The atmosphere is the blanket of gases that surrounds the Earth and is held by gravity. It provides air to breathe, traps heat and protects life from harmful rays. Its layers and composition are core physical geography exam topics.
Composition of the Atmosphere
- Nitrogen makes up about 78% of the air.
- Oxygen makes up about 21%.
- The rest includes argon, carbon dioxide and water vapour.
Troposphere and Stratosphere
- The troposphere is the lowest layer where all weather happens.
- The stratosphere lies above it and contains the ozone layer.
- The ozone layer absorbs harmful ultraviolet rays.
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Higher Layers
- The mesosphere is where meteors burn up.
- The thermosphere contains the ionosphere, which reflects radio waves.
- The exosphere is the outermost layer that merges into space.
Importance of the Atmosphere
- It supplies oxygen for breathing and carbon dioxide for plants.
- It keeps the Earth warm through the greenhouse effect.
- It protects the surface from harmful rays and meteors.
Quick Revision Points
- The atmosphere is about 78% nitrogen and 21% oxygen.
- The troposphere is the layer of weather.
- The ozone layer is in the stratosphere.
- Ozone absorbs harmful ultraviolet rays.
- Meteors burn up in the mesosphere.
- The ionosphere reflects radio waves.
- The exosphere is the outermost layer.