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What we know about the Earth’s Interior |
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Definition
comes from the study of seismic waves that travel through the Earth |
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How Earthquakes (Seismic Waves) Reveal the Inside of the Earth |
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Definition
1. Velocity 2. Reflection and Refraction 3. Type of Wave |
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Velocity of Seismic Waves |
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Definition
velocities of seismic waves increase when traveling through denser materials. |
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Density differences may be due to: |
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Definition
1.different compositions 2.changes in pressure and temperature 3.changes in physical state (solid vs. liquid) |
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return of waves toward surface after encountering a boundary |
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the bending / change in direction of a wave when it passes from one medium into another |
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1.P-waves transmitted through solids and liquids. 2.S-waves transmitted only through solids |
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1.composed mostly of silicate rich igneous rocks. 2.Density increases with depth. |
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1.Oceanic crust 2.Continental crust 3.Moho |
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1.mostly basaltic rocks (slightly denser than continental crust) 2.thin 3.forms at mid-ocean ridges (divergent plate boundaries) |
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1.composition varies (less dense than oceanic crust) 2.thick |
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boundary between crust and mantle |
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crust and uppermost mantle |
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1.solid, composed of dense iron and magnesium silicate minerals. 2.Accounts for >82% of Earth’s volume 3.Layers of differing densities occur in the mantle as increasing pressure causes mineral structures to become more compact |
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1. Upper Mantle(100 km-660 km) 2. Lower Mantle(660km–core: 2900 km) 3. "D" Layer |
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1.Mantle lithosphere (moho–100 km) 2.Asthenosphere(100-410 km)–low velocity zone 3.Transition Zone (410-660) |
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1.bottom few hundred km 2.large horizontal variations in temperature and density 3.boundary with core is very uneven |
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composed of dense metals (mostly iron and nickel) |
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1.Liquid outer core–S waves extinguished 2.solid inner core 3.Earth’s magnetic field is generated by circulation of the outer core |
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1.heat left over from collisions during planetary accretion 2.heat due to decay of radioactive isotopes 3.heat increases with depth (geothermal gradient) |
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Conduction and Convection |
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flow of heat through a material; only manner of heat transfer between Earth layers |
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transfer of heat by circulation of material; cold sinks-hot rises |
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Where does convection occur? |
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Definition
1. in outer core (liquid) 2. in mantle (even though solid) |
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