GEOLOGY1 - Chapter 1 • History of Universe: Earth—only...

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Chapter 1 History of Universe: Earth—only planet w/ liquid water on surface Started w/ Big Bang 15 billion yrs ago Composition today: 75% H, 23% He, 2% other Expansion: galaxies are separating Nebulae collapsed due to gravity Temperature raises… fusion 2H-He…star ignites Other elements made in core of stars by fusion Big stars end in a supernova explosion Our galaxy is the Milky Way Our sun: middle-sized, middle-aged star… 5 billion years ago Hydrogen (H) = 1 proton, 1 neutron Helium (He)= 2 protons, 2 neutrons o Solar System: Terrestrial Planets —inner planets (including Earth), heavy, rocky, few moons Jovian Planets —farther from sun, gaseous, large, low density, many moons Planetesimal accretion (terrestrial planets) Differentiated= divided into chemical layers In molten stage, heavier elements sink to form core (Fe, Ni), Silicates (Mg, Fe) form the mantle, and the crust is formed by the lightest Out-gassing of atmosphere => precipitation => formation of oceans (also, comets) To “accrete”: to add material to make a bigger body o Life on Earth Oxygen was added to atmosphere only after life started photosynthesis (began w/ cyanobacteria…single cells w/ no nucleus) Life evolved around hydrothermal vents in the oceans Hard parts appeared became frequent 400 m.y.a. forest develops 350 m.ya. amphibians appear—problem: had to reproduce near water 250 m.y.a. reptiles were successful land conquerors Asteroid impact produces collapse of food chain, dust, fires, etc. Dinosaurs went extinct, but mammals prospered 3-4 m.y.a first hominids (ancestors of humans) in Rift Valley Oldest homo sapiens 35,00 (Europe) – 150,000 (Africa) yrs ago.
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Chapter 2 Scientific method: o Hypothesis—tentative explanation to be tested o Theory—highest rank of scientific knowledge, widely accepted explanation for observed phenomena Population: o Natural systems are in equilibrium… large disruptions may permanently change things o Earth’s carrying capacity—the number of individuals the earth can sustain in moderate health and comfort o Depletion of nat. resources… deforestation, starvation, social unrest… use alternative resources? Save energy? Plant trees? o Exponential pop. Growth rate o Doubling time ( 70/ growth rate % ) 117 yrs N. America Earth Materials: o Elements—cannot be changed into other by normal chem. means o Atom—minimum unit an element can be divided into, but still retain chemical properties o Isotopes—same element, different number of neutrons o Ions are charged atoms… Cation—lost e (+), Anion—gained e (-) o Octet rule: an atom tries to achieve a stable configuration w/ its outermost electron shell
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This note was uploaded on 04/01/2008 for the course GEOL 1121 taught by Professor Wyld during the Spring '07 term at UGA.

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GEOLOGY1 - Chapter 1 • History of Universe: Earth—only...

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