1. GEOLOGIC TIME
Earth’s History Compressed:

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

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

5. 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.

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

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

8. II. Constancy of Natural Laws

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

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

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

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

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

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

15. 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

16. 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

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

18. An Example……

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

21. III. Types of Geologic Dating
alpha decay

22. III. Types of Geologic Dating
alpha decay

23. III. Types of Geologic Dating
beta decay

24. III. Types of Geologic Dating
beta decay

25. III. Types of Geologic Dating
electron capture

26. III. Types of Geologic Dating
electron capture

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

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

30. An Example….
Parent
U238

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

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

33. 92 protons 8 {lose 2 protons} +
An Example….
Parent
U238 → 8 alpha beta
92 protons 8 {lose 2 protons} +
8{lose 2 neutrons}

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

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

36. 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

37. 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

38. 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

39. 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

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 = - 10 protons
- 16 neutrons
- 32 atomic mass atomic number
U238 – 32 = “X” 206

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
- 32 atomic mass atomic number
U238 – 32 = “X” 206
92 protons – 10 protons = 82 protons

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

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

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

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

46. 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)

48. C14 → N14 5730 years organic carbon

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

50. B. Carbon Dating

51. IV. Geologic Time