1. Prentice Hall EARTH SCIENCE
Tarbuck Lutgens 

2. Chapter 3
Rocks

3. Rocks
3.1 The Rock Cycle
Rocks are any solid mass of mineral or mineral-like matter occurring naturally as part of our planet.
What makes up the solid parts of Earth
 3 Types of Rocks

4. 3.1 The Rock Cycle  Types of Rocks
Igneous rock is formed by the crystallization of molten magma.
The word is Latin for “from Fire”
It FORMS when Magma or molten rock cools and hardens
Magma is called lava when its exposed at Earth’s surface

5. Sedimentary rock
2. Sedimentary rock is formed from the weathered products of preexisting rocks that have been transported, deposited, compacted, and cemented.
Erosion (wind, waves etc) break down ALL types of rock into pieces/fragments which is known as sediment.

6. Metamorphic rock
3. Metamorphic rock is formed by the alteration of pre-existing rock deep within Earth (but still in the solid state)
Forces and process (tremendous pressure, extreme heat, and chemical processes) Change the FORM of existing rock.
The word metamorphic means “changes form”
Any of the 3 major types can be changed into another of the 3

8. 3.1 The Rock Cycle The Rock Cycle
 Shows the interrelationships among the three rock types (igneous, sedimentary, and metamorphic)
 Magma is molten material that forms deep beneath the Earth’s surface.
 Lava is magma that reaches the surface.
 Weathering is a process in which rocks are broken down by water, air, and living things.
 Sediment is weathered pieces of Earth elements.

9. 3.1 The Rock Cycle Energy That Drives the Rock Cycle
 Processes driven by heat from the Earth’s interior are responsible for forming both igneous rock and metamorphic rock.
 Weathering and the movement of weathered materials are external processes powered by energy from the sun.
 External processes produce sedimentary rocks.

10. Bowen’s Reaction Series
Early 1900’s Canadian geologist N. L. Bowen began studying how minerals crystallize from magma.
HE LEARNED that as magma cools, certain minerals tend to crystalize first.
Minerals crystallize in a predictable order, over a large temperature range

11. These sequences could be assembled into a composite sequence.

12. Bowen’s hypothesis Minerals form in 2 ways
1) gradual, continous formation of minerals that have similar chemical compositions
2) sudden changes in mineral types
The pattern of mineral formation depends on the chemical composition of the magma

13. Chemical Stability/Physical Stability of Minerals and Rocks
Chemical Stability: is a measure of the tendency of a chemical compound that maintains the original mineral composition.
Minerals that are most resistant to weathering have the highest number of bonds.
Pg. 128
Write in Cornell Notes why is Devils Postpile broken down into columns?

14. 3.2 Igneous Rocks Formation of Igneous Rocks
1. Intrusive igneous rocks are formed when magma hardens beneath Earth’s surface.
2. Extrusive igneous rocks are formed when lava hardens.

15. 3.2 Igneous Rocks Classification of Igneous Rocks
 Igneous rocks can be classified based on their composition and texture.
1. Texture
• Coarse-grained texture is caused by slow cooling resulting in larger crystals.
• Fine-grained texture is caused by rapid cooling resulting in smaller, interconnected mineral grains.

16. Course-Grained Igneous Texture

17. Fine-Grained Igneous Texture

18. 3.2 Igneous Rocks Classification of Igneous Rocks
1. Texture (continued)
• Glassy texture is caused by very rapid cooling.
• Porphyritic texture is caused by different rates of cooling resulting in varied sized minerals.
2. Composition
• Granitic composition rocks are made mostly of light-colored quartz and feldspar.

19. Obsidian Exhibits a Glassy Texture.

20. Porphyritic Igneous Texture

21. 3.2 Igneous Rocks Classification of Igneous Rocks
2. Composition (continued)
• Basaltic composition rocks are made mostly of dark-colored silicate minerals and plagioclase feldspar.
• Andesitic composition rocks are between granitic light-color minerals and basaltic composition dark-colored minerals.
• Ultramafic composition rocks are made mostly from iron and magnesium-rich minerals.

22. Basalt

23. Classification of Igneous Rocks

24. 3.3 Sedimentary Rocks Formation of Sedimentary Rocks
 Weathering, Erosion, and Deposition
• Erosion involves the weathering and the removal of rock.
• Deposition occurs when an agent of erosion—water, wind, ice, or gravity—loses energy and drops sediments.

25. 3.3 Sedimentary Rocks Formation of Sedimentary Rocks
 Compaction and Cementation
• Compaction is a process that squeezes, or compacts, sediments.
• Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments.

26. 3.3 Sedimentary Rocks Classification of Sedimentary Rocks
 Three Main Groups
1. Clastic sedimentary rocks are composed of weathered bits of rocks and minerals.
• Classified by particle size
• Common rocks include
- Shale (most abundant)
- Sandstone
- Conglomerate

27. Shale with Plant Fossils

28. Conglomerate

29. 3.3 Sedimentary Rocks Classification of Sedimentary Rocks
 Three Main Groups
2. Chemical sedimentary rocks form when dissolved substances precipitate, or separate, from water.
Common rocks include
- limestone—most abundant chemical rock
- microcrystalline quartz known as chert, flint, jasper, or agate
- evaporites such as rock salt or gypsum
- coal

30. 3rd class Organic Sedimentary Rocks
Forms from the remains of living things.
Exa. Coal, some limestones
Form when marine organisms such as coral, clams, oysters and plankton remove chemical components of the minerals calcite and aragonite from the seawater.
Organisms make shells from aragonite when they die the shell becomes limestone.
Chalk is an example

31. Fossiliferous Limestone

32. Classification of Sedimentary Rocks

33. 3.3 Sedimentary Rocks Features of Some Sedimentary Rocks
 Features of sedimentary rocks are clues to how and where the rocks are formed

34. 3.4 Metamorphic Rocks Formation of Metamorphic Rocks
 Metamorphism means “to change form.”
 Most metamorphic changes occur at elevated temperatures and pressures.
 Conditions for formation are found a few kilometers below the Earth’s surface and extend into the upper mantle.

35. 3.4 Metamorphic Rocks Formation of Metamorphic Rocks
 Contact metamorphism occurs when magma moves into rock.
Occurs near a body of magma
Changes are driven by a rise in temperature.

36. 3.4 Metamorphic Rocks Formation of Metamorphic Rocks
 Regional metamorphism results in large-scale deformation and high-grade metamorphism.
Directed pressures and high temperatures occur during mountain building.
Produces the greatest volume of metamorphic rock

37. 3.4 Metamorphic Rocks Agents of Metamorphism  Heat  Pressure
Provides the energy needed to drive chemical reactions
 Pressure
Causes a more compact rock with greater density

38. Origin of Pressure in Metamorphism

39. 3.4 Metamorphic Rocks Agents of Metamorphism  Hydrothermal Solutions
Hot water-based solutions escaping from the mass of magma
Promote recrystallization by dissolving original minerals and then depositing new ones

40. 3.4 Metamorphic Rocks Classification of Metamorphic Rocks
 Two main categories
1. Foliated Metamorphic Rock
Has a banded or layered appearance
2. Nonfoliated Metamorphic Rock
Does not have a banded texture

41. Classification of Metamorphic Rocks

42. Gneiss Typically Displays a Banded Appearance

43. Marble—A Nonfoliated Metamorphic Rock