Simply put, the shaking of the earth caused by a sudden shifting of rocks below its surface, is called an earthquake. The earths crust or outermost layer, is not made of one single piece of solid rock. It is actually made up of independent sheets of rocks called tectonic plates.
These plates slide against each other, giving rise to physical changes in the earths topography. The places where these tectonic plates meet each other, are called fault lines.
To understand what happens when two plates slide against each other, try out this experiment:
- Break a thick block of thermocol into half, and place the two pieces on a smooth table.
- Put the rough edges of the thermocol pieces together.
- First put a light pressure to push the two pieces together.
- Almost at the same time, push the thermocol under your right palm away from your body, and pull the other piece toward yourself. See how they stick?
- Keep pushing and pulling, increasing the pressure with each stroke. See the thermocol pieces give a sudden jerk – a little piece will fall from the crack (the fault). Then the two pieces will suddenly slip past each other.
That sudden jerk and breaking away of the thermocol is the earthquake. That’s just what happens along a fault.