1. Our Changing Earth

2. What is a Theory? In science, it’s almost the same as a fact
Must be some sort of evidence to support a theory
Even with evidence there is still debate about how true it is

3. Continental Drift Theory
Alfred Wegener said the world used to be one large land mass millions of years ago
The land was called Pangaea
Pangaea kept moving apart a few centimeters each year
After millions of years it became the world we see today

5. Continental Drift Theory
Evidence for Continental Drift
includes
includes
includes
includes
Continental Edges
Rock Structures
Same Fossils
Climate
fit like
showed
seen in evidence from
found
Mountains with similar features
Puzzle Pieces
Continental ice sheets
On different continents

6. Plate Tectonics
Plate Tectonics – a more advanced theory about how the continents move
Explains that there are loose plates in the earth that shift causing:
Oceanic Trenches
Mountains
Volcanoes
Earthquakes.

7. How Do the Plates Move?

8. So…
Continental Drift – theory that says continents drift around on plates
Plate Tectonics – theory that explains WHY scientists believe the continental drift theory is true

9. Now it’s time for a…
REVIEW

10. What is Continental Drift?
Theory that says the continents are moving on plates

11. What is Plate Tectonics?
Theory that explains WHY scientists think continental drift occurs
It tells us how the earth’s plates move

12. Divergent Boundaries This is when the plates move apart
It happens mostly between oceanic plates
The rising magma causes volcanoes and underwater mountains to be formed

13. Convergent Boundary
When the two plates are in the OCEAN they collide and form deep trenches.
When the two plates are on the CONTINENTS they collide to form mountains.

14. Transform (Sliding) Boundaries
This is when the plates slide past each other or move horizontally
The sliding is what causes earthquakes
This type of boundary is found in California