1. Review Day Grab a book off windowsill Turn to page 66
Complete questions 1-6 on your own sheet of paper

2. THE ATMOSPHERE
Composition & Layers

3. Objectives Describe the composition of Earth’s atmosphere.
Describe the layers of Earth’s atmosphere.
Explain 3 mechanisms of heat transfer in Earth’s atmosphere.
Explain the greenhouse effect.

4. The Atmosphere Is the mixture of gases surrounding the Earth
Composed of:
Nitrogen
Oxygen
Carbon Dioxide
How can gases be added/removed to atmosphere?
Animals remove Oxygen, breath out Carbon Dioxide
Plants take in CO2, add O2 to atmosphere
Volcanic eruption adds gases
Vehicles add & remove gases

5. Composition of Atmosphere
Nitrogen 78%
Oxygen 21%
Argon
Carbon Dioxide
Methane
Water vapor
Addition to gases: atmospheric dust (soil, salt, ash, matter from combustion, skin, hair, bits of clothing, pollen, bacteria & viruses, and aerosols.

6. Air Pressure
The atmosphere is pulled toward Earth’s surface by GRAVITY.
Atmosphere is denser near surface.
Most atmospheric gases located within 30 km of our surface (18.6 miles).
The amount of air decreases at higher altitudes.
So breathing at higher elevations is more difficult.

7. Why do planes fly so high, often 10km above the ground?
Most commercial planes fly at about 10,000 m b/c the air at that altitude is less than half as dense as air 1,500 m about the ground
Planes experience less drag & require less fuel when they move through thinner, less dense air. Less turbulent above cloud level.

8. Layers of the Atmosphere
Divided into 5 layers based on temperature changes that occur at different distances
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere

9. 1. Troposphere Layer nearest Earth’s surface
Extends to about 18km above surface
Almost all weather occurs in this layer
Densest atmospheric layer

10. 2. Stratosphere Above troposphere Extends from 18km – 50km
Temperatures rise as altitude increases b/c ozone in this layer absorbs the sun’s ultraviolet energy & warms the air.
Ozone (O3)
Almost all ozone is concentrated in stratosphere
Ozone reduces the amount of harmful UV radiation that reaches Earth.

11. 3. Mesosphere Layer above the stratosphere
Extends to an altitude of about 80 km
Coldest layer of the atmosphere
Temp: as low as -93oC
(-135oF)

12. 4. Thermosphere (ionosphere)
Farthest from Earth’s surface
N & O absorb solar radiation = results in temps above 2,000oC (3,632oF)
Air particles that strike each other transfer heat
Air is so thin that particles rarely collide so little heat is transferred

13. 5. Exosphere
Uppermost region of Earth's atmosphere as it gradually fades into the vacuum of space.
Air is extremely thin (almost airless)
Extends from 400mi – 800mi

14. ATMOSPHERE
Energy in the Atmosphere

15. Objectives Describe the composition of Earth’s atmosphere.
Describe the layers of Earth’s atmosphere.
Explain 3 mechanisms of heat transfer in Earth’s atmosphere.
Explain the greenhouse effect.

16. Energy in the Atmosphere
There are 3 mechanisms that transfer energy from the sun to the atmosphere
Radiation: is the transfer of energy as electromagnetic waves
Example: warmth you feel from fire
Conduction: is the transfer of E in the form of heat from a warmer object to a colder object when they contact each other
Convection: is the transfer of E that takes place when variations in temperature move the matter making up air.
Example: vents in house

17. Convection
Conduction
Radiation

18. Greenhouse Effect
The process in which greenhouse gases absorb & reradiate infrared radiation near the Earth
Without it – Earth would be too cold for life to exist
The gases in our Atmosphere trap the heat = greenhouse gases

19. Greenhouse gases Most abundant Water vapor Carbon dioxide Methane
Nitrous oxide

20. Video: Greenhouse Effect
be.com/watch?v=5 zLuqSYF68E