I. Earth’s Past Atmospheres:
1.) Earth’s current atmosphere was very different
compared to what it had in the past.
2.) Many events had to take place to get an
atmosphere like we have today.
A. Changing of earth’s first atmosphere:
1.) Volcanoes and lava covered earth which gave
off NH3, CH4, which enters earth’s first atmosphere.
2.) Earth’s surface was bombarded with Comets
and meteoroids, bringing H20 to our planet. This
water then evaporated and entered earth’s
atmosphere.
3.) The suns rays broke down the first atmosphere
into more simple substances over a long time.
4.) Earth cools down and stops giving off as much
NH3, and CH4.
B. Changing of earth’s second atmosphere:
1. The second atmosphere has N2, H2, CO2, &
H20.
2. H2 gets pushed to the outer parts of our
solar system by the solar wind after it
escapes earth’s gravitational pull.
3. Earth cools to the point that most of the
H20 can turn into liquid. This liquid begins to
cover the earth’s surface.
4. This allows for the beginnings of life.
Bacteria use CO2 and sun light to make food.
As a waste product O2 is given off and
enters the atmosphere.
5. After millions of years our current
atmosphere of N2, O2, CO2 & H2O forms.
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II. Earth’s Present Atmosphere:
A. Divisions of Earth:
1. Lithosphere - Solid portion of the earth.
2. Hydrosphere - Water portion of the earth.
3. Atmosphere - Gas portion of the earth.
B. Composition of the Earth’s Atmosphere:
1. 78 % Nitrogen
2. 21 % Oxygen
3. 1 % - 4 % Trace Elements
B. Composition of the Earth’s Atmosphere Cont.:
4.) Trace Elements- the smallest
portion of our atmosphere 1-4 %.
Many Gases.
5.) Examples of trace elements are:
H2O (Solid, Liquid or Gas), CO2, He,
O3, Methane, Dust and Salt etc..
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III Structure of the Earth’s Atmosphere:
1.) Made up of five layers.
2.) Temperature & Air Pressure changes
help scientists distinguish the difference
between each layer.
A. Troposphere:
1.) Layer closest to the ground.
2.) Nicknamed the “Weather Sphere”.
3.) Most dense layer of the atmosphere.
( 75 % of the atmosphere)
4.) As you get higher in this layer
temperature decreases.
B. Stratosphere:
1.) 2nd layer of earth’s atmosphere.
2.) The ozone layer is part of this layer.
3.) Temperature increases, as you get
higher due to the ozone absorbing UV
Radiation.
4.) The highest large passenger air crafts
will fly.
C. Mesosphere:
1.) 3rd layer of the atmosphere.
2.) Most meteors burn up by the time
they leave this layer.
3.) As you get higher in this layer
temperature decreases.
D. Thermosphere:
1.) 4th layer of the atmosphere.
2.) T.V. & Radio satellites revolve around
earth in this layer.
3.) The Ionosphere is a very important
part of the Thermosphere.
a.) Ionosphere- area inside the
thermosphere where, from the suns rays,
change gases into ions.
b.) Radio waves bounce off of these ions.
c.) Aurora Borealis occur there when
energy strike these ions, which creates
awesome light shows
E. Exosphere:
1.) Outer most layer of the earth’s
atmosphere.
2.) The space shuttle orbits earth in this
layer on most space missions.
3.) No clear boundary between this layer
and space.
4.) Sometimes considered part of the
thermosphere.
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IV. Earth’s Ozone Layer:
A. Ozone:
1. Ozone is a form of oxygen.
2. One atom of oxygen is O, one molecule
of breathing oxygen is O2, and one
molecule of ozone is O3.
B. Effects of Ozone:
1. Ozone absorbs most of the ultra violet
radiation that enters the earth.
2. Too much exposure to UV radiation can
damage most living things.
3. In mammals it WILL! cause CANCER!
4. About 800,000 to 1,000,000 Americans
develop skin cancer every year.
5. About 10,000 Americans die every year
from skin cancer.
C. Thinning of the Ozone Layer:
1. The ozone layer is thinning and in
some areas does not even exist.
2. The biggest hole is over Antarctica.
3. Chlorofluorocarbons or CFC’s are
being blamed for thinning most of the
ozone layer.
4. CFC’s are made up of 3 Chlorine
atoms, 1 Fluorine atom, and 1 Carbon
atom.
5. CFC’s are found in refrigerating
systems, aerosol cans, and Styrofoam
packaging.
D. Effect of CFC’s:
1. One chlorine atom, from a CFC molecule,
reacts with one of the oxygen atoms, from
an ozone molecule.
2. That splits up the ozone molecule into a
chlorine oxygen compound and a breathing
oxygen molecule.
3. A free oxygen atom can break the bonds
of the chlorine oxygen compound. This
forms a single chlorine atom and a
breathing oxygen molecule.
4. The chlorine atom then will attack
another ozone molecule, which will start
the process all over again.