Download Earth`s Atmosphere

Earth’s Atmosphere
Atmosphere
The atmosphere is a
thin layer of gases
that surround the
Earth.
The atmosphere
protects the Earth by
balancing the
amount of heat
absorbed from the
Sun and the amount
of heat that escapes
back into space.
The Past Atmosphere
Earth’s early atmosphere was
created from volcanic
gasses.
It is theorized
that 4 billion
years ago
the Earth’s
atmosphere
contained
two deadly
gases:
methane and
ammonia.
How did the atmosphere
change?
Methane is made up carbon and hydrogen.
Ammonia, is composed of nitrogen and
hydrogen.
Sunlight caused chemical reaction among
the methane, ammonia and water in the air.
New materials, nitrogen, hydrogen and
carbon dioxide, were formed as the
methane and ammonia broke down.
Ancient Atmosphere
The water vapor
remained.
Hydrogen, a
lightweight gas,
escaped into space.
Nitrogen, carbon
dioxide and water
vapor were left.
Oxygen
Sunlight then broke
down the water vapor
in the upper
atmosphere into
hydrogen and oxygen.
The hydrogen again
escaped.
Other oxygen was
generated by
stromatolites
Ozone Layer
The oxygen in the upper
bonded, in sets of three, to
form a gas known as ozone.
A layer of ozone gas formed
about 30 km above the
Earth’s surface.
The ozone layer absorbs
harmful ultraviolet radiation
from space.
Ozone Layer
Most of the ozone in the
atmosphere is found
between 16 km and 60
km about the surface of
the Earth. Most are
between 35 and 60 km.
Ozone molecules absorb
much of the het and uv
rays from the sun..
Ozone shields the Earth
from ultraviolet radiation.
CFCs
Chlorofluorocarbons are chemical compounds
used in refrigerators, air conditioners and aerosol
cans. This enter the atmosphere and break the
bond of the three oxygen molecules that from
ozone.
One of the chlorine molecules combines with one
of the three oxygen atoms, leaving a two atom
molecule.
These new atoms do not absorb ultraviolet rays.
Hole in the Ozone Layer
The destruction of
ozone molecules by
CFCs seems to
cause a seasonal
reduction in ozone
over Antarctica called
the Ozone hole.
Ozone concentration
is lowest in October
in this location.
Earliest Life
Before the ozone layer formed, the only
living things on Earth were microscopic
organisms that lived far below the surface of
the oceans.
After the ozone layer
formed, certain types
of these
microorganisms called
blue-green bacteria
started to appear on
or near the water’s
surface.
Blue-green Bacteria
These bacteria used the
energy in sunlight to
combine carbon dioxide
from the air with water to
produce food.
A byproduct of this foodmaking process was
oxygen. This was the first
“free oxygen”.
These were the
stromatolites.
Oxygen
Unlike ozone, oxygen remains near the
surface of the Earth.
This is the oxygen that animals breathe
today.
Green plants began to grow on land and
take in carbon dioxide and release oxygen
in the food-making process.
Today’s Atmosphere
600 million years ago the amounts of
oxygen and carbon dioxide in the
atmosphere began to level off.
Since that time, the composition of the
atmosphere has remained fairly constant.
Composition of the Atmosphere
Nitrogen gas makes up about 78 percent of
the atmosphere.
Oxygen accounts for 21 percent.
• The remaining 1
percent is a
combination of
carbon dioxide,
water vapor, argon
and trace gases.
Layers of the Atmosphere
The atmosphere is
divided into layers
according to the
major changes in its
temperature. Layers
with thinner particles
can hold less heat.
Air Pressure
The layers of air that surround
the Earth are held close to it
by the force of gravity.
Because of gravity, the layers
of air push down on the
Earth’s surface. This is called
air pressure.
The upper layers push down
on the lower layers so the air
pressure near the surface is
greater than the air pressure
further away.
The Troposphere
This is the layer closest to the Earth.
Weather occurs in this layer. Life occurs in the
troposphere.
The height of the
troposphere varies
from 17 km at the
Equator to 8 km at
the poles. (17-8 km)
This layer contains
99% of the water
vapor.
The Stratosphere
The stratosphere extends from the troposphere to
an altitude of about 50 km.
In the lower stratosphere, the temperature is
around –60 degrees C.
Here very strong
eastward winds called
the jet streams reach
speeds of 320 km per
hour. The jet streams
move faster in the
winter than in the
summer helping
storms move across
the United States.
The Mesosphere
In the mesosphere, 50-90km above the earth, the
temperature begins to decrease to –100 degrees
C.
The upper region is the coldest. If water vapor is
present thin clouds of ice form, noctilucent.
The mesosphere
protects the Earth from
meteoroids. When they
reach the mesosphere,
they burn up from the
friction of rubbing
against the particles of
gas.
Thermosphere
The thermosphere begins at
a height of about 90 km.
Thermosphere means heatsphere. The temperatures
reach 2000ºC because this
layer absorbs the ultraviolet
radiation from space and
convert it into heat.
A thermometer placed in the
thermosphere would register
nothing because the particles
are so far apart that not
enough of them are present
to affect a thermometer.
Ionosphere
Within the mesosphere and the
thermosphere is a layer of electrically
charged particles called the Ionosphere. It
allows radio waves to travel around the
earth.
The Exosphere
The upper thermosphere is called the
exosphere.
The exosphere extends from 550 km above
the surface for thousands of km.The air is
very thin.
Artificial satellites orbit in the exosphere.
Air Movement
Uneven heating of the earth due to the
curved surface of the globe produces winds.
Wind is the movement of air from an area of
higher pressure to an area of lower
pressure.
Uneven Heating of the Earth
Cold dense air from the poles sinks and
moves toward the equator.
The hot less dense air near the equator is
pushed up and moves back toward the
poles.
Coriolis Effect
The rotation of the
Earth causes moving
air and water to
appear to turn to the
right north of the
equator and to the
left south of the
equator.
Global Wind Belts
The Coriolis Effect
and differences in
solar radiation
creates wind patterns
on earth, known as
Wind Belts.
We live in the
prevailing Westerlies
where winds move
west to east.
Summary
The atmosphere protects the Earth by balancing
the amount of heat absorbed and that escapes.
Earth’s early atmosphere was created from
volcanic gasses.
Oxygen came from the breakdown of water
vapor, and from stromatolites.
The ozone layer absorbs harmful ultraviolet
radiation from space.
Summary Cont.
Blue-green algae were the first
photosynthesizers, formed stromatolites.
The evolution of plants created sustainable
oxygen levels.
Atmosphere is 78% nitrogen, 21% oxygen
Pressure near the surface is higher
Summary Cont.
Troposphere – weather and water
Stratosphere – jet streams
Mesosphere – coldest, meteor protection
Thermosphere – hottest, UV radiation
turned into heat
Ionosphere – in meso/thermosphere,
reflects radio waves
Exosphere – where artificial satellites orbit
Summary Cont.
Uneven heating of the surface causes winds
Warm air rises at the equator and descends
at the poles
The rotation of the Earth causes moving air
to turn to the right north of the equator and
to the left south of the equator.
The Coriolis Effect and differences in solar
radiation creates wind patterns on earth,
known as Wind Belts.