Untitled Flashcards Set

The Vast World Ocean 

• Northern Hemisphere: 61%  water, 39% land 

• Southern Hemisphere 81% water, 19% land

• Average elevation of continents above sea level is 840m ocean depth is 3800m 

• Pacific ocean is the biggest ocean, has greatest average depth, contains less marginal seas than Atlantic or Indian Ocean

• The Atlantic Ocean has the lowest depth.

Composition of Seawater 

• Seawater contains Salt + 3.5% dissolved mineral substances

• Salinity is the percentage of dissolved salts in pure water. 

• Scientists express salinity in parts-per-thousand: ‰ 

  • Example: 35‰ is 35/1000 and is the average salinity of the ocean. 

• Salts is a category, there are more elements involved: chlorine, sodium, magnesium, calcium, sulfate and potassium. 

• Most salt is sodium chloride (NaCl)

• The most common elements are common throughout the ocean. 

• Variations in salinity are a consequence of changes in the water content of the solution (Seawater) 

• Higher salinity, more evaporation in certain areas, high precipitation, lower salinity 

• Higher salinity, water is more dense = more buoyant 

• Sources of Sea Salts: Chemical weathering of rocks, earth interior (through outgassing) ((when gas is released from an area it was trapped in))

• Solubility - the ability of dissolving in a solution. 

• Hypothesis: volcanic action is largely responsible for the current oceans. 

  • Elements that are found in the Earth’s crust, are also found in the ocean in higher amounts

• Material is being disposed of as fast as it is being added (some elements are taken from seawater by plants and animals and others are forming sediment) ((chemical precipitation)), salinity of seawater is stable. 

Resources From Seawater 

• Some materials from seawater are common salt, magnesium, and bromine. 

• Different salts precipitate at different salinities (as the salinity changes, different salts are available to form through evaporation) 

• Desalination - the removal of salts and other chemicals from seawater. 

  • Generally an artificial process. 

• Freshwater is low salinity water 
  The Ocean’s Layered Structure 

  
  

  • The temperature of the water and the salinity of the water depend on the depth of the water. 

  • 3 main layers of the ocean: shallow surface mixed zone, transition zone, deep zone. 

    • Shallow surface mixed zone 

      • water temp is warmest because of the amount of sunlight it receives.

      • Waves mix the temperature of the water to relatively the same throughout. 

      • Zone thickness, 450 meters, 21-26 C and 70-80 F

      • Surface water around the equator is hotter 

      • High salinity in the water due to evaporation 

    • Transition zone 

      • Thermocline: layer with large temperature change - temperature drops rapidly. Halocline: area of rapid salinity change (decreases) 

    • Deep zone 

      • Deep zone starts 1500 meters below the surface, and goes on to the bottom of the ocean 3800 meters 

      • Temperature is below 4 C (39 F)

      • Lower salinity levels. 

  Mapping the Ocean Floor 

  
  

  • Ocean floor consists of chains of volcanoes, underwater plateaus, canyons, and rift valleys

  • Echo sound (Sonar): machine that detects how deep the ocean is based off of sound waves 

  Continental Margins 

  
  

  • Continental margins: the transition zone of the land and the deep ocean. 

    • Passive margins 

      • Not in areas where tectonic plates meet

      • Little volcanic activity 

      • Little earthquakes

      • More sediment buildup. 

      • Found in coastal areas around the Atlantic ocean

      • Different features: continental rise, continental slope, continental shelf. 

        • Continental shelf

          • barley below the water, a very small slope, comes from the shoreline. 

          • Varies in width

          • Ex. average: 80 km wide and 130 meters deep. 

          • Has natural mineral deposits, and fishing grounds for food. 

        • Continental slope

          • The “end” or the edge of the continental shelf

          • Steep structure: bigger slope

          • Narrow in width 

          • Shrinking 

          • Boundary between oceanic and continental crust

        • Continental rise 

          • Does not exist where trenches exist 

          • Comes after continental slope

          • Less steep 

          • Large in width 

          • Sediments are delivered to the bottom of the continental slope by turbidity currents: fast dense water caused by large amounts of sediments. 

          • Deep sea fan: sediment deposition pattern 

          •  Deep sea fans all combined make the continental rise

    • Active margins 

      • Subduction occurs: oceanic plate goes under continental plate

      •  Is found around the pacific ocean

      • Accretionary wedge: is the sediment that gets scraped off of the oceanic plate as it subducts under the continental plate. 

      • Sometimes there is no accumulation of sediment 

  Submarine Canyons and Turbidity Currents 

  
  

  • Submarine canyons: deep big valleys (underwater) 

  • Turbidity currents can also be created when sediment from the continental shelf and slope are dislodged. 

