1. Plate Tectonics
Alfred Wegener did not know the earth’s composition, but by the 1960’s scientists were able to revise Wegener’s hypothesis into a theory now known as Plate Tectonics.

2. Plate Tectonics
The lithosphere is composed of 7 major and 13 minor plates.
A plate can be composed of continental and/or oceanic crust.
Continental crust-felsic
Oceanic crust-mafic

3. Plate Tectonics
The areas where plates are in contact with each other are called plate boundaries.
There are three types of plate boundaries.

4. Plate Boundaries (type 1)
Divergent-two plates are moving away from each other. New crust is formed. Most divergent boundaries are on the ocean floor. These are marked by mid-ocean ridges.

5. Plate Boundaries (type 2)
Convergent- two plates are moving towards each other.
Oceanic/continental oceanic crust has a higher density than Continental crust, therefore it sinks below the continental crust. This is called a subuction zone.
Volcanoes, mountains and trenches form.

6. Plate Boundaries (type 2)
Continental/continental neither plate is subducted. In this case, both edges are crumpled and uplifted producing large mountain ranges.
Himalayan Mountains (India is colliding with Asia)

7. Plate Boundaries (type 2)
Oceanic/oceanic These are rare and create deep trenches.
Marianas Trench deepest trench in the world.

8. Plate Boundaries (type 3)
Transform Fault Boundaries- two plates grind past each other.
They do not slide easily-they stick and slip.
When these plates slip they create earthquakes.
San Andreas Fault in California

9. Science Tip 5/16/2011 1. What is Plate Tectonics
2. State one piece of evidence used to support plate tectonics

10. MOUNTAIN BUILDING

11. MOUNTAIN BUILDING Deformation
The bending, tilting and breaking of Earth’s Crust.

12. MOUNTAIN BUILDING Stress Force applied to rock material from Isostasy.
Strain
Change in shape or volume of rocks from rocks being squeezed, twisted or pulled apart.

13. MOUNTAIN BUILDING Folding
Permanent deformation or bending of a rock under stress.
Faulting
Break in rock along which rocks on either side of the break have moved.

14. MOUNTAIN BUILDING Faulted
Faulting breaks Earth’s crust into large blocks and those blocks become tilted.
Ex. Sierra Nevada Mountains

16. MOUNTAIN BUILDING Folded Plates collide (Convergent boundary)
Ex. Appalachian Mtns, Himalayas

19. MOUNTAIN BUILDING Dome
Molten rock pushes up rock layers on Earth’s surface creating a dome. Over time this top layer erodes away leaving the igneous rock exposed.
Ex. Black Hills, South Dakota

21. MOUNTAIN BUILDING Volcanic
Molten rock that has erupted onto Earth’s Surface.
Cascade Mtns., Mid-Atlantic Ridge