Rocks (Book)

This chapter discusses the rock cycle and each of the three major types of rocks that form on Earth. Separate sections cover igneous, sedimentary, and metamorphic rocks individually.

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- Cooling and forming crystals

Deep within the Earth, temperatures can get hot enough to melt rock. This molten material is called magma. As it cools, crystals grow, forming an igneous rock. The crystals will grow larger if the magma cools slowly, as it does if it remains deep within the Earth. If the magma cools quickly, the crystals will be very small.