CH 14.1 The Ocean Floor

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CH 14.1 The Ocean Floor

• Oceanography the study
• 71 of earth covered by oceans
• Southern Hemisphere is 81 water
• Northern Hemisphere is 61 water
• 4 major ocean basins
• Pacific largest and deepest
• Atlantic narrow
• Indian
• Arctic

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Mapping the Ocean Floor

• The topography of the ocean floor is as diverse
  as that of continents
• Bathymetry measurement of ocean depths
• HMS Challenger 1872 - 1876
• SONAR Sound Navigation and Ranging
• Satellites Surface height from oc floor
• Submersibles manned and remote

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14.2 Ocean Floor Features

• 3 major regions
• 1. Continental margins
• 2. Ocean basin floor
• 3. Mid-ocean ridges

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1 - Continental Margins

• Passive margins wide shelves, no trench,
  sediment accumulation
• Active margins narrow shelf, trenches,
  volcanoes and EQs
• Continental shelf relatively flat extension of
  continent underwater
• Continental slope sloped surface beyond the
  shelf break (submarine canyons)
• Continental rise base of cont slope (turbidity
  currents)

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2 - Ocean Basin Floor

• Between cont margin mid-ocean ridge
• Covers 30 of earth
• Deep ocean trenches (subduction)
• Mariana Trench
• Abyssal plains - Deep and flat
• Seamounts - Underwater volcanoes
• Guyots - Flat topped underwater volcanoes

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3 - Mid-ocean Ridges

• Underwater mountain ranges
• Long and wide
• Rift zone
• Transform faults
• Seafloor spreading
• Hydrothermal vents

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14.3 Seafloor Sediments

• Can be classified according to their origin
• 3 categories
• Terrigenous originates on land
• Biogenous biological in origin
• Calcareous ooze
• Silicous ooze
• Hydrogenous originates from ocean water
• Manganese nodules

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Seafloor Resources

• Oil and natural gas
• Gas hydrates
• Sand and gravel
• Manganese nodules
• Evaporative salts