By Alex Smith Updated Mar 24, 2022
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The Earth's atmosphere is a thin veil of gases that encases the planet, with an average depth of about seven miles. It is stratified into four distinct layers: the troposphere, stratosphere, mesosphere, and thermosphere. Each layer contains a mixture of gases—two main components dominate the composition, while several others exist only in trace amounts.
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Nitrogen constitutes roughly 78% of the atmosphere. As an inert gas, it occupies the space not taken by more reactive constituents.
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Oxygen makes up 20–21% of the air. It is essential for aerobic life but becomes hazardous when its concentration rises significantly above 21%.
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The remaining 1–2% of the atmosphere is composed of trace gases, including:
• Argon – 0.93%
• Carbon Dioxide – 0.036%
• Neon – 0.00182%
• Helium – 0.000524%
• Methane – 0.00015%
• Krypton – 0.000114%
• Hydrogen – 0.00005%
