Metamorphic Rocks


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Most rocks in mountainous regions show an evidence of change. All these in course of time become metamorphic or changed forms of rocks. Metamorphic rocks are formed under the influence of heat or pressure on sedimentary or igneous rocks. Tremendous pressure and high temperature change the colour, hardness, structure and composition of all types of pre-existing rocks. The process which bring about the change is known as Metamorphism and the ultimate products, formed due to operation of such processes are defined as the Metamorphic rocks.

Temperature, pressure stress and access of chemically reactive substances are the main agents, which are responsible for metamorphism. Heat causes the minerals to recrystallise in the rock. The process of change by heat is called thermal or contact metamorphism. When molten magma or lava comes in contact with surrounding rocks, it bakes them and changes them into metamorphic rocks.

Similarly the formation of metamorphic rocks due to tremendous pressure is known as dynamic or regional metamorphism. Slate, gneiss, schist, marble and diamond are good examples of metamorphic rocks. Metamorphic rocks are hard and tough in comparison to the parent rocks from which they are formed. Examples of metamorphic rocks are given in below table with their parent rock from which they have been formed.

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Name of the Rock Type of Rock Name of the Metamorphic Rock
Limestone Sedimentary Rock Marble
Dolomite Sedimentary Rock Marble
Sandstone Sedimentary Rock Quartzite
Shale Sedimentary Rock Slate
Slate Metamorphic Rock Phylite/Schist
Coal Sedimentary Rock Graphite/Diamond
Granite Igneous Rock Gneiss
Phyllite Metamorphic Rock Schist

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Different types of metamorphic rocks are found all over the world. In India, marble is found in Rajasthan, Bihar and Madhya Pradesh, whereas slates are available in plenty in Orissa, Andhra Pradesh and Haryana. In Kangra and Kumaun regions of Himalaya, slates of different colours are found.

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Bibliography : NIOS – Geography

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