

33. ACTIVE CONTINENTAL MARGINS
PASSIVE CONTINENTAL MARGINS

34. Passive Continental Margins:
East Coast of Canada
shelf
Margin characteristics:
slope
•Few earthquakes
rise
• Wide continental shelf (20-200km wide)
• Economically rich- oil, gas, fisheries

35. Example: West coast of North and South America
Active Continental Margins
mountains
Example: West coast of North and South America
Margin characteristics:
shelf
slope
• Frequent earthquakes
(steep)
• Active volcanoes in
convergent zones)
No rise!
• Narrow continental shelf
trench
• Troughs
• Trenches, Island arcs

36. http://www. windows. ucar