Transcript Air Pressure

Layers of the
Atmosphere
6-4.1 Compare the composition and
structure of Earth’s atmospheric layers
(including the gases and differences in
temperature and pressure within the
layers).
Essential Question

How do each of the layers of the
Earth’s atmosphere compare to each
other?
These are the layers in
order from the Earth
upwards





Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere
Create a saying to
remember them

Such as “Try sending me to the
exosphere!”
The Troposphere






Lowest layer.
Weather occurs here
and therefore clouds.
We live in it.
“Tropo” means turning
or changing conditions.
Densest layer.
Temperature is warmer
at the surface and
decreases with altitude.
Temperature/Density and
the Troposphere



Troposphere:
temperature at surface
is warmed by the earth
absorbing energy from
the sun.
Convection currents
carry the heat upward,
so the air cools as it
rises.
Density decreases
since there is less air
above.
The Stratosphere



“Strato” means layer or
spreading out
Contains the ozone
layer which absorbs
energy and causes the
temperature to rise.
The ozone layer
protects the surface
from dangerous UV
rays (ultraviolet
radiation from the
Sun).
Temperature and the
Stratosphere


Ozone, made of
oxygen, absorbs
ultraviolet radiation
from the sun, causing
the temperature to
increase.
Density still
decreases.
The Mesosphere



Drop in
temperature
marks beginning of
mesosphere
“Meso” means
middle
Most meteors burn
up here
Temperature and the
Mesosphere


This layer does
not absorb energy
from the sun, so it
starts to cool
again.
Without
greenhouse gases,
energy pretty
much passes
straight through!
The Thermosphere





“Thermo” means heat
Very hot (over 1000°C), but
since air is so thin (not very
dense) it would not feel warm at
all.
The space shuttle orbits here.
So even though it is very hot
(over 1000°C), it would feel cold
because there are so few
particles to transfer heat to
you.
It takes special instruments to
measure the temperature.
Temperature and the
Thermosphere


Solar radiation first hits
this layer, so the few
particles that are here can
gain lots of energy. They
move rapidly, so they have a
very high temperature.
But the air is so thin here
that it takes special
instruments to measure the
temperature accurately.
The Exosphere





“Exo” means outer
Extends for 1000’s
of miles
Satellites orbit
here
No definite edge
Molecules
gradually escape
out into space
Atmospheric gases



Two most
common?
Nitrogen is the
most common
Oxygen is the
second most
common

These gases are
found throughout
all the atmospheric
levels.
Atmospheric gases
Inflating example

Air inside a ball
pushes against the
sides. The more air
we put in a ball, the
more the molecules
push. So the
pressure increases
as we add air.
Air Pressure



Air pressure is the
result of the column
of air that is above
you.
There is so much air
above you that at sea
level you have 14.7
lbs/in2 pushing on you.
Gravity causes most
of the air to be pulled
down to the surface.
Why are we not crushed
by air pressure?


Air pressure is
equal in all
directions.
So air pushes
equally in all sides
of us. The forces
are balanced!
Altitude and Density


As the air pressure
decreases, the density of
the air decreases. The
air particles are not
squashed together as
tightly the higher one
goes. This is caused by
gravity!
The air at sea level and
at 6km has the same 21%
oxygen, but at 6km there
are fewer molecules, so
you take in less oxygen
with each breath.
A journey through the
Atmosphere YouTube.wmv