1. The Atmosphere
Copyright © Houghton Mifflin Harcourt Publishing Company

2. What is Earth’s atmosphere?
The Atmosphere
What is Earth’s atmosphere?
The atmosphere is the mixture of gases that surrounds Earth.
Functions of the atmosphere:
Protects organisms from the sun’s damaging UV rays
Maintains the right temperature range for life.
Supplies gases necessary for breathing. 2

3. What is Earth’s atmosphere?
The Atmosphere
What is Earth’s atmosphere?
Properties of the atmosphere:
Density: The mass of gas in a given volume of air. It depends on the number of molecules present and types of molecules.
Pressure: The amount of force exerted to a surface by the weight of air.
Temperature: The measure of hotness or coldness of an object. 3

4. Composition: Gas components: 78 percent nitrogen gas,
The Atmosphere
Composition:
Gas components:
78 percent nitrogen gas,
21 percent oxygen gas
1 percent other gases. 4

5. Air Pressure: how does it change with distance from the Earth?
The Atmosphere
Air Pressure: how does it change with distance from the Earth?
Air pressure is the measure of the force with which air molecules push on an area of a surface.
As we increase our distance from the Earth (greater altitude), air pressure decreases.
Why?
(Hint: relate it to the number of gas molecules in the atmosphere at different altitudes) 5

6. How does temperature vary with altitude?
The Atmosphere
How does temperature vary with altitude?
The change in temperature depends upon the characteristics of the atmospheric layer that is being measured.
In some atmospheric layers, the temperature increases in altitude, while in other layers, it decrease. 6

7. The layers of the atmosphere
What are the layers of the atmosphere?
Divided into 4 layers:
Troposphere
Stratosphere
Mesosphere
Thermosphere
Layers are separated based on:
How temperature varies with altitude
Composition of gases
Density
Air pressure within the layer. 7

8. Troposphere The layer closest to the Earth. As altitude increases,
The Atmosphere
Troposphere
The layer closest to the Earth.
As altitude increases,
temperature decreases
density decreases
air pressure decreases as there are fewer numbers of air molecules
Weather happens here
Layer where most organisms on Earth live
How is the troposphere heated?
Radiation from the Earth’s surface. Therefore, the further away from the Earth’s surface, the colder it gets. 8

9. Stratosphere The layer above the troposphere. As altitude increases,
The Atmosphere
Stratosphere
The layer above the
troposphere.
As altitude increases,
the air pressure and
density decrease
Air Temperature: increases with increasing altitude (different than the troposphere). Why?
The stratosphere contains the ozone layer.
Ozone molecules absorb ultraviolet light and give off heat as the molecules are formed and broken apart. 9

10. Mesosphere The layer above the stratosphere.
The Atmosphere
Mesosphere
The layer above the stratosphere.
The gases become thinner, or less dense, with altitude.
Meteor showers occur in this layer: when meteoroids enter the Earth’s atmosphere, they burn up in this layer.
Temperatures decrease with increasing altitude:
Why? There are fewer gas molecules to absorb radiation from the sun. 10

11. Thermosphere The layer above the mesosphere
The Atmosphere
Thermosphere
The layer above the mesosphere
Oxygen (as we breathe it, O2) breaks up into individual oxygen atoms.
The individual atoms are easily heated by radiation from the sun: this causes the temperature to increase with increasing altitude.
Aurora lights occur in this layer. 11

12. The Atmosphere
Thermosphere
Aurora Borealis  A glow in the night sky produced in the upper atmosphere by ionized particles from the solar wind interacting with Earth’s magnetic field. 12

13. Ionosphere Communication on Earth depends on satellites.
The Atmosphere
Ionosphere
Communication on Earth depends on satellites.
Satellites transmit information used for television shows, radio broadcasts, data and photos used in weather reports, and long distance telephone calls. 13

14. The Atmosphere
Exosphere
The exosphere begins at about 500 kilometers above Earth and does not have a specific outer limit.
Satellites orbit Earth in the exosphere. 14

15. How do temperatures differ with altitude in the atmosphere?15

16. How does the atmosphere protect life on Earth?
1. The ozone layer: absorbs harmful UV radiation
2. Greenhouse effect: helps to maintain an average global temperature that can sustain life and liquid water.
How? Gases in the atmosphere,
such as carbon dioxide and
water vapor, absorb and
reradiate thermal energy. 16

17. How does the atmosphere protect life on Earth?
How is the heat inside of a closed car in the summer similar to the greenhouse effect? 17