What Causes Earthquakes? | Overview
We could describe an earthquake as when energy is released, causing a movement of the ground. There are several causes for this. One is sudden slippage along faults. Then there are crustal plate boundaries. The third is mid-oceanic sea floor spreading zones.
Basically, what happens is we have accumulated stress between plates. Another word for accumulated stress is potential energy. We have this potential energy from plate tectonic movements. This potential energy is released as kinetic energy.
If you think about a rock sitting at the top of a cliff, it has potential energy. It is not exerting any energy right now, but it has the potential to have a lot of energy if someone pushed it. Then it would have the energy of it moving down and plummeting to the ground.
After that rock has been pushed and it is moving, it now has kinetic energy. Potential energy is the potential to have energy, or the accumulated energy, whereas kinetic energy is more energy in motion. When this potential energy is released, it’s released as kinetic energy.
The effect of that release of kinetic energy is for the ground to shift and for an earthquake to occur. You can think about it this way. We have these faults and they’re moving up next to each other. It causes stresses along those fault lines. The problem is there’s friction.
There has to be enough stress to overcome the friction in order for an earthquake to occur. Think about it if I had a box and there was a box sitting on the ground. Say I just look at the box. The box isn’t moving and I’m not exerting any stress on the box. There’s no stress on the box.
Then, say I start barely exerting force on the box. The box still isn’t moving, but now there’s stress accumulating on the box. The reason the box isn’t moving is because there’s friction between the box and the ground.
Eventually, if I keep pushing and I push harder, the force of me pushing will be able to overcome the friction between the box and the ground. In other words, if I put enough stress on the box, the stress overcomes the friction.
You can see the difference here is that, at first, if I just look at the box, or I just barely push the box, both times the box isn’t moving but one time stresses accumulated. Eventually, when there’s enough accumulated stress, or potential energy, it’s released as kinetic energy and the box moves.
In this case, the ground shifts and then an earthquake occurs. Earthquakes can also be caused by volcanic activity, massive landslides, nuclear explosions, and other events.