Geologic Time

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Geologic Time

• Earths History

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Uniformitarianism

• The past is the key to the future

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

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Dating 2 types

• Relative Dating

• Know order of events but not dates

• Absolute Dating

• Know exact age

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Relative Dating Key Concepts

• Law of Superposition

• Principle of Original Horizontality

• Principle of Cross-Cutting Relationships

• Inclusions

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Law of Superposition

• Each bed is younger than the bed below it.

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Principle of Original Horizontality

• Sedimentary layers are deposited horizontally

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Principle of Cross-Cutting Relationships

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

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Inclusions

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

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Relative Dating
Youngest ? G A B C F D Oldest ? E
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Conformable Beds

• Beds that have not been disturbed

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Uncomformities

• Substantial break or gap in the rock record

• 3 types

• Angular

• Disconformity

• Nonconformity

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Angular Unconformity

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

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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

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Nonconformity

• Sedimentary layers overlie igneous or metamorphic
  layers

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Unconformities
Question
Answer
1. Surface 1 is an example of ?
Nonconformity
Angular unconformity
2. Surface 2 is an example of ?
Disconformity
3. Surface 3, 4 and 5?
4. Granite is _________ than the Schist.
Younger
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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

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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)

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Radioactive Decay - Stable Isotopes

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

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Radioactive Decay - Carbon Isotopes

• Carbon-14 also referred as

• C-14
• Radiocarbon

• Types of carbon

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

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Radioactive Decay

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

• The proton number (atomic number) changes.

How long does this take?
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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

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How is Carbon-14 Made?
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When Does the Clock Start?

• When a plant or animal dies, the clock starts.

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How the Carbon Clock Works

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

• 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)

A fossilized starfish has a different ratio
A living starfish has the same ratio as the
atmosphere
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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.
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C-14 ExampleTurin Shroud

• Believed to be the burial cloth of the crucified
  Christ.

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ExampleTurin Shroud

• An artistic impression matching the images above
  (right)

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ExampleShroud of Turin

• Evidence
• Blood Stains
• Wounds
• Weave of cloth
• Pollen grains
• Serum albumin
• Skeptics
• Painting
• Blood - red

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Carbon-14 Results
Is the Shroud authentic?
When was Jesus born?

• Carbon-14 dates the Turin Shroud to

1356 A.D.
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More ExamplesDead Sea Scrolls

• Qumran Caves

Aerial view
Caves
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More ExamplesDead Sea Scrolls

• Evidence
• gt500 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.

Dead Sea Scrolls were found in jars

• Fragment of Dead Sea Scroll

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Carbon-14 Results

• Carbon-14 pre-dates Christianity
• 150 B.C 5 B.C.

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One More ExampleSolomons Temple Stone Tablet

• Evidence
• Confirms the existence of Solomons Temple 9th
  Century B.C.
• 10 lines of Phoenician script describing the life
  of King Jehoash.
• Repair to temple.
• War
• Etc.

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Carbon-14 results

• Its authentic! Carbon-14 dates stone tablet to
• 9th Century B.C.

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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
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Known Carbon-14 Inconsistencies

• Mollusks that are living dated at 2,300 years
• Seal skins (fresh) dated 1,300 years

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Important Questions

• Are these true biblical artifacts or just plain
  old relicts?

• You be the judge!!

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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