3 TYPES OF ROCKS

HOW ARE ROCKS CLASSIFIED?

• There are 3 classes of rocks: igneous, sedimentary, and metamorphic.
• You can classify rocks by their composition and texture.

IGNEOUS ROCKS

• There are two different types of igneous rocks: intrusive igneous rocks and extrusive igneous rocks.
• Intrusive igneous rocks cool very slowly and form underground. They also have large crystals.
• Extrusive igneous rocks cool very rapidly and have little to no crystals.

SEDIMENTARY ROCKS

• Sedimentary rocks form mainly at or near the surface of Earth.
• They form by weathering, erosion,deposition, burial, and cementation.
• Clastic sedimentary rock forms when sediments are buried, compacted, and cemented together by calcite or Quartz. Sandstone is a clastic sedimentary rock.
• Chemical sedimentary rocks form when water, usually seawater, evaporates. Halite is a chemical sedimentary rock.
• Organic sedimentary rock forms from the remains or fossils, of once-living plants and animals. Limestone is a organic sedimentary rock. *Fun fact: chalk is made of limestone*

METAMORPHIC ROCKS

• Metamorphic rocks form by being exposed to high pressure, the crystal structures of the minerals in the rock change to form minerals.
• The metamorphic process in which mineral grains are arranged in planes or bands is called foliation. Slate is foliated metamorphic rock.
• Metamorphic rocks that do not have mineral grains that aligned in planes or bands are called non-foliated. Marble is a non-foliated

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