Here's why:
* Intense Pressure: Mountain building involves the collision of tectonic plates, which results in immense pressure on the existing rocks. This pressure is a key factor in the transformation of rocks.
* Heat: The collision also generates significant heat, either from friction or from the intrusion of magma. This heat provides the energy for chemical reactions and recrystallization within the rocks.
* Fluids: During mountain building, fluids are often released from the rocks. These fluids can facilitate chemical reactions and transport minerals, further contributing to metamorphic transformation.
While some metamorphic rocks can be formed in other environments like contact metamorphism (near igneous intrusions) or regional metamorphism due to burial, the scale and intensity of mountain building events far surpass these in producing the largest volumes of metamorphic rock.
