Section 3: Earth's Modern Atmosphere

SLOs: atmospheric composition, temperature, and function, the ozone layer and UV, atmospheric pollution.


Lesson 1:

Instruction

The atmosphere of modern Earth is generally defined using three types of criteria: composition, temperature, and function. The image below is a generalized chart of the atmosphere from the surface of the Earth to the top of the atmosphere.  The composition of the atmosphere is divided into the Homosphere (evenly mixed gases, except ozone) and the Heterosphere (unevenly mixed gases).  The temperature profile of the atmosphere is sectioned into the Troposphere (most atmospheric mass including water and all life forms), the Stratosphere (location of the ozone layer), the Mesosphere (coldest region which receives space dust), and the Thermosphere (hottest region which is also the outer layer of atmosphere).  Functions are determined by the Ozonosphere (variational ozone layer that filters out shortwave radiation and protects Earth's life forms), and the Ionosphere (layer that filters out the shortest-wave radiation as the first line of protection to Earth's life forms).      

Photos and Images
 (Earth's modern atmosphere)  

Quiz

All of the layers of the atmosphere are necessary in allowing life to flourish on Earth.  Name the functional layer of the atmosphere that protects Ventura County residents from incoming Ultraviolet light (UV).  Review Section 2 for more information on the electromagnetic spectrum which includes UV.      

 


Lesson 2:

Instruction

In Ventura County, as well as all over the world, people are noticing the effects of the ozone layer loss.  Scientists widely agree that certain man-made chemicals released into the atmosphere are causing the holes in the ozone layer.  Some chemicals that cause ozone layer loss include chlorofluorocarbons (CFCs) and bromine sources.  When the ozone layer is thinned or removed, less Ultraviolet (UV) radiation is filtered out of the atmosphere; thus more UV reaches the surface of the Earth. 

Photos and Images

 
 (the UV index)

Quiz

What is one effect of ozone depletion that you notice living in Ventura County?  Think about being at the beach on a nice, sunny summer day.  What happens if you remain in direct sunlight for too long?  If you want to protect yourself from UV on an outing in the sun, check your local news/weather station or search the Environmental Protection Agency (EPA) or National Weather Service (NWS) websites for the current UV exposure category.  If the UV is high, remember to use sun block and spend less time in direct sun light! 

 


Lesson 3:

Instruction

Atmospheric pollution is multivariate.  In other words, there are many factors that lead to atmospheric pollution, both natural and human-induced.  Natural pollution sources include erupting volcanoes, decay of living organisms, and forest fires.  Winds, specific landscapes, and temperature inversions can also amplify these natural factors.  However, currently, the worst atmospheric pollutants are anthropogenic or human-induced.  Anthropogenic pollution sources include the release of carbon monoxide, nitrogen oxides, volatile organic compounds, ozone, peroxyacetyl nitrates, sulfur oxides, particulate matter, carbon dioxide, methane, and even water vapor.  Combustion of fuels and chemicals make up the majority of these releases into the atmosphere.  In Ventura County, the main types of air pollution are ozone (photochemical reactions) and particulate matter (dust, salt, metals, erosion, and so on).  You may remember that ozone is a necessary part of the atmosphere at altitudes miles above the Earth.  But, when ozone is produced by human activities in the lower atmosphere near the surface of the Earth, it causes very harmful smog.  Particulate matter is also of concern because it is known to cause respiratory ailments in humans.                

Photos and Images
(air pollution above Ventura and Ojai)          (air pollution above Port Hueneme and Mugu)     (air pollution above Moorpark)

Quiz

The good news is that the federal Clean Air Act (CAA) was passed and updated throughout 1970-1990.  This legislation attempts to reduce the anthropogenic releases of pollution in the air.  Although there have been many improvements in air pollution since 1970, not all U.S. political leaders (and society in general) support the goals of this act.  Therefore, we still have a great deal of anthropogenic air pollution problems that will need to be solved now and in the future if we want our atmosphere (and the whole Earth in general) to be healthy and sustainable for all life forms.  Can you name three human diseases that are caused by air pollution?  Look in the Christopherson text, Chapter 3, or any air pollution source for ideas.        


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2006 Jessica Douglas