L1-Introduction to Earth - B u ild in g a p la n e t 1 2 3...

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Building a planet 1. Origin of our planetary system 2. Plate tectonics: How Earth works 3. The Earth system, revisited 4. Chemical evolution and differentiation
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Last time What is geology? The Scientific method and how it works Earth systems Logistics: No labs until Sept 10 (3 rd week) Check out website Field trips on Sunday Sept 27, Saturday Oct 10 Last two lectures: YOU pick topics (let us know)
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Origin of our system of planets Sir Fred Hoyle (1915-2001) Big Theory: Universe began between 12 -13.5 Ga Phrase “ Big Bang ” coined by astronomer Sir Fred Hoyle for expansion from a single dense point as the alternative idea to his own preferred concept of a universe that was infinite in time and space Big Bang:The universe has been expanding and thinning to form the galaxies and stars
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Nebular Hypothesis: 1755 Kant suggested a rotating cloud of gas and dust at the dawn of time
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Composition and Temperature gradient Narrow Habitable Zone of liquid water Ice 0 < T < 100 degrees C Water Vapor (at a pressure of 1 atmosphere) LIQUID water is the Main Enabling factor of life (as we know it) comet
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The structure of the solar system The structure of the solar system ------
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Testing the nebular hypothesis Some basic characteristics of the planetary system: - the orbits of the planets lie nearly in a plane with the sun at the center - most planets revolve in the same direction - most planets rotate in the same direction and their rotational axes are nearly perpendicular to the orbital plane These characteristics are consistent with the nebular hypothesis
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Meteorite Types 1) Primitive: Unchanged in composition since they first formed 4.566 ± 0.002 billion years ago 2) Processed: Younger (but at most only a few 100 million years younger), have experienced processes such volcanism or differentiation
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Meteorite Types Differentiation : Separation of heavy and light material by (gravity) Bodies of 100 km diameter or larger could be heated and differentiated (by 26 Al decay?)
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Primitive Meteorites: simple, all ingredients mixed together
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Processed Meteorites: shattered fragments of larger objects Iron from a core Volcanic rock from a crust
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Examples of Nucleosynthetic reactions: 1 H + 1 H = 2 D+ n Hydrogen Burning 2 D + 1 H = 3 He 3 He + 1 H = 4 He + n 12 C( α , γ ) = 16 O where α is a 4 He Carbon Burning 20 Ne( α , γ ) = 24 Mg 16 O( 16 O, α ) = 28 Si Oxygen Burning These spontaneous reactions occur at billions of degrees C. Start with H. Where do the other elements come from?
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Composition of our solar system One star can make up to Fe Heavier than Fe requires reprocessing in a younger star (proton and neutron capture) You are stardust
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Early Earth: forming a layered planet • Earth heats up and melts, forming magma ocean • Differentiation • Impact formation of the Moon (4,510 Ma).
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