1. Topic 4: The Moving Crust

2. Antarctica is a frozen land, so cold and icy that no trees can grow there. Yet scientists have discovered fossils of ancient trees in Antarctica
What do you think this means?

3. The Himalayas (central Asia) are the tallest mountains in the world
The Himalayas (central Asia) are the tallest mountains in the world. But fossils of seashells can be found high in these mountains, far from any ocean
How do you think they got there?

4. Have the continents always looked this way?

5. How well do the continents fit together?
Is it a perfect fit?

6. If the continents were fixed in place, why do they look as though they could be joined?
Supercontinent
At one time, the continents had been joined together in a large single land mass
Pangaea

8. Since the time of Pangea, the continents have slowly drifted apart
CONTINENTAL DRIFT
Started about 200 million years ago and is still continuing today

9. What evidence supports this hypothesis?
1. Biological
Fossils of the same plants & animals were found on different continents

11. 2. Geology
Rocks found on either side of the Atlantic Ocean were similar in formation, age and other properties

12. 3. Climate
Coal is formed in warm, swampy climates
Coal beds in North America, Europe, & Antarctica seem to be connected

13. 4. Glacial Deposits
Rocks moved and laid down by glacier movement
Found spread over the southern hemisphere
Grooves under the glaciers show the direction the glaciers moved

14. Plate Tectonics
The Earth’s crust is divide into large, irregular pieces
TECTONIC PLATES
Plates are always moving on Earth’s MOLTEN mantle

15. 3 ways plates can move: Converge Two plates pushing together
Creates ridges
Form subduction zones
One plate passes below another
Diverge
Two plates pulling apart
Creates trenches (openings)

16. Transform / Shear
Plates slide past each other in opposite directions

17. Why do tectonic plates move?
Convection currents
Flow resulting from the warmer materials of the Earth’s core rising and then sinking as it cools