thermal is when the rock is metamorphosed by heat more than pressure. regional is the opposite. so if a rock is close to the surface and gets metamorphosed next to a pluton, it is mainly heat (its...
Regional metamorphism is the creation of metamorphic rock from large geographically significant processes like plate tectonics. Contact metamorphism is the creation of metamorphic rock from the...
Weathering is the decomposition of earth rocks, soils and their minerals through direct contact with the planet's atmosphere. Metamorphism is the solid-state recrystallisation of pre-existing rocks...
Both contact and regional metamorphism result in new types of rock from pre-existing types of rock whether it be from recrystallization, new crystal formation, or realignment of existing minerals.