Igneous rocks are the oldest kind of rock. They are formed deep inside the earth where the temperature is very hot. The minerals in the earth are in liquid form and are called magma. Magma pushes toward the earths surface and cools as it reaches the surface. Sometimes the magma cools very slowly and forms rocks. Igneous rocks that cool slowly deep within the earth have large crystals. Sometimes magma erupts from a volcano, it is called magma when it reaches the earths surface. Lava cools quickly and forms igneous rocks.
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