The Earth's crust – the outermost layer of planet Earth, formed by rocks – is subdivided into several “pieces”, which, despite being separated, are always in contact with each other. The set of these pieces is called plates tectonics.
O tectonism – also known as the tectonic plate movement – exerts transformations that can be directly perceived by people on the earth's surface, such as the earthquakes, a movement of continents, the formation of volcanoes and also the emergence of mountains. It is a process that, for us, is not fully visible, as it happens very slowly, over billions of years.
But then, the question remains: why do tectonic plates move?
As we know, the Earth's crust is located just above another layer of our planet: the mantle. It is basically composed of magma, which is nothing more than rocks in a liquid state, with a slightly pasty consistency, all because of the high temperatures existing in the Earth's interior. Plate tectonics literally float on top of magma.
Thus, what makes the tectonic plates move is precisely the movement of this magma! And this movement does not happen in any way, but obeying a cyclical variation, which we call Earth currents or convection cells.
Look at the following diagram and see how this movement happens:
Earth's convection cells, which influence tectonic plates *
Convection cells move in this way because temperatures are higher in the areas closest to the nucleus. The magma located further down heats up and therefore becomes lighter and rises. Upon reaching the higher areas, it loses temperature, becomes denser and descends again towards the core, where this process is continued.
Therefore, the movement of magma in the form of convection currents causes the earth's mantle function as if it were a "conveyor belt" on which the tectonic plates of the crust move terrestrial. Thus, the direction of the various existing convection cells also determines the direction of the different plates influenced by them.
* Image credits: Surachit and Wikimedia Commons.
By Me. Rodolfo Alves Pena