1. The Earth’s Atmosphere

2. What is the atmosphere? View of the atmosphere from the space shuttle
thin layer of gases surrounding the Earth
no well-defined upper boundary – just fewer and fewer atoms
density decreases with altitude because number of atoms decrease

3. Air Pressure atmosphere – exerts pressure
Why? Because the atoms have weight.
Gravity holds it on the Earth
Pressure is higher near surface because more atoms pressing from above.
sea level pressure = 15 lb/in2

4. Think about air pressure as being a stack of books.
Here at the surface of the earth, we have more air “stacked” on top of us. That means we feel more pressure than if we were higher in the atmosphere.

5. Fill in this as we go along

6. Composition of Atmosphere
atmosphere is a mixture of
gases
solid particles
water droplets
Small changes are always happening

7. Permanent Gases – they are always in the air!
N2: nitrogen
78%
O2: oxygen
21%
This means that most of what you breath is NOT oxygen!
lesser amounts of other gases

8. Variable Gases – This means the percents are always changing.
Water vapor (H20) – can change by the minute!
Carbon Dioxide (CO2)
Ozone (O3)

9. Water Vapor
This satellite image shows the relative amounts of water vapor: Dark – low water, white – high water vapor
source of this gas: evaporation from Earth’s surface
water cycle – moves water between oceans, land and atmosphere
75% Earth’s surface covered by some form of water

10. Carbon Dioxide
(CO2)
What do you think this graph is telling us about the amount of carbon dioxide in the air year by year?
sources: respiration, organic decay, volcanoes, natural and man-made caused fires, burning of fossil fuels.
important Greenhouse gas
More Carbon dioxide means more heating of the Earth

11. highest concentration in stratosphere
Ozone
(O3)
consists of 3 O atoms (O2 + O = O3 )
highest concentration in stratosphere
shields surface from UV radiation
It is good for us up in the stratosphere but bad at the surface where we are.
Why? Because it forms smog – a type of air pollution.

12. Solids in the atmosphere
Pollen
Copyright © Michael Collier
Dust particles from combustion
small solid particles put in the air by nature or humans
examples: volcanic ash, salt in sea spray, pollen from plants, and ash from burning vegetation or fossil fuels

13. Fill in this chart Root prefix Prefix meaning New Word Fact(s) Sphere
Ball, globe (layer of the atmosphere)
Tropo-
Turn, turning, change
Troposphere
Strato-
Layer
Stratosphere
Meso-
Middle
Mesosphere
Thermo-
Heat
Thermosphere
Iono-
Charged; characterized by ions
Ionosphere
Exo-
Out of; away from; former
Exosphere

14. Structure of the Atmosphere
no clearly defined upper limit
density decreases with elevation
We divide the atmosphere into layers based on:
Changes in temperature

15. Layers from Earth’s surface
Troposphere
Stratosphere
Mesosphere
Thermosphere
The thermosphere has two parts: ionosphere and exosphere.
Let’s learn a little about each layer!

16. Troposphere lowest layer; temperature decreases with altitude
thinnest layer (8-16 km, avg. 11 km)
where weather occurs, where we live

17. Troposphere – when a cloud reaches the top of this layer, they cannot go higher so they flatten out.
Picture taken by the space shuttle.

18. Stratosphere found above the troposphere
temperature rises with elevation
Ozone Layer located here. Remember what we learned about ozone already?
Without the ozone layer protecting us, we could not live on the surface of the Earth!

19. Mesosphere above the stratosphere temperature decreases with altitude
Meteorites and space dust burns up in this layer

20. Thermosphere above the mesosphere temperature increases with altitude
contains two parts – ionosphere and exosphere

21. Ionosphere contains ions: charged particles
Visible light is given off when ions are hit by energy from the sun. This produces auroras. They are often called northern lights and are seen at night.
Quartz Lake State Park, Alaska (Curtis, 1996)

22. Exosphere
The exosphere is the outer part if the atmosphere. Fewer and fewer atoms are found as you get farther from the surface of the earth.
Because of this, there cannot be an actual point where you are no longer in the atmosphere.
Satellites orbit in the exosphere.

23. What do you know about these layers?

24. Final 5 2 C questions Homework question:
Using what we have discussed in class today, write a definition of the Earth’s atmosphere in your own words.