1. Chapter 9.2
Plate Tectonics

2. Earth’s Major Plates
Remember the lithosphere is the upper part of the mantle and crust, it is strong and rigid.
The asthenosphere is right below and it is a weaker region.
The lithosphere is divided into segments called plates, which move and change shape and size.
There are 7 major plates, the Pacific plate being the largest.
The plates move very slowly – only about 5 cm a year.

3. The plates move by convection currents
The plates move by convection currents. This is hot material that is found deep in the mantle that slowly moves upward and as it moves upward it cools. When it cools it becomes denser and will sink down into the mantle.
Plate movement is responsible for earthquakes, volcanoes, and mountain formation.

4. Types of Plate Boundaries
There are 3 types of boundaries: convergent, divergent, and transform fault.

5. Divergent Boundaries
This is when 2 plates move apart. This process produces upwelling of material from the mantle to create new seafloor.

6. Convergent Boundaries
This is where two plates move together. Usually the oceanic lithosphere will go below the overriding plate. Or continental plates may collide and merge.

7. Transform Fault Boundaries
These is where 2 plates grind past each other with out making more, or getting rid of the lithosphere.
The San Andreas Fault zone is an example of this type of boundary.