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Geol106-1 - HISTORICAL GEOLOGY GEOLOGY 106 Observe the...

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1 HISTORICAL GEOLOGY GEOLOGY 106 Observe the Earth and it shall teach thee. (Job 12:8) ORIGIN OF THE EARTH ACCRETIONARY ORIGIN OF THE EARTH begins with BIG BANG THEORY of origin of universe that produces matter then, SOLAR NEBULA THEORY of solar system origin leads to formation of planets
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2 STAR FORMATION The BIG BANG THEORY explains radial movement of galaxies from central point and points to origin of matter at 13 billion years ago (red shift) Explosive origin produces nuclear particles, atoms (mostly Hydrogen) , and energy - determines amount of hydrogen & helium in universe - radiant energy still present as 5°K background radiation Millions years after explosion, matter aggregates into stars, nebulae, and galaxies , including nebular clouds that form stars and planetary systems. Our Sun is a late generation star - Later generation stellar systems are more enriched in heavy elements SECONDARY ENRICHMENT OF HEAVY ELEMENTS Heavy elements formed by thermonuclear fusion reactions in interior of stars A series of fusion reactions: H - He (main energy source) He - C at higher temps C cycle produces N & O, F, Ne, Na, Mg, P, S, and Fe Fe fusion at extreme temps Heavier elements formed by neutron capture “Waste products” of fusion are heavy elements Why is solar system enriched in heavy elements? Why is Solar System enriched in heavy elements?
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3 NUCLEAR FUSION IN STARS Iron ( 56 Fe) is the end product of ‘normal’ fusion in big stars (with some cobalt and nickel produced as well) Heavier elements formed during nova explosions NOVA Nova & supernova explosions of stars blast gas into space, spreading nuclear waste through galaxy Enrich nebular clouds with heavy elements . Heavy elements may also form in some nebulae by high energy radiation of lighter elements
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4 ACCRET IONARY ORIGIN OF SOLAR SYSTEM ORIGIN OF SOLAR SYSTEM Sun &planets form 4.56 b.y.ago Formed in nebula cloud of dust and gas - Sun is a small mass star Earth, Sun, & planets form at same time - all have similar rotation & all orbit in same plane
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5 SOLAR NEBULA THEORY 1) Nebular cloud contract to central ball with 90% mass & turbulent, rotating outer disk 2) Solids condense in nebula - heavy elements condense to refractory rocks in inner area (high temps) - lighter elements condense to ices in outer areas (low temp) - ‘snow line’ at 2.7 astronomical units (AU) 3) Sun forms: gravitational contraction heats and starts thermonuclear fusion reactions 4) Sun produces explosive blast driving light materials out of inner areas of nebula 5) Magnetic fields of Sun & nebula interact and slow Sun's rotation 6) Planets accrete from solids - Terrestrial - Jovian 7) Residual material present in outer edge of Solar System - Kuiper belt beyond Neptune with small icy planetoids like Pluto; have irregular orbits; some captured by Jovian planet as moons - Oort cloud in outermost zone contains comets; orbits easily disturbed and changed SOLAR NEBULA THEORY
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6 PLANETARY ACCRETION ACCRETION OF THE EARTH Rock: Earth formed by accretion of refractory materials - metals (Fe, Mg, Al, Ni, Ca, Na, K) much more abundant
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