I think the answer is plate tectonics theory because when the are moving, they sometimes hit each other and it makes earthquakes and volcanic eruptions
According to the plate tectonics theory, the plates making the earth float on the partially molten mantle, moving away from the mid ocean ridges at varying speeds. At a point where the plates pull apart, slide or collide, a tectonic activity will be manifested as earthquakes.
Earthquakes take place when the plate boundaries get stuck together while the plates keep moving. Volcanoes on the other hand take place when plates crash into or pull away from each other and hot magma from below rises up to the surface in an eruption.
