The word metamorphic refers to “metamorphose” which means a change in the form. These rocks are transformed under the action of pressure, volume, and temperature. Thus, metamorphic rocks refer to rock that changes their form without disintegration. The appearance, mineral composition, and texture are modified due to temperature and pressure. These rocks are the modified version of igneous and sedimentary rocks. Sometimes, metamorphic rock is again metamorphosed. In other words, all rocks whether igneous, sedimentary, or metamorphic may be changed under great heat and pressure. For example, clay may be metamorphosed into slate, limestone into marble, and coal into graphite. Metamorphism is the process behind forming metamorphic rocks. Therefore, metamorphism is a process by which rocks undergo recrystallization and reorganization of materials within original rocks. Granite, marble, slate, schist, etc. are some examples of metamorphic rocks. These rocks can also be divided into two major groups i.e., foliated and non-foliated.
The process of metamorphism can be classified in two ways-
PHYSICAL METAMORPHISM- It refers to the changes in the texture and appearance of a rock.
CHEMICAL METAMORPHISM- It refers to the changes in the composition of a rock.
There are different types of metamorphism are as follows-
DYNAMIC METAMORPHISM- Mechanical disruption and reorganization of the original minerals within rocks due to breaking and crushing without chemical changes.
THERMAL METAMORPHISM- When the material of rock changes its chemical composition and recrystallizes. The two types of thermal metamorphism are as follows-
- Contact Metamorphism- When the rocks come in contact with hot encroaching magma and lava, then the rock materials recrystallize under high temperatures.
- Regional Metamorphism- The rocks undergo recrystallization due to deformation caused by tectonic shearing together with high temperature or pressure or both.
- FOLIATION- It is also known as lineation. In this process, rock grains are arranged in layers. These arrangements of minerals in the metamorphic rock are known as foliation.
- BANDING- In this process, minerals are arranged into alternating thin to thick layers appearing in light and dark shades. These structure in metamorphic rock is known as banding. The rock displaying the banding is known as banded rock.