1. Continents change position over time

2. Alfred Wegener
Evidence
Hypothesis – continental drift
Earth’s continents were once joined
Super Continent called Pangaea
Fossils
Climate
geology

3. Fossils
Climate
Geology
Mesosaurus – found on the west coast of Africa and the east coast of South America
Ice scratches on South America
Tropical plant fossil in Greenland
Rocks that make up the continents
North America lines up with Scotland

4. Theory
Sea Floor Evidence
Evidence and explanations lead to the Theory of Plate Tectonics
Sea Floor Spreading
Age of the Sea Floor
Trenches

5. Sea Floor Spreading
Age of the Sea floor
Ridges form on the sea floor
As the plates move apart molten rock pushes up
Called spreading centers
Mid-Atlantic Ridge
The rocks are older the further you move away from the spreading centers

6. Ocean Trenches
Size of earth
Deep canyons on the ocean floor
Dense crust is sinking into the asthenosphere
Earth isn’t changing size because at the same rate that new crust is forming (at spreading centers), old crust is being destroyed (at trenches)

7. How does it happen? Convection Currents Hot molten rock rises
Cooled rock sinks
Moves the tectonic plates like a conveyer belt

8. Convection Currents

9. Hypothesis becomes theory
Based on the facts from the ocean floor the hypothesis of Continental Drift becomes the Theory of Plate Tectonics