1. 3 What does the bottom of the ocean look like? OR What is the topography or bathymetry of the ocean floor?

2. 3 Fnft: The major plates of the earth's crusts Courtesy of Reto Stockli, NASA Earth Observatory

3. 3 Topography of the Ocean Floor echo soundings (1920’s) ocean was not deepest in the center deepest part of the ocean lie near its edges

4. 3 Figure 3.3- Side-scan SONAR (Sound Navigation and Ranging)

5. 3 Figure 3.2- Multibeam SONAR (Sound Navigation And Ranging)

6. 3 An echo sounder trace. A sound pulse from a ship is reflected off the seabed and returns to the ship. Transit time provides a measure of depth. For example, it takes about 2 seconds for a sound pulse to strike the bottom and return to the ship when the water depth is 1,500 meters (4,900 feet). Bottom contours are revealed as the ship sails a steady course. In this trace, the horizontal axis represents the course of the ship, and the vertical axis represents the water depth. The ship has sailed over a small submarine canyon.

7. 3 Ridges/trenches in South Atlantic Sea Floor

8. 3 Figure 3.C

9. 3 Fig nft Bathymetry can tell you where things are: Oceanic ridge system

10. 3 Figure 3.6

11. 3 BATHYMETRY – OCEAN FLOOR CONTOURS Fig 4-5, g

12. 3 Atlantic Ocean

13. 3 fnft

14. 3 Fnft: Some large-scale features of the North Atlantic seafloor Courtesy National Geophysical Data Center/NOAA

15. 3 Mid-Atlantic Ridge between Florida and western Africa  Canyon in middle of ridge

16. 3 Topography of the Ocean Floor REMEMBER: deepest part of the ocean lie near its edges

17. 3 fnft

18. 3 Topography of the Ocean Floor Submerged outer edge of the continents are called continental margins Deep-sea floor beyond these is called the ocean basin

19. 3 Fig 4-9, g

20. 3 Figure 3.8

21. 3 Florida coast

22. 3 but What goes UP must go DOWN! & There are 2 sides to every…OCEAN!

23. 3

24. 3 Figure 3.7

25. 3 Fig 4-7, g

26. 3 2 types of “margins” PASSIVE MARGIN: Continental margins that face diverging plates. These do not coincide with plate boundaries. Little or no activity. Typically associated with the Atlantic. ACTIVE MARGIN: Continental margins that face converging plates. These coincide w/plate boundaries. A lot of activity (earthquake/volcano). Typically associated with the Pacific.

27. 3 Continental Margins Passive margins – –continental margins not located on plate boundaries –Atlantic-type margins

28. 3

29. 3 Continental Margins Active margins- –continental margins on the edge of convergent or transform plate boundaries –Pacific-type margins

30. 3 Fig 4-8, g

31. 3 Continental Margin: Continental SHELF Continental BREAK Continental SLOPE Continental RISE

32. 3 Fig 4-9, g

33. 3 Continental Margins (Shelves) Width of Continental Shelf is determined by : proximity to a plate boundary (active margins have narrow shelves while passive margins have broad shelves)

34. 3 Continental Margins (Shelves) Continental Shelves –Shallow, submerged extension of a continent –broad, gently sloping –7.4% of earths Ocean area

35. 3 Fig nft

36. 3 Continental (Passive) Margins Shelf break – –transition between the continental shelf and the continental slope There are also changes from the continental slope (edge of shelf) to the continental rise (ends at edge of ocean floor).

37. 3 Continental Margins Continental Slopes –Steeper than the shelf –end at the deep ocean

38. 3 Fig 4-9, g

39. 3 Continental Margins Continental rises –at the base of continental slope –covered by a blanket of accumulated sediment –gradual slope

40. 3 Folded ridges of sediment cover the ocean floor west of Oregon

41. 3 Continental Margins Submarine Canyons –cut into the continental shelf and slope –formed by turbidity currents (avalanche-like sediment movements)

42. 3

43. 3 Submarine Canyon Off of The coast Of New Jersey

44. 3

45. 3 What comes next? Where the Continental Slope/Rise (granite rock) meets the “deep” ocean floor you get a sediment covered area (Continental Rise) that meets the “true” ocean floor (basalt rock)…what do you find there? What does it look like?

