Geology

1
Geology
2

• 1. Determining relative age 185
• 1. How old do geologists estimate the earth to
  be? 4.6 billion years

3
James Hutton
4

• 2. Uniformatarianism 185
• 2. What does the principle of Uniformatarianism
  tell us? Current geologic processes, like
  erosion, also occurred in the past. The present
  is the key to the past!

5

• 3. Earths age 186
• 3. Why did Hutton believe the earth to be older
  then the 6,000 year estimate first proposed by
  scientists?
• The earth must be very old for slow processes
  like erosion to have created complex rock
  structures

6
(No Transcript)
7

• 4. Relative age 186
• 4. What is relative age? Relative age tell which
  rock layer is older then the other but does not
  tell the exact age in number of years.

8
(No Transcript)
9

• 5. Law of superposition 187
• 5. What does the law of superposition tell us?
  Superposition tells us that the oldest layers of
  rock are on the bottom because they were
  deposited first and the youngest are on the top
  because they were deposited most recently.

10
(No Transcript)
11

• 6. Principle of original Horizontality187
• 6. What does this principle tell us about the
  rock layers? Original horizontality tells us that
  when rock layers are put down they form
  horizontal beds and unless something disturbs
  them they will stay that way.

12
(No Transcript)
13

• 7. Graded bedding 188
• 7. Where are the coarse particles found in a
  graded bed?_
• Graded bedding means that coarse layers are found
  on the bottom because they are heavier. They will
  remain there unless something causes them to be
  overturned.

14
(No Transcript)
15

• 8. Cross-beds 188
• 8. What type of sediment forms cross beds? Sandy
  sediment forms cross beds because the tops of the
  layers often erode away before the next layer is
  deposited.

16
(No Transcript)
17

• 9. Ripple marks 188
• 9. What causes ripple marks? Water or wind

18
Ripples and mud cracks
19

• 10. Unconformities 189
• 10. What is an unconformity?
• Break in the geologic record due to erosion or no
  sediment being deposited.

20

• 11. Types of unconformities chart 189
• 11. List the three types of unconformities.
• non conformity
• Angular unconformity
• Disconformity

21
(No Transcript)
22
Angular unconformity
23
(No Transcript)
24

• 12. Crosscutting relationships 190
• 12. What is a fault? ___
• A break or crack in the earths crust along with
  a shift in rock position.

25
(No Transcript)
26

• 12. Which is older? The fault material or the
  original rock? The fault is younger then the
  rock through which it breaks

27
(No Transcript)
28

• State the principle of uniformitarianism.
• uniformitarianism a principle that geologic
  processes that occurred in the past can be
  explained by current geologic processes

• an idea that was first proposed by James Hutton
  in the 18th century.

29

• Explain how the law of superposition can be used
  to determine the relative age of rocks.

30
Law of Superposition
Chapter 8

• The diagram below illustrates the law of
  Superposition.

31

• Compare three types of unconformities.

32

• Apply the law of crosscutting relationships to
  determine the relative age of rocks.

33

• relative age the age of an object in relation to
  the ages of other objects
• Layers of rock, called strata, show the sequence
  of events that took place in the past.
• Relative age indicated that one layer is older or
  younger than another layer but does not indicate
  the rocks age in years.

34
law of superposition

• the law that a sedimentary rock layer is older
  than the layers above it and younger than the
  layers below it if the layers are not disturbed

35

• Scientist know that sedimentary rock generally
  forms in horizontal layers.

36
unconformity

• a break in the geologic record created when rock
  layers are eroded or when sediment is not
  deposited for a long period of time

37
(No Transcript)
38
Which layer is the oldest? How do you know? Is
the igneous intrusion older or younger then the
rocks it cuts across? What principle is used to
answer this question?
39

• Complete the problem solving lab on page 560 of
  the Glencoe book.
• Write the answers 1-6 on your paper.

