1. Course: Geography of Ocean Transport Lecturer: K. Facey
Plate Tectonics
Course: Geography of Ocean Transport
Lecturer: K. Facey

2. Plan Interesting Observations Continental Drift theory by A Wegener
Sea Floor Spreading by H. Hess
Transform Faults and Hot Spots by J. Tuzo Wilson
Plate Tectonics Theory
Types of crustal plates
(major, minor, oceanic and continental)
Types of Plate Margins
Summary

3. Interesting Observations I
After the major exploration of the 16th to 19th Centuries, the following observations were noted:
(a) Parts of the earth appeared to be able to fit
together. Eg East coast of S. America and
West Coast of Africa

4. Interesting Observations II
Some fossils (remains of plants or animals) that were from one or few areas were found in places now far apart. See below

5. Interesting Observations III
Some coastlines have been found with the same rock and rock structure present. See below

6. Interesting Observations IV
The following was also noted:
Ancient climates : evidence was found the present climate in some areas are much different from past climates as seen in rock spaces.
There has been changes in the direction of the N and S Pole as seen in older rocks

7. Continental Drift Theory
Alfred Wegener proposed that the continents moving (drifting) over the mantle in 1910
According to Wegener, the earth used to look like this =>

8. Continental Drift Theory
The Break up of the Continents involved several stages:

9. Continental Drift Theory
Then the 2 super-continents split into:

10. Continental Drift Theory
The movement of the continents continued over time
Until they ended up at their present position or location

11. Sea Floor Spreading
Harry Hess (1960’s) proposed the concept of Sea Floor Spreading. Plates moved apart following geo-thermal energy currents causing magma to escape unto the surface forming Mid- Oceanic Ridge

12. Sea Floor Spreading
Sea floor was observed to occurring off the coast of South America in the Pacific Ocean in the 1960’s.
This observation helped to cement the concept proposed by Hess and the role of geo-thermal energy currents in this process.

13. Transform Faults and Hot Spots
J. Tuzo Wilson proposed that some crustal plates move pass each other following geo thermal currents instead converging or diverging. As the rub past each other then faults and major earthquakes would be produced.
He also proposed that volcanoes do not occur only at Plate margins but also at areas where the crust is no very thick, i.e. Hot Spots.

14. Transform Faults and Hot Spots
Plates are sliding past each other
Look at where Hot spots are in relation to Plate Boundaries

15. Plate Tectonics Theory
Definitions of terms:
What is the meaning of the following terms?
Crustal plate
Crustal plate margins
Geo thermal energy currents

16. Plate Tectonics Theory
J. Tuzo. Wilson in the 1965 coined the term Plate Tectonics to describe the movement of crustal plates and the effect of their motion.
This theory combines the work of Wegener, Hess, Wilson and others in a single theory.
In 1967, Jason Morgan proposed that the Earth's surface consists of 12 rigid plates that move relative to each other.

17. Plate Tectonics Theory
Two months later, Xavier Le Pichon published a synthesis showing the location and type of plate boundaries and their direction of movement.
Since the mid-1960s, the plate tectonic model has been rigorously tested. Because the model has been successfully tested by numerous methods, it is now called the plate tectonic theory and is accepted by almost all geologists.

18. Types of Crustal Plates
Crustal plates may be classified based on either:
(a) their size ( major or minor)
(b) their composition (continental or oceanic)
Thus a crustal plate may be described using both criteria for classification. Eg major continental; minor continental; major oceanic and major continental.
N.B. Crustal plates are named based mainly on the feature or landform that lies on top of them

19. Types of Crustal Plates
Continental crustal plate see below
Oceanic crustal plate see below

20. Types of Crustal Plates
Some of the crustal plates found across the world

21. Caribbean Crustal Plates
The Caribbean is a minor oceanic plate that shares boundaries or plate margins with several plates; these are:
G = North American
F= Caribbean
E = Nazca
D = Cocos

22. Types of Crustal Plate Margins
Crustal plate margins are the areas where two or more crustal plates meet or interact. There are three main types of margins:
(a) Destructive / Zone of Convergence
(b) Constructive / Zone of Divergence
(c) Conservative / Transform Fault Margin/ Neutral / Passive

23. Destructive Plate Margin Part 1
Destructive Plate Margin forms when two plates move towards each other forming either a Collision or a Subduction Zone. A Collision Zone (see below) is formed when two continental plates meet. They form Fold Mountains.

24. Destructive Plate Margin Part 2
Subduction zones are formed when mainly Oceanic and Continental crustal plates meet. This results in the formation of Deep Oceanic Trenches where Oceanic plate is drawn under the Continental Plate and volcanoes (in some cases Island Arcs)

25. Constructive Plate Margin
This occurs when two plates , usually Oceanic are moving away from each other. This creates a gap to be created and eventually a Mid Oceanic Ridge to be formed. See diagram below:

26. Transform Fault Plate Margins
This occurs when two plates are sliding past each other either as they go in opposite directions or the same direction at different speeds. This results in the formation of large cracks or faults on the earth’s surface and is associated with major earthquakes.

27. Summary of Crustal Plate Margins Complete this table to help you review what you have covered
Name of Plate Margin
Mov’t of plates
Involves
Associated Processes
Resultant Landforms
Destructive –Collision Zone
Plates move towards each other
Folding, slight Faulting. Earthquakes
Fold Mts
Destructive- Subduction Zone
Mainly Continental and Oceanic plates
Deep Oceanic Trench
Volcanoes (Island Arcs)
Constructive
Plates move away from each other
Mainly Oceanic plates
Faulting, volcanic action, Earthquakes
Transform Fault
Either Oceanic or Continental plates
Faulting and Major earthquakes
Faults / Fissures

28. For further information
Egger, Anne, (2014), ‘The Origins of Plate Tectonics’
Visionlearning Vol. EAS-1 (1), 2003.
Available Online at:
Last Accessed: 15/10/2014
Oskin, Becky (2013), ‘What is Plate Tectonics ?’
Available Online at: