oceanography

• Oceanography


  The scientific study of oceans. An interdisciplinary science that draws the methods and knowledge of geology, chemistry, physics and biology to study all aspects of the world ocean.
• Branches of Oceanography


  • Physical oceanography
  • Chemical oceanography
  • Biological oceanography
  • Geological oceanography
• In the Northern Hemisphere (Land Hemisphere), nearly 61% is water, and about 39% is land.
• In the Southern Hemisphere (Water Hemisphere), almost 81% is water and about 19% is the land.
• Pacific Ocean


  • Largest ocean and the largest single geographic feature on the planet, accounts for more than 1/3 of all surface area on Earth
  • Deepest ocean, with an average depth of 3940 meters
• Atlantic Ocean


  • Second-largest ocean, covers 29% of all of the Earth's water surface
  • Deepest point is the Milwaukee Deep off the coast of Puerto Rico, 27,500 feet deep
• Indian Ocean


  • Slightly smaller than Atlantic but has about the same average depth
  • Largely a Southern Hemisphere water body
• Arctic Ocean


  • About 7 percent the size of the Pacific Ocean and is only more than one-quarter as deep as the rest of the oceans
• The Challenger expedition made the first comprehensive study of the global ocean


  1872-1876

  
• Mapping the Seafloor


  1. Lowering a weighted line overboard to measure water depth

  2. Using sound energy (SONAR) to measure water depths
• The Challenger expedition discovered the deepest-known point on the ocean floor in 1875, later named the Challenger Deep.
• Bathymetry


  The measurement of ocean depths and the charting of the shape (topography) of the ocean floor
• Echo sounders


  • Devices that use sound to measure water depth by transmitting a pulse of sound and measuring the time for the echo to return
• Satellites equipped with radar altimeters can measure subtle differences in the ocean surface to map the ocean floor

  
• Passive continental margin


  Geologically inactive regions located a great distance from the closest plate boundary, not associated with strong earthquakes or volcanic activities
• Passive continental margin


  • Consists of the continental shelf, continental slope, and continental rise
• Continental shelf


  A gently sloping, submerged surface that extends from the shoreline toward the deep-ocean basin, consisting mainly of continental crust capped with sedimentary rocks and sediments
• Continental slope


  A relatively steep zone that marks the boundary between continental crust and oceanic crust
• Continental rise


  A more gradual incline at the base of the continental slope, consisting of a thick accumulation of sediment that has moved down the continental slope and onto deep-ocean floor
• Submarine canyons


  Cut into the continental slope and may extend across the entire continental rise to the deep-ocean basin
• Turbidity currents


  Episodic downslope movements of dense, sediment-laden water that erode and transport sediment to the deep-ocean floor
• Active continental margin


  Located along convergent plate boundaries where oceanic lithosphere is being subducted beneath the leading edge of a continent
• Active continental margin


  • Characterized by a narrow continental shelf, a steep continental slope, and a deep ocean trench just offshore
• Accretionary wedge


  A chaotic accumulation of deformed sediment and scraps of oceanic crust scraped from the descending oceanic plate and plastered against the edge of the overriding plate
• Subduction erosion


  The process where sediment and rock are scraped off the bottom of the overriding plate and transported into the mantle by the subducting plate
• Deep-ocean basins


  • Include deep-ocean trenches, abyssal plains, seamounts, guyots, and oceanic plateaus
• Deep-ocean trenches


  Long, relatively narrow troughs that are the deepest parts of the ocean, sites of plate convergence where slabs of oceanic lithosphere subduct and plunge back into the mantle
• Abyssal plains


  Deep, incredibly flat features, likely the most level places on Earth
• Volcanic structures on the ocean floor


  • Seamounts, volcanic islands, guyots (submerged, flat-topped seamounts)
• Oceanic plate is a type of volcanic structure on the ocean floor
• Oceanic plateaus


  • Piled one atop the other
• Deep-Ocean Trenches


  • Long, relatively narrow throughs
  • Deepest parts of the ocean
  • Sites of plate convergence where slabs of oceanic lithosphere subduct and plunge back into the mantle
• Abyssal Plains


  • Deep, incredibly flat features
  • Likely the most level places on Earth
• Volcanic structures on the ocean floor

  • Isolated features that resemble volcanoes on land
  • Long, narrow chains that stretch for thousands of kilometers
  • Massive structures
• Seamounts


  Volcanic structures on the ocean floor
• Volcanic islands


  Volcanic structures on the ocean floor
• Guyots


  Submerged, flat topped seamounts formed by erosion and weathering
• Oceanic plateaus


  • Resemble lava plateaus composed of flood basalts found on the continents
  • Generated from vast outpouring of fluid basaltic lavas
• Types of seafloor sediments

  • Terrigenous
  • Biogenous
  • Hydrogenous
• Terrigenous sediments


  • Mineral grains that were weathered from continental rocks and transported to the ocean
  • Larger particles settle rapidly near shore, smaller particles take years to settle and may be carried thousands of kilometers by ocean currents