1. 7.3 Plate Tectonics

2. The Theory of Plate Tectonics
Plate Tectonics – the theory that explains how large pieces of the Earth’s outermost layer called tectonic plates, move and change shape.

3. Tectonic Plate Boundaries
Boundary – a place where tectonic plates touch.
There are three different types of boundaries:
Convergent
Divergent
Transform

4. Convergent Boundaries
Convergent Boundary – the boundary formed by the collision of two lithospheric plates.
There are three different types of convergent boundaries:
Oceanic – Oceanic
Oceanic – Continental
Continental - Continental

5. Oceanic – Oceanic Plate Boundaries
oceanic-oceanic.gif

6. Oceanic – Oceanic Convergent Boundary
Normally one of the oceanic plates will subduct below the other.
The older plate is usually the one that gets pushed down because it has a greater density.
Eventually magma is formed because of the increased pressure causing volcanoes to form over the top of the layer.
Eventually the volcanoes will peak out of the water and if they continue to grow the will form island chains.
Ex. Japan

7. Oceanic – Oceanic Plate Boundary

8. Continental – Oceanic Plate Boundaries “Mt. Adams”
oceanic-continental.gif

9. Continental – Oceanic Plate Boundaries
When the two plates collide the less dense continental plate will rise up on top of the more dense oceanic plate.
The subducted plate will become molten due to the increase in temperatures.
The magma will then rise because it is less dense than the mantle that is surrounding it.
As the magma rise it will cause volcanic and earthquake activity.

10. Continental – Oceanic Plate Boundaries

11. Continental – Continental Plate Boundaries

12. Continental – Continental Plate Boundaries
The process in which two land masses collide together. Normally the landmass that is the least dense will subduct only slightly below the other.
Mountains will form because the two colliding plates are very light in comparison to the mantle.

13. Divergent Plate Boundaries
Divergent Boundary – the boundary between two tectonic plates that are moving away from each other.
New Sea floor forms at divergent boundaries.
Mid-ocean ridges is the most common type of divergent boundary.

14. Divergent Plate Boundaries

15. Transform Boundaries
Transform Boundary – The Boundary between tectonic plates that are sliding past each other.
Ex. San Andreas Fault in California.
One of the few faults that can be visibly seen.
One of the major causes of Earthquakes.

16. Output: Pushing and Pulling Mountains
Draw an example of the five different plate boundaries.
Label and describe what happens at each different plate boundary.

17. Transform Plate Boundaries

18. Plate Summary

19. Possible Causes of Tectonic Plate Motion
Asthenosphere flows very slowly.
This movement occurs because of the change in density within the asthenosphere.
Density changes because of the outward flow of energy within the Earth.
Hot rock expands and rises.(Less Dense)
Cool rock contracts and sinks. (More Dense)

20. Possible Causes of Tectonic Plate Motion

21. Tracking Tectonic Plate Motion
Tectonic plates move roughly 5cm per year.
The rate is so slow that it cannot be seen nor felt except during an Earthquake.
Plate movement is tracked by GPS.