40
Problem solving Lab

• 1. Layer B
• 2. Between D And F Between E and F
• 3. Changes by contact metamorphism.
• 4. A fault occurred/ a break along which movement
  occurred caused misalignment
• 5. The dike is younger according to the cross
  cutting relationship principle.
• 6. b,c,d, e superposition
• A intrusion cross cutting relationship
• Folding of layers ABCD
• D eroded
• FGHI deposited superposition / horizontality
• Faulting principle of crosscutting relationship

41
Section 2

• 13. Determining absolute age/absolute dating
  methods intro 191
• 13. What does absolute age mean? _ Numeric age
  exactly how old in years something is.

42
(No Transcript)
43

• 14. Rates of erosion 191
• 14. How can rate of erosion be used to get the
  absolute age of something?
• By seeing how much erosion happens in one year
  it can be estimated how old something is by
  measuring the amount of erosion per year.

44

• 14. When is it most accurate? Best used for
  things under 20,000 years old.

Niagara Falls moves 1.2 meters a year! Due to
erosion it has moved 11 kilometers since the Ice
Age, when it was formed
45

• 15. Rates of deposition 192
• 15. What is deposition?
• Deposition is placement of Sediments over time.

46

• 15. What is a rate?
• Rate is amount deposited over time

Amount time
47

• 15. Is the rate always constant?
• Rate is not always constant

48

• 16. Varve count 192
• 16. What is a varve? __ A varve is a layer in
  sedimentary rock that shows sand and silt that
  are deposited based on the season.
• They have light and dark sections.
• How are they like rings of growth in trees? Like
  tree rings they show annual growth and can be
  counted to determine the age of the structure.

49
They have light and dark sections. How are they
like rings of growth in trees? Like tree rings
they show annual growth and can be counted to
determine the age of the structure.
50
radiometric dating

• a method of determining the absolutes age of an
  object by comparing the relative percentages of a
  radioactive (parent) isotope and a stable
  (daughter) isotope.

51

• 17. Radiometric dating 193
• 17. What do radioactive isotopes release? They
  release energy at a constant rate.

52

• 17. What happens to the atom as it releases
  energy? The atom changes into a different
  isotope as it releases energy.

53

• 17. How is absolute age determined?
• By comparing how much of the original isotope is
  present and how much has changed, they can
  determine the absolute age of the rock

54
(No Transcript)
55

• 18. Radioactive decay of uranium 193
• 18. Uranium 238 emits 2 protons and 2 neutrons in
  a process called __ Alpha decay

56

• 18. When does the radioactive isotope stop
  changing? It continues until a stable
  non-radioactive form of lead is formed.

57

• Scientists use the natural breakdown of isotopes
  to accurately measure the absolute age of rock,
  which is called radiometric dating.

58

• To do this, scientists measure the concentration
  of the parent isotope or original isotope, and of
  the newly formed daughter isotopes. Then, using
  the known decay rate, they can determine the
  absolute age of the rock.

59
(No Transcript)
60

• 19. Half-life 194
• 19. What is half life? ___ The time it takes for
  ½ of a radioactive element to decay back to its
  daughter isotope.

61

• 20. Radioactive isotopes 195
• 20. Why is a different isotope needed depending
  on the age of the rock being dated?
• The isotopes decay at different rates (the half
  lives are different) so the rate must match the
  approx age of the rock being tested.

62

• 21. Carbon dating 196
• Carbon dating uses organic material in rock that
  is less then 70,000 years old.
• The ratio of carbon 14 to carbon 12 is
  determined.

63

• Living things have more carbon 14. Dead things
  have nitrogen 14.
• ( the isotope carbon 14 becomes after many years
• (The isotope carbon 14 becomes after many years)
  

64

• 21. Carbon dating 196
• Carbon dating uses organic material in rock that
  is less then 70,000 years old.
• The ratio of carbon 14 to carbon 12 is
  determined.
• Living things have more carbon 14. Dead things
  have nitrogen 14. ( the isotope carbon 14 becomes
  after many years
• (The isotope carbon 14 becomes after many years)
  

65
Objectives
Chapter 8

• Describe four ways in which entire organisms can
  be preserved as fossils.
• List five examples of fossilized traces of
  organisms.
• Describe how index fossils can be used to
  determine the age of rocks.

