Rocks

3.1

The Rock Cycle

Igneous Rocks

• Form from the solidification of melted minerals (magma or lava).– Magma = melted rock underground– Lava = melted rock aboveground

• Extrusive Igneous Rocks – Rocks formed from hardened lava.– Quick cooling results in extrusive igneous rocks with fine-grained

or glassy textures.• Intrusive Igneous Rocks – Rocks formed from hardened

magma.– Slow cooling results in intrusive igneous rocks with coarse-

grained textures.

Sedimentary Rocks

Sedimentary rocks may be made of rock fragments—sediments—or by chemical reactions. The classification of sediments is shown below.

3 Types of Sedimentary Rock

• Clastic– Sedimentary rocks made of cemented sediments.

• Chemical– Form from chemical precipitation. When minerals

settle out from a solution, they come together to form chemical rocks.

• Organic– Rocks that come from the remains of organic

matter. A good example is coal.

Clastic

Chemical

Organic

Metamorphic Rocks

• Formed when heat and pressure changes existing rock.

• This can be done 2 ways:• Contact Metamorphism (heat driven) – when magma

intrudes into a previously existing rock layer, and “bakes” the surrounding rock.• Regional Metamorphism (pressure driven) – when

intense pressure is applied to previously existing rock. Is driven by plate tectonics.

Contact Metamorphism

Previously Existing Rock

Contact Metamorphism

Contact Metamorphism Cont…

Regional Metamorphism

Pressure Pressure

Types of Metamorphic Rocks

Foliated• Have a banded appearance.

Non-Foliated• No banded appearance.