The Atmosphere and Air Pressure
The air around you has weight, presses on everything, and is arranged in layers that stretch far above your head. The atmosphere protects life, holds the weather, and thins out as you rise. Understanding its layers and air pressure is a core piece of earth science.
This lesson covers the atmosphere’s layers and how air pressure works.
The atmosphere is the layer of gases surrounding Earth, mostly nitrogen and oxygen. It is arranged in layers, starting with the troposphere where weather happens. Air pressure is the weight of the air pressing down, and it decreases as you go higher.
What is the atmosphere made of?
The atmosphere is the blanket of gases held to Earth by gravity. It is about 78 percent nitrogen and 21 percent oxygen, with small amounts of other gases like carbon dioxide and water vapor. This thin shell protects life by blocking harmful radiation, burning up most meteors, and trapping enough heat to keep the planet warm.
What are the layers of the atmosphere?
The atmosphere is divided into layers by temperature. The lowest is the troposphere, where we live and where nearly all weather occurs. Above it is the stratosphere, which contains the ozone layer. Higher still are the mesosphere, where meteors burn up, and the thermosphere, the hot outer layer. As you go up through these layers, the air gets thinner.
| Layer | Note |
|---|---|
| Troposphere | Weather happens here |
| Stratosphere | Contains the ozone layer |
| Mesosphere | Meteors burn up |
| Thermosphere | Hot outer layer |
What is air pressure?
Air pressure is the weight of the air pushing down on a given area. At sea level there is a lot of air above you, so the pressure is high. As you climb a mountain or fly higher, there is less air above, so air pressure drops and the air feels thinner. This is why your ears pop when you change altitude quickly and why high peaks have less oxygen to breathe.
Watch: A Short Video Lesson
Miacademy Learning Channel walks through this skill clearly in a few minutes. It is a helpful companion to the reading above:
A routine for atmosphere questions
- Recall the atmosphere is mostly nitrogen and oxygen.
- Know the layers in order: troposphere, stratosphere, mesosphere, thermosphere.
- Remember weather happens in the troposphere and ozone is in the stratosphere.
- Air pressure is the weight of air above you.
- Pressure and air thickness decrease with altitude.
Practice questions
- What two gases make up most of the atmosphere?
- In which layer does weather occur?
- Which layer contains the ozone layer?
- What is air pressure?
- How does air pressure change as you go higher?
- True or false: the air gets thicker as you climb higher.
Answers:
- Nitrogen and oxygen.
- The troposphere.
- The stratosphere.
- The weight of the air pressing down on an area.
- It decreases.
- False. The air gets thinner with altitude.
Where this fits
The atmosphere is one of Earth’s systems from atmosphere, oceans, and Earth systems, and its lowest layer holds the weather covered in heating, humidity, and clouds. Air pressure connects to heat, temperature, and pressure. Find all topics on the ASVAB General Science Learning Hub.
Recommended Prep Books
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