Historical Geology

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Historical Geology

• A Brief History of Earth

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James Hutton (1726-1797)

• James Hutton is considered to be the founder of
  modern Geology. A physician and gentleman
  farmer, Hutton was very well educated and a
  brilliant observer with great deductive talents.
• (Portrait of James Hutton by Abner Lowe in the
  1920s.)

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James Hutton, contd

• Huttons studies of the rock formations of his
  native Scotland helped him to formulate his most
  famous work, "Theory of the Earth". This work was
  interpreted and used by many as the basis for
  geological theory. Hutton made many observations
  about rock formations and how they were effected
  by erosion. His terminology and rock formation
  theories became known as "Huttonian" Geology.
• From wikipedia.com James Hutton

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A Time Scale for Geology

• In 1869 John Wesley Powell looked at the rock
  layers of the Grand Canyon and realized that it
  contained a piece of Earth history.
• Geologists aim to understand the Earth in all of
  its complexities but the overriding goal is the
  history of Earth.

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A Time Scale for Geology, contd

• The geologic time scale has revolutionized our
  perception of Earth and the time it took to form
  it.
• Earth is much older than previously assumed.
• The same geologic processes that shaped the
  planet in the past are still active today.

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Early Geology

• Mid 1600s
• James Ussher, Archbishop
• of Armagh
• Created chronology of Earth history
• Dated creation to 4004 B.C.
• 17th/18th century
• Catastrophism
• Earths features created by immediate,
  catastrophic events
• Unknowable causes
• Causes no longer in operation

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Modern Geology

• James Hutton
• Theory of Earth
• Weak, slow acting processes
• Long periods of time
• Same effect as catastrophic events
• The present is the key to the past
• Uniformitarianism

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Uniformitarianism

• Laws in operations today
• Physical
• Chemical
• Biological
• Laws in operations in the past
• Physical
• Chemical
• Biological

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Dating Earth

• Relative dating
• Sequence of formation
• Fossils
• Absolute dating
• Radioactivity

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Relative Dating

• Sequence of formation
• Law of Superposition
• Principle of Original Horizontality
• Principle of cross-cutting relationships
• Inclusions
• Unconformities
• Fossils
• animation

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Absolute Dating

• Radiometric dating
• Atomic structure
• Radioactivity
• Half-life
• Carbon-14
• Tree rings

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The Geologic Time Scale

• Eons
• Eras
• Periods
• Epochs

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Visible Life and Beyond

• Phanerozoic (present 540 mya)
• Precambrian (540 mya 4500 mya)
• Proterozoic (540 mya 2500 mya)
• Archean (2500 mya 3800 mya)
• Hadean (3800 mya 4500 mya)

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Visible Life - Phanerozoic Eras

• Cenozoic (present 65 mya)
• Recent life
• Mesozoic (65 mya 250 mya)
• Middle life
• Paleozoic (250 mya 540 mya)
• Ancient life

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