Igneous rocks form as molten magma or lava as it cools. This can happen on the surface of the earth, or deep inside of its crust. Magma is thrust through the layers of the earth, collecting various minerals and gasses that are absorbed through the melting of other sediment. Magma that cools within the earths surface forms igneous rock that is known as intrusive, magma that reaches the surface and cools is known as extrusive. Granite is a form of igneous rock, and this picture illustrates the use of granite with in the construction of a down town building in Edmonton.
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