2. Section 2 Chapter 14 Rocks: Mineral Mixture

3. Introduction  This section examines the relationship between magma and rock.  It discusses how temperature, pressure, and composition affect the melting point of rock.  Changes in all 3 of these conditions can occur simultaneously, interacting in complex ways.  We will learn the difference between felsic and mafic igneous rock as well as the difference between intrusive and extrusive igneous rock.

4. Igneous Rock  The word igneous comes from the Latin word for “fire”.  Magma cools into various types of igneous rock depending on the composition of the magma and the amount of time it takes the magma to cool and solidify.

5. Origins of Igneous Rock  Magma and lava solidify in much the same way that water freezes, when it cools down enough, it solidifies and igneous rock is formed.  Water freezes at zero degrees Celsius and magma and lava freeze between 700 and 1250 degrees Celsius.

6. Origins of Igneous Rock  3 ways magma can form: when rock is heated, when pressure is released, or when rock changes composition.  See figure 1 page 368.

7. Composition and Texture of Igneous Rock  Light colored rocks are called felsic, they are less dense and are rich in silicon, aluminum, sodium, and potassium.  Darker rocks are denser than felsic rocks. These rocks are rich in iron, magnesium, and calcium and are called mafic.  The longer it takes for magma to cool, the more time mineral crystals have to grow, the more time to grow means coarser the texture of the igneous rock.

8. Igneous Rock Formations

9. Extrusive Igneous Rock