What are the major rock types?

• The three major rock types are igneous, metamorphic, and sedimentary

• These rocks are all formed by physical changes

• Those changes include melting, cooling, compacting, eroding, and deforming

• All the changes listed above are a part of the rock cycle

• Rocks are classified by the way they look and are formed

• Forms from the cooling and hardening of molten magma in various environments

• Can cool slowly beneath the surface or rapidly at the surface

• Intrusive igneous rocks form when magma is trapped deep inside the earth

• Extrusive igneous rocks form when magma exits and cools above Earth’s surface

• Igneous rocks can be classified into 4 categories based on the chemical composition: felsic, intermediate, mafic, and ultramafic

• Forms when minerals in a existing rock are changed by heat or pressure below the surface

• When a rock is in contact with direct extreme heat or pressure but does not melt, the rock then is metamorphosed

• Metamorphic rocks can change the mineral compositions and texture or rock

• Gradually change into another rock