Lecture 6 - Absolute Time

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Historical Geology
Lecture 6 Absolute Time and Dating Geochronology
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Historical Geology
Outline
I Early Dating Attempts II Isotopic
Dating A) Radioactive Decay 1) Isotopes 2)
Types of Decay 3) Half-life 4) Decay
Series 5) Uses B) Fission Track
Dating C) Effect of Metamorphism III Combining
Relative and Absolute Dating
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Historical Geology
Estimating Earths Age
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Historical Geology
Estimating Earths Age
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Historical Geology
Early Dating Attempts Quantitative
William Thomson, Lord Kelvin (1824-1907)

• method cooling rate of molten Earth through
  conduction and radiation
• result 24-40 million years

John Joly (1857-1933)

• method rate of delivery of salt to the ocean
• result 90-100 million years

Total salts in ocean / rate of addition age
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Historical Geology
Early Dating Attempts Quantitative
Archibald Geikie (1835-1924) many others

• method sedimentation rates
• result 3-1500 million years

Charles Lyell (1797-1895)

• method evolution of marine mollusks
• result Cenozoic Era - 80 million years

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Historical Geology
The Discovery of Radioactivity
Henri Becquerel (1852-1908)
Marie Curie (1867-1934) Pierre Curie (1859-1906)
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Historical Geology
Isotopes
isotopes - atoms of the same element that
have different
numbers of neutrons but the same number of protons
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Historical Geology
Radioactive Decay Types
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Historical Geology
Half-Life
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Historical Geology
Radioactive Decay Systems
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Historical Geology
Fission Track Dating
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Historical Geology
Effect of Metamorphism
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Historical Geology
Using Absolute and Relative Dating
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Historical Geology
Using Absolute and Relative Dating