Plate Tectonics

source:usgs.gov

-Divergent boundaries :where new crust is generated as the plates pull away from each other. e.g. Mid atlantic Ridge
-Convergent boundaries: where crust is destroyed as one plate dives under another. e.g. Ring of fire
-Transform boundaries: where crust is neither produced nor destroyed as the plates slide horizontally past each other. e.g. San Andreas Fault
-Plate boundary zones: broad belts in which boundaries are not well defined and the effects of plate interaction are unclear.

Sources:"Understanding Plate Motions" May 1999 [http://pubs.usgs.gov/publications/text/understanding.html]