Metamorphism and Plate Tectonics
Metamorphic rocks result from the forces active during plate tectonic processes. The collision of plates, subduction, and the sliding of plates along transform faults create differential stress, friction, shearing, compressive stress, folding, faulting, and increased heat flow. The tectonic forces deform and break the rock, creating openings, cracks, faults, breccias, and zones of weakness along which magmas can rise. Generally speaking, the greater the tectonic forces, the higher the pressures and temperatures affecting a rock mass and the greater the amount of resulting structural deformation and metamorphism.