1. Theory of Plate Tectonics
Theory is a well tested, widely accepted scientific idea
Plate is a large, rigid slab of solid rock
Tectonic comes from Greek word “to build”
Theory of plate tectonics states that Earth’s lithosphere is broken into plates that move because of convection in the mantle

2. Three types of plate boundaries
Moving plates collide, pull apart and slide past each other Plate boundaries are classified according to the type of movement.
Three types of plate boundaries
Divergent
Convergent
Transform

3. Divergent Boundary
As plates move apart molten magma erupts to fill the gap....seafloor spreading...rift valley
Divergent Plate Boundary Animation

4. Iceland is on the Mid-Atlantic Ridge
Divergent plate boundary

5. Convergent Boundary Where plates collide
Three types of collisions possible: Continent-continent collision
Continent-oceanic crust collision
Ocean-ocean collision
Convergent boundaries are where the plates move towards each other.
There are three types of convergent boundary, each defined by what type of crust (continental or oceanic) is coming together.
Therefore we can have: continent-continent collision, continent-oceanic crust collision or ocean-ocean collision….

6. Continent-Continent Convergent Boundary
Continental crust is less dense – buoyant and thick
When continents collide they buckle, crack and push each other up forming mountains
Continent-Continent Collision Animation

7. Himalayas
India collides with Asia creating the Himalayan Mountains

8. Continent-Oceanic Crust Collision
Called SUBDUCTION Denser oceanic crust sinks beneath less dense continental crust
Ocean-Continent Convergent Boundary Animation

9. Subduction
Oceanic lithosphere sinks underneath the continental lithosphere
Melting slab forms volcanoes
Continental crust buckles forming mountains
Andes Mountains of South America
The Andes mountain range along the western edge of the South American continent is an example of a mountain belt formed by subduction.
The continental crust of the South American plate has buckled under the compressional strain of converging with the Nasca and Antarctic plates. Additionally there are many volcanoes, the result of melting of the subducting slab and the production of new material that has risen through the crust to the surface.

10. Ocean-Ocean Convergent
Plate Boundary
When two oceanic plates collide, one pushes over the other which causes it to sink into the mantle forming a subduction zone.
The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench.
The worlds deepest parts of the ocean are found along trenches.
Ocean-Ocean Convergent Boundary Animation

11. Transform Plate Boundary
Where plates slide past each other
Above: View of the San Andreas transform fault
More Animations!

12. Map of tectonic plates showing relative directions and velocities
NASA plate motion maps
Cornell University - Discover our Earth link

13. Ridge-push Hypothesis
...one idea of how convection in the mantle moves tectonic plates

14. Slab-Pull hypothesis
...another idea of how convection in the mantle moves tectonic plates

15. Magma Plumes hypothesis
...another idea....maybe all three mechanisms are at work moving tectonic plates

16. WORKS CITED
Kious, W. Jacquelyne, and Robert I. Tilling. "USGS Developing
the Theory." This Dynamic Earth: The Story of Plate
Tectonics. USGS Publications Warehouse, n.d. Web. 6
Apr
Plummer, Charles, David McGeary, and Diane Carlson. "Chapter 19 Plate Tectonics Animations and Movies." Physical Geography Online Learning Center. Version Nonthe Edition. McGraw-Hill, n.d. Web. 6 Apr <
"Discover Plate Boundaries." N.p., n.d. Web. 6 Apr <
"Earth Science." ClassZone. N.p., n.d. Web. 6 Apr <