Earth ScienceEarth ScienceUnit 1Unit 1Chapter 3Chapter 3Lesson 1Lesson 1

Igneous RocksIgneous Rocks

Types of RocksTypes of Rocks Rock- A hard substance composed of Rock- A hard substance composed of

one or more mineralsone or more minerals– Rocks can be organized by the way they Rocks can be organized by the way they

formform– Three types of rocks: Igneous, Three types of rocks: Igneous,

metamorphic, sedimentary metamorphic, sedimentary

Igneous RocksIgneous Rocks Defined: rocks formed by cooled and Defined: rocks formed by cooled and

hardened magma or lavahardened magma or lava– Magma- melted rocks beneath the Magma- melted rocks beneath the

Earth’s surfaceEarth’s surface– Lava- Magma when it reaches the Lava- Magma when it reaches the

Earth’s surfaceEarth’s surfaceComposed of melted rock, water vapor, Composed of melted rock, water vapor,

carbon dioxide, and rock crystalscarbon dioxide, and rock crystals

ClassificationsClassifications Felsic Rocks-Lightweight, light-Felsic Rocks-Lightweight, light-

colored, igneous rockscolored, igneous rocks– They are rich in silicon, aluminum, They are rich in silicon, aluminum,

sodium, and potassiumsodium, and potassium– They form from minerals that are acidicThey form from minerals that are acidic– Granite is an exampleGranite is an example

Classifications Classifications Mafic Rock- Dark colored, heavy Mafic Rock- Dark colored, heavy

igneous rocksigneous rocks– Rich in iron, magnesium, and calciumRich in iron, magnesium, and calcium– They form from minerals that are They form from minerals that are

alkaline (bases)alkaline (bases)– Example: Basalt Example: Basalt

Other ClassificationsOther Classifications TextureTexture SizeSize ShapeShape ArrangementArrangement Distribution of mineralsDistribution of minerals

Intrusive RocksIntrusive Rocks Igneous rocks that form when Igneous rocks that form when

magma cools beneath the Earth’s magma cools beneath the Earth’s surfacesurface– If they cool quickly they form fine grain If they cool quickly they form fine grain

crystals that can’t be seen with the crystals that can’t be seen with the naked eyesnaked eyes

– If they cool slowly, they form large If they cool slowly, they form large coarse grained crystals that can be seen coarse grained crystals that can be seen with the naked eyewith the naked eye

Extrusive RocksExtrusive Rocks Formed when lava cools above the Formed when lava cools above the

Earth’s surfaceEarth’s surface– Have finer crystals than intrusive rocksHave finer crystals than intrusive rocks– Example: cooled lava from volcanoes Example: cooled lava from volcanoes

Thought QuestionsThought Questions How are intrusive and extrusive How are intrusive and extrusive

rocks formed?rocks formed?