1. THE ATMOSPHERE Earth’s atmosphere is UNIQUE!
No other planet has the mixture of gases that we have that are vital to our existence.
From the ground it is hard to tell, but there is a lot going on in the sky that all life on Earth needs to appreciate

2. Changing composition of air
The atmosphere was thought to have started as gases emitted during volcanic eruptions
Evidence shows that oxygen did not start to accumulate until 2.5 billion years ago
Atmosphere continues to exchange material with oceans and life on Earth’s surface.

3. Composition of Atmosphere
Nitrogen (78%) and
oxygen (21%)
dominate
the volume of gases
composing dry
air

4. 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.

5. Height and Structure of the Atmosphere
can be divided
vertically into
Four layers based on temperature.

6. • Troposphere = bottom layer of the atmosphere, temperature decreases with an increase in altitude. (where weather occurs)
• Stratosphere = gradual increase in temp. (contains the OZONE layer)

7. • Mesosphere = characterized by decreasing temperatures with height
• Mesosphere = characterized by decreasing temperatures with height. (where shooting stars burn up, meteors)
*** COLDEST layer of the atm
Thermosphere = characterized by increasing temperatures due to the absorption of very short-wave, high energy solar radiation by nitrogen & oxygen.
*** Warmest layer of the atm

8. Weather vs. Climate Climate Weather is constantly changing!
Weather is the state of the atmosphere at any given time and place.
Climate
based on observations of weather that have been collected over many years = “AVERAGE WEATHER” (helps describe a place or region ).
Ex: farmer’s need to know the AVERAGE rainfall for growing season