The theory of continental drift proposed by Alfred Wegener around 1910 and the theory of the expansion of the ocean floor proposed by Harry Hammond Hess in the 1960s served as the basis for a new, more general theory: plate tectonics. This new theoretical framework of geology explains the way in which the lithosphere, the rigid outermost layer of the planet, is structured. Thus, the earth's crust is made up of various rigid plates that are in constant motion. These blocks remain on a layer of hot, flexible rock known as the asthenosphere.
Plate subduction is one of the tectonic movements
The rocky part of the Earth or geosphere has three different structures: crust, mantle and core. The first is the most superficial and the last the deepest. What we observe on the earth's surface is the geological consequence of millions of years of transformation processes.
The movement of tectonic plates is due to the high temperatures inside the Earth. Slowly and constantly the plates are moving and one of the phenomena that occurs is subduction.
It consists of a plate of the lithosphere dipping below a continental plate. This means that two tectonic plates collide and as a consequence the heavier one is introduced below the lighter one (the descending plate goes towards the Earth's mantle). With subduction, the sediments that have been formed over millions of years are dragged.
The phenomenon of subduction is directly related to earthquakes and volcanoes
There are six major tectonic plates: America, Africa, Eurasia, India, Antarctica, and the Pacific. All of them float on the basaltic mantle and this generates a movement, continental drift.
At the bottom of the oceans are mountain ranges of volcanoes known as mid-ocean ridges. The earth's crust is progressively destroyed by the effect of subduction. In this way, intense pressures are produced in the union areas of the plates that lead to seismic or volcanic activity.
Underwater volcanoes can rise above the ocean surface and end up forming islands with great volcanic activity.
The plates that rub sideways are also unstable and this circumstance is what triggers the majority of earthquakes (the famous San Andreas fault in California is the direct consequence of a subduction zone).
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