Chapter: Formation of Mountain Ranges

The Theory of Plate Tectonics

The tectonic plates move with the ductile (plastic) underground, resp. they nearly swim on it. But how can something this heavy "swim" on the underground? In this case the underground is called asthenosphere.

We can find so called convective cells/currents in the asthenosphere. In order to explain this I have an everyday example: You certainly have cooked water once. Maybe you noticed how the hot water always rises in the middle. In doing so it releases heat and sinks again to the bottom at the edge of the pan. There it gets reheated and rises and so on. Now we will apply this example to our earth.

The earth's interior is much hotter compared to the crust. As earth has the tendency to balance differences it wants to release heat from the inner shells to the crust. Like this several convection cells (convection currents) are formed in the asthenosphere. The overlying lithosphere moves with the underground and thus splits in multiple plates. You have certainly noticed already that plates move toward each other in one place and move away from each other somewhere else. On the nex page we want to have a look at the different events on the borders of the plates.