Chapter 4: Atmosphere

Section 1: Earth's Atmosphere

Focus: Definition of atmosphere

The composition of the atmosphere

The layers of the atmosphere

The importance of the atmosphere

The greenhouse effect and the ozone layer

• What is atmosphere?

• It is a thin layer of gas that forms a protective layer around the planet

***The importance of the atmosphere

1- contains the oxygen that we need to survive

2- it is a shield that protects us from the ultraviolet radiation

3- It keeps us warm- absorbs heat from the sun preventing all of it from radiating out into space

Other important aspects:

4- protects us from objects falling from space –pieces of rock burn out due to the friction of the air.

5- has Carbon Dioxide necessary for photosynthesis that produces oxygen

6- sound waves travel through air, allowing us to listen to one another

Makeup of the Atmosphere

• Earth's atmosphere is a mixture of solids (dust, pollen) , liquids and gases.

•What is air made of ?????

Air in made of Atoms

Air has mass

What do you feel when you have something with

mass on your lap?

Air has mass and can exert pressure

Atmospheric Pressure

• We have lots of gases on top of us

• All these gases are matter

• These atoms and molecules will exert a force called Atmospheric Pressure

***Definition:

Atmospheric Pressure is pressure caused by the weight of the atmosphere.

At sea level you have maximum atmosphericpressure Atmospheric pressure reduces with increasing altitude because the molecules of the gases are further apart.

Temperature in Atmospheric layers

**Various layers have different temperatures, because they have a different gas composition and will absorb the heat from the sun differently

Text and Graph page 95 – read

The development of the Earth’s atmosphere

With the increasing level of Oxygen and Ozone in the atmosphere, organisms migrated to land and new life forms developed.

More oxygen was formed, the atmosphere kept on changing and is still changing.

Millions of years ago, the atmosphere was rich in Carbon Dioxide and water vapor

the amount of oxygen increased slowly mostly due to the photosynthesis from algae life was mostly under water

more oxygen was formed Ozone layer appeared allowing life out of the water, by protecting life from damaging sun rays

More oxygen was formed, the atmosphere kept on changing and is still changing.

Nowadays mostly due to man intervention

The development of the Earth’s atmosphere

The Ozone Layer

• The ozone layer is located in the stratosphere

• Ozone is a molecule made of 3 atoms of oxygen.

Your life depends on Ozone

• The ozone layer shields you from the Sun's harmful rays(UV rays mostly UVC)

The effect of CFCs

• Evidence exists that some air pollutants such as CFCs are destroying the ozone layer.

• CFC breaks the ozone molecule

Chlorofluorocarbons (CFCs): are chemical compounds used in some refrigerators, air conditioners, aerosol sprays and in the production of some foam packaging.

Chlorofluorocarbon molecules destroy ozone exposing the Earth to more radiation

The Ozone Hole

*The destruction of ozone molecules by CFCs seems to cause a seasonal reduction in ozone over Antarctica, called the ozone hole or ozone depletion.

*The fluctuation of the levels of Ozone over the polar regions follows a pattern, increasing and decreasing during the year.

Oct. 2014 Ozone hole Nasa update – Good news!

The 2014 Ozone hole is comparable to the size of the holes in 2010, 2012, 2013.

It is smaller than the sizes observed during the period of 1998- 2006.

The smaller ozone hole could be a result of the lower level of CFCs in the atmosphere – 9% less than in 2000

Hydrofluorocarbons based products are being used instead of CFCs.

• Man intervention in the atmosphere

• The composition of the atmosphere is changing in small but important ways.

• The constant burning of fossil fuels is increasing the levels of certain gases in the atmosphere

•these gases are called greenhouse gases

•Fossil fuels are………….

***Fossil fuel: nonrenewable energy resources

Ex: coal, oil, natural gas

Fossil fuels were formed in the earth from dead plants or animals, millions of years ago.

The more we burn, the less we will have

***Greenhouse gases are: methane, carbon dioxide, water vapor, chlorofluorocarbons (CFCs)

**Greenhouse effect: heat-trapping feature of the atmosphere due to the presence of greenhouse gases

**This is usually good because these gases – IN THE RIGHT AMOUNT - help us keep warm guaranteeing life on earth.

BUT: The increased amount ofgreenhouse gases in the atmosphere accentuates the greenhouse effect,affecting the climate certainareas. (it is reversible)

***Global Warming – definition

•Global warming is the unusually rapid increase in Earth’s average surface temperature over the past century.

**Causes of Global Warming

a) Natural causes:

•Variations in Sun's energy

• Subtle shifts in the Sun’s orbit – if the Sun is closer to the Earth, we will receive an increased amount of heat

• Fluctuation in ocean currents

•Volcanic eruptions

b) Man – related Causes of Global Warming

•Global warming is primarily happening due to the greenhouse gases released by people burning fossil fuels.

•Methane, water vapor, carbon dioxide, fluorinated gases such as CFC (chlorofluorocarbons) – trap heat. The amount of this gases is too high, there will be an increase the greenhouse effect, causing global warming.

*Effects of Global Warming

• Not only the increase in Earth temperature, but also:

• Modification of rainfall patterns

• Amplification of coastal erosion

• Melting of ice caps and glaciers

All this affects the living organisms in the planet