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The Earth: Understanding Our Terrestrial World

Learn about Earth's composition, structure, and tides. Understand earthquakes, weather, and climate. Discover how measurement methods and laws help calculate Earth's mass and density.

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The Earth: Understanding Our Terrestrial World

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  1. The Terrestrial PlanetsI The Earth

  2. Topics • Introduction • Earth • Density and Mass • Structure • Crust • Tides • Atmosphere

  3. Introduction • Terrestrial Planets • Small, rocky worlds • Mercury • Venus • Earth • Mars • Comparative Planetology • Helps us understand • Weather • Earthquakes • Climate

  4. Venus Earth

  5. Basic Facts about Earth • Radius • About 6400 km • Shape   • Oblate spheroid • Polar radius 21 km shorter • Composition • Mostly made of materials denser than rock. • The average density is 5,520 kg/m3.

  6. Density = Mass / Volume • Mass of Earth • M = 6 x 1024 kg • Radius of Earth • R = 6.4 x 106 m • Volume of Earth • V = 4 p R 3 / 3 • V = 1.1 x 1021 m3

  7. Measuring the Earth’s Mass • In order to compute the Earth’s density we need • The Earth’s radius • The Earth’s mass • To measure the mass we need to consider • Newton’s laws of motion • Newton’s law of gravity

  8. Newton’s 2nd Law and the Law of Gravity m1 Newton’s 2nd Law Acceleration is Force divided by Mass (kg) R m2 Newton’s Law of Gravity

  9. Recap of Basic Units • Acceleration • meters per second per second: m / s2 • Mass • Kilograms: kg • Force = Mass x Acceleration • kg x m / s2 = Newton (N) • Gravitational Constant (G) • Gravity Force = G x mass x mass / distance2 • G has units: N x m2 / kg2

  10. All Objects Fall with Same Acceleration m R M (Earth mass)

  11. Measuring the Earth’s Mass – II • Radius of Earth is measured to be • R = 6.4 x 106 m • Newton’s constant is measured to be • G = 6.7 x 10-11Nm2/kg2 • The acceleration due to gravity at Earth’s surface is measured to be • a = 9.8 m/s2 Re-arrange to get M = 6 x 1024 kg

  12. Structure of Earth • Crust • Solid, thickness: 35-60km; silicates (Oxygen and Silicon compounds). • Mantle • Plastic, thickness: 2800 km; silicates (Oxygen, Silicon, Iron). • Outer Core • Liquid, thickness: 2400 km; metallic (Iron and Nickel) • Inner Core • Solid, thickness: 1200 km; metallic (Iron and Nickel). The density is about 14 g/cm3. Temperature 5000 K.

  13. Structure of Earth – II

  14. Structure of Earth – III • How have we determined the Earth’s structure? • By using seismology: The study of planetary vibrations; that is, studying the way seismic waves travel through the Earth's interior.  • P waves • Compression waves (like sound waves) – the waves oscillate along the direction of motion of the wave. These waves can travel through solids and liquids. • S waves • Transverse waves (like water waves) – the waves oscillate at right angles to the direction of motion. These waves can travel only through solids.

  15. Earth’s Fractured Crust

  16. Continental Drift • Plate Tectonics • In 1924, Albert Wegener proposed that the Earth’s plates are mobile. • Plates • Can collide and form folded mountains • Can sink beneath others • Can split apart and create rift valleys

  17. AST0616.jpg

  18. Fault Lines California Europa

  19. Tides • Gravitational Tides • Caused by the gravitational interaction between the Moon, Sun and the Earth Moon B C A

  20. How Much Sunlight per Second? • In direct sunlight, Earth receives about 1.3KW(1300 Watts) of power from the Sun. • 1 Watt = 1 Joule (of energy) per second • The cross-sectional area of Earth is given by pR2where R is the radius of Earth. • Total wattage = (Watts/unit area) x Area

  21. And the Answer Is… Total = (Watts / unit area) x Area =1300(W/m2) xp R2(m2) =1300(W/m2) x3.14x (6.4 x 106m)2 =1300 x 3.14 x 6.42 x 106x2W =1.67 x 1017W 167 Peta Watts (1015 W)

  22. ..That is.. • A hydrogen bomb releases about 4 x 1015 Joules • Energy received on Earth every second is equivalent to that released by the detonation of about 1.67 x 1017 J/s/ 4 x 1015 J40 H-bombs / s !

  23. The Coriolis Effect • Gustave Gaspard Coriolis (1792-1843) • First to study in detail the effect of planetary rotation on the movement of objects. • The Coriolis effect influences the movement of the atmosphere on rotating planets. 835 km/h 1,674 km/h

  24. Blue Skies and Beautiful Sunsets • Blue Skies • Nitrogen scatters blue light in all directions across the sky, but leaves the redder light largely unaffected • Beautiful Sunsets • When the Sun is low in the sky, and less bright, we see the residual red light that comes straight at us.

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