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CUNY GEOL 180 - Origins

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111Chapter 2 Chapter 2 OriginsOrigins¾¾Formation of Universe, Solar System Formation of Universe, Solar System and Earthand Earth¾¾Creation of Creation of OceansOceans22Formation of the UniverseFormation of the Universe¾¾Big Bang, 13*10Big Bang, 13*1099years agoyears ago¾¾Formation of elementary particlesFormation of elementary particles¾¾Gravitational formation of dense Gravitational formation of dense regionsregions¾¾1*101*1099yrs lateryrs laterÆÆfirst starsfirst stars33Supporting Evidence for the Big Bang•Edwin Hubble discovered spreading of galaxies. •Cosmic background radiation (the glow left over from the explosion itself) discovered in 1964. 44Origin of a GalaxyOrigin of a Galaxy¾¾Huge rotating aggregation of stars, dust, Huge rotating aggregation of stars, dust, gas and other debris held together by gas and other debris held together by gravity.gravity.55Origin of the Solar SystemOrigin of the Solar System¾¾Rotating cloud of gas from which sun and Rotating cloud of gas from which sun and planets formedplanets formed¾¾Initiated by Initiated by ““supernovasupernova””= exploding star= exploding star66Nuclear Fusion: The joining of atoms under tremendous temperatures and pressures to create atoms of a heavier element. In the Sun, four hydrogen atoms are fused to create each helium atom. Two of the hydrogen's protons become neutrons in the process277Moderate Size Stars (Our Sun): C & OLarge Stars (more, H & He): FeSupernova: Heavier Elements Formed88A nebula (a large, diffuse gas cloud of gas and dust) contracts under gravity. As it contracts, the nebula heats, flattens, and spins faster, becoming a spinning disk of dust and gas.Star will be born in center.Planets will form in disk.Warm temperatures allow only metal/rock “seeds” to condense in the inner solar system.Hydrogen and helium remain gaseous, but other materials can condense into solid “seeds” for buildingplanets.Cold temperatures allow “seeds” to contain abundant ice in outer solar system.Terrestrial planets are built from metal and rock.Solid “seeds”collide and stick together. Larger ones attract others with their gravity, growing bigger still.The seeds of gas giant planets grow large enough to attract hydrogenand helium gas, making them into giant, mostly gaseous planets; moons form in disks of dust and gas that surround the planets.Terrestrial planets remain in inner solar system.Gas giant planets remain in outer solar system.“Leftovers” from the formation process become asteroids (metal/rock) and comets (mostly ice).Not to scaleCondensation Theory99Early EarthEarly Earth¾¾Accretion (Gaining material)Accretion (Gaining material)¾¾Differentiation (Separating based on Differentiation (Separating based on density density ÆÆdensity stratificationdensity stratification))¾¾Evidence of waterEvidence of water--3.9*103.9*1099yrs agoyrs ago1010The planet grew by the aggregation of particles. The planet grew by the aggregation of particles. Meteors and asteroids bombarded the surface, Meteors and asteroids bombarded the surface, heating the new planet and adding to its growing heating the new planet and adding to its growing mass. At the time, Earth was composed of a mass. At the time, Earth was composed of a homogeneous mixture of materials.homogeneous mixture of materials.The result of density stratification: The result of density stratification: an inner and an inner and outer core, outer core, a mantle, a mantle, and the crust.and the crust.Earth lost volume because of gravitational Earth lost volume because of gravitational compression. High temperatures in the interior compression. High temperatures in the interior turned the inner Earth into a semisolid mass; turned the inner Earth into a semisolid mass; dense iron (red drops) fell toward the center to dense iron (red drops) fell toward the center to form the core, while less dense silicates move form the core, while less dense silicates move outward. Friction generated by this movement outward. Friction generated by this movement heated Earth even more.heated Earth even more.Earth, Ocean and Atmosphere accumulated in layers sorted by density1111How did water and water vapor form on early How did water and water vapor form on early Earth?Earth?¾¾The Sun stripped away EarthThe Sun stripped away Earth’’s first atmospheres first atmosphere¾¾Gases, including water vapor, released by the Gases, including water vapor, released by the process of process of outgassingoutgassing, replaced the first , replaced the first atmosphere.atmosphere.¾¾Water vapor in the atmosphere condensed into Water vapor in the atmosphere condensed into clouds.clouds.¾¾After millions of years, the clouds cooled enough for After millions of years, the clouds cooled enough for water droplets to form.water droplets to form.¾¾Hot rain fell and boiled back into the clouds.Hot rain fell and boiled back into the clouds.¾¾Eventually, the surface cooled enough for water to Eventually, the surface cooled enough for water to collect in basins.collect in basins.1212Sources of WaterSources of Water**Mantle rocksMantle rocks¾¾Evidence from meteoritesEvidence from meteorites¾¾Release through volcanic activityRelease through volcanic activity**Outer spaceOuter space¾¾Evidence from Dynamics ExplorerEvidence from Dynamics Explorer31313Fig. 2-11, p. 49100Methane, ammonia75Atmosphere unknown50NitrogenWaterConcentration of Atmospheric Gases (%)25Carbon dioxideOxygen04.54321Time (billions of years ago)The evolution of our atmosphereEarly atmosphere quite different from today’s initial rise of O22.7 b. y. ago – but conclusive evidence is from 2.3 b. y. ago1414Fossil of a bacteriaFossil of a bacteria--like organism (with like organism (with an artistan artist’’s s reconstruction) that reconstruction) that photosynthesized photosynthesized and released oxygen and released oxygen into the atmosphere. into the atmosphere. Among the oldest Among the oldest fossils ever fossils ever discovered, this discovered, this microscopic filament microscopic filament from northwestern from northwestern Australia is about Australia is about 3.5 billion years old.3.5 billion years old.Life probably originated in the ocean1515Fig. 2-15, p. 51Billions of years ago13Big bangBillions of years ago4.6Earth forms11 First galaxies form4.2Ocean formsMillions of years ago3.8Oldest dated rocks8003.6First evidence of lifeSolar


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