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Ocean Water Chapter 14. Composition of seawater. Seawater consists of about 3.5% (by weight) dissolved minerals Salinity Total amount of solid material dissolved in water Typically expressed in parts-per-thousand (‰) Average salinity is 35‰ Major constituent is sodium chloride .

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ocean water chapter 14
Ocean Water

Chapter 14

composition of seawater
Composition of seawater
  • Seawater consists of about 3.5% (by weight) dissolved minerals
  • Salinity
    • Total amount of solid material dissolved in water
    • Typically expressed in parts-per-thousand (‰)
    • Average salinity is 35‰
    • Major constituent is sodium chloride
composition of seawater4
Composition of seawater
  • Sources of sea salts
    • Chemical weathering of rocks
    • Outgassing – gases from volcanic eruptions
  • Processes affecting seawater salinity
    • Variations in salinity are a consequence of changes in the water content of the solution
composition of seawater6
Composition of seawater
  • Processes affecting seawater salinity
    • Surface salinity in the open ocean ranges from 33‰ to 38‰
composition of seawater7
Composition of seawater
  • Processes affecting seawater salinity
    • Processes that decrease salinity (add water)
      • Precipitation
      • Runoff from land
      • Icebergs melting
      • Sea ice melting
    • Processes that increase salinity (remove water)
      • Evaporation
      • Formation of sea ice
ocean temperature
Ocean temperature
  • Temperature variation with depth
    • Low-latitudes
      • High temperature at the surface
      • Rapid decrease in temperature with depth (thermocline)
    • High-latitudes
      • Cooler surface temperatures
      • No rapid change in temperature with depth
ocean density
Ocean density
  • Density is mass per unit volume - how heavy something is for its size
  • Determines the water’s vertical position in the ocean
    • Saltier water is more dense ~ sinks
  • Factors affecting seawater density
    • Salinity
    • Temperature - the greatest influence
ocean density13
Ocean density
  • Ocean layering
    • Layered according to density
    • Three-layered structure
      • Surface mixed zone
      • Transition zone
      • Deep zone
where does the salt come from
Where does the salt come from?
  • Chemical weathering
    • at about 2.5 billion tons per year
  • In the hydrologic cycle notice that fresh water is transported to the sea
    • carrying sediments (salts)
    • sodium transported via from overland flow.
why aren t streams rivers salty
Why aren’t streams/rivers salty?
  • Lack some of the basic salts
  • No Chlorine for example
where does cl come from
Where does Cl come from
  • Volcanic outgassing from emergent and submergent structures
    • Source of chlorine and other dissolved salts
  • Deep thermal vents confirmed in 1970s
    • with discovery of superheated vents 350C
    • mineral chimneys
where does the salt go
Where does the salt go?
  • Salinity is not increasing
  • Material must be removed at the same rate in order to maintain a steady salinity
  • Uptake by organisms to make hard parts (shells)
  • Precipitate to form sediments
origin of ocean water
Origin of Ocean Water
  • Can’t look to the hydrologic cycle.
    • Can’t have evaporation w/o precipitation
  • Matter of “educated speculation”
  • Condensed from hot vaporized cloud
    • As heavier radioactive elements sank towards the core, water was “boiled off” into a vapor cloud that eventually cooled and precipitated
  • Condensed from core materials
    • High concentration of hydrogen and oxygen in mantle. 
    • Water may form and be excreted to the surface with magma, as crystallization occurs
    • water is a by-product and accumulates over billions of years
ocean life
Ocean life
  • Marine environment is inhabited by a wide variety of organisms
  • Most organisms live within the sunlight surface waters (photosynthesis)
  • Classification of marine organisms
    • Plankton
      • Floaters
      • Algae (phytoplankton)
ocean life20
Ocean life
  • Classification of marine organisms
    • Benthos
      • Bottom dwellers
      • A great number of species exist on the shallow coastal floor
      • Most live in perpetual darkness in deep water
ocean life21
Ocean life
  • Marine life zones
    • Several factors are used to divide the ocean into distinct marine life zones
      • Availability of light
        • Photic (light) zone
          • Upper part of ocean
          • Sunlit
          • Euphotic zone is near the surface where the light is strong
ocean life22
Ocean life
  • Marine life zones
    • Several factors are used to divide the ocean into distinct marine life zones
      • Availability of light
        • Aphotic (without light) zone
          • Deep ocean
          • No sunlight
ocean life23
Ocean life
  • Marine life zones
    • Several factors are used to divide the ocean into distinct marine life zones
      • Distance from shore
        • Intertidal zone – area where land and ocean meet and overlap
        • Neritic zone – seaward from the low tide line, the continental shelf out to the shelf break
        • Oceanic zone – beyond the continental shelf
ocean life24
Ocean life
  • Marine life zones
    • Several factors are used to divide the ocean into distinct marine life zones
      • Water depth
        • Pelagic zone – open ocean of any depth
        • Benthic zone – includes any sea-bottom surface
        • Abyssal zone – a subdivision of the benthic zone
          • Deep
          • Extremely high water pressure
          • Low temperatures
ocean life25
Ocean life
  • Marine life zones
    • Several factors are used to divide the ocean into distinct marine life zones
      • Water depth
        • Abyssal zone – a subdivision of the benthic zone
          • No sunlight
          • Sparse life
          • Food sources include decaying particles from above, large fragments falling, and hydrothermal vents
marine life zones
Marine life zones

Figure 14.10