1. Unit 4: Earth Science
Chapter 20:
Earth Materials

2. Chapter 20: Earth Materials (pages 606-643)
UNIT 4: Earth Science
Chapter 20: Earth Materials (pages )
I. Minerals
A. Common Elements
1. Of the first 92 elements on the periodic table, 90 are found in Earth
a. Only small number combine to make up most of common minerals in Earth’s crust

3. b. Major elements in Earth’s crust includes:

4. 2. Composition of Earth’s Crust
a. Crust is outer most layer
b. Includes all continental material and ocean bottom
c. Extends down tens of kilometers

5. 3. Chemical Element Building Blocks- most minerals of the crust contain abundant oxygen and silicon

6. B. What’s a Mineral
1. Mineral- a naturally occurring element or compound that is inorganic, solid, and has a crystalline structure
a. Have predictable chemical compositions
b. Can be indicated by single elements or chemical formulas

7. C. Physical Properties
1. Each mineral has characteristic set of physical properties
a. Physical properties- Any characteristic of a material that you can observe without changing the identity of the substances that make up the material (color, shape, size, density, melting point, boiling point)

8. Blue Corundum (Sapphire) Red Corundum (Ruby)
b. Care should be taken studying mineral properties, especially color (may be due to impurities)
Blue Corundum (Sapphire) Red Corundum (Ruby)

9. 2. Atom arrangement- Some physical properties controlled by the arrangement of atoms in mineral
a. Orderly pattern is what makes a mineral crystalline
b. Arrangement of atoms reflect way mineral breaks, hardness, and what type of crystal shape it has

10. 3. How Minerals Break
a. Cleavage- when mineral breaks along planes creating flat surface

11. b. Fracture- Do not split along well-defined flat surfaces- breaks unevenly

12. 4. Hardness- The physical property that measures resistance to scratching
a. Determined by strength of bonds that connect atoms

13. b. Measured in scratching test called Mohs Scale
1). When rub two objects together, the softer of the two will wear away
2). Mohs Scale of Hardness

14. 5. Luster and Streak-
a. Luster- Physical property- way a mineral reflects light

15. b. Streak- physical property- color mineral in powdered form
1). May be same color as mineral or different
2). Performed by rubbing on white porcelain plate

16. 6. Crystal shape- Arrangement of atoms often indicated by its external crystal shape (Sorted by 6 crystal systems)

17. D. Mineral Formation
1. Mineral crystals grows as atoms are added
a. Types of atoms added depends on atoms available
b. Growth controlled by how fast atoms can migrate to crystal, temperature, and pressure conditions

18. 2. Minerals from hot water- Some minerals produced from hot-water solutions rich in dissolved mineral matter
a. Occurs around edges of hot springs

19. b. Also formed when hot water passes through cracks in cooler rock (i
b. Also formed when hot water passes through cracks in cooler rock (i.e. gold, silver,or copper)

20. 3. Minerals from Magma- occurs when magma cools

21. 4. Minerals from Evaporation- Also form from water on Earth’s surface when water slowly evaporates

22. E. Mineral Groups
1. Over 3800 minerals identified in nature
2. Only a few minerals needed to make up almost the entire crust of Earth

23. 3. Silicates- The most important by volume of Earth’s crust
a. Most minerals contain silica
b. Common term for compound containing silicon plus oxygen or silicon dioxide
c. Forms tetrahedron shape
d. Other metal atoms can attach to the oxygen atoms

24. 4. Minerals of the Crust- silicate groups form most of Earth’s crust
a. Quartz and feldspar make up most of continental crust
b. Oceanic crust is denser

25. 5. Important non-silicates- many important mineral groups are not silicates
a. Include carbonates, oxides, halides, sulfides, sulfates, and native metals
b. Source of many valuable ore minerals (I.e. Iron ore, bauxite (aluminum), carbonate (used to make cement)

26. F. Mineral Uses
1. Humans have relied on minerals for their everyday needs
2. Used minerals either directly as objects of wealth, or as raw materials to make things.

27. II. Igneous Rocks
A. What is a Rock?
1. Rock- a naturally formed consolidated mixture containing minerals, rock fragments, or volcanic glass
2. Identified by their composition and texture

28. B. Intrusive Igneous Rocks
1. Rocks formed from molten rock material called magma
a. Termed “plutonic” after Pluto, Greek god of the underworld
b. Called intrusive because form within,or push into, regions of Earth’s crust

29. 2. Nature of Magma- As it passes through rock, magma might cause partial melting of rock it intrudes

30. 3. Intrusive Igneous Rock Composition
a. Composition of intrusive igneous rocks gives clues to where in Earth they formed
b. Denser rock settles toward bottom and less dense float to top of magma chamber

31. 4. Intrusive Igneous Rock Texture
a. Texture describes size and arrangement of rock components
b. Size of individual mineral crystals tells you how quickly or slowly the magma cooled

