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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