Spreading and Subduction 

Earthquakes, volcanoes and other activities tell us much about the surface of the Earth. Earth is the only planet in the solar system to have large plates float around the hot mantle below. Plate tectonics is the study of this type of activity and is based upon two major concepts: spreading and subduction.

Spreading is the process in which plates move away from each other and interior processes bring forth a new plate that emerges from the magma. Subduction is when two plates collide with each other and one plate's edge sinks the other plate below it, and it is destroyed by the hot mantle.