46. 3 Fig 4-9, g

47. 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

48. 3 Figure 3.15

49. 3 Ocean Basin Oceanic ridges –Underwater mountain chain –an active spreading center –offset at regular intervals by transform faults –You know this as “Sea Floor Spreading” (divergent plate boundary)

50. 3 Fig nft WHERE THE RIDGES ARE!

51. 3 Fig. 4-16a, p. 89

52. 3 Midoceanic Ridge Province consists of a continuous submarine mountain range. It covers about one third of the ocean floor. It extends for about 60,000 km around the Earth.

53. 3 Other examples of what “exists” on the Ocean Floor SeaMounts Guyots Abyssal Hills Abysall Plains Trenches Island Arcs (seen above “land”) Hydrothermal Vents

54. 3 Ocean Basin Seamounts –Inactive volcanoes that do not rise above the surface of the ocean –They are tall with steep slopes –(Made of) Basalt!

55. 3 Ocean Basin Guyots –Flat-topped seamounts that were eroded by wave action Abyssal Hills –abundant, small sediment-covered extinct volcanoes Both still BASALT!

56. 3 guyots (G) and seamounts

57. 3 Figure 2.26

58. 3 Ocean Basin Island Arcs –Curving chains of volcanic islands and seamounts found paralleling the edge of trenches –Part of an “Ocean-Ocean” Convergent Plate Boundary geographic result

59. 3

60. 3

61. 3 Ocean Basin Abyssal Plains –Flat, featureless, sediment-covered ocean floor Trenches –Arc-shaped depression in the deep seafloor –a converging oceanic plate is subducted

62. 3 Deep Ocean Province is between the continental margins and the midoceanic ridge. It includes a variety of features from mountainous to flat plains: –Abyssal plains –Abyssal hills –Seamounts –Deep sea trenches

63. 3 Figure 3.12

64. 3 Ocean Basin Trenches –Arc-shaped depression in the deep seafloor –a converging oceanic plate is subducted (either Oceanic-Oceanic or Oceanic- Continental Crust)

65. 3 Figure 3.13

66. 3

67. 3 Ocean Basin Hydrothermal vents –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 bacteria

68. 3 Approximate locations of confirmed hydrothermal vents and cold seeps

69. 3 Cross-section of a ridge axis and the plumbing connected to a vent chimney

70. 3

71. 3 A black smoker on the Galápagos Rift Zone. Courtesy of UCSB, University S. Carolina, WHOI/NOAA

72. 3

73. 3

74. 3 Red-plumed tube worms Courtesy of Monika Bright, University of Vienna, hydrothermalvent.com

75. 3 Importance of Vent Ecosystem Discovery 1.Life in extreme environments 2.Life independent of sun

76. 3 Chemosynthesis = a type of primary production Photosynthesis  uses sunlight + carbon dioxide  coverts to food Chemosynthesis  uses sulfur + carbon dioxide  converts to food Photosynthesis reaction: CO 2 + H 2 O + sunlight  CH 2 O + O 2 Chemosynthesis reaction: O 2 + CO 2 + H 2 O + H 2 S  CH 2 O + H 2 SO 4 where H 2 S is hydrogen sulfide, H 2 SO 4 is sulfuric acid, and CH 2 O is “food” or organic material

77. 3 PHOTOSYNTHESIS + CO 2 + H 2 O O 2 + [CH 2 O] CHEMOSYNTHESIS CO 2 + H 2 O + H 2 S + O 2 [CH 2 O] + H 2 SO 4

78. 3 Importance of Vent Bacteria Base of vent ecosystem -- chemosynthesis Possible origin of life on Earth Illustrate link between biology and habitat

79. 3 Coral Reefs? All of these different land/(under)water formations can yield MANY different types of coral reefs (a very diverse, valuable, marine community) too!

80. 3 Coral Reef Development Fringing reefs – develop along margin of landmass Barrier reefs – separated from landmass by lagoon Atolls – reefs continue to grow after volcanoes are submerged

81. 3 Coral Reef Development

82. 3 Fnft

83. 3

84. 3

85. 3

86. 3

87. 3 Figure 4-6c Present-Day Margin Southeast of Cape Cod Fnft – Reefs can exist FAR offshore (relics from years ago)