  • Turbidity water flows down continental slope like a snowball (collecting more sediment and eroding more of the slope on the way) 

  • Turbidity currents can change the seafloor and create submarine canyons.

  •  Turbidites: deposits of turbidity currents 

  • Graded bedding: bigger sediment on bottom, smaller sediment on top

  
  The Ocean Basin Floor 

  
  

  • Between the continental margin and the mid-ocean ridge

  • Ocean basin contains a lot of flat features: abyssal plains, seamounts, deep ocean trenches. 

    • Deep ocean trenches 

      • Long and deep 

      • Most are found in the pacific ocean

      • Volcanic activity present 

    • Abyssal plains 

      • Flat because of sediment deposits

      • The seafloor is not flat, but more sediment makes it flat. 

      • Sediment deposit happens because of turbidity currents 

      • Found in the Atlantic ocean because the Atlantic has fewer trenches. 

    • Seamounts

      • Isolated volcanic peaks 

      • Mostly found in the pacific ocean

      • Forms around volcanic hot spots or near oceanic ridges 

      • Seamounts can become islands 

      • Flat-topped seamounts are called guyots

   

  Mid-Ocean Ridges 

  
  

  • Mid ocean ridges have elevation, volcanos and faulting

  • Ridges are interconnected through all major oceans 

  • Rift valleys: rifts inside rifts  

  • Have low slopes 

  • Rift that forms between two tectonic plates when they pull apart 
    
    
    Marine Life Zones 

    
    

    • Based on where the marine organism is living, they are influenced by the amount of sunlight, salinity, distance from shore, and temperature, etc.

      • Availability of light 

        • Photic zone: upper part of the ocean which receives sunlight. 

          • Different areas receive different amounts of sunlight because of minerals, microscopic organisms, air bubbles, etc. 

        • Euphotic Zone: top layer of the photic zone (not on top) where photosynthesis takes place. 

          • The depth of this layer depends on the turbidity of the water 

          • Phytoplanktons are algae, which use photosynthesis to make food. (bottom of the food chain) 

          • Zooplankton - protozoa, crustaceans, jellyfish, larvae

          • Zooplankton eats phytoplankton 

          • Small fish eat zooplankton 

          • Apex predators: sharks and orcas

        • Aphotic zone: no sunlight 

          • Limited light is produced by bioluminescent organisms

      • Distance from shore 

        • Intertidal zone: where the land and ocean meet (between the high and low tide

          • Not many species live here

        • Neritic zone: end of the intertidal zone to the shelf break

          • Shelf break: where the sea floor transitions to continental slope

          • Lots of organisms thrive 

          • Photosynthesis occurs

        • Oceanic zone: beyond the continental shelf

          • Not as many organisms because of lack of nutrients

          • Thermal stratification: when there are distinct heat layers in the water

          • Upwelling: water with nutrients rising to surface, which cause algal blooms

      • Depth

        • Pelagic zone: open ocean 

          • Different parts contain different animals 

        • Benthic zone: any sea bottom surface 

          • Contains animals that either live in the ground or burrow in the ground 

        • Abyssal zone: subdivision of the benthic zone

          • No sunlight, higher pressure, low temperatures, low oxygen, and few nutrients. 

          • Sources of food: dead materials from higher zones

    
    Other Marine Habitats 

    
    

    • Estuaries: the area where the river meets the ocean 

      • Constant supply of nutrients and organic matter (dead stuff) 

      • Good place for organism growth. 

    • Coral reefs and atolls 

      • Coral 

        • Shell is made out of calcium carbonate

        • Can fuse structures to form a reef 

        • Very diverse and productive habitats. 

      • Atolls 

        • :Reef formed around a lagoon 

        • Forms on top of volcanic rock 

    Seafloor Sediments 

    
    

    • More sediment gets deposited by turbidity currents and settling sediment from above 

    • Generally spread out (the amount) 

    • Mud is the most common sediment 

    • Types of seafloor sediments 

      • Terrigenous: from land 

        • Rock material, weathering 

        • Everywhere on the seafloor 

        • Takes long for sediment to collect on the deep ocean floor 

        • Chemical reactions occur 

      • Biogenous: from organisms

        • Skeletons and shells of marine plants and animals 

        • Organic matter from above (sunlit waters) 

        • Calcareous oozes (type of sediment)

        • Calcareous dissolves in cold water and never reaches the bottom because there is more carbon dioxide in deep old sea water. 

      • Hydrogenous: from water 

        • Crystalized minerals from chemical reactions 

      • They are all mixed together in the ocean

      • Seafloor sediments and climate change 

        • Ocean floor sediments contain parts of organisms that used to live near the surface 

        • Climate impacts what marine organisms live near the surface 

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