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Earth’s Structure and Composition

Earth’s Structure and Composition. What is geology? What are the characteristics of Earth’s three layers?. Geology = The study of the planet Earth’s composition & structure. How do we know about Earth’s interior if we can’t see it? Interpret seismic (earthquake) waves

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Earth’s Structure and Composition

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  1. Earth’s Structure and Composition What is geology? What are the characteristics of Earth’s three layers?

  2. Geology = The study of the planet Earth’s composition & structure How do we know about Earth’s interior if we can’t see it? • Interpret seismic (earthquake) waves • Waves travel at different speeds in different mediums and materials Seimic waves & E’s interior: http://www.classzone.com/books/earth_science/terc/content/investigations/es0402/es0402page01.cfm

  3. 2 Forces that Change Earth’s Surface A. Constructive Forces = Forces that build up mountains etc. B. Destructive Forces = Forces that slowly wear away any feature

  4. Uniformitarianism • The idea that geological process that operate today also operated in the past. • Ancient rocks formed under the same situations as current geological processes.

  5. Earth: Cross Section Major Layers 1. Core (inner and outer) 2. Mantle 3. Crust • Why does Earth have layers? Most dense material sinks to center / Light stuff “floats” on top • Temperature and pressure increase with depth. Temps: Inner core (13 000 F = surface of sun); Mantle (Range fr. 7 000 – 1 600F) - Each layer varies in physical properties: density, temp., ability to flow (viscosity)

  6. Core Mantle Crust Sulfur (4%) Nickel (11%) Iron (85%) Density: ~3 g/cm3 Density: ~5 g/cm3 Density: ~11 g/cm3

  7. The Composition of the Earth

  8. Crust Composition • Light Rock layer • Thin layer • Made of silicates(Light rocks of silicon & oxygen) Types of Crust A.Continental • Less dense rocks like granite • 8 – 40 km thick • Older B.Oceanic • Dense rocks like basalt • ~7 km thick • Younger

  9. Abundances of Elements in Earth’s Crust Silicon & Oxygen compounds = silicates ( ~ 74%) These make crust light!

  10. “Moho” =boundary b/w crust & upper mantle

  11. Mantle Convection http://www.see.leeds.ac.uk/structure/dynamicearth/convection/index.htm

  12. The Mantle Composition: Hot Heavy Rock! Made of silicates; but also a lot of iron & magnesium (heavier) • Temps: 1,600  7,000 F • Pressure increases as you descend! Not COMPLETELY solid • Middle part is “plastic”/ taffy like • Hot rock moves in CONVECTION CURRENTS

  13. 3 Divisions of the Mantle Lithosphere = Upper mantle + Crust “Plates”, Rigid Slabs Asthenosphere = Softer, moving hot rock (Convection Currents) Mesosphere = Stiffer rock near core

  14. How do we know what’s in the mantle? How do we know what it is made of? • Scientists infer based on: • Pushed up rock • Ocean floor/molten rock • Seismic waves What is it like? • Like the mineral olivine • Large amounts of iron and magnesium

  15. Core • Composition: Heavy Metals! • Iron & Nickel (How do we know? Earth’s magnetic field & seismic waves) • Pressure 3.6 million times that at surface • Temps: 6 700 C (same as surface of sun)

  16. 2 Layers of Core • Inner Core • Solid iron and nickel • High pressure keeps it solid Outer Core • Liquid iron and nickel • High temp. keeps it liquid • Responsible for Earth’s magnetic field

  17. Visualizations • Earth Science Classzone: • http://www.classzone.com/books/earth_science/terc/navigation/investigation.cfm • Visuals on plate convection: http://www.gps.caltech.edu/~gurnis/Movies/movies-more.html • Mantle Convection:http://www.youtube.com/watch?v=p0dWF_3PYh4&feature=results_main&playnext=1&list=PL8873B6173CE6E948 • Pole Reversal: • http://www.youtube.com/watch?v=x-p49IBuR1Y • Polar Shift • http://www.youtube.com/watch?v=akBvr_ZUCro&feature=related • Polar Shift 2012: • http://www.youtube.com/watch?v=23uwKo6vd0Y&feature=related • 2012 mag reversal: • http://www.youtube.com/watch?v=zOk7_6pcUns Early Earth & Plate Tectonics: http://www.youtube.com/watch?v=QDqskltCixA&feature=related Journey to the center of the Earth Part 1: http://www.youtube.com/watch?v=kibQWhiymtM Part 6: 4 min.- mineralogy & seismo. http://www.youtube.com/watch?v=XYbE5jA0plA Part 7: Seismic waves http://www.youtube.com/watch?v=ZP9R20QgDNs&feature=related

  18. Sulfur (4%) Nickel (11%) Iron (85%) Density: ~11 g/cm3 The Core

  19. Upper mantle Label Each Layer. Be able to describe each layer.

  20. Self Quiz • Compare how constructive and destructive forces affect Earth’s surface. • List the 3 layers of Earth. • Which layer has currents of moving rock? • Which is the most dense layer? • Which layer is made of light rocks like silicates? • Which is more dense: Continental or Oceanic Crust? • Which layer of the mantle is part of Earth’s plates? • Which layer is made of heavy metals?

  21. Answers to Self Quiz • Constructive forces build new land/crust and destructive forces destroy crust. • Crust, Mantle, Core • The asthenosphere – which is in the mantle • The core • The crust • Oceanic crust is denser (but thinner) • The upper mantle (and the crust make up the lithosphere, or plates) • Core

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