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Earth’s Formation and Structure

Earth’s Formation and Structure. How Did Earth Form?. Evidence comes from Earth, other bodies in the solar system, and the universe. Earth's surface and internal structure and composition. Rock samples from the Moon. Asteroids. Planetary probes and rovers. Telescope observations.

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Earth’s Formation and Structure

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  1. Earth’s Formation and Structure

  2. How Did Earth Form? • Evidence comes from Earth, other bodies in the solar system, and the universe. • Earth's surface and internal structure and composition. • Rock samples from the Moon. • Asteroids. • Planetary probes and rovers. • Telescope observations.

  3. Pluto has been demoted Structure of Our Solar System • Differentiation – separation based on mass or composition. Rocky Planets Gaseous Planets

  4. Structure of Our Solar System • Why is the solar system differentiated? Fig 9.2 Fig 9.2 Outer planets – large, mostly gas with solid core Inner planets – small, solid, dense minerals

  5. Formation of the Solar System • Contracting dust/gas cloud flattens and begins rotating. • Gravity draws dust into larger bodies. • Most of the mass is drawn to the center, heats up, protosun begins to burn. Fig 9.3

  6. Formation of the Solar System • Solar wind blows gas/dust away from the protosun. • Heavier elements condense closer to sun, lighter elements further from sun. Fig 9.3

  7. Formation of the Solar System • Rocky planets – dense elements condense at higher temperatures closer to sun. Fig 9.5

  8. Formation of the Solar System • Gas giants – lighter elements condense at lower temperatures further from the sun. Fig 9.5

  9. Differentiation of Earth • Earth is divided into layers based on density. • Solid Layers • Core (iron-nickel) • Mantle (pyroxene, olivine) • Crust (feldspars) • Liquid/gas Layers • Hydrosphere (water) • Atmosphere (gases) Fig 1.3

  10. Differentiation of Earth • Early Earth was mostly molten ("liquid rock"). • More dense material pulled by gravity to the center of Earth. • Less dense feldspars formed solid crust. Fig 9.8

  11. Origin of Earth's Water • Earth is unique in the solar system because it has lots of water. • Old hypothesis – water from comets late in Earth's formation. • New hypothesis – Earth formed "wet" (hydrated minerals in meteorites),and water later erupted from volcanoes.

  12. Origin of Earth's Water • Evidence: • Isotopic ratio of hydrogen (2H/1H) of Earth's water more like meteorites than comets. Fig 9.14

  13. Origin of Earth's Atmosphere • Was the atmosphere also released from volcanic eruptions? Fig 9.16 Then why are volcanic gases so different than the atmosphere?

  14. Origin of Earth's Atmosphere • Early atmosphere was probably more like volcanic gases. • Changes due to: • CO2 is stored in limestone, which is made of the mineral calcite (CaCO3). • O2 produced photosynthetic plants (first appeared 2.3 billion years ago). • Biology and geology are intimately linked.

  15. Origin of Earth's Atmosphere • Why does nitrogen (N2) make up 77.5% of the atmosphere, but only 0.0011% of volcanic gases? • Hint: N2 is not very reactive. Fig 9.16

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