The above boundaries (divergent, convergent and transform) are all places where two plates meet. Triple junctions, places where three plates come together, are also common. They are found at the end of plate boundary segments. The geometry of all these systems is made all the more complex because all motion takes place along the curved surface of the earth. 
 
 

Hot Spots are places where rising plumes of asthenosphere "melt" a hole into the lithosphere, resulting in vulcanism directly above the hot spot. As the lithospheric plate moves, it carries the volcano with it. Because it no longer has a supply of magma, the volcano is no longer active, and a new volcano erupts above the hot spot. This results in a long string of volcanos and sea mounts (when the volcano subsides below sea level) that indicate past plate motion over the hot spot. The classical example of this is the Hawaiian Island chain and the Emperor sea mounts. Note the dog-leg in the long string of volcanos that indicates that the Pacific Plate changed the direction of its motion. 
 
 

This is a NOAA plot of earthquakes [for a more detailed view (760K file) click on the image itself]. Yellow means shallow focus; green intermediate focus; and blue, deep focus earthquakes. Note that they tend to occur in belts, especially along present plate margins. Shallow focus earthquakes tend to occur within plates and along all boundaries.  Greater focus depths are associated with convergent boundaries along subduction zones. 
 
 

Just as for earthquakes, volcanos occur along plate margins and hot spots. A very prominent group of volcanos occurs along the subduction zones rimming the Pacific plate and have justifiably given the Pacific rim the name of Ring of Fire.
 
 
 
 
 

Summary Chart of Plate Tectonics Features