GEOLOGIC TIME Earth’s History Compressed:

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

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

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.

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

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

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 Relative Dating 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 N P

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

92 protons 8 {lose 2 protons} + An Example…. Parent U238 → 8 alpha + 6 beta 92 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

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

8 {lose 2 protons} + 6 (add 1 proton) 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

8 {lose 2 protons} + 6 (add 1 proton) An Example…. Parent U238 → 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

8 {lose 2 protons} + 6 (add 1 proton) An Example…. Parent U238 → 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

8 {lose 2 protons} + 6 (add 1 proton) An Example…. Parent U238 → 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

8 {lose 2 protons} + 6 (add 1 proton) An Example…. Parent U238 → 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

8 {lose 2 protons} + 6 (add 1 proton) An Example…. Parent U238 → 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 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)

C14 → N14 5730 years organic carbon

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

B. Carbon Dating

IV. Geologic Time