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A View of Earth

A View of Earth. Luc Ikelle. A View of Earth (Apollo 17). Dry lands (deserts ). oceans. Wetter climate. Antarctica: Glacial ice. Ocean and atmosphere. Earth’s spheres (1). The most dynamic portion of Earth Atmosphere Thin gaseous envelope surrounding Earth Hydrosphere

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A View of Earth

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  1. A View of Earth Luc Ikelle

  2. A View of Earth (Apollo 17) Dry lands (deserts) oceans Wetter climate Antarctica: Glacial ice Ocean and atmosphere

  3. Earth’s spheres (1) The most dynamic portion of Earth • Atmosphere • Thin gaseous envelope surrounding Earth • Hydrosphere • Water dominated by the oceans • Biosphere • All living things on the planet • Lithosphere • Rocky outer shell

  4. Earth’s spheres: the atmosphere (2) Composition is unique in the solar system • Provides Air we breathe and protects from the Sun’s intense heat. • Thin (90% in 16 km) and tenuous • 78% nitrogen • 21% oxygen (not present in early atmosphere) • Minor amounts of carbon dioxide, argon and water vapor

  5. Earth’s spheres: the hydrosphere (3) (blue planet) Total mass of water on or near Earth’s surface • Covers 71% of Earth’s surface • ~98% in oceans • 2% in glaciers, groundwater, lakes and streams (fresh water)

  6. Earth’s spheres: the biosphere (4) All life on Earth • Animals & plants on land, in the sea and air (tree roots, flying insects and birds, …) • There life in ocean floor the pressure is extreme and no light penetrate. • Microorganisms - the most common form of life • Evolved within narrow zone near the Earth’s surface

  7. A view of Earth • Earth’s spheres • Earth’s interior: description • Earth’s interior: evidence • Major features of Earth’s surface

  8. Earth’s internal structure • Solid Earth has a layered structure • Layers defined by composition and physical properties • Compositional layers • crust - mantle - core • Physical layers • lithosphere - asthenosphere - mesosphere - outer core - inner core

  9. Compositional Layers Crust • Outermost compositional layer • Definite change in composition at the base of the crust • 2 types: • Continental crust (up 75 km thick in Himalaya), • Oceanic crust (~ 8 km thick)

  10. Compositional Layers Mantle • Largest layer in the earth • 2900 km thick • 82% by volume • 68% by mass • Composed of silicate rocks with abundant iron and magnesium • Density ranges from 3.2 to 5 g/cc

  11. Compositional Layers Core • Central mass about 7000 km in diameter • Average density of 10.8 g/cc • 16% by volume, 32% of mass • Indirect evidence of composition • Metallic iron

  12. Lithosphere/asthenosphere Lithosphere = crust + uppermost part of the mantle Astenosphere = part of the mantle beneath the lithosphere Continental crust Oceanic crust Lithosphere mantle Asthenosphere Lithosphere The uppermost part of the mantle is strong and solidly attached to crust).

  13. Physical layers:lithosphere • Crust + upper portion of the mantle • Solid & rigid • Thickness ranges from 10 km beneath oceans to 300 km in continental areas

  14. Physical layers:continental crust • Thick - up to 75 km • Lower density - 2.7 g/cm3 • Strongly deformed • Much older - may be billions of years old

  15. Physical layers:oceanic crust • Thinner - about 8 km • More dense - 3.0 g/cm3 • Comparatively undeformed • Much younger < 200 million years old

  16. A view of Earth • Earth’s spheres • Earth’s interior: description • Earth’s interior: evidence • Major features of Earth’s surface

  17. Waves • Elastic waves are generated whenever there is • a sudden deformation • a sudden movement of a portion of the medium

  18. Waves • Examples of man-made seismic sources • Explosion • Weight drop • Drilling • Vibroseis (tractions), ...

  19. Two types of deformations • Volumetric change (P-waves, compressional waves) • Change of shape (S-wave, shear waves) Source: Duan (2010)

  20. P-waves (compressional waves) • P-waves (i) similar to sound waves, (ii) series of contractions and relaxations, (iii) fastest, ~5 km/sec (depends on rock type), (iv) travel through solid, liquid and gas Source: Ikelle and Amundsen (2005); IPS

  21. S-waves (shear waves) • S-waves motion is (i) right angles to direction of wave, (ii) about half the speed of P waves, and (iii) travel only through solids Source: Ikelle and Amundsen (2005); IPS

  22. P-wave S-wave Source: Duan (2010)

  23. 2.5 km 1.5 km Horizontal source Source: petroleum-seismology.com

  24. Sea surface (marine/offshore)(Air/water/solid) 2.5 km 1.5 km Source: petroleum-seismology.com

  25. 2.5 km 1.5 km Free surface (land/onshore)(Air/solid/solid) Source: petroleum-seismology.com

  26. Exploring Earth’s interior with seismic waves Seismic waves travel at different speeds in different rocks

  27. Seismic waves & ground shaking • Surface waves: propagate near the Earth surface, slower than body waves • L-waves: Love, move back/forth (snake) • R-waves: Rayleigh, move like ripples on a pond Source: Duan (2010)

  28. Source: Duan (2010)

  29. Recording seismic waves: seismograms • Seismograms: records of ground shaking • Waves arrive in sequence. • P waves first • S waves second • Surface waves last (cause most of the property damage in an earthquake). Source: Duan (2010)

  30. Interior with seismic waves Discovery of Core-Mantle boundary: P-waves do not arrive in the P-wave shadow zone (103° – 143°) Source: Duan (2010)

  31. Interior with Seismic Waves (cont.) • Discovering two parts of the core: liquid outer core & solid inner core • S-waves do not arrive in the S-wave shadow zone • P-wave reflection within the core Source: Duan (2010)

  32. Source: Duan (2010)

  33. refraction Source: Duan (2010)

  34. A View of Earth • Earth’s spheres • Earth’s interior: description • Earth’s interior: evidence • Major features of Earth’s surface

  35. World map

  36. World map

  37. World map

  38. North and Central Americas

  39. Central America Caribbean sea

  40. South America

  41. Europe

  42. Africa

  43. Asia

  44. Oceania

  45. ArcticOcean Atlantic Ocean Pacific Ocean Indian Ocean All oceans and seas together = the “world ocean”

  46. Northern Hemisphere • 61% ocean Equator Southern Hemisphere • 81% ocean http://www.uwsp.edu/geO/faculty/ritter/geog101/textbook/images/maps/oceans_CIA_base.jpg • BUT, on a planetary scale, the ocean is small • 0.13% of Earth’s volume • more water within Earth’s interior than in its ocean and atmosphere

  47. Some Additional Statistics Average land elevation = 840 m Average ocean depth = 3,800 m Average ocean temperature = 3.9oC About 50% of Earth’s population lives <240 km from the ocean • In Japan, 96% of the population lives <100 km from the ocean

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