(a)   is the vibration of the earth due to the rapid release of energy.

Moving of plates towards each other is called (a)  

Oceanic crust is thinner and (a)   than continental crust which is thicker and less dense.

(a)   is a device used to record earthquake waves.

A molten rock formed at depth, including dissolved gases and crystals is called (a)  

(a)   is a concentration of heat in the mantle capable of creating magma.

(a)   is the outer portion /layer of the earth.

A boundary produced when two plates slide past each other is called (a)  

(a)   is a theory which suggests that earth crust is made up of plates that interacts in various ways, thus producing different geologic events.