Intro to Oceanography
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  • 1. CHAPTER 1 EARTH’S OCEANOGRAPHIC HISTORY
  • 2. How did our Earth form? Science and modern technology provide scientists with good ideas. This study is a part of astronomy called cosmology
  • 3. Astronomy The science that deals with the material universe beyond the Earth’s atmosphere Cosmology The branch of astronomy that deals with the history, structure, and constituent dynamics of the universe
  • 4. Tarantula Nebula in Large Magellanic Cloud Cosmologists believe our solar system was originally a large cloud of gas and Dust which began to form about 4.5 billion years ago.
  • 5. Gravity and centripetal forces caused the cloud to spin and take shape as a huge disk, with our infant Sun in its center.
  • 6. Gravity The natural force of attraction exerted by a celestial body upon objects, drawing them toward the center Centripetal Moving or directed toward a center or axis, Tending to move toward a center; “centripetal force”
  • 7. Centripetal , Tending to move toward a center; “centripetal force”forces and gravity draw force heavier materials (iron) toward the center core. Centrifugal force draws lighter materials (silica) towards the outer edge. Moving or directed toward a center or axis.
  • 8. Descending iron “drops Iron core accumulation Gravity Centripetal Centrifugal forces at Rising lighter material work
  • 9. Inner Core (solid) Crust (solid) Outer core (liquid) Crust (solid) After millions of years, Earth has: ~ a hot, heavy, center core ~ a cooler, lighter, shell ~ a liquid material in between.
  • 10. Magma (molten rock) flows to the surface through large cracks or individual volcanoes emerging as lava.
  • 11. At the surface, lava expels hydrogen and other gases, water vapor, and solid materials.
  • 12. The Sun’s rays act on the released gases and distribute them about the Earth to form an atmosphere.
  • 13. Virunga Volcanoes in Central Africa As compression continued, volcanoes released the intense inner heat bringing lava and water vapor to the surface.
  • 14. Titan Titan’s Atmosphere Earth Over billions of years, radiation from the sun converted the water vapor (H²O) into an atmosphere. Lighter hydrogen (H) escaped, and oxygen (O) remained.
  • 15. Gradually, the atmosphere cooled enough to allow the water vapor to condense and return to the surface as rain and eventually snow. This continued for millions of years. The buildup of the polar icecaps has kept an almost constant amount of water in the seas
  • 16. The low areas filled with water forming a gigantic pool (the world ocean) covering about 70% of the surface of the Earth, shaped very different than today’s.
  • 17. The evaporation/condensation cycle continues today with most water vapor coming from oceans and groundwater.
  • 18. Our continually changing world: ~ polar icecaps ~ erosion ~ earthquakes ~ landslides
  • 19. Most natural geological change is too slow to be noticed, Mount St. Helens 18 May 1980 except for violent change such as massive earthquakes or volcanic eruptions.
  • 20. 62 Miles ± 1,800 Miles ± 860 Miles ± Earth is made of several shells. The lithosphere floats on the mantle’s magma (asthenosphere).
  • 21. Lithosphere The outer part of the Earth, consisting of the crust and upper mantle, approximately 62 miles thick
  • 22. Mantle The portion of the Earth, about 1,800 miles. Thick , which surrounds the molten outer core of the earth
  • 23. Asthenosphere The region below the lithosphere, variously estimated as being from fifty to several hundred miles (eighty-five to several hundred kilometers) thick, in which the rock is less rigid than that above and below but rigid enough to transmit transverse seismic waves
  • 24. The crust (upper part of the lithosphere) may be only 3 - 10 miles thick under oceans but up to 40 miles thick under mountains.
  • 25. There are six major and many lesser plates. Most volcanic eruptions and earthquakes occur on their margins. American Pacific IndoAustralian Antarctic Eurasian African
  • 26. Continental Drift Alfred Wegener As proposed by Wegener in 1912, the movement of landmasses on the Earth’s surface was known as “Continental Drift” Theory.
  • 27. Continental Drift The lateral movement of continents resulting from the motion of crustal plates
  • 28. Continental Drift Theory Pan·gae·a Hypothetical super-continent that includes all the landmasses of the Earth. Continental drift breaks Pangaea into Laurasia and Gondwanaland. 225 million years ago
  • 29. Continental Drift Theory Laur·a·sia and Gond·wa·na·land Hypothetical continents that break up later into North America-Europe-Asia and India-AustraliaAfrica-South America-Antarctica 200 million years ago
  • 30. Continental Drift Theory Laurasia and Gondwanaland breakup further, India moves northward independently. 135 million years ago
  • 31. Continental Drift Theory North and South America drift westward creating Sierras and Andes mountains. Africa creates Pyrenees, Alps, and Apennines in southern Eurasia. 65 million years ago
  • 32. Continental Drift Theory Australia is completely separated from Antarctica, while India is creating the world’s highest mountains, the Himalayas.
