1. 3 Bathymetry of the Ocean Floor Bathymetry= measuring ocean depths and charting the shape or topography of the ocean floor “Sounding” lines (started in 85 B.C.) echo soundings (1920’s) ocean was not deepest in the center

2. 3 Fig. 4-2a, p. 79 Echo sounding- not always accurate

3. 3 Figure 3.1- An Echo Sounding of US East Coast

4. 3 Figure 3.2- Multibeam SONAR (Sound Navigation And Ranging)

5. 3 Figure 3.3- Side-scan SONAR (Sound Navigation and Ranging)

6. 3 With the use of satellite altimetry, sea surface levels can be measured more accurately, showing sea surface distortion. (left) Distortion of the sea surface above a seabed feature occurs when the extra gravitational attraction of the feature “pulls” water toward it from the sides, forming a mound of water over itself. Satellites Can Be Used to Map Seabed Contours

7. 3 Figure 3.5

8. 3 Figure 3.6

9. 3 Figure 3.8

10. 3 Fig. 4-5, p. 82

11. 3 Figure 3.9

12. 3 Shape of the Ocean Floor shallow extensions of the continents extended seaward underwater

13. 3 Figure 3.8

14. 3 Shape of the Ocean Floor Submerged outer edge of the continents are called continental margins Deep-sea floor beyond these is called the ocean basin

15. 3 Fig. 4-7, p. 83

16. 3 Continental Margins Passive margins – –continental margins not located on plate boundaries –Atlantic-type margins

17. 3 Continental Margins Active margins- –continental margins on the edge of convergent or transform plate boundaries –Pacific-type margins

18. 3 Fig. 4-8, p. 84

19. 3 Figure 3.7

20. 3

21. 3

22. 3 Continental Margins Continental Shelves –Shallow, submerged extension of a continent –broad, gently sloping

23. 3 Figure 3.8

24. 3 Fig. 4-9, p. 85

25. 3 Continental Margins Average width of Continental Shelf is about 70 km (43 miles) –Varies from 10s of m to 1500 km Width of Continental Shelf is determined by : proximity to a plate boundary current speed in the region sea-level

26. 3 Fig. 4-8, p. 84

27. 3

28. 3 Continental Margins Shelf break – –transition between the continental shelf and the continental slope –Occurs at about 140m (360 ft) Continental Slopes –Steeper than the shelf –Average slope= about 4 degrees (but varies from 1 to 25 degrees)

29. 3 Figure 3.8

30. 3 Continental Margins Continental rises –base of continental slope covered by a blanket of accumulated sediment –gradual slope –on Passive margins only

31. 3 Fig. 4-9, p. 85

32. 3

33. 3 Continental Margins Submarine Canyons –cut into the continental shelf and slope –formed by turbidity currents (avalanche-like sediment movements)

34. 3

35. 3 Figure 3.10a

36. 3 Submarine Canyon Off of The coast Of New Jersey

37. 3

38. 3 Figure 3.11

39. 3 Fig. 4-7, p. 83

40. 3 Figure 3.6

41. 3 Ocean Basin thick layer of sediment (up to 5 km or 3mi thick) covering basaltic rocks Make up more than ½ of the earth’s surface

42. 3 Ocean Basin Oceanic ridges –Underwater mountain chain –an active spreading center –Central rift valley –offset at regular intervals by transform faults

43. 3 Fig. 4-16a, p. 89

44. 3 Figure 3.15

45. 3 Figure 3.19

46. 3 Ocean Basin Hydrothermal vents –1977 Robert Ballard & J F Grassle –average temp is about 8-16 o C (46-61 o F) much warmer than the typical 3-4 o C (37- 39 o F) –support a unique community of organisms that depend on chemosynthetic bacteria

47. 3 Figure 3.17

48. 3 Fig. 4-19, p. 91

49. 3

50. 3 Figure 2.26

51. 3 Ocean Basin Seamounts –Volcanic peaks that do not rise above the surface of the ocean –They are tall (1 km or 0.6 mi) with steep slopes Guyots or Tablemounts –Flat-topped seamounts that were eroded by wave action Abyssal Hills –abundant, small (200m or 650 ft tall) sediment-covered extinct volcanoes

52. 3 Ocean Basin Abyssal Plains –Flat, featureless, sediment-covered ocean floor

53. 3 Figure 3.12

54. 3

55. 3 Ocean Basin Trenches –Arc-shaped depression in the deep seafloor –a converging oceanic plate is subducted

56. 3 Figure 3.13

57. 3 Figure 3.14

58. 3 Fig. 4-25, p. 96

59. 3 Ocean Basin Island Arcs –Curving chains of volcanic islands and seamounts found paralleling the edge of trenches

60. 3

61. 3 Figure 3.C