A mountain is an elevation of the ground surface of at least 700 meters from its base. They are grouped into mountain ranges or into larger units called MOUNTAIN CHAINS. They do not “sink” due to the state of gravitational equilibrium in the earth’s crust or ISOSTASY, based on the Archimedes´ principle.
The mountains are generally formed by the folding and deformation of the earth’s relief, caused by the tectonic plates colliding into each other. The climate and erosion over millions of years, will give mountains their final form, to disappear in the end. Glacier erosion shapes circuses, ridges and peaks we see and climb.
This process occurs in the Lithosphere, the region of the Earth’s crust that sustains us all. Similarly, it is essential to understand the lithologic cycle (rock cycle).
Tectonic plates are huge rigid blocks that “slide” or “float” like icebergs on the Asthenosphere. This is only the top of the EARTH’S MANTLE, which is an area conformed by solids and semisolid materials, up to 2,900 kms of depth
Plates can be Continental, Oceanic or mixed: there are 7 major plates (6 continental and one oceanic) to which we add 2 dozen other secondary plates
When two plates collide, usually one rises (forming a mountain), while the other, sinks into the interior of the Earth. The latter is melted (subduction), and subsequently ascends as magma to form new mountains, volcanoes and islands.
The movements of the tectonic plates at a global level (CONTINENTAL DRIFT) note the continuous movement of the continents, from the primitive and only continent (Pangea), to the current situation.
If the plates are separated at sea, underwater mountain ranges called OCEAN RIDGES appear. This is a much more geologically active process than its continental counterpart, since in the middle of the ridge; magma is filtered, forming new oceanic crust.
The tectonic plates are in continuous creation (in oceanic ridges) and continued destruction (melted in the mantle at subduction zones). It is a balanced process, as the size of Earth remains constant.
Actually, Continental Drift and formation of mountain chains, both inland and underwater, are merely the effect of heat release from the metallic core of the Earth, through a process called CONVECTION
Fenomenalmente explicado en éste vídeo: