![]() The rate of cooling below the earth’s surface is very slow which gives rise to the formation of large crystals in the rocks.They are formed when magma solidifies below the earth’s surface.On the basis of their mode of occurrence, igneous rocks can be classified as Intrusive and Extrusive Igneous Rocks.They are the most abundant rocks in the earth’s crust.As they comprise the earth’s first crust and all other rocks are derived from them, they are also called as the parents of all rocks or the Primary Rocks.They might be formed directly by cooling of magma from the interior of the earth itself or by cooling of lava from the surface of the earth.Asthenosphere, which is just below the upper mantle, a region beneath Lithosphere is the main source of magma.Igneous rocks are formed by the cooling of highly heated molten fluid material called as Magma.On the basis of mode of formation, rocks may be classified into three:.As we said above, rocks differ in their properties, the size of particles and mode of formation.The science dealing with the study of rocks is called as Petrology.Feldspar and quartz are the most common minerals found in all type of rocks.Rocks may be hard or soft and in varied colours.They are aggregates or a physical mixture of one or more minerals. ![]()
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