An igneous rock is a rock that is formed from the magma found in the mantle just below the crust. When magma is forced up into the crust and becomes trapped, it begins to cool very slowly. Rocks formed this way are know as intrusive igneous rocks. Igneous rocks that form when lava reaches the earth's surface are called extrusive. As the lava spreads out on the surface and meets the air, it cools and hardens very quickly. Example of an intrusive igneous rock is granite and an example of an extrusive igneous rock is basalt.
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Igneous rock is rock that is formed when magma rises from the mantle. As it does, some may become trapped below the surface and begins to cool very slowly. This is known as intrusive igneous rock. The magma that reaches the surface flows outwards, and once it hits the open air it begins to cool and for extrusive igneous rock.