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Geo101.19.First4GA

Geo101.19.First4GA - The rst 4 billion years Present...

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1 The first 4 billion years Present composition of Earth’s atmosphere… …during the first 600 million years of Earth History, what we call the Hadean Eon , the temperature of the Earth increased with the accumulation of planetesimals, molten iron began to sink to the center of the core, leaving behind the shell of rock we call the mantle…we refer to this as the iron catastrophe …the Hadean grew so hot that a magma ocean consisting of ultramafic melt rock (rich in Mg and Fe) rose from the mantle and flooded the surface of the Earth The Hadean might have appeared like… …a magma ocean with small crusts of solid basalt, with no permanent crust, no permanent oceans Outgassing of the mantle …the atmosphere during the Hadean was unbreathable, high NH 3 (ammonia) and in N 2 (nitrogen), CH 4 (methane), CO 2 (carbon dioxide), SO 2 (sulfur dioxide) and water vapors
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2 As Earth’s differentiates, the upper part of the Earth outgasses…and an atmosphere develops … a N 2 - CO 2 -sulfur rich atmosphere develops from gases released from volcanic eruptions. Earth’s early atmosphere was unbreathable, high NH 3 (ammonia) and in N 2 (nitrogen), CH 4 (methane), CO 2 (carbon dioxide), SO 2 (sulfur dioxide) and water vapors … The early atmosphere and water intereact and the atmosphere begins to evolve…. More to come one this… As the surface of the Earth begins to cool, water vapors condense and water begin to accumulate. Has Earth’s Atmosphere evolved over the past 4.5 Ga? A closer look… Composition of dry atmosphere, by volume ppmv: parts per million by volume Gas Volume N2 780,840 ppmv (78.084%) O2 209,460 ppmv (20.946%) Ar 9,340 ppmv (0.9340%) CO2 383 ppmv (0.0383%) Ne 18.18 ppmv (0.001818%) He 5.24 ppmv (0.000524%) CH4 1.745 ppmv (0.0001745%) Kr 1.14 ppmv (0.000114%) H2 0.55 ppmv (0.000055%) Not included in above dry atmosphere: H2O vapour ~0.25% over full atmosphere, typically 1% to 4% near surface Has Earth’s Atmosphere evolved over the past 4.5 Ga? 1) The original atmosphere was primarily helium and hydrogen . Heat from the still-molten crust , and the sun, plus a probably enhanced solar wind , dissipated this atmosphere. What about the Moon formation?
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3 Earth’s magnetosphere The Solar System is a dangerous place to live… Large amounts of radiation (cosmic rays, solar wind) are present in interplanetary space… On Earth, we are protected from these harmful cosmic rays by our atmosphere and magnetosphere. Earth’s magnetic field forces these cosmic rays to deflect away from Earth. Formation of Earth’s moon Soon after the Earth forms, a small planet collides with it, blasting debris that forms a ring around the Earth. The Moon forms from the ring of debris. Comparing ages of the oldest Meteorites (maximum age) at 4.55 (Canyon Diablo Meteorite) with those of the Moon (minimum age) at 4.53 Ga. The Moon is considered to have formed shortly after the formation of the Earth and other planets, but because of the deficiency in Fe, after the formation of the Core the most likely occurred within 30 to 50 myr!
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