1. I-4 Dynamic Planet Notes

2. The Earth’s Lithosphere
The boundary between the lithosphere and the asthenosphere is a temperature boundary
Below the boundary the rocks are hot enough to flow
Above the boundary they are cooler and rigid

3. Two types of lithospheric plates
Oceanic crust
Continental crust

4. Oceanic Crust Thickens as it moves away from the hot mid-ocean ridge
Thinner
More dense
Newer crust

5. Continental Crust
Less dense
Thicker
Older crust

6. Lithospheric plates The lithosphere is not one continuous piece
Made of very large pieces as well as a lot of smaller pieces
These pieces are called lithospheric plates

7. Plate Boundary
Where two plates are in contact with each other

8. Plate Movement
3 Types
Plates are in motion relative to one another

9. Divergent Boundary Plates are moving away from each other
Mid-ocean ridges
New plate material produced on either side of ridge

10. Convergent Boundaries
Plates are moving towards one another

11. Transform Boundary Plates slide past one another
Example – the San Andreas Fault
The Pacific Plate is moving northwest relative to the North American Plate
Transform boundaries are sometimes called conservative (lithosphere is neither created nor destroyed)

13. Subduction Surface area of the Earth is not changing
Must be a place where plates are consumed and created

14. Subduction Zone
Plate boundaries where one plate dives underneath another plate
The down going plate is an oceanic plate
The plate that stays at the surface can be an oceanic plate or a continental plate
The place where the down going plate bends downward is marked by a deep trench on the ocean floor
Earthquakes and volcanoes are very common

15. Copy Diagram

16. Continent-Continent Collision
Subduction zones can make an ocean basin close up
Two continents may meet at a subduction zone
Continents are less dense than the mantle, so they do not go down a subduction zone

17. When two continents meet, one of the continents is pushed horizontally beneath the other continent
The movement eventually stops, when the force of friction between the continents becomes large enough
Continent-continent collision zones are where the continent is the thickest

19. Example India is slowly being pushed under southern Asia
Produces the Himalayas – the highest mountain chain
Also produces the Tibetan Plateau

20. AYR Questions 1. What is the difference between crust and lithosphere?
What is the difference between oceanic crust and the continental crust?
What is the difference between a subduction zone and a continent-continent collision zone?
Why do continents not go down subduction zones?

21. Review and Reflect Questions
What type of plate boundaries are found in or along the continental United States?
Why does the surface of a thicker continent stand higher above sea level than the surface of a thinner continent?

22. Answers to I-4 AYR Questions
The curst is the outermost shell of the Earth. The lithosphere consists of the crust and the upper, rigid part of the mantle (the part that does not take part in the mantle convection).
Continental crust is thicker, less dense, and generally much older than oceanic crust.
A subduction zone occurs where oceanic lithosphere is subducted under another oceanic lithospheric plate). A trench forms on the sea floor as one lithospheric plate descends below the other.

23. In a continent-continent collision, one of the two continental plates slides horizontally under the other for some distance. That thickens the continental crust and forms high mountain ranges.

24. 4. Continents cannot go down subduction zones because continental lithosphere is less dense than the mantle.