The earth is a solid and there is a mixture of gases surrounding the earth. The mixture of gases is called air. So the mixture of gases or the air envelope which surrounds the earth is called atmosphere. The atmosphere is held to the earth by the force of gravity.
The major part of atmosphere extends up to a height of about 40 kilometers above the earth’s surface.
https://www.qries.com/What-is-atmosphere-and-what-is-its-composition/answer/Daneel-Yunus
daneelyunus 
It’s nice to read the geography again
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Thank you dear
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Interesting topic
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Thanks for appreciation and reading my post
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We often take it for granted but we wouldn’t be here if it wasn’t for the atmosphere.. when you think about it for a long time it’s so wondrous and almost unreal isn’t it?
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The study of universe and atmosphere is unlimited and full of mysteries which is very interesting
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