Earth Science Unit 1 Chapter 3 Lesson 1 Igneous Rocks

Types of Rocks  Rock- A hard substance composed of one or more minerals –Rocks can be organized by the way they form –Three types of rocks: Igneous, metamorphic, sedimentary

Igneous Rocks  Defined: rocks formed by cooled and hardened magma or lava –Magma- melted rocks beneath the Earth’s surface –Lava- Magma when it reaches the Earth’s surface  Composed of melted rock, water vapor, carbon dioxide, and rock crystals

Classifications  Felsic Rocks-Lightweight, light- colored, igneous rocks –They are rich in silicon, aluminum, sodium, and potassium –They form from minerals that are acidic –Granite is an example

Classifications  Mafic Rock- Dark colored, heavy igneous rocks –Rich in iron, magnesium, and calcium –They form from minerals that are alkaline (bases) –Example: Basalt

Other Classifications  Texture  Size  Shape  Arrangement  Distribution of minerals

Intrusive Rocks  Igneous rocks that form when magma cools beneath the Earth’s surface –If they cool quickly they form fine grain crystals that can’t be seen with the naked eyes –If they cool slowly, they form large coarse grained crystals that can be seen with the naked eye

Extrusive Rocks  Formed when lava cools above the Earth’s surface –Have finer crystals than intrusive rocks –Example: cooled lava from volcanoes

Thought Questions  How are intrusive and extrusive rocks formed?