L1-Introduction to Earth

L1-Introduction to Earth - Building a planet 1. Origin of...

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Unformatted text preview: 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 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 http://seismo.berkeley.edu/~dreger/EPS050/ Field trips on Sunday Sept 27, Saturday Oct 10 Last two lectures: YOU pick topics (let us know) 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 Nebular Hypothesis: 1755 Kant suggested a rotating cloud of gas and dust at the dawn of time 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 The structure of the solar system The structure of the solar system------ 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 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 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?) Primitive Meteorites: simple, all ingredients mixed together Processed Meteorites: shattered fragments of larger objects Iron from a core Volcanic rock from a crust 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( , ) = 16 O where is a 4 He Carbon Burning 20 Ne( , ) = 24 Mg 16 O( 16 O, ) = 28 Si Oxygen Burning These spontaneous reactions occur at billions of degrees C. Start with H. Where do the other elements come from? 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 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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L1-Introduction to Earth - Building a planet 1. Origin of...

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