An Introduction to the Oceans

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An Introduction to the Oceans
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AN OCEAN WORLD

• 71 of Earths surface
• 97 of the water on Earth
• The ocean is Earths most prominent feature
• There is only 1 ocean we have named its parts
  for our convenience
• Oceans are only temporary features of a single
  world ocean
• Average ocean depth is about 4½ times greater
  than the average height of the continents above
  sea level

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Earth is a Water Planet

• Unequal distribution of water with respect to the
  equator
• 61 of the northern hemisphere
• 80 of the southern hemisphere
• Presence of oceans is function of
• geological activity
• planet's location in relation to sun
• too far away -- water will be in a frozen state
• too close -- water will evaporate
• Earth is in a perfect location to allow water to
  be in liquid state

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Oceans

• Today's oceans are traditionally divided into 5
  large basins
• North and South Pacific
• North and South Atlantic
• Indian
• Arctic and Antarctic (Southern)
• Oceans are really interconnected
• Connected to these 5 large basins are smaller,
  marginal seas
• Mediterranean, Gulf of Mexico, South China Sea,
  Red Sea, Caribbean, Baltic Sea, Bering Sea, etc.
• Each basin or marginal sea varies in its ability
  to support life
• climatic differences
• shapes and positions of present-day continents
• Ocean basins consist of
• the deep seafloor (13,000-20,000 ft 4-6 km)
• cover most of Earth's surface (30)
• continents only cover 29

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Distribution of land and sea by latitude
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Hypsographic Curve Elevation areas above And
below sea-level
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Bathymetric Chart of the Sea Floor
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Physiographic Map of the Sea Floor
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3-D Computer Generated Image of the East Pacific
Rise
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The Origin of the Oceans

• Differentiation of the Earth
• Densest material sunk to the center of the Earth
• Core alloys of iron high temperatures high
  pressures
• Mantle less dense than the core, more dense
  than the crust
• Solid, very hot, near melting point flows like a
  very viscous liquid
• Makes up 70 of Earths Volume
• Least dense material rose to the surface
• Crust two types
• Oceanic crust higher density basaltic (low Si,
  high Fe Mg)
• Continental crust Lower density granitic (high
  Si, low Fe Mg)
• Thus, continents lie above sea level and oceanic
  crust lies below sea level because of density
  differences

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Oceans Byproduct of Differentiation

• As the earth warmed and partially melted water
  locked in the minerals as hydrogen and oxygen was
  released and carried to the surface by volcanic
  venting activity
• Trapped Volatiles
• Water (H2O)
• Nitrogen (N2)
• Carbon Dioxide (CO2) - most abundant
• Hydrochloric Acid (HCl), source of the chloride
  in sea salt (mostly NaCl).
• Volcanoes released additional volatiles
  throughout the Earth's history
• Decreased over Earth history with cooling.
• Oceans formation
• Earth was cool enough for water to condense, 4
  billion years ago

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The Hydrologic Cycle

• Water occurs as a solid, liquid and gas
• Amount of water on Earth is fixed
• The places where water resides are called
  Reservoirs
• Water constantly moves from one reservoir to
  another

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Comparison of the amount of water supply held in
each of the major reservoirs If the total earths
water supply was a 55 gallon drum
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The Origin of Sea Salts

• Volatile Chemicals released from Earths
  interior/volcanoes
• Hydrochloric Acid
• Hydrogen Sulfide
• Chemicals leached from crust by weathering
• Ocean Salinity has been constant for 1 billion
  years.
• input of salts (mainly by rivers)
• output (mainly by deposition of salt as
  sediment).
• The early ocean, 3.8 billion years ago, was
  probably similar in composition to today, except
  for changes caused by living things. The most
  important of these is the production of oxygen by
  plants.

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The Origin of Life
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