Know lot of knowledge about our Atmosphere.

1. Chapter 17

2. Earth’s Early Atmosphere
Atmosphere is the blanket of
gases that envelops the living
planet to sustain life.
Early atmosphere was similar
to the atmosphere of the
Titan.
Factors of changes:
 Sun’s Activities
 Presence of Active volcanoes

3. Evolution of the Early atmosphere
Four stages: The origin, Chemical or the pre-biological era,
the microbial era, and the biological era.
The Biological Era- The formation of Atmospheric
Oxygen
Three important consequences:
1. Due to Eukaryotic Metabolism. Possible if the level of
oxygen is reached about 0.2%. This was possible because
of the earlier photosynthesis carried out by the latter.
2. Accumulation of oxygen in the Stratosphere. It
happens when oxygen is acted upon by the radiation
emanating from the sun to form ozone.

4. 3. Oxygen available in the atmosphere. Oxygen
produced by plants with the process known as
photosynthesis.
6CO2 + 6H2O C6H12O6 + 6O2

5. Modern Atmosphere
Composition:
1. Heterosphere. Extends from 50 miles to 300 miles
where gases are not evenly mixed. (Hydrogen and
Helium on top, and Oxygen and Nitrogen at the
bottom.
2. Homosphere. 0-50 miles evenly blended except
ozonosphere at 70°F.

6. Temperature and Layers
(From topmost to bottom):
1. Thermosphere. Very high
temperature about 2200°F.
Hottest layer and is located
before the exosphere or te
outer space.
2. Mesosphere. 130°F due to
freezing ice of cosmic dust
and is therefore considered
as the coldest layer.
3. Stratosphere. -70°F where
ozone layer is located.
4. Troposphere. 70°F where
life and weather reside.

7. Problems in the Atmosphere:
1. Air Pollution. The presence of
contaminants (suspended
particulate matter, soot, etc.) in
air thereby affecting the overall
air quality. Sources: industries,
powerful machines, cars, and
other human activities that
would all release Sulfur and
Nitrogen Oxides.
2. Primary Air Pollutants.
* sulfur dioxide (SO2)
* nitrogen oxide (NO) and
nitrogen dioxide (NO2)
*carbon mnoxide (CO)
* volatile organic compounds
(VOCs)

8. Ozone Layer Depletion
Ozone layer is found in the
stratosphere which is
composed of three atoms of
oxygen.
Depletion happens when
chlorine atom disintegrates
from chemical compounds
that have it, Example is the
chlorofluorocarbons (CFCs)
from various products.