66

• fossils the trace or remains of an organism
  that lived long ago, most commonly preserved in
  sedimentary rock
• paleontology the scientific study of fossils
• Fossils are an important source of information
  for finding the relative and absolute ages of
  rocks.
• Fossils also provide clues to past geologic
  events, climates, and the evolution of living
  things over time.

67

• Section 3 the fossil record
• 22. The fossil record 197
• Why is the study of paleontology important to
  learning about the past events on the earth?
  Plant and animal remains give clues of past
  climate, geologic events and the types of living
  things at that time.

68

• 23. Interpreting the fossil record 197
• What does it mean if fossils of marine animals
  are found far from a current ocean?
• The area may have once been under water years
  ago.

69

• 24. Fossilization 198
• Why do most plants and animals not leave fossils?
  The remains are usually broken down by bacteria.

70

• 25. Table 1 page 198
• List 4 ways fossils may be produced
  Mummification, Amber, Freezing ,petrification
• 26. Table 2 page 199
• What is left behind to form imprints? A carbon
  rich film
• What is fossilized waste material called? _
  coprolites

71

• 26. Table 2 page 199
• What is left behind to form imprints? A carbon
  rich film
• What is fossilized waste material called? _
  coprolites

72

• Almost all fossils are discovered in sedimentary
  rock.
• The fossil record provides information about the
  geologic history of Earth.
• Scientists can use this information to learn
  about how environmental changes have affected
  living organisms.

73

• 27. Types of Fossils 199
• What type of fossil leaves behind evidence of
  movement or activity of a living organism?
• Trace fossils
• 28. Index fossils 200
• If a fossil only appears in rocks of a certain
  age they are called index fossils.
• Index fossils and absolute age 200
• 29. Index fossils usually live for relatively
  short periods of geologic time. This helps
  paleontologists estimate the age of the rock in
  which they are found more accurately.

74
Index fossils
75
Review questions

• Chapter 8
• 8-14,16,18,20, 21,29,30,33-35
• Chapter 9
• 8,9,10,14,15,17,22,31,32

76
Chapter 8

• 8,10,11,12,13,14,16,18,19,20,29,33,35

77
(No Transcript)
78
Chapter 9
79
Extended responsepage 204 6
80
Part Acontrast the nodules found in modern-day
Illinois with more common ones

• Usually nodules contain only hard parts like
  bones, shells and teeth
• Illinois nodules are unusual because they contain
  both soft and hard parts

81
Part B What might scientists hope to learn

• Soft parts might have muscle impressions or organ
  impressions
• This might tell us more about internal structures
  or body systems of ancient organisms.
• Scientists can compare structures to present day
  organisms to see change over time.

82
Page 230 5

• Precambrian time ended about 542 million years
  ago. One reason that fossils in Precambrian rock
  are rare is that Precambrian organisms did not
  have hard body parts that commonly form fossils.
  
• What geophysical reasons account for the rarity
  of fossils in rocks of Precambrian time?

83
Answers should include

• Volcanic activity
• Erosion
• Crustal movement
• all destroy fossils that did exist
• Precambrian time was 542 Million years ago so the
  fossils have been exposed to geophysical events
  for a very long time
• Much longer then the more recent time periods
  like Cenozoic and Mesozoic etc.

84
(No Transcript)
85
Interpreting Graphics

• Use the figure below to answer question 11. The
  graph shows the rate of radioactive decay.

86
Interpreting Graphics,

• 11. How many half-lives have passed when the
  number of daughter atoms is approximately three
  times the number of parent atoms?
• A. one
• B. two
• C. three
• D. four a waning moon.

87
(No Transcript)
88
(No Transcript)