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Earth’s Interior

Join us in a journey to the heart of the Earth as we uncover the composition and properties of its crust, mantle, and core. Learn how seismic waves help reveal the hidden layers and understand why iron plays a crucial role. Discover the wonders of Earth's interior in this fascinating workshop.

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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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