Transcript 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
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.
 Sunlight then broke down the water vapor in
the upper atmosphere into hydrogen and
oxygen. The hydrogen again escaped.
Ozone Layer
 The oxygen that was left
behind joined together, 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.
Oceans
 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”.
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.
Solid Particles
 Tiny particles of dust, smoke dirt and salt
float in the air.
 Every time a wave breaks, tiny particles of
salt from ocean water are suspended.
 Dust in the air comes from the eruption of
volcanoes.
 Dirt and smoke comes from people as they
burn fuels and drive cars.
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 the Equator to
the poles. (17-8 km)
 It is highest at the
equator.
 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.
The Thermosphere
 The thermosphere begins above the mesosphere
at a height of about 90 km.
 The air is very thin. The density of the atmosphere
and the air pressure are one ten-millionth of what
they are at the Earth’s surface.
 The temperature is very high in this layer because
the rays from the sun are absorbed in this layer.
Heat- sphere
 Thermosphere means heat-sphere. The
temperatures reach 2000 degrees
C.because this layer absorbs the ultraviolet
radiation from space and convert it into heat.
 A thermometer placed in the thermosphere
would register below 0 because the particles
are so far apart that not enough of them are
present to bombard 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.
Atmospheric Pressure
 Air pressure is caused by
Earth’s gravity pulling the
air particles toward the
Earth.
 As you move away from
the Earth, air pressure
decreases.
 Jets that fly in the
stratosphere need
pressurized cabins for
the passengers.
Temperature in the
Layers
 The sun is the source of
energy for Earth. As the
sun’s light passes through
the layers some layers
contain gases that absorb
the energy.
 The troposphere is warmed mainly by heat
from the ground.
 The air temperature decreases 6.5º every
kilometer you climb up.
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.
Water Cycle
 The three steps of
the water cycle are
evaporation and
transpiration,
condensation and
precipitation.
Evaporation
 Evaporation occurs when heat from the
sun causes water to change from a
liquid to a gas.
Condensation
 If the water vapor or gas is cooled enough it
will change back into a liquid.
 The process of vapor changing back into a
liquid is called condensation.
 Clouds form when condensation occurs.
 Clouds are made of tiny drops of water that
collect to form larger drops.
Precipitation
 As water drops grow in a cloud, they will
become heavy enough to fall to Earth as
precipitation.
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 poles.
 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.