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1 24 11 - Solar System Formation o The Nebular Theory The...

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Solar System Formation o The Nebular Theory The nebula condenses into an accretion disc, center of which eventually ignites and becomes the sun The ball at the center grows dense and hot Fusion reactions begin; the Sun is born Dust in the rings condenses into particles Particles coalesce to form planetesimals Soon, a small planetoid collides with Earth Debris forms a ring around the Earth The debris coalesces and forms the Moon The atmosphere develops from volcanic gases When the Earth becomes cool enough: Moisture condenses and accumulates The oceans are born Journey to the Center of the Earth o The earth is not a solid, singular unit but is made up of a series of concentric shells Some layers liquid, plastic, moveable o There is slow movement of material within the earth o Geotherm Temperature increases at a rate between 70 and 150 F per kilometer into the Earth Seismic waves released as energy (nuclear explosions, earthquakes) “How do we know about the interior of the earth” Seismic waves. Deepest hole: 12 km. o Earth’s Interior Layers Crust Continental Oceanic Mantle Upper Lower Core
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Outer – liquid; decrease in pressure; magnetic field protects from radiation Inner – solid; nickel and iron under pressure o The Core An iron-rich sphere with a radius of 3,471 km 2 components with differing seismic wave behavior Outer core o Liquid iron-nickel-sulfur o 2,255 km thick o Density – 10-12 g/cm3 Inner core o Solid iron-nickel alloy o Radius of 1,220 km o Density – 13 g/cm3 Flow in outer core generates magnetic field KNOW NUMBERS IN RELATION TO OTHER ONE (which is more dense, etc.) o Lithosphere Rigid shell of rock; ~70 km Small in comparisoin to other layers Makes up earth’s tectonic “plates” = uppermost mantle + crust Divided by “Mohorovic Discontinuity/Moho” @appros 45 km Beneath uppermost mantle; asthenosphere Plastic; moves/flows Movement causes plates to converge/diverge Lithosphere density: 2.7-3.0 g/cm3 Asthenosphere density: 3.3 g/cm3 (lithosphere floats on
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