Plates typically contain both oceanic and continental lithosphere. Oceanic lithosphere is continually created and destroyed. Continental lithosphere can not be destroyed but continents can be subdivided and assembled into super-continents. Interactions at plate boundaries cause volcanic activity and earthquakes. The depth of earthquakes becomes progressively deeper underlying ocean trenches.
Earthquakes occur due to the break up of the descending plate as it pushes into the asthenosphere.
The oceanic lithosphere in the descending plate was heated to form magma which in turn generated volcanoes. Divergent plate boundary - where plates move apart. Convergent plate boundary - where plates converge. Transform plate boundary - where plates slide past each other. Describe the evolution of a divergent plate boundary.