32. 5. Classification of Intrusive Igneous Rocks
a. Granite- rich in quartz and feldspar (dominant rock of continental crust)
b. Gabbro- no quartz and abundant felds

33. C. Extrusive Igneous Rocks
1. Rocks that cool from lava that has erupted at Earth’s surface
a. Have same composition as intrusive igneous rocks, but different textures
b. Often contaminated by rocks as it passes through them on way to surface

34. 2. Extrusive Igneous Rock Textures
   
a. Rapid cooling results small or no crystals
b. Volcanic eruptions can result in many different textures and forms (large blocks to ash)

35. 3. Effect of Gases
a. Can break apart lava to form ash
b. Can form lava with many small holes (pumice- can float on water)

36. III. Sedimentary Rocks
A. Rocks from Surface Materials
1. Surface Attack- exposed rocks attacked by weather
a. Action over long time breaks rocks down into smaller-sized pieces
b. Slow, constant smashing, grinding, and dissolving of clasts can take place in rivers and streams
clasts- small bits and pieces of rocks

37. clasts- small bits and pieces of rocks

38. 2. Transportation and Deposition
a. Can be eroded or removed from original position
b. When transported to new location, clasts often become rounded

39. c. Porosity- space between clasts
1). Porosity can vary
2). Porosity is what can hold water, oil, and natural gas stored in the Earth

40. 3. Buried Clasts
a. Eventually, clasts can become consolidated into sedimentary rock

41. 1). Making of clasts by weathering is surface process
 2). Making of sedimentary rock occurs below the surface

42. 4. Force of pressure (gravity) causes clasts to stick together
a. Water carries dissolved minerals that can act like cement

43. b. Cementation- process where minerals fill spaces between clasts to make sedimentary rock

44. B. Detrital Sedimentary Rocks
1. Detritus, from Latin deterere, means “to lessen or wear away”
a. Sedimentary rock made mostly from clasts are detrital sedimentary rocks

45. b. In order of decreasing size, clasts are known as- gravel, sand, silt, or clay

46. 2. Detrital Sedimentary Rock Textures-
a. Scientist use size of clasts as clue to the kind of environment in which a rock forms
b It takes more force (or energy) to move gravel than sand
c. When water is moving, silt and clay particles mixed up in water
d. When water is calm, most clast sizes settle out

47.  3. Detrital Sedimentary Rock Compositions
a. Depends on sources of rock material that were eroded
b. Some minerals tend to be more common in detrital sediments (i.e. quartz)

48. 4. Detrital Rock Classification
a. Classified according to composition and texture
  b. Classified as follows

49. C. Chemical Sedimentary Rock
1. Formed through the activity of chemicals dissolved in water
2. Crystals settle our of water to build and form new rock
3. Precipitation- the crystallization of excess dissolved materials
4. Evaporation- Dissolved matter crystallizes when water evaporates
Rock salt

50. D. Biochemical Sedimentary Rocks
1. Contain the remains of living organisms
2. Limestone contains remains of marine organisms that had body parts of calcium carbonate

51. 3. Variety of limestone (Coquina) is made from shell fragments

52. 4. Coal- originates from remains of mostly plant material
a. Composed of mostly carbon
b. Usually develops from peat found in swamps or bogs
c. Transformed into coal by compaction after buried by sediments

53. IV. Metamorphic Rocks and the Rock Cycle
A. Metamorphic Rock
1. Rocks that have been changed by some combination of thermal energy, pressure, and chemical activity

54. 2. Atoms rearrange and sometimes form new minerals
a. The word metamorphic comes from “meta”- meaning to change, and “morph”- meaning form
b. Occurs at temperature between that which forms sedimentary (low) and igneous (high)

55. B. Metamorphic Rock Composition
1. Changing Minerals
a. Clay minerals tend to form micas
b. Garnet forms with increased temperature and pressure

56. 2. Environments of Metamorphism
a. Movements of large parts of Earth’s crust and uppermost mantle
b. Contact of preexisting rock with magma

57. C. Metamorphic Rock Textures
1. Foliated Rocks- most common sedimentary rocks in Earth’s crust are mudrocks such as shale and siltstone
a. Contain abundant clay minerals
b. Metamorphizes into minerals in the mica group
c. When squeezed and heated, layers of mica line up in direction perpendicular to direction of compression

58. 2. Nonfoliated Rocks
a. Tend to have random crystal orientation and uniform grain size
b. Results in marble (chemically equivalent to limestone)

59. D. Metamorphic Rock Classification
  1. Classified based on texture and composition (Can be foliated or nonfoliated)
2. Mineral composition- can tell you clues about the original rock type

60. E. The Rock Cycle
1. Includes any chemical and physical conditions that continuously form and change rocks

61. 2.Some happen at Earth’s surface, while others happen deep below the surface

62. 3. All material is conserved through process (matter is conserved)
4. Can take many different paths

63. 5. . Occur over millions of years or suddenly (erupting volcanoes)
6.. No beginning or end to rock cycle