1. CONTINENTAL DRIFT

2. Alfred L. Wegener
Meteorologists Alfred Wegener noticed similar rocks & fossil remains were found on continents which seemed to fit together
He called this “super” continent called Pangaea

3. PANGAEA Supercontinent from Wegner’s theory of continental drift

4. Theory of Continental Drift
Wegner proposed that the continents were plowing through oceanic crust

5. Support for Continental Drift
1. SHAPE of the continents
Continents fit together like puzzle pieces

6. Support for Continental Drift
1. SHAPE of the continents
Wegener was not the only one to notice the fit of the continents.
1858: Antonio Pelligrini depicted Africa and South America connected.
He was one of the first scientists to publish maps depicting the apparent fit of the continents.

7. Support for Continental Drift
2. FOSSIL EVIDENCE
SAME FOSSILS: DIFFERENT CONTINENTS
Cynognathus was incapable of swimming across a large ocean.

8. Support for Continental Drift
3. ROCK EVIDENCE – Mountain ranges
SAME ROCK: DIFFERENT RANGE Existing mountain ranges separated by vast oceans contain rocks of identical mineral content.
A prime example are the Appalachian Mountains in the eastern U.S and the Caledonian Mountains in the British Isles.

9. SAME SCARS: DIFFERENT CONTINENTS
Support for Continental Drift
4. GLACIAL SCARS
SAME SCARS: DIFFERENT CONTINENTS

10. CONTINENTAL DRIFT IN DOUBT
Why didn’t people believe in continental drift?
He couldn’t explain the mechanism as to how the continents were moving
People couldn’t image how the earth could be millions of years old
People couldn’t image a force great enough to move the continents
BUT by the 1960’s evidence would prove continental drift is TRUE and…. The story continues (as does all good science!)

11. He was right!. . .well mostly
He died before his hypothesis was accepted as a theory.
New technology allowed scientists to examine the structure of Earth
They found that the lithosphere was moving due to Earth’s internal heat  Convection
This developed into the theory of Plate Tectonics

12. ... Theory of Plate Tectonics
States that the Earth’s crust and ridged upper mantle are broken into plates that move at different rates and in different areas

13. Plate Tectonics Evidence
Earthquakes and Volcanoes:
Most earthquake and volcano activity happen along plate boundaries.
Plates are moving apart, moving together, or sliding past one another.
This creates earthquakes
Where plates move apart and come together magma is brought to the surface
This creates volcanoes

14. 3 Types of Plate Boundaries:
Divergent - Plates are moving away from each other
Convergent – Plates are moving towards each other
Transform
- Plates are sliding past one another

15. Where do tectonic plates interact?
At mid-ocean ridges
At plate centers
In deep-sea trenches

16. Divergent boundary of two continental plates.
Creates a __________. Example: _____________
rift valley
East African Rift

17. Convergent boundary of two oceanic plates.
Creates an ________ and a _____. Example: _____
island arc
trench
Japan

18. Convergent boundary of an oceanic plate and a continental plate
Convergent boundary of an oceanic plate and a continental plate. Forms a _______ mountain range and a ______. Examples: _______ or _______ Mts.
volcanic
trench
Cascades
Andes

19. Convergent boundary of two continental plates
Convergent boundary of two continental plates. Forms a ______ mountain range. Examples: ___________, Alps, ______________
Himalayas
folded
Appalachians

20. Transform-fault boundary where the North American and Pacific plates are moving ____ each other.
Example: ________________ in California
past
San Andreas Fault

21. Plate Boundaries Review
Places where plates move apart are called _____________ boundaries.
When continental plates diverge a ___________ is formed.
When two oceanic plates converge what is created? ____________________
The Appalachians formed mainly from continental plate collisions and therefore are a __________ mountain range.
The force moving the plates is ________________ .
divergent
rift valley
an island arc and a trench
folded
Convection currents