Overview of Earth Reading Earth Science Chapter 1 pages 9 24 Review Questions 1 2 7 10 13 Hypothesis 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 Paradigm is a theory that explains wide ranging sets of observations Scales Nebular Hypothesis Formed our solar system Sun Planets Asteroids and comets Rotating cloud of dust and gases collapses into these bodies Nebular Hypothesis of Solar System Formation Nebular Hypothesis Gravitational contraction caused heating Sun formed Inner planets accreted from stony elements Outer planets got ices also Three spheres of Earth Atmosphere Hydrosphere Geosphere Internal Structure compositon Compositional Zones Crust Mantle Core Compositional Zones Crust Thinnest of the three zones Least dense of the three zones Two types distinguished by Density thickness Crust Oceanic Continental Crust Oceanic Averages 7 km thick Composed of basalt and gabbro Density is about 3 g cm3 Crust Continental Averages about 40 km thick Composed of many rock types Denstiy about 2 7 g cm3 Compositional Zones Crust Mantle Core Internal Structure compositon Mantle More than 4 5 of Earth s volume Depth of 2900 km Solid rocky shell from crust to core Density about 3 4 g cm3 Core Iron nickel alloy Density nearly 13 g cm3 Nearly 3500 km radius Internal Stucture Interior defined by physical properties Solid vs not solid Metal vs not metal Interior defined by physical properties Five zones from surface to center Lithosphere Athenosphere Lower mantle Outer core Inner core Lithosphere 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 age Asthenosphere Nearly even slightly melted due to increased temperature with depth WEAK compared to overlying lithosphere Goes to a depth of about 660 km Lithosphere Asthenosphere relationship Lower 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 brittle Core Two distinct physical properties of the core Outer core is liquid Inner core is solid Core Outer core Over 2200 km thick Movement of molten iron creates Earth s magnetic field Core Inner core is solid due to increase in pressure at center of Earth Over 1200 km radius Earth s internal structure Lithospheric Plates Crust diagram Lithosphere diagram Lithosphere types Plate Boundaries Crustal Surface Features Continent Ocean Division Continent Ocean Division 71 of surface covered with ocean 40 of surface is continental Not all of the continental surface is dry North American Continental Features Mt St Helens Be 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 another
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