1. Chapter 10 section 2
Plate Tectonics

2. Vocabulary Plate tectonics Asthenosphere Lithosphere
Divergent boundary
Convergent boundary
Transform boundary
Convection
Ridge push
Slab pull

3. Plate tectonics
The theory that explains why and how continents move and is the study of the formation of features in Earth’s crust.

4. How continents move
Lithosphere forms the thin outer shell of the Earth
Broken into several blocks called TECTONIC PLATES
Asthenosphere- the layer of “plastic rock” just below the lithosphere
Tectonic plates “ride” on the asthenosphere

5. Two types of Crust Low density Rock rich in silica Very dense
Oceanic crust
Continental crust
Low density
Rock rich in silica
Very dense
Rock rich in Mg and Fe

8. Where to find plate boundaries?
Study data from Earthquakes
Location of volcanoes

9. Types of Plate boundaries
Divergent
Convergent
Transform

10. Divergent Plate Boundaries
Two plates move away from each other.
Mid-ocean ridges
Rift valley – a narrow valley along the center of the mid ocean ridge where the plates separate.
Most located on the ocean floor

11. Convergent Plate Boundaries
Form when two plates collide
3 types of collision
Oceanic –continental
Continental – continental
Oceanic-oceanic

12. Oceanic - Continental
Ocean crust is denser so as the plates collide the oceanic plate SUBDUCTS (sinks) beneath the continental plate.
This is called a SUBDUCTION ZONE
Subduction releases fluid into mantle above it causing it to melt forming magma. Gives rise to volcanic mountains.

13. Andes Mountains form from this type of collision
Andes Mountains form from this type of collision. Also the Cascade Range in the NW region of the U.S

14. Continental-Continental
Neither plate subducts (not dense enough)
The edges crumple
and thicken causing UPLIFT that forms large mountains
HIMALAYA MOUNTAINS
Plates are still moving, so Himalayas are still growing taller.

15. Oceanic-Oceanic One plate subducts under another
Deep ocean trench forms
Subduction releases fluid into mantle above it causing it to melt forming magma.
Magma rises forming an ISLAND ARC ( a chain of volcanic islands)
Example: Japan

16. Folded Mountains
Form when tectonic movements squeeze rock layers together into accordion-like folds
(C-C collision)
Many of the highest mountain ranges formed this way.

17. Transform Boundaries Two plates slide past each other
Edges scrape against each other (often felt as earthquakes)
Do not produce magma
San Andreas Fault is a transform boundary between NA Plate and the Pacific Plate
Also occurs along mid ocean ridges.

18. Transform motion along mid ocean ridge

19. San Andreas Fault

20. Causes of Plate Motion
Mantle Convection
Ridge Push
Slab Pull

21. Mantle Convection

22. Ridge Push
New parts of a plate rise because they are warm and the plate is thin. As hot magma rises to the surface at spreading ridges and forms new crust, the new crust pushes the rest of a plate out of its way. This is called ridge push.

23. Slab Pull
Old parts of a plate are likely to sink down into the mantle at subduction zones because they are colder and thicker than the warm mantle material underneath them. This is called slab pull.