The Atmosphere
Earth's atmosphere has layers from troposphere to exosphere.
About this topic
Earth's atmosphere is a layer of gases held by gravity: 78% nitrogen, 21% oxygen, plus argon, CO₂ and water vapour. Layers from the ground up: troposphere (weather, where temperature falls with height), stratosphere (ozone layer, temperature rises), mesosphere (meteors burn up), thermosphere (auroras, very hot but thin) and exosphere.
The atmosphere provides air to breathe, shields us from radiation and meteoroids, keeps the planet warm via the greenhouse effect, and moves water and heat around.
Air pressure falls as you climb, because there is less air above. At the top of Mount Everest at about 8,849 m, pressure is about a third of that at sea level, so each breath contains much less oxygen, even though the percentage remains 21. About half the atmosphere's mass is below 5.5 km, and 99 percent is within 30 km. The temperature profile changes direction at each layer because of what heats it: the ground warms the troposphere, ozone absorbing UV warms the stratosphere, and the thermosphere is heated by the absorption of X-rays and extreme UV.
Airliners cruise in the lower stratosphere, above most weather, and the ISS orbits in the thermosphere. The Karman line at 100 km is often used as the edge of space. The greenhouse effect is natural and necessary: without it, Earth would average about minus 18 degrees C instead of about 15. A common misconception is that the atmosphere is mostly oxygen, but nitrogen dominates. Also, the thermosphere has high temperature by particle energy, yet you would feel freezing because the air is so thin.
Key ideas
- Troposphere holds weather
- Ozone in the stratosphere
- 78% nitrogen
Quick check
Use cases: where The Atmosphere helps
- Homework: review the key idea behind The Atmosphere before you start a problem set.
- Exam revision: use the quick check to test whether you can recall The Atmosphere without notes.
- Visual learning: play with the interactive lab to see how The Atmosphere changes when you adjust its inputs.
- Teaching a friend: explain The Atmosphere in your own words, then compare your version with the key ideas.
Earth science helps with weather forecasts, natural hazards, energy and climate planning.
Frequently asked questions
What is The Atmosphere?
Earth's atmosphere has layers from troposphere to exosphere.
What will I learn in The Atmosphere?
Troposphere holds weather. Ozone in the stratosphere. 78% nitrogen.
Is The Atmosphere part of Earth & Space?
Yes. It is one of 60 Earth & Space topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the The Atmosphere lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study The Atmosphere?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.