1. Chapter 22: Earth’s Atmosphere

2. Ch 22-1: Characteristics of the Atmosphere
The origin of the atmosphere
When the Earth formed, it was too hot for an atmosphere
As it cooled, first atmosphere contained
Methane
Ammonia
no free oxygen
First atmosphere driven off by outgassing from volcanoes
carbon dioxide
Water Vapor which condensed to form oceans

3. Early life, such as cyanobacteria (blue green algae) generated free oxygen through photosynthesis
Animal life became possible after free oxygen was created
Free oxygen in Earth’s atmosphere makes it unique

4. Earth’s current Atmosphere
78% Nitrogen
21% Oxygen
1% other gases

5. Effects on the composition of the atmosphere
The Greenhouse Effect and Global Warming
Carbon dioxide in the atmosphere traps heat energy in atmosphere like a greenhouse
Trapped heat warms the Earth → leads to global warming

6. Ozone Depletion a. Ozone is a thin layer of O3 in the upper stratosphere which blocks UV light which damages living tissue b. Chlorofluorocarbons (CFC’s) break down ozone in a photochemical reaction (a chemical reaction caused by light)

7. CFC’s were banned and hole in Ozone has shrunk –an environmental success story
CFCs were used in aerosol cans and as coolants in air conditioners and refrigerators

8. Natural influences on Earth’s Atmosphere
Volcanic eruptions
Ash and dust can prevent absorption of sunlight
Earth cools
Meteorite impacts can create dust and ash

9. Atmospheric Conditions
Pressure
the pressure exerted in all directions due to the weight of the atmosphere
entire mass is within 32 miles of Earth’s surface
Measuring pressure
Mercurial barometer
Aneroid barometer

10. Solar Energy
Latitude- primary factor that influences amount of sunlight received and climate
Equator receives most direct sunlight
Poles receive more indirect sunlight

11. Circulation
pressure differences cause movement of air
air always moves from high to low pressure
Coriolis effect
rotation of the Earth causes moving object to travel in an apparent curved path
Direction of curve depends on location
Northern hemisphere- curves right
Southern Hemisphere-curves left
Coriolis Effect

12. Jet Streams- narrow bands of high speed winds
in upper troposphere and lower stratosphere
caused by density differences in heavy polar air and lighter air from mid-latitudes
Influence weather globally
Local winds
Land and sea breezes
Mountain and valley breezes