1. Igneous Rocks
Intrusive and extrusive rocks formed from the cooling and crystallization of magma.

2. Magma vs. Lava Magma is molten rock beneath Earth’s surface
Lava is magma that has flowed out onto Earth’s surface

3. Two types of Igneous Rocks
Extrusive Igneous Rocks
Fine grained igneous rocks that cool quickly on the Earth’s surface(forms from Lava). Ex. Rhyolite
Intrusive Igneous Rock
Course grained Igneous rock that cools slowly beneath the Earth’s surface(forms from magma).Ex. granite

4. Rhyolite- extrusive rapid cooling

5. Granite- Intrusive slow cooling

6. Composition of Magma A slushy mix of : Molten rock Gases
Mineral crystals

7. Elements in Magma Oxygen (O) Silicon (Si) Aluminum (Al) Iron (Fe)
Potassium (K)
Sodium (Na)
Magnesium (Mg)
Calcium (Ca)

8. Magma is classified based on the amount of silica it contains.
SiO2

9. Types of magma Rhyolitic Andesitic Basaltic 70% 60% 50% Group
SiO2 Content
Rhyolitic
Andesitic
Basaltic
70% 60% 50%

10. Origins of Magma
In labs, most rocks melt when they hit 800°C to 1200°C
These temps are found in the upper mantle & lower crust
Scientists think this heat comes from the decay of radioactive elements & the remaining energy from Earth’s molten formation

11. Check Point What is the difference between magma and lava?
What are the two types of igneous rocks?
Which type of magma has the most silica content?

12. Factors That Affect Magma Formation
1.Temperature
Temp ↑ with depth in Earth’s crust
2. Pressure
Pressure ↑ with depth because of the weight of overlying rock
As pressure ↑, so does the melting point

13. 4.Mineral’s composition
3.Water content
Rocks & minerals contain little water
The higher the water content , the lower the melting point
4.Mineral’s composition
Different minerals have different compositions and therefore have different melting points

14. How Rocks Melt
Partial Melting – process in which different minerals melt into magma at different temperatures, changing its composition.
Some minerals melt, while others remain solid
As minerals melt, different elements are added to the magma “stew,” thereby changing its composition

15. Fractional Crystallization – process in which different minerals crystallize from magma at different temperatures, removing elements from magma.
Changes composition of magma by removing elements

16. Bowen’s Reaction Series
Discovered by a geologist named Bowen
Sequential, predictable, dual-branched pattern in which minerals crystallize from cooling magma
Two main patterns or branches of crystallization
1. Continuous, gradual change of mineral composition
Ex. feldspars (change from calcium rich to sodium rich)

17. Magma is made up of different minerals that crystallize at different temperatures.
So during the cooling and crystallization process some minerals become solid while others remain molten.

18. Bowen’s Reaction continued…
2. An abrupt change of mineral type
Iron-rich minerals change into other minerals.   Ex. At 18000C Olive forms once that substance reaches 1557 degrees a new mineral is formed (pyroxene).

19. Magmatic Differentiation
As minerals form in the Bowen series the solid more dense ones fall to the bottom and are not available for the reaction anymore so the material that is available is now different.

21. Bowens reaction https://www.youtube.com/watch?v=K6aQlYA4BHU

22. Crystal separations
Under certain conditions newly formed crystals can be separated from rock that explains why olivine is found in the rock that is why olivine did not convert to pyroxene during cooling.

23. Layered Intrusions
Sometimes during cooling layered intrusions form. Scientist are uncertain why. Maybe temperature differences. Valuable rare metals maybe found here. Ex. Platinum, chromium, nickel, and gold.

24. Check Point
1. What happens to temperature with depth? 2. As depth increases does pressure decrease or increase? 3. What is partial melting? 4. Summarize Bowen’s reaction?

25. 5.2 Classifying Igneous Rocks
Igneous rocks are broadly classified as intrusive or extrusive.
However, they are further classified by
mineral composition
what minerals are found in the rock
color
grain size

26. if lava cools quickly then small crystals form
Example: Obsidian has no visible mineral grains
if magma cools slowly then large crystals form
Example: Gabbro has large mineral grains

27. early forming minerals may have well shaped crystals
texture
early forming minerals may have well shaped crystals
later forming minerals may have irregular shaped crystals
porphyritic texture – contains both large & small crystals

28. Classification of Igneous Rocks

29. Four Main Groups of Igneous Rocks
1. Felsic
Light colored
High silica content
Contain quartz, feldspar,orthoclase, and plasioclase
Ex, granite

30. 2. Mafic Dark colored Low Silica
Plagioclase, biotite, amphibole, pyroxene, and olivine
Rich in Iron and Magnesium
Example, Gabbro

31. Contain moderate amounts of biotite, amphibole, pyroxene, and olivine.
3. Intermediate page107
Contain moderate amounts of biotite, amphibole, pyroxene, and olivine.
Ex. diorite

32. 4. Ultramafic
Low Silica
High Iron and Magnesium
Ex, Peridotite and dunite

33. Check Point
What are the four mineral composition types and two facts about each? (you have 5 minutes)
What is a pegmatite?
What is a kimberlite?
Answer #6 on p. 106

34. Igneous Rocks as Resources
Igneous rocks are good resources as building materials because of their strength, durability, ability to resist weathering, and beauty.

35. Ore Deposits
Ore deposits can be found within igneous rocks or in the cracks and voids surrounding the rocks, called veins
Dissolved silica & common metals (Ex: gold, silver, lead, copper) are released at the end of magma crystallization in a hot, mineral rich fluid that fills the veins.
Fluid solidifies to form metal-rich quartz veins
Ex, gold-bearing quartz in Sierra Nevada Mountains in California

36. Pegmatite- vein deposits of extremely large-grained minerals that can contain rare ores such as lithium and beryllium
Kimberlites – rare, ultramafic rock that contain diamonds and other minerals formed only under very high pressures