Any type of rock - igneous, sedimentary, or metamorphic  can become a metamorphic rock. All that is needed is enough heat and/or pressure to alter the existing rocks physical or chemical makeup without melting the rock entirely. Rocks change during metamorphism because the minerals need to be stable under the new temperature and pressure conditions. The need for stability may cause the structure of minerals to rearrange and form new minerals. Ions may move between minerals to create minerals of different chemical composition. Hornfels, with its alternating bands of dark and light crystals, is a good example of how minerals rearrange themselves during metamorphism. Hornfels is shown in the table for the "Metamorphic Rock Classification" concept.  Extreme pressure may also lead to foliation, the flat layers that form in rocks as the rocks are squeezed by pressure (Figure 1.1). Foliation normally forms when pressure is exerted in only one direction. Metamorphic rocks may also be non-foliated. Quartzite and marble, shown in the concept "Metamorphic Rock Classification," are non-foliated. A foliated metamorphic rock.  The two main types of metamorphism are both related to heat within Earth: 1. Regional metamorphism: Changes in enormous quantities of rock over a wide area caused by the extreme pressure from overlying rock or from compression caused by geologic processes. Deep burial exposes the rock to high temperatures. 2. Contact metamorphism: Changes in a rock that is in contact with magma. The changes occur because of the magmas extreme heat. Click image to the left or use the URL below. URL:
Any type of rock - igneous , sedimentary , or metamorphic can become a metamorphic rock . All that is needed is enough heat and/or pressure to alter the existing rocks physical or chemical makeup without melting the rock entirely . Rocks change during metamorphism because the minerals need to be stable under the new temperature and pressure conditions . The need for stability may cause the structure of minerals to rearrange and form new minerals . Ions may move between minerals to create minerals of different chemical composition . Hornfels , with its alternating bands of dark and light crystals , is a good example of how minerals rearrange themselves during metamorphism . Hornfels is shown in the table for the " Metamorphic Rock Classification " concept . Extreme pressure may also lead to foliation , the flat layers that form in rocks as the rocks are squeezed by pressure ( Figure 1.1 ) . Foliation normally forms when pressure is exerted in only one direction . Metamorphic rocks may also be non - foliated . Quartzite and marble , shown in the concept " Metamorphic Rock Classification , " are non - foliated . A foliated metamorphic rock . The two main types of metamorphism are both related to heat within Earth : 1 . Regional metamorphism : Changes in enormous quantities of rock over a wide area caused by the extreme pressure from overlying rock or from compression caused by geologic processes . Deep burial exposes the rock to high temperatures . 2 . Contact metamorphism : Changes in a rock that is in contact with magma . The changes occur because of the magmas extreme heat . Click image to the left or use the URL below . URL :
the type of metamorphism occurs over a large area.
the type of metamorphism occurs over a large area .
regional metamorphism
regional metamorphism