Earthquakes occur mainly because of the movement of the plates that make up the Earth's crust ¹ ² ³ ⁴:
- The Earth's crust is made up of rock plates or tectonic plates that are free to move.
- The movement of these plates is very slow and can not be felt by humans.
- Despite their slow movement, shifts in the plates sometimes cause major geological events that can be felt on the surface of the Earth.
- The plates have theoretically been in motion since the birth of the earth, and have shifted very gradually over time.
- The movement of the plates sometimes causes the buildup of energy which is released suddenly as seismic waves, causing the earth to shift, buckle, or wave.
- Earthquakes, and seismic activity tend to occur along plate borders and edges.
