1. GEOLOGIC TIME
Earth’s History Compressed:

3. GEOLOGIC TIME
Question: Where did our modern ‘scientific method’ originate?

4. St. Thomas Aquinas (13th century): “Faith and Reason”

5. GEOLOGIC TIME
I. Early Efforts of Dating the Age of the Earth

6. GEOLOGIC TIME I. Early Efforts of Dating the Age of the Earth
A. James Ussher (mid 1600's)
4004 B.C.

7. I. Early Efforts of Dating the Age of the Earth
B. Georges Buffon (mid 1700's)
C. Lord Kelvin (late 1800's)
75,000 yr
20-40 m.y.

8. I. Early Efforts of Dating the Age of the Earth
D. Charles Walcott (1893)
75 m.y.

9. Early Efforts of Dating the Age of the Earth E. John Joly (1899)
90 m.y.

10. Early Efforts of Dating the Age of the Earth
E. Henri Becquerel (1896)
‘Discovered Radioactivity of
certain elements’

11. II. Constancy of Natural Laws

12. II. Constancy of Natural Laws
A. Catastrophism
Georges Cuvier (late 1700's)

13. A. Catastrophism
Georges Cuvier (late 1700's)
B. Uniformitarianism
James Hutton (late 1700's)

14. III. Types of Geologic Dating
Relative Dating
Radiometric Dating

15. III. Types of Geologic Dating
A. Relative Dating
1. Law of Superposition

16. III. Types of Geologic Dating
A. Relative Dating
1. Law of Superposition
2. Law of Original Horizontality

17. III. Types of Geologic Dating
A. Relative Dating
1. Law of Superposition
2. Law of Original Horizontality
3. Law of Cross Cutting Relationships

18. III. Types of Geologic Dating
A. Relative Dating
1. Law of Superposition
2. Law of Original Horizontality
3. Law of Cross Cutting Relationships
4. Law of Faunal Succession

19. III. Types of Geologic Dating
A. Relative Dating
1. Law of Superposition
2. Law of Original Horizontality
3. Law of Cross Cutting Relationships
4. Law of Faunal Succession
5. Unconformities

20. III. Types of Geologic Dating
5. Unconformities
Disconformity
Angular Unconformity
Non Conformity

21. An Example……

22. III. Types of Geologic Dating
B. Radiometric Dating
1. Types of decay

24. III. Types of Geologic Dating
alpha decay

25. III. Types of Geologic Dating
alpha decay

26. III. Types of Geologic Dating
beta decay

27. III. Types of Geologic Dating
beta decay

28. III. Types of Geologic Dating
electron capture

29. III. Types of Geologic Dating
electron capture

30. III. Types of Geologic Dating
neutron capture N P

31. III. Types of Geologic Dating
B. Radiometric Dating
1. Types of decay
alpha decay
beta decay
electron capture
neutron capture

33. An Example….
Parent
U238

34. An Example….
Parent
U238
92 protons
146 neutrons

35. An Example….
Parent
U238 → 8 alpha beta = ?
92 protons
146 neutrons

36. 92 protons 8 {lose 2 protons} +
An Example….
Parent
U238 → 8 alpha beta
92 protons 8 {lose 2 protons} +
8{lose 2 neutrons}

37. An Example…. Parent U238 → 8 alpha + 6 beta 8 {lose 2 protons} +
8 {lose 2 neutrons}
- 16 protons
- 16 neutrons

38. An Example…. Parent U238 → 8 alpha + 6 beta 8 {lose 2 protons} +
8 {lose 2 neutrons}
- 16 protons
- 16 neutrons

39. 8 {lose 2 protons} + 6 (add 1 proton)
An Example….
Parent
U238 → 8 alpha beta
8 {lose 2 protons} (add 1 proton)
8 {lose 2 neutrons}
- 16 protons
- 16 neutrons

40. 8 {lose 2 protons} + 6 (add 1 proton)
An Example….
Parent
U238 → 8 alpha beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons
- 16 neutrons

41. 8 {lose 2 protons} + 6 (add 1 proton)
An Example….
Parent
U238 → 8 alpha beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons
- 16 neutrons
- 10 atomic number

42. 8 {lose 2 protons} + 6 (add 1 proton)
An Example….
Parent
U238 → 8 alpha beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons
- 16 neutrons
- 32 atomic mass atomic number

43. 8 {lose 2 protons} + 6 (add 1 proton)
An Example….
Parent
U238 → 8 alpha beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons
- 16 neutrons
- 32 atomic mass atomic number
U238 – 32 = “X” 206

44. 8 {lose 2 protons} + 6 (add 1 proton)
An Example….
Parent
U238 → 8 alpha beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons
- 16 neutrons
- 32 atomic mass atomic number
U238 – 32 = “X” 206
92 protons – 10 protons = 82 protons

45. 8 {lose 2 protons} + 6 (add 1 proton)
An Example….
Parent
U238 → 8 alpha beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons
- 16 neutrons
- 32 atomic mass atomic number
U238 – 32 = “X” 206
92 protons – 10 protons = 82 protons
“X” 206 with 82 protons

46. U238 – 32 = “X” 206
92 protons – 10 protons = 82 protons

47. An Example….
Parent
U238 → 8 alpha beta = ?
Pb206
Atomic # = 82

48. III. Types of Geologic Dating
B. Radiometric Dating
2. Half lifes, Parents, and Daughters

49. III. Types of Geologic Dating
B. Radiometric Dating
2. Half lifes, Parents, and Daughters
half life (def)
n : the time required for something to fall to half its initial value (in particular, the time for half the atoms in a radioactive substance to disintegrate)

51. C14 → N14 5730 years organic carbon

52. III. Types of Geologic Dating
B. Radiometric Dating
3. An example

53. B. Carbon Dating

54. IV. Geologic Time