Overview of EarthHypothesis vs. TheoryScalesNebular HypothesisNebular Hypothesis of Solar System Formation.Nebular HypothesisThree spheres of EarthInternal Structure--compositonCompositional ZonesCompositional ZonesCrustCrustCrustCompositional ZonesInternal Structure--compositonMantleCoreInternal StuctureInterior defined by physical propertiesInterior defined by physical propertiesLithosphereAsthenosphereLithosphere-Asthenosphere relationshipLower MantleCoreCoreCoreEarth’s internal structureLithospheric PlatesCrust diagramLithosphere diagramLithosphere typesPlate BoundariesCrustal Surface FeaturesContinent-Ocean DivisionContinent-Ocean DivisionNorth American Continental FeaturesMt. St. HelensBe sure to attend lab next week1Overview of EarthReading: Earth ScienceChapter 1, pages 9-24Review Questions 1, 2, 7, 10, 13Hypothesis vs. Theory• Hypothesis is an explanation that requires testing• Theory has been tested, and is supported by the evidence, and predicts things not used to formulate the hypothesis• Paradigmis a theory that explains wide ranging sets of observationsScales Nebular Hypothesis• Formed our solar system–Sun–Planets– Asteroids and comets• Rotating cloud of dust and gases collapses into these bodiesNebular Hypothesis of Solar System Formation.Nebular Hypothesis• Gravitational contraction caused heating• Sun formed• Inner planets accreted from stony elements• Outer planets got ices also2Three spheres of Earth• Atmosphere• Hydrosphere• Geosphere3Internal Structure--compositonCompositional Zones•Crust• Mantle•Core•Crust– Thinnest of the three zones– Least dense of the three zones– Two types distinguished by ¾Density¾thicknessCompositional ZonesCrust• Oceanic• ContinentalCrust• Oceanic– Averages 7 km thick– Composed of ‘basalt’ and ‘gabbro’– Density is about 3 g/cm34Crust• Continental– Averages about 40 km thick– Composed of many rock types– Denstiy about 2.7 g/cm3Compositional Zones•Crust• Mantle•CoreInternal Structure--compositonMantle• More than 4/5 of Earth’s volume– Depth of 2900 km• Solid rocky shell from crust to core• Density about 3.4 g/cm3Core• Iron-nickel alloy• Density nearly 13 g/cm3• Nearly 3500 km radiusInternal Stucture5Interior defined by physical properties• Solid vs. not solid• (Metal vs. not metal)Five zones from surface to center–Lithosphere–Athenosphere–Lower mantle–Outer core–Inner coreInterior defined by physical propertiesLithosphere• Brittle, solid, resonant to seismic waves• Composed of all of the crust, and uppermost part of the mantle• Between 100 and 250 km thick, depending on its ageAsthenosphere• Nearly, even slightly, melted due to increased temperature with depth• WEAK compared to overlying lithosphere• Goes to a depth of about 660 kmLithosphere-Asthenosphere relationshipLower Mantle• Increased pressure with depth at base of asthenosphere leads to more strength• From base of asthenosphere to surface of core, lower mantle is solid, but not brittle6Core• Two distinct physical properties of the core– Outer core is liquid– Inner core is solidCoreOuter core• Over 2200 km thick• Movement of molten iron creates Earth’s magnetic fieldCore• Inner core is solid, due to increase in pressure at center of Earth• Over 1200 km radiusEarth’s internal structureLithospheric Plates Crust diagram7Lithosphere diagram Lithosphere typesPlate BoundariesCrustal Surface Features Continent-Ocean Division8Continent-Ocean Division• 71% of surface covered with ocean• 40% of surface is ‘continental• Not all of the continental surface is dryNorth American Continental FeaturesMt. St. HelensBe sure to attend lab next week• Bring the lab manual• Must pass lab to pass this class• Instructors will give percent lab grade to one
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