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CP Sci 9- 1st Sem.

Gen Chem - 1st Sem.

The Atmosphere in Balance


    1.    Describe the formation of Earth's atmosphere and the composition of the lower atmosphere.

    2.    Demonstrate how Earth system continually recycles gases and how certain activities disturb an atmosphere in balance.

Key Terms:


Notes: (17-1)

Early Atmosphere:

Our atmosphere is a mixture of gases in delicate balance with the Earth and the organisms that inhabit it.  Gases are maintained at certain percentages (partial pressures) so that the planet will remain hospitable to life.  The atmosphere as we know it was most likely the product of many volcanic eruptions as the Earth was forming.  Gases were released containing CO2 and other gases.  There are couple of theories to describe the formation of O2 at this point.
bulletenergy from the sun split water into H2 and O2
bulletenergy from volcanic vents provided the energy to split water into H2 and O2
bulletearly organisms started using CO2 to make energy while releasing O2 as a waste product

(www.mpm.edu/research/geology/third/ aa_pre-cambrian-02l.jpg)


Composition of the Atmosphere

Today's atmosphere must be able to support life on Earth.  There is a delicate balance that must be maintained between the major gases in order for this to be the case.  Nitrogen and oxygen dominate our environment while CO2 provides the fuel for photosynthesis and global warming.  Other elements are found as trace elements as the are in such low percentages near Earth's surface.
bulletN2 - 78%
bulletO2 - 20.9%
bulletCO2/Ar - 1%
bulletHe, H2, H2O, dust - trace elements 
Pie chart showing the composition of atmosphere

(www.saburchill.com/.../_derived/ chap0052.html_txt_00264.gif)

Although the percentages of N2 & O2 remain fairly consistent (through the recycling of resources), levels of CO2 have risen by about 16% in the last 40 years.

bulletraising CO2 levels mostly created by the burning of fossil fuels
bulletraising CO2 levels contribute to global warming
bulletraising CO2 levels increase the amount of acid rain

(www.life.umd.edu/classroom/ biol106h/L36/CO2.jpg)



Last modified: September 05, 2004