  • 33. Established science dismissed the theory (and Wegener) until modern oceanographic and geologic studies revived it in the 1960s. The Continental Drift theory has since evolved into the: Plate Tectonics theory as an all encompassing explanation for the Earth’s multiple geological activities.
  • 34. Plate Tectonics A theory of global tectonics in which the lithosphere is divided into a number of crustal plates, each of which moves on the plastic asthenosphere more or less independently to collide with, slide under, or move past adjacent plates
  • 35. Geological Plates Large blocks of the lithosphere that react to tectonic forces as a unit and moves as such The plates drift over the uppermost, semi-molten layer of the Earth’s mantle like giant chunks of ice, moved by the churnings in the interior.
  • 36. Plates drift over the asthenosphere. Earthquakes Plates Where plates meet, inhabitants experience geological activity along the fault lines. Volcanoes
  • 37. Seismograph An instrument for automatically detecting and recording the intensity, direction, and duration of a movement of the ground, especially of an earthquake
  • 38. The best known fault line in the U.S. is the San Andreas Fault in California, caused by the Pacific Plate moving North and the North American Plate moving South.
  • 39. The entire West Coast is an earthquake fault line. Approximately 40% of the U.S. population lives and works near the nation’s seacoasts.
  • 40. On the San Andreas Fault, in 1906, San Francisco was nearly destroyed by a large earthquake and following fire.
  • 41. In 1902, Mount Pelee near St. Pierre, Martinique, erupted killing 30,000 people within seconds.
  • 42. Tangshan, China, 1976 In the world’s largest single earthquake disaster, almost 700,000 people died.
  • 43. Tsunami Due to the depths, tsunamis can race undetected across open oceans in all directions at up to 450 miles an hour!
  • 44. When they near shore, they slow to 25 - 30 miles an hour, but build in height and momentum as the sea floor rises along coastlines. They can reach 100 feet (50 ft above and below normal sea level) as surging walls of water.
  • 45. Tsunamis build as the sea floor rises. A rapidly emptying shoreline often precedes a tsunami. Observers should move away and to higher ground immediately.
  • 46. Pacific Rim Ring of Fire Proximity to trenches and volcanoes make the Hawaiian Islands, Alaska, and western Pacific susceptible to tsunamis. Populated areas can have heavy losses.
  • 47. 26 December 2004 The world’s worst tsunami disaster By some estimates 370,000 people were killed Seaquake of 9.0 magnitude
  • 48. The volcano Krakatoa between Java and Sumatra erupted in 1883. The resultant tsunami, as high as 120 feet, killed 36,000.
  • 49. Dirty rain (ash debris) from Krakatoa orbited the Earth for many years.
  • 50. In 1896, a tsunami in Japan killed 27,000 and wrecked 7,000 fishing boats.
  • 51. In 1976, a tsunami killed 5,000 in the Philippines.
  • 52. Q.1. What is the definition of oceanography? A.1. The study of what happens on, in, and under the seas
  • 53. Q.2. What are the four reasons the study of oceanography is important to the Navy? A.2. Political, Social, Economic, Strategic
  • 54. Q.3. What is cosmology? A.3. The study of the theory of the origin and development of the universe
  • 55. Q.4. How do cosmologists believe that our solar system began? A.4. From a large cloud of gas and dust - a cosmic cloud
  • 56. Q.5. What are the structural layers of the Earth? A.5. Inner core, outer core, and mantle
  • 57. Q.6. What are the two layers of the Earth’s lithosphere? A.6. The mantle and the crust
  • 58. Q.7. What do scientists believe first made the huge land mass break up? A.7. Fault lines in the crust caused by stress and pressure from below
  • 59. Q.8. What is the name of the theory about the formation of the continents? A.8. Continental drift theory
  • 60. Q.9. What are the three phenomena that cause great disasters? A.9. Earthquakes, volcanoes, and tsunamis
  • 61. Q.10. What is a seismograph? A.10. An instrument used to Measure and record the vibrations of earthquakes
  • 62. Q.11. What is the name of the “best known” fault on the west coast of the United States? A.11. The San Andreas Fault
  • 63. Q.12. What is a tsunami? A.12. An unusually large sea wave caused by a seaquake or undersea volcanic eruption