As we saw in the theory of plate tectonics, the main cause of mountain formation is the collision between plates. Specifically, it is the collision between plates carrying continental crust that would give rise to mountains.
According to the theory of plate tectonics we can, for simplicity, trace orogenic phenomena back to two main causes: on the one hand vertical thrusts, that is, with a direction perpendicular to the Earth's crust; on the other tangential thrusts, that is, those with a direction parallel to the Earth's crust.
These thrusts originate near the faults between the plates, where movement is essentially driven by the convective motions of the fluid material that makes up the asthenosphere.
Near the mid-ocean ridges we would have the continuous outpouring of material, which would result in slight but constant seismic activity.
Near the continental margins, collision and subduction of lithosphere give rise to intense seismic activity.
Subduction, in fact, would cause magmatic material to rise from the mantle towards the lithosphere, with the resulting formation of volcanoes.
As for the collision between continental plates, this would cause the plates themselves to fold and be uplifted.
The three models usually referred to in describing the formation of mountains are:
- The Andean-type orogeny model;
This is the case in which the oceanic plate, being made of heavier materials such as basaltic rocks, tends to slide beneath (subduction) the continental plate. In the collision the latter tends to be compressed, the plate begins to fold, the land rises, forming mountains. - The island-arc orogeny model;
The model is typical of areas such as Japan and the Philippines, where two oceanic plates collide and one of the two begins to slide beneath the other. The pressure at the collision margin causes magmatic material to rise, giving rise to the formation of volcanoes. - The collisional orogeny model;
The last model is the one in which two continental plates collide. There is no subduction but a folding and compression of the lithosphere.
The reliefs generated by the collision and subduction movements of plate tectonics are also subject to continuous shaping by climatic agents.
We're talking about shaping due to glacial erosion, and shaping due to erosion by water and wind.
We're talking about the continued action of climatic and atmospheric agents that profoundly affect the morphology of mountains; they are erosive agents that, through their transporting action, manage to wash away and erode rocks, as in the case of karst phenomena, in which the passage of water manages to dissolve the carbonates of which some rocks are made.
To see how these processes have acted on the peninsula read Formation of the Italian mountains.