a1_10n11_Earth_v2

a1_10n11_Earth_v2 - The Starting Point for Comparative...

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Planet Earth: Home The Starting Point for Comparative Planetology
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Some basic numbers Semi-major axis: 1.00 AU (92.8 million miles, 150 M km) Orbital Eccentricity: 0.0167 Orbital Inclination: 0.0 degrees (by definition) Orbital Period: 365.26 days Sidereal rotation period: 23h 56m 3.8s (24 hr wrt the Sun) Diameter 12,756 km (~ 7900 miles) Density: 5.5 g/cc (4.2 uncompressed) Mass (Earth = 1): 1.0 (5.9 x 10 24 kg) Obliquity: 23.45 degrees Number of satellite: 1 Surface temperature: -50 to +50 C (-60 to 120 F) Albedo (cloud tops): 0.36 Atmospheric Pressure at surface: 1013 millibars
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Earth has lots of surface water, a paper thin, oxygen-rich atmosphere, a relatively strong magnetic field, and a very active crustal plate system which generates volcanoes, earthquakes, and deep ocean trenches.
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Four Stages of Planetary Development • Differentiation: formation of a dense core and lighter outer layering • Cratering: a `brief’ period of heavy bombardment of meteorites and asteroids hitting the newly forming planet • Flooding: radioactive decay heats up the planet creating floods of lava and lava-filled basins • Surface evolution: slow processes that changes the planet’s surface features.
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All the terrestrial planets were once molten (at least partially) and maybe even molten twice. The heavier materials sank towards the interior while the lighter materials rose to the surface. Differentiation
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Earth ʼ s interior nickel-iron rich core rock mantle and crust Planet ʼ s Mass Crust 00.4% Mantle 67.1% Core 32.5%
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A cross-section of the Earth interior .
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The Earth’s interior has been deduced mostly through the study of earthquakes. Seismology
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P S We know the outer core of the Earth is liquid because shear (S) waves don ʼ t penetrate that portion of the Earth ʼ s interior. Only pressure (P) waves do. So there ʼ s a S wave shadow opposite an earthquake site.
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The Earth ʼ s increasing interior temperature with depth creates a molten outer core….which is then re-solidifed with the enormous pressures at even greater depth. Pressure Freezing Why is only the outer portion oF the core molten?
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Earth ʼ s Variable Magnetic Field At the moment it's located in northern Canada, about 600 km from the nearest town: Resolute Bay, population 300.
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Scientists have long known that the magnetic pole moves. It was pinpointed frst by James Ross in 1831 near the end oF a grueling expedition in which his ship got stuck in the ice For Four years. In 1904, Roald Amundsen located the magnetic pole again and discovered that it had moved--at least 50 km since the days oF James Ross. The pole kept going northward during the 20th century, north at an average speed oF 10 km per year, lately accelerating to 40 km per year.
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This note was uploaded on 05/05/2010 for the course ASTR 001 taught by Professor Robertfesen during the Spring '10 term at Dartmouth.

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a1_10n11_Earth_v2 - The Starting Point for Comparative...

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