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The Atmosphere
 layer
of gases that surrounds the planet
 makes conditions suitable for living things
You probably never think about this
but….
What is air? What is it made of?
 Air is made up of molecules
 When we breath, we not only breathe in
oxygen, but lots of other gasses, too
 Air is a mixture of gases held on Earth by
gravity.

OTHER GASES:
Water Vapor
Carbon monoxide (formula CO)
Neon (Ne)
Oxides of nitrogen
Methane (CH4)
Krypton (Kr)
Air Pressure
 Although
air molecules are invisible, they
still have weight and take up space.
 Air pressure is the force exerted on you
by the weight of air molecules JUST
LIKE when you are under water you feel
the weight of the water around you.
 The deeper you go in the ocean, the
more pressure you feed - - - the higher
you go in the atmosphere the less air
molecules and therefore lower pressure.
Air Pressure and Density
 The
amount of air molecules in a given area
determines the air’s pressure
 More molecules in a given volume = greater
density
 Less molecules in a given volume = lower
density
 The higher you are in the air, the less air
pressure
 The closer you are to the ground, the higher
the air pressure
Where do these gases come from?
The Earth’s early atmosphere contained mostly
hydrogen and helium
 These gases were lost and replaced by gases
from volcanic eruptions, like water vapor and
carbon dioxide
 Oxygen was created by photosynthetic
organisms in the ocean.
 The Ozone Layer was created from the
conversion of Oxygen molecules from intense
sunlight.

 The Ozone Layer now protects us from harmful UV
rays….ironic!
Why does air stay on the Earth?
The Structure of the Atmosphere
 The Atmosphere
extends more than
1,000 km or 621 miles
above the surface.
 There are 4 layers of
the atmosphere that are
separated by their
height above the
surface.
The Troposphere is
the lowest layer.
Extends 10 km
Contains over 75
percent of all the
atmosphere's gases
and water and dust.
The sun heats the
ground which cause
movement in the water
vapor and atmospheric
gases
.
This movement
causes weather
The warmest part of
this layer is at ground
level and then it cools
towards the upper
boundary
The Mesosphere is the next
layer above the stratosphere
xtends 50km to 80 km above the
ground.
The gases in the mesosphere
are too thin to absorb much of
the sun's heat.
The temperatures in the
mesosphere drop to -184 ºF(120 ºC)
The Stratosphere extends from
the 10-50 km level
It has much less “air” molecules
and much less water vapor.
This layer contains the ozone
layer that absorbs harmful UV
rays of the sun.
In the stratosphere higher you
get, the warmer the air gets.
The temperature ranges -76 ºF
to about 5 ºF
The Mesosphere is the next
layer above the stratosphere
xtends 50km to 80 km above the
ground.
The gases in the mesosphere
are too thin to absorb much of
the sun's heat.
The temperatures in the
mesosphere drop to -184 ºF(120 ºC)
The Thermosphere is the next
layer
The gases of the thermosphere
are very thin.
BUT since they absorb ultraviolet
light from the sun
The temperature can rise to
3,600 ºF (2,000 ºC) at the top.
Isn’t planet Earth so nice and warm!
This occurs because the sun heats the
Earth’s surface which in turn heats the
atmosphere.
 The Earth’s surface becomes a radiator!

The Surface of the Earth
Snow, ice, water, vegetation, and bare soil all
reflect different amounts of solar radiation back
to space. They also heat up at different rates.
 For example, dry land heats up rapidly and
gives most of that heat back into the
atmosphere.
 Water temperature changes slowly and stores
heat, releasing it over time.
 This uneven pattern of surface heating cause
changes in pressure and creates wind patterns
based upon air pressure.

Sea Breeze
Sea Breeze
Night Breeze (land breeze)
Water in the Atmosphere
The uneven heating of the Earth’s surface
produces currents of air that carry water
vapor up into the atmosphere and forms
clouds.
 Warm Air rises and Colder Air sinks creating
a cyclic pattern known as the water cycle.
