German geologist Alfred Wegener proposed the theory of continental drift in 1912, which hypothesized that the continents were once joined together in a single landmass called Pangaea before drifting apart to their current locations. Wegener provided three key pieces of evidence to support this: the continental margins fit together like puzzle pieces, matching fossil and rock formations were found on separated continents, and the same fossils of non-marine animals were discovered on continents far apart. Later, scientists developed the theory of plate tectonics to explain the forces causing the continental drift, proposing that movements in underground plates pushed the continents apart or together.

1. What
happens
when earth
plates
move? Ch.5: Less.2:

2. Alfred Wegener
German Geologist
(Geologist is a
scientist who studies
rocks to find about
earth’s history and
structure)

3. Wegener’s Hypothesis
• In 1912 Alfred Wegener proposed the theory of
continental drift.
• Continental drift theory: States that the
continents once formed a single land that broke
up, and drifted to their current location today.
• Wegener used several different types of evidence
to support his hypothesis

4. PANGAEA
When all the continent where
1 landmass, it was called:

5. Continental
Drift Theory

6. Wegener used
several different
types of evidence
to support his
hypothesis

7. 1) Wegener noticed that the continents fit each
other like jigsaw puzzle pieces (as time passed
some force pulled the puzzle pieces apart)

8. 2) Scientists found that the mountains in south
America and Africa had the same types of rocks
and the same age.

9. 3) Similar fossils where found on different
continents.
Mesosaurus (a fresh water reptile)
The mesosaurus fossil was found in South
America and Africa (it cannot swim in the ocean)

10. Fossil Evidence

11. What forces
caused the
continental
drift?

12. Scientists came up with the “Plate tectonics theory”
“Plate tectonics theory”
States that the lithosphere is made of huge plates
of solid rock and these plates slide on the slippery
surface of the asthenosphere causing the
continents on them to move.

13. There are 3 types of tectonic plate
movement.
Divergent Convergent Transform

14. 1) Divergent tectonic
plates

15. Magma (hot melted rocks) from the
mantle moves upwards pushing the
plates apart causing tension (push).
This push causes:
1) Ocean floor spreading and
2) mid ocean ridges.
(Because the continents are resting on these
plates they also move apart)

16. 2) Convergent tectonic
plates

17. When the plates are pushed into each
other, they form a compression force.
Compression causes:
1) Folded mountains(earth crust is
folded) and

18. Example.
Himalayas are folded mountains
(formed when Asia and India collided
together)

19. 3) Transform tectonic
plates

20. When the plates are rub together, they
form a shear force.
The break in the earth’s crust where the
plates rub against each other is called
faults.
Break in the crust at faults cause:
1) Fault block mountains

21. Sierra Nevada Mountains (U.S.A)