Volcanoes and Igneous Activity Earth Chapter 4

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Chapter 17
The Atmosphere Structure and Temperature
Buffalo, New York was under a state of emergency
in late December 2001 after receiving almost 7
feet of snow.
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17.1 Atmosphere Characteristics

• Weather vs. Climate
• Weather is constantly changing.
• Refers to the state of the atmosphere at any
  given time and place.
• Climate is based on observations of weather that
  have been collected over many years.
• Helps describe a place or region.

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17.1 Atmosphere Characteristics

• Properties
• The most important measurable
• properties of weather climate are
• air temperature
• humidity
• type and amount of precipitation
• air pressure
• speed and direction of wind

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17.1 Atmosphere Characteristics
17.1 Atmosphere Characteristics
How did it all start?

• Scientists believe that our original atmosphere
  was created during constant volcanic eruptions
  after the Earth formed.
• Oxygen wasnt added
• until 2.5 million years ago.

Composition of the Atmosphere
Air is a common named for our atmosphere and
it consists of a mixture of different gases and
particles, each with its own physical properties.
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17.1 Atmosphere Characteristics
17.1 Atmosphere Characteristics
Major Components of Air

• Nitrogen and Oxygen gases make up 99 of the
  volume of clean dry air.
• Neither gas has much of an affect on the
  weather despite their large composition of air.

• 1 of dry air is mostly argon plus a few other
  gases such as carbon dioxide.

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17.1 Atmosphere Characteristics
17.1 Atmosphere Characteristics
Major Components of Air
Despite the fact that CO2 gas is only .039 of
our atmosphere, it plays a significant role in
the heating of the Earth which directly
influences weather and climate.
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Volume of Clean, Dry Air

• What is the most common gas in our atmosphere?

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17.1 Atmosphere Characteristics
17.1 Atmosphere Characteristics
Variable Components of the Atmosphere

• Water vapor is the source of all clouds
  precipitation.
• Like carbon dioxide, water vapor absorbs heat
  given off by the Earth and some solar energy.

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17.1 Atmosphere Characteristics
17.1 Atmosphere Characteristics
Variable Components of the Atmosphere

• Our atmosphere also contains visible and
  microscopic dust particles from a variety of
  sources such as
• ocean sea salts from breaking waves
• fine soil blown into the air
• smoke and soot from fires
• pollen and microorganisms lifted by the wind
• ash and dust from volcanic eruptions

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17.1 Atmosphere Characteristics
17.1 Atmosphere Characteristics
Variable Components of the Atmosphere

• Ozone is a form of oxygen that combines 3
• oxygen atoms into each molecule (O3).
• There is very little ozone in the atmosphere
• and it is not distributed evenly, but it is very
  
• important!
• Ozone is essential to the survival of our
  planet. If ozone gas did not filter most UV
  radiation and all of the suns UV rays reached
  the surface of Earth, our planet would be
  uninhabitable for many living organisms.
• It is concentrated in a layer of the atmosphere
  called the stratosphere, which is located 10-50
  km above the Earths surface.

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17.1 Atmosphere Characteristics
17.1 Atmosphere Characteristics
Human Influence on the Atmosphere

• Air pollutants are airborne particles and gases
  that
• occur in concentrations
• large enough to endanger
• the health of organisms.
• Primary pollutants are
• those emitted from known
• or identifiable sources.

• Secondary pollutants are not emitted directly
  into the air, instead they form when reactions
  take place among primary pollutants and other
  substances.

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• Use the graph of primary pollutants and their
  sources above (from page 478) to answer the
  questions in your verbal notes.

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17.1 Atmosphere Characteristics

• Height Structure of the Atmosphere
• The atmosphere rapidly thins as you travel away
  from Earth until there are too few gas molecules
  to detect.

Pressure Changes

• Atmospheric pressure is simply the weight of the
  air above.

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Atmospheric Pressure vs. Altitude

• This graph shows how atmospheric pressure varies
  with altitude.
• One half or 50 of the atmosphere lies below an
  altitude of 5.6 km
• Above 100 kilometers, only 0.00003 of all the
  gases making up the atmosphere exist.

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17.1 Atmosphere Characteristics
17.1 Atmosphere Characteristics
Layers of the Atmosphere

• The atmosphere can be divided vertically into
• four major layers based
• on temperature
• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere

The boundary between each layer is called a
pause.
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17.1 Atmosphere Characteristics
17.1 Atmosphere Characteristics
Layers of the Atmosphere
The troposphere is the bottom layer of the
atmosphere where temperature decreases with an
increase in altitude. Unlike other layers, the
thickness of the troposphere varies with latitude
and season.
Weather occurs in this layer.
The stratosphere is the layer of the
atmosphere where temperature remains constant to
a height of about 20 kilometers. It then begins a
gradual increase until the stratopause. This
layer contains the ozone layer.
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Snowy Mountaintops Contrast with Warmer Snow-Free
Lowlands

• The Earths troposphere, the lowest layer of the
  atmosphere, becomes colder as you climb higher in
  altitude away from the Earths surface.
• Snow-capped mountains like those in the picture
  are a great example of this. While the base of
  the mountain may be very warm with lush
  vegetation the peak is very cold and snow covered.

Jasper National Park in Alberta, Canada.
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17.1 Atmosphere Characteristics
Height and Structure of the Atmosphere
The mesosphere is the layer of the atmosphere
immediately above the stratosphere and is
characterized by decreasing temperatures with
height. This is the coldest layer brrrr!!!
The thermosphere is the region of the
atmosphere immediately above the mesosphere and
is characterized by increasing temperatures due
to the absorption of very short-wave solar energy
by oxygen. This layer contains the ionosphere
which has glowing ions called the aurora borealis
and the exosphere which blends into space.
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Thermal Structure of the Atmosphere

• This diagram (from page 480) illustrates the
  thermal structure of the atmosphere which means
  the temperature changes in each layer of the
  atmosphere.
• How do the air temperatures change with height
  in each layer of the atmosphere?

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17.1 Atmosphere Characteristics
Earth-Sun Relationships Earths Motions

• Earth has two principal motionsrotation and
  revolution.

• Rotation is the spinning of the Earth on its
  axis.
• The Earths axis is tilted 23.5 degrees.

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Tilt of Earths Axis
Earth-Sun Relationships Earths Motions

• Revolution is the movement of the Earth in its
  orbit around the sun.

Earths Orientation

• Seasonal changes occur because Earths position
  relative to the sun continually changes as it
  travels along its orbit and revolves around the
  sun.

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17.1 Atmosphere Characteristics
Earth Sun Relationships Solstices and Equinoxes
During a solstice one of the hemispheres receives
the maximum hours of daylight while the other
hemisphere receives the maximum hours of darkness.
The summer solstice occurs on June 21 or 22 in
the Northern Hemisphere and is the official
first day of summer.
The winter solstice occurs on December 21 or
22 in the Northern Hemisphere and is the
official first day of winter.
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17.1 Atmosphere Characteristics
Earth Sun Relationships Solstices and Equinoxes
During an equinox, the entire Earth experiences
12 hours of daylight (equal day) and 12 hours of
darkness (equal night.)
The autumnal equinox occurs on September 22 or
23 in the Northern Hemisphere.
The spring equinox occurs on March 21 or 22 in
the Northern Hemisphere.
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Solstices and Equinoxes

• Length of Daylight
• The length of daylight compared to the length of
  darkness is determined by the Earths position in
  orbit.

• For example, the further you are north of the
  equator on the summer solstice, the longer the
  hours of daylight.
• The Artic Circle experiences 24 hours of
  daylight on the summer solstice.