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Chapter 2 H. Thiele Earth Science The Earth Circumference: 40,007km at poles, 40,074 at equator Rotates on its axis at a 23.5° angle 71% water on the surface 91% of water is oceans 3% of water is fresh Atmosphere 78% Nitrogen 21% Oxygen 1% Other Discovering the Earth’s Interior Determined through indirect measurement Seismic waves- vibrations that travel through the earth from explosions or earthquakes. • P-waves: Travel fast, through solids, liquids, and gases. • S-waves: Travel slower, through solids only. Zones of the Earth Crust: thin, solid, outermost layer 1% of earth’s mass Oceanic crust: more dense, 5km to 10km thick Continental crust: less dense, 32km to 70km Mantle: middle layer 66% of earth’s mass 2 parts • Lithosphere-solid layer, 65km to 100km thick • Asthenosphere- “plastic” layer 200km thick Core: innermost dense liquid layer Center of the earth composed mostly of iron 33% of earth’s mass Other Weird Earth Stuff The earth is a magnet: It acts like a bar magnet with magnetic north near the north pole Causes the aurora The earth has a strong gravitational force As the distance from the center of the earth increases weight decreases The position of the north pole changes Precession- axis moves in a circle over 26,000yrs Movement of the Earth Revolution: Earth goes around the sun 1 year 365.24 days • Perihelion- closest to the sun • Aphelion- farthest away from the sun Rotation: Earth spins on its axis 1 day 24 hours The Seasons Summer:begins with Summer Solstice Fall: begins with Autumnal Equinox June 21 or 22 Sun’s rays 90° at Tropic of Cancer 16 hrs of daylight September 22 or 23 Sun’s rays 90° at Equator 12 hrs of daylight Winter: begins with Winter Solstice Spring: begins with Vernal Equinox December 21 or 22 Sun’s rays 90° at Tropic of Capricorn 8 hrs of daylight March 21 or 22 Sun’s rays 90° at Equator 12 hrs of daylight Time Zones Standard time zones 24 zones 1 hr apart 15° apart (360/24) International Date Line Where one day changes to the next Over pacific oceans Daylight savings time Move clocks ahead in spring Move clocks back in fall Conserves energy Artificial Satellites Satellite: any object in orbit of another object with larger mass Geosynchronous orbit: remains in the same place around the equator Polar orbit: Remains in the same line north to south. Orbits Perigee: point closest of earth Apogee: point farthest away from the earth THE END
