Transcript Monday May 6, 2013


The atmosphere is a layer of gases that
surround the Earth.

These layers differ in temperature, in density, and in
the relative amounts of the different gases that are
present.
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
The two main gases in the atmosphere are nitrogen and
oxygen.
Nitrogen makes up about 70% of the atmosphere, Oxygen
about 20%, and the rest is a mixture of various other gases
such as Carbon Dioxide, Methane, Hydrogen, Neon, etc.

Layers of the
Atmosphere




troposphere
stratosphere
mesosphere
thermosphere

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Troposphere: the
lowest layer
Temperature drops as
altitude increases
The troposphere is the
densest layer
Almost all weather
occurs in the
troposphere.

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
stratosphere: between
the troposphere and
the mesosphere
temperature increases
as altitude increases;
contains the ozone
layer

The ozone layer shields
living things on Earth’s
surface from ultravioletradiation damage.


mesosphere: the
coldest layer of the
atmosphere,
temperature decreases
as altitude increases

Temperatures in the
mesosphere decrease to
about -80º C.


thermosphere: the
uppermost layer of
the atmosphere
temperature increases
as altitude increases

Temperatures average
about 980 °C (1,796 °F)
because the small amount
of oxygen absorbs intense
solar radiation.

The ionosphere: the
lower thermosphere
and upper mesosphere

When solar energy is
absorbed, charged ions
are formed.

Radio waves are
reflected in the
ionosphere.

Auroras take place in
the ionosphere.

When Earth began to
solidify, about 4.4
billion years ago,
volcanic eruptions
released a variety of
gases.
•
The gases released by
volcanoes did not
include oxygen.

Photosynthetic bacteria
contribute oxygen to the
atmosphere.

Organisms evolved
photosynthesis, a method
of capturing energy from
the sun.

Photosynthesis produces
oxygen as a waste
product.

Gradually the oxygen
content increased to what
it is today.

Animals produce
carbon dioxide
necessary for
photosynthesis.

Oxygen breathing
organisms evolved and
released carbon dioxide
as a waste product.

The oxygen-carbon
dioxide cycle maintains
a balance of
atmospheric gases on
Earth.

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Human-made chemicals can
deplete the ozone layer.

Ozone forms when the
sun’s ultraviolet rays strike
molecules of O2.

Ozone absorbs much of the
sun’s ultraviolet radiation.

Without the ozone layer,
ultraviolet radiation would
damage living cells.
Chlorofluorocarbons, CFCs,
are chemicals that destroy
the ozone layer, but are now
banned in most countries.

greenhouse effect: the
warming of the surface
and lower atmosphere
of Earth that occurs
when carbon dioxide,
water vapor, and other
gases in the air absorb
and reradiate infrared
radiation

Greenhouse gases trap
the sun’s heat and keep
Earth’s surface warm.

Too much carbon dioxide
may cause global
warming/climate change

If too much energy is
absorbed by the
atmosphere, global
temperatures will rise.

Global warming could
cause problems, such as
rising ocean levels,
because of melting polar
icecaps, and droughts.

Combustion of coal, oil,
and gas has added more
carbon dioxide to the air.