PowerPoint Presentation

							(Pflueger )
  Today’s Objectives
Students will be able to:
1. Discuss how we have arrived
  at the current atmosphere
  from the original atmosphere.

2. Compare and Contrast the
  (3) major atmospheres and
  their compositions.
Origin of the Atmosphere
• Has our our atmosphere always
  been like it is today?
  The correct answer is NO!

…and here is some evidence
why scientist think this.
  4.6 Billion Years Ago
• The earliest atmosphere is
  believed to have been mainly…
    Hydrogen and Helium
 • These were the 2 most
   abundant gases found in the
   early universe.
• Methane and Ammonia were
  also found at high levels.
     Where did it go?
• It’s believed that this early
atmosphere escaped into space.
   Why might this be the case?
1.Early Earth gravity too weak.
2.Earth without differentiated core,
  thus no magnetic field to deflect
  solar winds.
3.Heat of Earth and solar system.
   As Things Got Older
• Eventually a second, more
  dense, atmosphere formed.
• Gradually surrounded the
  Earth as gases escaped into
  the atmosphere from
  volcanoes and steam vents.
  *This is assuming that volcanoes spewed
  out the same gases as they do today.*
 Atmosphere Part II
Gases used from volcanism
• 80% water vapor (H2O)
• 10% carbon dioxide (CO2)
• 4-6 % nitrogen (N2)

This continued on for millions of years!
       Making of a Wet Day
                 • Millions of
                   years of
                   constant
                   “outgassing”
                   provides a rich
                   supply of
                   water vapor.
                 • During Achaean
(DOMC - Haifi)
What Happened to the CO2
•   Large amounts of CO2 were
    dissolved into the oceans.
•   Through chemical and early
    biological processes, the
    CO2 became locked up in
    carbonate sedimentary
    rocks, such as Limestone.
  How Did We Get N2?
1.Much of the water vapor
 condensed, either as clouds,
 rain, or ground water.
2.The concentration of CO2
 was quickly dwindling.
3.Nitrogen gradually built up.
 This is due to it being chemically inactive.
   Then O2 Made it Big
• Believed oxygen concentrated
  extremely slowly as:
1. Photochemical Dissociation:
 splitting of H2O by UV-rays.
*The lighter hydrogen probably rose and
           escaped into space.*

• If O2 levels 1-2% of current,
  would be enough to form O3
    Now We Have Life
2. Enoughoxygen accumulated
 for primitive plants to evolve,
 around 2-3 billion years ago.
• With an increase in plant life,
  using photosynthesis, the
  atmosphere was greatly
  enriched with oxygen.
Evidence of an Early Atmosphere
1. Precipitation of limestone
  in great quantities.
2. The oxidation of iron to
  form banded deposits in early
  rocks.
3. The distribution of various
  minerals in most early
  sedimentary rocks.
Evidence of an Early Atmosphere

                                    Limestone
                         (Stone Museum)




Banded-iron
        (Stone Museum)
  Composition Today
• After 2-3 Billion years, the
composition is much different
today.
• There is more oxygen (that is a
good thing) and a lot less carbon
dioxide (also a good thing)
Lets compare today with yester-year.
Composition Comparison
 Today       Yester-Year
78 %           Nitrogen       4-6%
21%             Oxygen        < 1%
0.9%             Argon        0-1%
0.033%       Carbon dioxide   10%
0-4%          Water Vapor     80%
0-.000007%       Ozone         0%
< 1%          Other gases     3-4%
Assignment For Thursday




         (Stimac)
Works Cited
Department of Maritime Civilizations - University of Haifa. “Earth Origins and
   Formation.” 10 Apr 2006.
   <http://maritime.haifa.ac.il/departm/lessons/ocean/lect03.htm>.

Pflueger, Nathan. “The Origins of the Atmosphere.” 14 Oct 2003. 11 Apr 2006.
    <http://eugevir.tripod.com/origins/atmosphere.html>.

Stimac, John. “The Atmosphere – origin and structure.” 11 Apr 2006.
   <http://www.ux1.eiu.edu/~cfjps/1400/atmos_origin.html>.

Stone Museum. “Types of Rock.” 10 Apr 2006. <http://www.geol.sci.hiroshima-
   u.ac.jp/~geotect/stonemuseum/Classification-j.html>.