1. The Earth’s Drifting Continents

2. Theory of Continental Drift
Alfred Wegener suggested that the continents were once together and have since drifted apart. Was not accepted until 30 years later.

3. Pangea
The earth had a single landmass that broke up into large pieces, which have since moved apart.

5. Evidence to Support Continental Drift
Fossils- preserved remains of organisms
Rock formations and deposits; coal, limestone, salt, etc.

7. Basalt from a volcanic eruption.
                  
Basalt from a volcanic eruption.

8. Evidence Cont…
Mountain chains
Coal fields
Glacial deposits

9. The Earth’s Spreading Ocean Floor

10. Mid-ocean Ridges
Under water mountains and valleys.

11. Trenches
V shaped valleys at the bottom of oceans, which are usually found on the edges of continents and islands.
Deepest part of the ocean

14. Ocean Floor Spreading
Lava erupts at rift valleys and hardens to form new ocean floor.
Explains how the continents move.

16. Subduction Process in which old crust plunges back into the earth.
Rocks are pushed deep into trenches where they are melted by the heat of the earth. They recycle.

18. Evidence to Support Ocean Floor Spreading
Rock age- youngest rocks are found near rift valleys and oldest rocks are found near trenches.

19. Evidence Cont…
Magnetic Stripes- magnetic rock line up with the poles equally on both sides of the mid-ocean ridge.