Transcript Introductory Principles

Evolution of Life and
Earth
(Historical Geology)
Physical vs. Historical Geology
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Physical Geology- Origin, classification, and
composition of Earth materials and internal and
surficial processes
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Historical Geology- Earth evolution, changes
in lands and seas, mountain building and
destruction, fossil succession through time, and
history of the solar system
Scientific Method
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Questions
Collection of Data
Development of Hypothesis
Testing of Hypothesis
The beginning
► The
Big Bang
 Most scientist believe that the universe was
created in a single event known as the Big Bang
►This
occurred ~15 billion years ago
 Some studies suggest 22 bya
 Our Solar System started to form about 5 bya
Our Solar System
Solar Nebula Hypothesis
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Cold, Rarified cloud of gas and dust
particles
Dust cloud starts counterclockwise
rotation around proto-sun
Eddies in dust cloud begin planetary
development: cold homogeneous
accretion
Final Phase of Formation
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Eventually, gravitational collapse at core of
rotating disc forms the Sun
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Solar wind drives out lighter elements
Leaving heavy elements in inner solar system
and lighter elements in outer system
Earth
Formative Interval
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Hadean Eon: 4.6-3.9 bya
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Accretion and Differentiation
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Heating, partial melting and solid diffusion
Ni and Fe migration to core
Mantle separation forming lighter crust
Differentiation
►Source
of Internal heat
 Accretionary heat
 Heat caused during bombardment
 Radioactive decay
►Development
of Magnetic Field
 Caused by movement of liquid core
Crustal Develoment
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Crust formed by cooling magma ocean
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Komatitites formed early in Earth’s crust
Continental Crust and Water present as early as
4.4 bya
Evolution of the Atmosphere and
Hydrosphere
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Primitive atmosphere before 3.8bya
The Oceans
Origin of Oceans (After 4.4bya)
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Tied to the onset of the Hydrologic cycle
Salinity due to chemical weathering
Standard Geologic Time Scale
Divisions of Time
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Eons (largest): Hadean, Archean, Proterozoic,
and Phanerozoic
Eras- units within eons: Eras within the
Phanerozoic are the Paleozoic, the Mesozoic,
and the Cenozoic.
Periods, Epochs and Ages: decreasing order
subdivisions of geologic time
Understanding Earth’s Changes
Catastrophism - Earth surface changes through large scale
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events
Uniformitarianism
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James Hutton
Dynamic/Cyclic Concept of Earth History
► Used principle of actualism (uniformitarianism)
► Wrote first great Geology text ( Theory of the Earth)
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