Explain the three major types of rocks.


Rocks are solid mineral matter forming part of the surface of a planet either exposed on the surface or lying underneath the soil.
The three major types of rocks on the basis of colour, size and texture are igneous, sedimentary and metamorphic rocks.

  • Igneous rocks are formed by the cooling of magma and lava that comes out of the volcanoes. Intrusive ingneous rocks have large grains as they are formed by slow cooling below the earth's surface. Extrusive igneous rocks have small grains as they are formed by quick cooling above the surface of the earth. Granite is an example of igneous rock.
  • Sedimentary rocks are formed by compression and hardening of sediments transported and deposited by wind and water.
  • Metamorphic rocks are formed by metamorphism or the change in the form of rocks under great heat and pressure. Limestone changes into marble by the process of metamorphism.


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