Answer: Tectonic plates or plate tectonics
Explanation:
Definition of plate tectonics:
This is a geological theory which states that the earth consist of number of plates which has liquid like substance (lava or magma hot material)in between them that make them float and the move over the mantle and this is where various seismic activity occur. These plates are solid. There are composed of lithospheric material and continental material.
Near these plates it is where the volcanic activity will originate.