1. Plate Movement Chapter 17 Section 3

2. Plate Tectonics Theory that describes how tectonic plates move and shape Earth’s surface –They move in different directions and at different rates relative to one another –They interact with one another at their boundaries Combines continental drift and seafloor spreading to explain how & why Earth’s Crust moves

3. Earth’s Crust Two types –Oceanic crust: makes up the ocean floor Very dense. –Continental crust: makes up the landmasses Less dense than the oceanic crust.

4. Spheres Crust + Rigid Upper Mantle = Lithosphere –Lithosphere = Earth's surface composed of rigid plates Thin outer shell of Earth –Aesthenosphere = layer of plastic under pressure beneath the lithosphere

5. Tectonic plates Huge pieces of crust and rigid upper mantle that fit together at their edges to cover Earth’s surface Plates move slowly but continuously on the order of a few cm/year

7. Plates These plates are not the continents! Some are part of the ocean Some have oceanic and continental crust All plates move, BUT NOT the same way

8. Plate Boundaries Three Types –Divergent –Convergent –Transform

9. Divergent Boundary Plates move AWAY from each other Mostly on the ocean floor in rift valleys As plates move, asthenosphere moves upward and fills in rift Accounts for high heat flow, volcanism, and earthquakes associated with these boundaries

10. Divergent Boundary Some divergent boundaries form on continents When continental crust begins to separate, the stretched crust forms a long, narrow depression called a rift valley Mid Ocean Ridge –Series of rift valleys Red Sea formed from a huge rift valley

12. Convergent Boundary Two plates collide When two plates collide, the denser plate eventually descends below the other, less- dense plate in a process called subduction Types of collisions –Oceanic-Continental –Continental-Continental –Oceanic-Oceanic

13. In-Class Assignment In a group with 2-4 people, draw the three types of plate boundaries. It needs to be more than just two arrows, make it pretty, colorful, and 3-D esq.

14. Oceanic-Continental Denser oceanic crust is subducted (forced under) the less dense continental crust Subduction Zone – plate boundary where one plate moves under another plate –Ocean Trenches normally form along subduction zone Ocean crust heats up and releases water into mantle –Mantle melts and magma rises to surface –Volcanic Mountains Produces a trench and volcanic arc –Mountain range with many volcanoes

16. Oceanic-Oceanic A subduction zone is formed when one oceanic plate, which is denser as a result of cooling, descends below another oceanic plate. Ocean trenches form when one plate is subducted Water from subducted causes mantle to melt Magma rises to surface –Forms chain of volcanic Islands –Island arc

18. Continental-Continental Colliding edges of two crust –Neither is subducted –Edges collide and crumple upward to form mountain rangles –Ex. Himalayas

21. Transform Boundary Two plates grinding past each other Scrape together Move in sudden spurts = earthquake Ex. San Andreas Fault

23. Here you have the North American plate moving south, against the Pacific plate moving north. What type of boundary is this?

24. In-Class Assignment

25. 17.4

26. Cause of Plate Movement Convection = transfer of heat through movement of heated material –Ex. Boiling water Heat comes from radioactivity within the mantle

28. Convection current Cycle of warm water rising and cool water sinking