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Rock Families
For more information and images, see pages 326-333 in your textbook.
A rock is a mixture of two or more minerals.
Rocks are grouped into three major families (or types) based on how they form:
1) Igneous Rock: results from the cooling of molten rock material. As the material
cools, crystals form.
-Magma: molten material found below Earth’s surface
-Intrusive rock: formed when magma has cooled and hardened below the
surface
-Extrusive rock: formed when magma breaks through Earth’s surface in the
form of a volcanic eruption
2) Sedimentary Rock: forms from the compaction and cementation of sediments into
visible layers called beds.
-Sediment: loose particles, such as bits of rock and minerals and decaying
plants and animals.
-Compaction: the process of squeezing together layers of sediment
-Cementation: the process in which pieces of sediment are held together by
another material
3) Metamorphic Rock: made when heat, pressure, or hot fluids change one type of
rock into another type of rock. Can be made from igneous and sedimentary rocks and
other forms of metamorphic rock.
-Parent rock: the type of rock that has been changed into metamorphic rock