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The interior of our planet is at enormous temperatures that generate the innermost layers in a plastic or semi-molten state. Precisely for this reason, convection systems appear very similar to those produced in gas stoves and radiators. Melted rock masses being hot and decreasing their density, amount to that part of that flow that cools and gains weight, descending and deepening towards the nucleus where it warms and ascends again.
In this rise of molten hot material, if there are areas of weakness in the layers above, there can be a leak of magma to the surface of the planet generating a separation at that point of the plates that make up the crust. Generally the areas where most volcanism occurs is in the calls ocean ridges, which correspond to areas where new land crust is being created. Correspondingly, there will be other areas of the earth's surface where crust is destroyed and are called subduction zones.
As we can imagine, the surface of our planet is not continuous, but is divided into portions or lithospheric plates named in honor of the lithosphere or rigid layer formed by the earth's crust (or surface, the outermost and thinnest layer of our planet) and the first 50 km of the mantle (the layer immediately below the crust).
As the convection cells drag the plates above them, they are dynamic, changing their shape and dimensions throughout geological time. In fact, it is currently estimated that they move 1 or 2 cm a year, dragging in their movement the oceans and continents they contain.
This movement of the plates explains the origin of oceans, the formation of mountains, volcanism or earthquakes. Its set constitutes the scientific theory called plate tectonics, composed of the continental drift by Alfred Wegener in 1912 and the expansion of the ocean floor, developed half a century later.
The seed of this idea arose in Wegener's mind by unifying mainly three fundamental observations: the coincidence between the coasts of eastern South America and the west of the African continent (geographical proof), the appearance of fossils and similar rocks on the continents that form the edges of an ocean that separates them (paleontological and geological tests). From all this he deduced that the continents have been changing their relative position and that at some point in Earth's history continents that are currently separated are in contact.
This is how Plate Tectonics was born, one of the fundamental theories of Geology. Wegener made some mistakes such as considering that each continent constituted a plate, ignoring the oceans and their bed; However, what cannot be reproached to the German geophysicist is to have had enough clarity of ideas to encompass the movements of the plates, the relief formations or the evolution and dispersion of species in the past.
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