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Carbon Cycle Was Already Disrupted Millions Of Years Ago

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  • Pat Neuman
    Carbon Cycle Was Already Disrupted Millions Of Years Ago by Staff Writers Amsterdam, The Netherlands (SPX) Apr 19, 2006 Dutch researcher Yvonne van Breugel
    Message 1 of 1 , Apr 19, 2006
      Carbon Cycle Was Already Disrupted Millions Of Years Ago
      by Staff Writers

      Amsterdam, The Netherlands (SPX) Apr 19, 2006
      Dutch researcher Yvonne van Breugel analysed rocks from seabeds
      millions of years old. Carbon occurs naturally in two stable forms;
      atomic mass 12 (99 percent) and atomic mass 13 (1 percent). Episodes
      in the Jurassic and Cretaceous periods were characterised by a
      relatively strong increase in 12C.

      The analyses have shown that this was caused by a sudden large-scale
      release of carbon from stocks stored in the ocean floor or peats and
      bogs.

      The atmospheric carbon dioxide concentration is increasing as a
      consequence of the large-scale use of fossil fuels in the industrial
      era. This has apparently brought about a stronger relative increase
      in the light carbon isotope 12C. Due to this the ratio of the stable
      carbon isotopes 13C/12C has show a clearly measurable decrease of
      0.1%. However in the Jurassic and Cretaceous periods, 180 and 120
      million years ago, there were periods with a shift four times as
      large in a period of just several tens of thousands of years. Where
      did all of that light carbon suddenly come from?

      Van Breugel investigated chemical fossils of marine algae and land
      plants from sediments deposited in the aforementioned periods.
      Plants and algae assimilate CO2 from the air and water. Consequently
      changes in the isotope ratio are recorded in organic material. These
      chemical fossils have been well preserved because large parts of the
      oceans in the Jurassic and Cretaceous periods contained little (if
      any) oxygen.

      In sediment cores from various widely-separated areas Van Breugel
      found a 0.4% decrease in the 13C/12C ratio. This means that there
      were large-scale changes in the carbon cycle over a short geological
      timescale of several tens of thousands of years. From the results
      Van Breugel deduced that large quantities of 12C in the form of CO2
      or methane were suddenly released into the atmosphere.

      This could have been the result of methane being released from gas
      hydrates which were buried in the ocean floor. It is not clear which
      mechanism was responsible for this. Methane could also have been
      formed under high pressure in coal seams and then subsequently
      released upon coming into contact with magma. A third option is that
      carbon from organically-rich sediment came into contact with hot
      magma. As a result of this the organic molecules combusted into CO2
      and water.

      File photo: Plant fossils preserved for millions of years.

      Yvonne van Breugel's research was funded by NWO

      http://www.terradaily.com/reports/Carbon_Cycle_Was_Already_Disrupted_
      Millions_Of_Years_Ago.html
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