Geologic Time

Earth’s History

Uniformitarianism

The past is the key to the future

Processes that happen today are the same processes that happened in ancient times

Modern RipplesFossilized Ripples Modern MudcracksFossilized Mudcracks

Dating – 2 types

• Relative Dating

• Absolute Dating

– Know order of events but not dates

–Know exact age

Relative Dating – Key Concepts

• Law of Superposition

• Principle of Original Horizontality

• Principle of Cross-Cutting Relationships

• Inclusions

Law of Superposition

Each bed is younger than the bed below it.

Principle of Original Horizontality

Sedimentary layers are deposited horizontally

Principle of Cross-Cutting Relationships

• Faults and intrusions are younger than the rocks they cut through

Inclusions

• Fragments of one rock unit that have been enclosed within another are older

Relative Dating

Youngest G A

BCFD

Oldest E

Conformable Beds

• Beds that have not been disturbed

Uncomformities

– Angular

– Disconformity

– Nonconformity

• Substantial break or gap in the rock record

• 3 types

Angular Unconformity

• Older layers have been deformed, eroded, and younger layers deposited above

Disconformity

• Beds are parallel relative to each other but there is a break in sequence

• Implies a cessation of sedimentation or erosion, but no tilting

• Hard to recognize

Nonconformity

Sedimentary layers overlie igneous or metamorphic layers

Unconformities

1. Surface 1 is an example of ? Nonconformity2. Surface 2 is an example of ? Angular unconformity3. Surface 3, 4 and 5? Disconformity4. Granite is _________ than the Schist. Younger

Question: Answer:

Absolute Age

• It is the age of a rock unit, fossil or geologic event expressed in units, such as years

• For example, your birthday . . .

– You were born on a specific day, month and year

• Absolute age can be determined by Radioactive Decay

Radioactive Decay - The Atom

Fundamental unit of matter. Made up of components called subatomic particles.

– Protons (positive charge)– Neutron (no electrical charge)– Electron (negative charge)

Radioactive Decay - Stable Isotopes

An atom is generally stable if the number of protons equals the number of neutrons in the nucleus.

Radioactive Decay - Carbon Isotopes

• Carbon-14 also referred as:

• Types of carbon

– C-14– Radiocarbon

– C-12 (stable)– C-13 (unstable)– C-14 (unstable)

Radioactive Decay

• The nucleus of an atom (decays) changes into a new element.

14C 14N6 7

How long does this take?

• The proton number (atomic number) changes.

Carbon-14 and Its Half-Life

The rate of decay is a measure by how long it takes for half an element to decay

The half life of C-14 is 5,730 years

How is Carbon-14 Made?

When Does the Clock Start?

When a plant or animal dies, the clock starts.

Organism diesNo more C-14 intake

C-14 begins to decay

How the Carbon Clock Works

• There are two types of carbon used in the dating process

A living starfish has the same ratio as the atmosphere

A fossilized starfish has a

different ratio

– C-12 (stable does not decay)– C-14 (radioactive decays)

• When an organism is alive, it has the same ratio (C-12 to C-14) that is found in the atmosphere (1 trillion to 1)

How the C-12/C-14 Ratio Works

Amount of stable C-12

Amount of unstable C-14

Ratio Years dead # of half-lives

100 trillion 100 1-T to 1 0 0

100 trillion 50 2-T to 1 5,730 1

100 trillion 25 4-T to 1 11,460 2

100 trillion 12.5 8-T to 1 17,190 3

100 trillion 6 16-T to 1 22,920 4

100 trillion 3 32-T to 1 28,650 5

Carbon-14 can date elements up to approximately 100,000 years.

C-14 ExampleTurin Shroud

Believed to be the burial cloth of the crucified Christ.

ExampleTurin Shroud

An artistic impression matching the images above (right)

ExampleShroud of Turin

• Evidence:– Blood Stains– Wounds – Weave of cloth– Pollen grains– Serum albumin

• Skeptics:– Painting– Blood - red

Carbon-14 Results

Carbon-14 dates the Turin Shroud to:

1356 A.D.

When was Jesus born?

Is the Shroud authentic?

More ExamplesDead Sea Scrolls

Qumran Caves

Aerial view Caves

More ExamplesDead Sea Scrolls

Fragment of Dead Sea Scroll

Dead Sea Scrolls were found in jars

Evidence:•>500 manuscripts.•15,000 fragments that describe every book of the Old Testament.•Some Papyrus samples bear exact dates w/in text that coincide with C-14 results.

Skeptics:•Some of the scrolls appear to be work of early Christians.

Carbon-14 Results

Carbon-14 pre-dates Christianity:

150 B.C – 5 B.C.

One More ExampleSolomon’s Temple Stone Tablet

Evidence:• Confirms the existence of

Solomon’s Temple – 9th Century B.C.

• 10 lines of Phoenician script describing the life of King Jehoash.

• Repair to temple.• War• Etc.

Carbon-14 results

It’s authentic! Carbon-14 dates stone tablet to:

9th Century B.C.

Carbon-14 Inconsistencies

In 1993, scientists found wood (trees) buried in basalt flows (69 feet deep).

Wood samples sent to two laboratories to be carbon-14 dated 44,000 years old.

Basalt sent to two laboratories to be potassium-argon dated 45,000 million years.

69 feet deep Wood encased in

basalt

Known Carbon-14 Inconsistencies

Mollusks that are living dated at 2,300 years

Seal skins (fresh) dated 1,300 years

Important Questions

You be the judge!!

Are these true biblical artifacts or just plain old relicts?

Important Radioactive IsotopesIn Geology

Parent Daughter Half-life Useful dating range (years)

Typical Minerals

Uranium 238 Lead 206 4.5 billion years

10 million to 4.6 billion

Zircon  Uraninite

Uranium 235 Pb 207 713 million years

 10 million to 4.6 billion

Zircon  Uraninite

Thorium 232 Pb 208 14.1 billion years

 10 million to 4.6 billion

 Zircon  Uraninite

Potassium 40 Argon 40 & Calcium 40

1.3 billion 50,000 - 4.6 billion

Whole volcanic rock

Rubidium 87 Strontium 87 47 billion years 10 million - 4.6 billion

Metamorphic/ igneous rock

Carbon 14 Nitrogen 14 5730 years 100-100,000 Organic materials