1. Plate Tectonics Theory
*The lithosphere (upper mantle) is divided into plates
Tectonic Plate=Lithosphere
The asthenosphere (lower mantle) is the soft, weak layer that the lithosphere lays on

2. Convection Currents
Plate motion is caused by convection currents in the mantle from heat within the Earth

3. Plate Tectonics Theory

4. Plate Boundaries
All major interactions among individual plates occur along their boundaries
3 main types of plate boundaries:

5. Plate Boundaries
1. Divergent : 2 plates move apart

6. Divergent Boundaries
Most are located along the crests of oceanic ridges
Where new ocean crust is created

7. Seafloor Spreading
The age of the seafloor is youngest at the mid ocean ridge and gets older as you move away

10. Plate Boundaries
2. Convergent Boundaries: 2 plates move together (crust destroyed)

11. Plate Boundaries
Subduction: Heavier plate sinks below lighter plate into mantle & melts

12. Subduction Zone
The boundary where 2 plates collide

13. Types of Convergent Boundaries
1. Oceanic-Oceanic= Volcanic Island Arcs

14. Trench: Topographic depressions on
the sea floor

15. 2. Oceanic-Continental= Continental Volcanic Arcs

16. 3. Continental-Continental=Mountains

17. Plate Boundaries
3. Transform Boundaries: 2 plates grind past each other (earthquakes occur) and does not create or destroy crust