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Earth’s Interior

Earth’s Interior. Let’s get to the heart of the Earth. By the Lunar and Planetary Institute For use in teacher workshops. Image credit: NASA. Compositional Crust Mantle Core. Physical / Mechanical Lithosphere Asthenosphere Mesosphere. Image credit: USGS. What We Know - Crust.

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Earth’s Interior

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  1. Earth’s Interior Let’s get to the heart of the Earth By the Lunar and Planetary Institute For use in teacher workshops

  2. Image credit: NASA

  3. Compositional Crust Mantle Core Physical / Mechanical Lithosphere Asthenosphere Mesosphere Image credit: USGS

  4. What We Know - Crust • Two types of crust: • Continental • 30% of crust • 40 Km thick • Oldest is 3.8 billion years (90% solar system age; missing ~700 m.y.) • Oceanic crust • 5-10 Km thick • 200 Ma oldest; 100 Ma average Image credit: USGS

  5. What We Know - Mantle • Density – between crust and core • 3.3 - 5.5 g/cm3 • Samples from volcanic eruptions, basalt composition; lab experiments Image credit: John Lahr, USGS Open-File Report 99-132

  6. What We Infer – Core • No direct samples • Probably heavy stuff • Liquid outer (molten iron), solid inner (iron, nickel) Image credit: John Lahr, USGS Open-File Report 99-132

  7. What We Infer – Core • Total density of Earth is ~5,500 km/g3 • Avg. surface density is ~3,000 km/g3 • Core must be very dense! • Why iron? Meteorites!

  8. Earth’s Interior • How do we infer the properties of the core?

  9. Seismic Waves Earthquakes generate three types of waves – P, S, & surface waves We will just concern ourselves with P & S waves Image credit: USGS

  10. Wave Types • Transverse (S) Waves – particles move perpendicular to direction of disturbance; rock is moved (sheared) Image credit: USGS

  11. Wave Types • Longitudinal (P) Waves – push-pull waves; particles move parallel to direction of disturbance; rock changes volume (compressed & dilated) Image credit: USGS

  12. Earthquake Waves • P-waves (longitudinal) travel through liquids & solids • S-waves (transverse) do NOT travel through liquids; solids only

  13. Earthquake Waves Hint at Internal Layering • P-waves(longitudinal) are able to travel through liquids (outer core) • S-waves (transverse) are NOT able to travel through liquids (outer core) Image credit: LPI

  14. Websites • Earthquake data • http://www.iris.edu/hq/ • TERC’s Exploring EarthFANTASTIC interactive lessons for students about Earth, visualizations, and more. In particular, explore how we have modeled Earth’s internal structure using seismic waves http://www.classzone.com/books/earth_science/terc/content/investigations/es0402/es0402page04.cfm?chapter_no=investigation

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