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The Dynamic Crust

The Dynamic Crust. Regents Earth Science. Seismic Waves and Earth’s Structure. How can we tell that the outer core is liquid and the inner core is solid?. Seismic Waves and Earth’s Structure. Velocity of Seismic Waves P-waves travel fastest (~2X faster than S-waves) S-waves second fastest

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The Dynamic Crust

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  1. The Dynamic Crust Regents Earth Science

  2. Seismic Waves and Earth’s Structure How can we tell that the outer core is liquid and the inner core is solid?

  3. Seismic Waves and Earth’s Structure • Velocity of Seismic Waves • P-waves travel fastest (~2X faster than S-waves) • S-waves second fastest • Increases in denser material • The waves are refracted (bent) as they pass from a material of one density to a material of a higher or lower density.

  4. P-waves Travel through solids, liquids and gases S-waves Travel only through solids Seismic Waves and Earth’s Structure

  5. Seismic Waves and Earth’s Structure • Scientists infer the properties of Earth's interior through the analysis of seismic wave data. • By studying thousands of seismograms scientists have discovered that seismic waves refract, reflect, change velocity, and become absorbed by various parts of Earth's interior. • The following diagram shows the results of these thousands of studies.

  6. P and S Waves

  7. Seismic Waves and Earth’s Structure

  8. P and S Waves

  9. Shadow Zone • The Shadow Zone is created by the refraction of P-waves and the inability of S-waves to travel through a liquid.

  10. Inferred Properties of Earth’s Interior

  11. Inferred Properties of Earth’s Interior

  12. Earth’s Layers - Detail • Crust • Lithosphere • Moho • Asthenosphere • Mantle • Asthenosphere (plastic) • Stiffer Mantle • Outer Core • Inner Core

  13. Continental Crust Beneath continents Thicker Thickest where highest (beneath mountains) Granitic Rocks Less Dense Oceanic Crust Beneath Oceans Thinner Basaltic Rocks Denser Earth’s Crust

  14. MOHO • Mohorovic Discontinuity • Interface between lithosphere and asthenosphere • Below Moho rocks become denser due to increased pressure at depth and solid phase

  15. Asthenosphere • Plastic portion of the upper mantle • Rocks are partially molten (plastic) • Detected due to decrease in velocity of seismic waves through this zone • Widely accepted theory that magma and lava originate in the asthenosphere

  16. Inferred Properties of Earth’s Interior

  17. Inferred Properties of Earth’s Interior

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