I. Earth

1

• I. Earths Past Atmospheres

1.) Earths 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 earths first atmosphere
1.) Volcanoes and lava covered earth which gave
off NH3, CH4, which enters earths first
atmosphere.
2.) Earths surface was bombarded with Comets
and meteoroids, bringing H20 to our planet. This
water then evaporated and entered earths
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.
2
B. Changing of earths 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 earths gravitational pull.
3. Earth cools to the point that most of the
H20 can turn into liquid. This liquid begins to
cover the earths 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.
3

• II. Earths 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 Earths Atmosphere
1. 78 Nitrogen
2. 21 Oxygen
3. 1 - 4 Trace Elements
4
B. Composition of the Earths 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..
5

• III Structure of the Earths 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.
6
B. Stratosphere
1.) 2nd layer of earths 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.
7
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.
8
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
9
E. Exosphere
1.) Outer most layer of the earths 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.
10

• IV. Earths 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.
11
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 CFCs are being blamed
for thinning most of the ozone layer.
4. CFCs are made up of 3 Chlorine atoms, 1
Fluorine atom, and 1 Carbon atom.
5. CFCs are found in refrigerating systems,
aerosol cans, and Styrofoam packaging.
12
D. Effect of CFCs
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.
13
(No Transcript)
14
(No Transcript)