I-4 Dynamic Planet Notes

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.