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Chapter 15
The Atmosphere
Page 450
The Atmosphere
 Thin
layer of air that forms a protective
covering around the planet!
 Absorbs
and traps heat from the sun
Without it, days would be extremely hot & nights
would be extremely cold!
 Protects
life from harmful ultra violet (UV) rays
 Provides
living things with necessary gases
such as oxygen
 Transports
& Recycles water
 Composition
 Air
 Relative
 Temperature
Composition or Makeup of the
 Mixture
of gases, solids, & liquids
 Extends from the surface of Earth to outer
 Has changed over time!
No oxygen on early earth.
Oxygen began to form from cyanobacteria (tiny
photosynthetic microorganisms)
Ozone layer (O3) formed which allowed life to
move onto land.
Gases in the Atmosphere
 Nitrogen
 Oxygen
(N2) – 78%
(O2) – 21%
 Water
Vapor – 4%
 Argon
- .93%
 Carbon
 Trace
Dioxide - .03%
Elements: Neon, Helium, Methane,
Hydrogen gas
The Layers of the Atmosphere
 Troposphere
 Stratosphere
 Mesosphere
 Thermosphere
 Exosphere
Atmospheric Pressure
 Gases
have mass.
 Hundreds of miles of gas above Earth's surface
 Earth's gravity pulls the gases toward its
surface creating pressure
 That pressure is called air pressure!
Atmospheric Pressure
 Air
pressure increases as you get closer
to earth.
 Which
layer has the highest air pressure?
 Directly
above the ground (crust)
 Extends 11 km or 7 miles up into the air
 Contains 75% of the atmospheric gases
Including the oxygen we breath
¾ of the atmospheric mass
 Contains
the Weather
 Gets colder the higher you go
Most of the heat comes from the ground
 Layer
above the troposphere
 11 to 50 km (7-31 miles)
 Max Temperature = -3oc or 27oF
 Contains the Ozone Layer!!!!
The Ozone Layer
 Ozone
is comprised of three oxygen
molecules (O3)
 The ozone layer shields us from UV
 UV radiation can damage DNA
So what?
Please Save The Ozone Layer!
Ultraviolet radiation
can damage DNA
Damage DNA =
Damaged DNA can
lead to skin cancer.
The Hole in The Ozone Layer
Chlorofluorocarbons (CFCs) used in
refrigerators, air conditioners, and aerosols
Destroy Ozone
Hole over Antarctica
Page 472
The hole in the ozone was one of the
most important problems in the 80s…
Fortunately, most countries banned CFCs
by the 1990s due to the Montreal Protocol!
The Layers of the Atmosphere
 Troposphere
 Stratosphere
 Mesosphere
 Thermosphere
 Exosphere
Mesosphere & Thermosphere
 Meso
means middle
 Thermosphere
Named due to its high temperatures (getting
closer to the sun)
Thickest layer  85 to 500 km
Ionosphere – layer of eclectically changed
particles (Northern Lights)
Changes to the atmosphere
Increased Levels of Carbon dioxide released by
burning fossil fuels.
Oil, Natural Gas, & Coal
The greenhouse effect
Increased levels of these gases can cause the earth to get
• Carbon Dioxide
• Methane
• Nitrogen Oxide
• Ozone
 Smog
Car exhaust gases & other emissions mix with
oxygen in the presence of sunlight
Creates a brown haze
Smoke + Fog
 Air
Air Pollution
Dust (animals, people, dirt)
Soot (burning)
Salt (ocean)
The Clean Air Act
Page 470
1st passes in 1963
 Revised
many times in order to set stricter
standards for air quality & strengthen the
government’s ability to enforce regulations.
 Measures
air quality in an attempt to reduce
emission of pollutants that cause health
problems such as asthma and cancer.