Download 7.5 Composition and Structure of the Atmosphere

7.5 Composition and Structure of
the Atmosphere
What is the composition of Earth’s
Atmosphere? SC.6.E.7.9, LA.6.2.2.3
Composition of Earth’s Atmosphere
The atmosphere is the protective covering of Earth. It
keeps Earth warm and protects it from harmful sun rays.
• The composition of the mixture of gases
that we call the atmosphere is:
Nitrogen
78%
Oxygen
21%
Total of just these 2 gases =
99 %
Less than 1% Carbon Dioxide,
Argon, &other trace gases
BTW – what is the most abundant element
in our earth’s soil?
OXYGEN!!!!!!
Which circle graph shows the correct
Composition of the atmosphere—page 261
Main Gases in Air
Composition Continued
• Water Vapor: water in the form of a gas
can be found in the air.
• The amount of water vapor in the air
is different from place to place and
time to time.
• Particles: Tiny solid particles of dust,
smoke, salt, and chemicals found in the
air.
• BTW – where does most of the dust in your
house come from?
Draw arrows showing which direction air
density decreases / temperature increases.
How did you draw your arrows?
As you rise into
atmosphere,
the Density of air
DECREASES
And as you sink the
Temperature of
the air
INCREASES
4 Main Layers
• These layers are classified according
to changes in temperature.
* Thermosphere
* Mesosphere
* Stratosphere
* Troposphere
Atmosphere Video Clip
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The Troposphere!
Lowest layer
We live here
Weather occurs
About 12 km thick
(10 K = 6.2 miles – a typical race distance)
So 12 km = about 7.5 miles thick
– varies from 9 km (at the north and south poles)
– To about 16 km (at the equator)
• Shallowest, but MOST dense
• As altitude ↑ The Temperature ↓
The Stratosphere
• 2nd layer: Extends from top of Troposphere to ~50 km
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Ozone layer is here. What is Ozone?
Ozone has 3 atoms of Oxygen, not just 2
Lower Stratosphere is cold, about ⁻60˚C
Upper Stratosphere is warmer than lower
– Why?
– Middle of Stratosphere is where Ozone layer is
– it absorbs energy and warms the air.
– The Ozone layer also protects us from UV
radiation from the sun.
The Mesosphere
• Middle Layer
• 50-80 km above Earth
• Temperatures approach ⁻90˚C
• Protects us from meteoroids –
where meteors first encounter
friction from gases in atmosphere.
The Thermosphere
• Outermost layer of the atmosphere
• Above 80 km
• Temperatures up to 1800˚C
because sunlight strikes it first
• Doesn’t feel warm though,
because the molecules are far apart
• Auroras happen here
– Ionosphere—is the lower layer of the Thermosphere
– Exosphere—is the outer layer from 400 km to
thousands of kilometers