1. The Atmosphere
Chapter 15

2. Chapter 15 - Atmosphere
Earth’s atmosphere is the covering of gases that surrounds Earth.
Compared to the size of Earth, the atmosphere is a very thin covering.
Weather is the condition of Earth’s atmosphere at a particular place and time.

3. Chapter 15 - Atmosphere
Earth’s atmosphere is made up of nitrogen, oxygen, carbon dioxide, water vapor and many other gases, as well as particles of liquids and solids.
Nitrogen - 78%
Oxygen - 21%
Argon %
Carbon dioxide makes up only .038%.
The amount of water vapor in the atmosphere varies.
Particles in the atmosphere include dust, smoke, and other chemicals.

5. Chapter 15 - Atmosphere
Earth’s atmosphere makes conditions on Earth suitable for living things.
The atmosphere traps heat energy from the sun.
The atmosphere prevents Earth from being hit by rocks from outer space.

6. Chapter 15 - Atmosphere Air has mass. Air has density.
Density is the amount of mass in a certain volume.
The greater the mass of air, the greater the density of air.

7. Chapter 15 - Atmosphere Air pressure decreases as altitude increases.
Altitude is the distance above sea level, also called elevation.
Altitude affects density.
As you go higher, air becomes less dense.
As you go lower, air becomes more dense.

8. Chapter 15 - Atmosphere The Earth’s atmosphere has four main layers.
Layers are classified based on changes in temperature.

10. Chapter 15 - Atmosphere Troposphere: Lowest layer of the atmosphere.
Weather occurs in this layer.
You live in the troposphere.
Contains almost all of the mass of the atmosphere.
Temperature decreases as the altitude increases.

11. Chapter 15 - Atmosphere Stratosphere:
Layer of atmosphere directly above the troposphere.
Middle portion of the stratosphere contains the ozone layer.
Ozone layer blocks harmful rays from the sun.
Temperature increases
as the altitude increases.

12. Chapter 15 - Atmosphere Mesosphere:
Layer of the atmosphere just above the stratosphere.
Temperature decreases as the altitude increases.
Most meteoroids burn up in the mesosphere.

13. Chapter 15 - Atmosphere Thermosphere: Top layer of the atmosphere.
Temperature increases as altitude increases.

14. Chapter 15 - Atmosphere Thermosphere (continued):
Divided into two layers.
Lower layer called the ionosphere.
Northern lights occur in the ionosphere.
Upper layer called the exosphere.
Exosphere gradually blends with outer space.

16. Chapter 15 - Atmosphere
Air can contain harmful particles and gases, called pollutants.
Some air pollution occurs naturally.
Volcanoes and forest fires add pollutants to the air.
Some air pollution occurs as the result of human activities.
Burning fossil fuels such as coal, oil and natural gas add pollutants to the air.

17. Chapter 15 - Atmosphere
Burning fossil fuels can cause smog and acid rain.
Smog is a combination of smoke and fog.
Acid rain is rain that has more acid than normal rain.

18. Chapter 15 - Atmosphere
In the US, the federal and state governments have passed a number of laws and regulations to reduce air pollution.
The EPA watches for air pollution in the US.
Air quality in the US has improved over the past 30 years. But many cities still have very polluted air.