Composition and Internal Structure of the Earth

Composition and Internal Structure of the Earth -...

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Composition and Internal Structure of the Earth How old is the Earth? o 4.5 billion years How do we know what the Earth’s deep structure is? (Seismic waves) o Through a seismograph that measures s and P waves known as P Compressional East to west and S as Shear waves up and down North and south. It illuminates the interior and can be recorded on seismometers. This allows scientists to take pictures of earths inner workings. Composition of the bulk Earth (Iron/Oxygen/Silicon/Magnesium & %) o (Iron35/Oxygen30Silicon15/Magnesium13 & %) ;If he asks for Mantle is Oxygen 44% Magnesium 22.8% Silicon 21% Aluminum 2.4% ;Iron 6.3% Calcium 2.5% ;If he asks for Crust is Oxygen 46% Silicon 28% Aluminum 8% Iron 6% Magnesium4% ;Calcium 2.4% Other 5.6% Layering based upon compositional differences: Core — Mantle — Crust compositions? thicknesses? different crystal types (oceanic/continental) o Crust :composed of low density silicates; outer 10-70 KM, lighter elements, more Na, K, Ca Silicates o Mantle : 70-2900 Km, intermediate density elements, Fe, Mg, Silicates o Core : 2900-6370 Km, highest density elements, pure Fe, Ni, outer liquid core, inner solid core Layering based upon strength differences: Asthenosphere — Lithosphere; why is one stronger? o Lithosphere: includes the crust and the top part of the mantle down to an average depth of about 100 Km. when subjected to force it acts as a rigid and brittle shell o Asthenosphere: flows a moldable or ductile solid, very hot and weak How does the strength layering correspond to the compositional layering? ( were assuming, don’t take verbatim) o The crust floats on the mantle (viscosity); it has to do with the density of the elements and how the core is pure iron and nickel, mantle has more iron but not so dense so its on the outside and crust is least dense so it is on the outer layer Plate Tectonics what were the lines of evidence that suggested movement of the continents (i.e. continental drift)? o Continental Drift In 1915, the German geologist and meteorologist Alfred Wegener first proposed the theory of continental drift which states that parts of the Earth's crust slowly drift atop a liquid core. The fossil record supports and gives credence to the theories of continental drift and plate tectonics.
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