The theory of the plate tectonics is how the earth works and the earth works by plates and plates are what's under neath us. and if the plates push together and they will put as much pressure against each other and give as much strength as possible and one will finally over lap each other and they will cause an earthquake. plate tectonics for example can be like to meter sticks forcing up against eachother and then finally one of them will over lap the other so thers a good example. or you can try putting your fist together and focing them as much as you can and one will finally over lap one and other. Me and my teacher did that together and it worked.