1. Earth Science
Tarbuck/Lutgens

2. Earth Science
Rocks:
Earth’s
Materials
Chapter 3

3. Chapter-3 Rocks Pretest
Describe the strength of bonds between atoms in a solid.
What is a mineral?
True or False: Only eight elements make up the bulk of the minerals found in Earth’s crust.
What is the most common mineral group?
What are rock-forming minerals?
What are some common properties of minerals?

4. Rocks
A rock is any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet.
Some rocks are composed of one mineral, however most rocks are a solid mixture of many minerals.
The three major types of rocks are igneous rocks, sedimentary rocks, and metamorphic rocks.

5. Rock cycle Shows the interrelationships among the three rock types.
It shows that interactions among Earth’s water, air, and land can cause rocks to change from one type to another.
Earth as a system: the rock cycle
Magma
Crystallization of magma or lava
Igneous rock
Weathering, transportation, and deposition

6. Rock cycle Earth as a system: the rock cycle Sediment Sedimentary rock
Lithification
Sedimentary rock
Metamorphism
Metamorphic rock
Melting
Magma

7. Rock cycle Earth as a system: the rock cycle
Full cycle does not always take place due to “shortcuts” or interruptions (alternate paths)
e.g., Sedimentary rock melts
e.g., Igneous rock is metamorphosed
e.g., Sedimentary rock is weathered
e.g., Metamorphic rock weathers

8. The
Rock Cycle

9. Igneous rocks Form as magma cools and crystallizes
Rocks formed inside Earth are called plutonic or intrusive rocks
Rocks formed on the surface
Formed from lava (a material similar to magma, but without gas)
Called volcanic or extrusive rocks

10. Igneous Rocks

11. Igneous rocks Crystallization of magma
Ions are arranged into orderly patterns
Crystal size is determined by the rate of cooling
Slow rate forms large crystals
Fast rate forms microscopic crystals
Very fast rate forms glass

12. Igneous rocks
Classification is based on the rock’s texture and mineral constituents
Texture
Size and arrangement of crystals
Types
Fine-grained – fast rate of cooling
Coarse-grained – slow rate of cooling
Porphyritic (two crystal sizes) – two rates of cooling
Glassy – very fast rate of cooling

13. Fine-grained igneous texture

14. Coarse-grained igneous texture

15. Porphyritic igneous texture

16. Obsidian exhibits a glassy texture

17. Composition of Magma
Silica (SiO2) is the most abundant compound found in magma and has the greatest effect on magma characteristics.
Silica content affects:
Melting temperature
Speed at which magma flows

18. Origins of Magma Most rocks melt between 800oC and 1200oC
Sources of Earth’s heat comes from:
Earth’s formation
Radioactive elements
Gravitational pull
Factors affecting magma formation
Temperature
Temperature increases with depth

19. Origins of Magma Factors affecting magma formation (continued)
Pressure
Pressure increases with depth
As pressure increases, its melting point also increases
Water Content
As water content increases, the melting point decreases
Mineral Content
Different minerals have different melting points

20. Origins of Magma How Rocks Melt Partial Melting
Process whereby some minerals melt at low temperatures while others remain solid
Magma chemistry can change if it partially melted

21. Origins of Magma How Rocks Melt Fractional Crystallization
Process wherein different minerals form at different temperatures

22. Igneous rocks
Classification is based on the rock’s texture and mineral constituents
Mineral composition
Explained by Bowen’s reaction series which shows the order of mineral crystallization
Influenced by crystal settling in the magma

23. Bowen’s reaction series

24. Origins of Magma Crystal Separation
Occurs when crystals settle to the bottom of the magma body, or when liquid magma is separated from the magma body
Layered Intrusions
In some magma bodies, the minerals form into distinct bands in the order shown in Bowen’s Reaction Series

25. Classification of igneous rocks

26. Classification of igneous rocks

27. Igneous rocks Naming igneous rocks Granitic rocks
Composed almost entirely of light-colored silicates – quartz and feldspar
Also referred to as felsic: feldspar and silica (quartz)
High silica content (about 70 percent)
Common rock is granite

28. Granite

29. Igneous rocks Naming igneous rocks Basaltic rocks
Contain substantial dark silicate minerals and calcium-rich plagioclase feldspar
Also referred to as mafic: magnesium and ferrum (iron)
Common rock is basalt

30. Basalt

31. Igneous rocks Naming igneous rocks Other compositional groups
Andesitic (or intermediate)
Ultramafic

32. End of Chapter 3 Sections 1 & 2