2. Rocks
Ch 5 CP/GHP Book

3. Extrusive igneous rocks
form on or near the surface.
Intrusive igneous rocks
form below the surface.

4. What are Igneous Rocks?
Form from crystallized magma (lava = magma that flowed out onto Earth’s surface)
Ignis is Latin for “fire”
Extrusive (fine-grained, cool quickly)
Intrusive (course-grained, cool slowly)

5. Magma Composition O, Si, Al, Fe, Mg, Ca, K and Na
96% of Earth’s crust is silica (SiO2)
Types of magma Rhyolitic 70%SiO2 Andesitic 60%SiO2 Basaltic 50%SiO2

6. Magma Origin Melting temperatures: 800°C-1200°C
Temperature, pressure, chemical composition and water content all affect magma
Types of Magma

7. Magma Origin
Geothermal gradient (page 101)

8. Magma Origin
Melting curve (page 102)

9. Pause for lab or demo
Bowen’s reaction series melting point of various items crystallization point of the same items
Materials: Red, orange and yellow crayons Chocolate chips Lots of gummy bears Candles Ice Hot plate

10. Results from the lab/demo
Ice begins to melt at 32˚F
Chocolate ˚F
M&M candy shell 98.6˚F
Gummy bears 115˚F
Candles 130˚F
Crayons ˚F

11. How rocks melt
Partial Melting – process when some minerals melt while others remain solid
Fractional Crystallization – cooling in the reverse order of melting

12. Bowen’s Reaction Series
Geologist Neil L. Bowen minerals form in predictable patterns

13. Bowen’s Reaction Series

14. Classifying Igneous Rocks Ch 5.2
Mineral Composition Felsic - light colored rocks such as granite Intermediate - medium colored, andesite Mafic – dark colored rocks such as basalt Ultramafic – very high levels of iron, low silica

16. Classifying Igneous Rocks
Grain Size

17. Classifying Igneous Rocks
Texture Phaneritic (A)- same size crystals throughout Porphyritic (B)- large crystals surrounded by finer-grained crystals

18. Igneous rocks as resources
Ore Deposits
Veins and Pegmatites

19. Igneous rocks as resources
Kimberlites - ultramafic rocks of peridotite that can contain diamonds