Post on 30-Mar-2015
GEOLOGIC TIME
I. Early Efforts of Dating the Age of the Earth
GEOLOGIC TIME
I. Early Efforts of Dating the Age of the Earth
A. James Ussher (mid 1600's)
4004 B.C.
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.
I. Early Efforts of Dating the Age of the Earth
D. Charles Walcott (1893)
75 m.y.
I. Early Efforts of Dating the Age of the Earth
E. John Joly (1899)
90 m.y.
II. Constancy of Natural Laws
II. Constancy of Natural Laws
A. Catastrophism
• Georges Cuvier (late 1700's)
A. Catastrophism
• Georges Cuvier (late 1700's)
B. Uniformitarianism
• James Hutton (late 1700's)
III. Types of Geologic Dating
A. Relative Dating
B. Radiometric Dating
III. Types of Geologic Dating
A. Relative Dating
1. Law of Superposition
III. Types of Geologic Dating
A. Relative Dating
1. Law of Superposition
2. Law of Original Horizontality
III. Types of Geologic Dating
A. Relative Dating
1. Law of Superposition
2. Law of Original Horizontality
3. Law of Cross Cutting Relationships
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
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
III. Types of Geologic Dating
5. Unconformities– Disconformity– Angular Unconformity– Non Conformity
An Example……
III. Types of Geologic Dating
B. Radiometric Dating
1. Types of decay
III. Types of Geologic Dating
• alpha decay
III. Types of Geologic Dating
• alpha decay
III. Types of Geologic Dating
• beta decay
III. Types of Geologic Dating
• beta decay
III. Types of Geologic Dating
electron capture
III. Types of Geologic Dating
electron capture
III. Types of Geologic Dating
neutron capture
NP
III. Types of Geologic Dating
B. Radiometric Dating
1. Types of decay
• alpha decay
• beta decay
• electron capture
• neutron capture
An Example….
Parent
U238
An Example….
Parent
U238
92 protons
146 neutrons
An Example….
Parent
U238 → 8 alpha + 6 beta = ?92 protons
146 neutrons
An Example….
Parent
U238 → 8 alpha + 6 beta92 protons 8 {lose 2 protons} +
8{lose 2 neutrons}
An Example….
Parent
U238 → 8 alpha + 6 beta 8 {lose 2 protons} +
8 {lose 2 neutrons}
- 16 protons
- 16 neutrons
An Example….
Parent
U238 → 8 alpha + 6 beta 8 {lose 2 protons} +
8 {lose 2 neutrons}
- 16 protons
- 16 neutrons
An Example….
ParentU238 → 8 alpha + 6 beta
8 {lose 2 protons} + 6 (add 1 proton)
8 {lose 2 neutrons}
- 16 protons - 16 neutrons
An Example….
Parent
U238 → 8 alpha + 6 beta 8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons
- 16 neutrons
An Example….
ParentU238 → 8 alpha + 6 beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons- 16 neutrons
- 10 atomic number
An Example….
ParentU238 → 8 alpha + 6 beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons- 16 neutrons- 32 atomic mass - 10 atomic
number
An Example….
ParentU238 → 8 alpha + 6 beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons- 16 neutrons- 32 atomic mass - 10 atomic
number
U238 – 32 = “X” 206
An Example….
ParentU238 → 8 alpha + 6 beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons- 16 neutrons- 32 atomic mass - 10 atomic
number
U238 – 32 = “X” 206
92 protons – 10 protons = 82 protons
An Example….
ParentU238 → 8 alpha + 6 beta
8 {lose 2 protons} + 6 (add 1 proton)
{lose 2 neutrons}
- 16 protons + 6 protons = - 10 protons- 16 neutrons- 32 atomic mass - 10 atomic
number
U238 – 32 = “X” 206
92 protons – 10 protons = 82 protons
“X” 206 with 82 protons
U238 – 32 = “X” 206
92 protons – 10 protons = 82 protons
An Example….
Parent
U238 → 8 alpha + 6 beta = ?
Pb206
Atomic # = 82
III. Types of Geologic Dating
B. Radiometric Dating
2. Half lifes, Parents, and Daughters
III. Types of Geologic Dating
B. Radiometric Dating2. 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)
C14 → N14 5730 years organic carbon
III. Types of Geologic Dating
B. Radiometric Dating
3. An example
B. Carbon Dating
IV. Geologic Time