Q1
What is the atmosphere mainly composed of?
ANitrogen and oxygen
BOnly carbon dioxide
COnly argon
DOnly water vapour
ICSEClass 9 (ICSE)GeographyCh 9 · Topic 1
The Atmosphere - Composition and Structure
Earth's atmosphere, composed mainly of nitrogen and oxygen, has distinct layers, each with different characteristics and functions.
Core concept
The atmosphere is mainly nitrogen (78%) and oxygen (21%), with smaller amounts of argon, carbon dioxide, and water vapour.
How it works
The troposphere, closest to Earth, is where weather occurs and where most atmospheric water vapour and clouds are found.
Why it matters
The stratosphere, above the troposphere, contains the ozone layer, which absorbs harmful ultraviolet radiation from the Sun.
Key detail
Higher layers, like the mesosphere and thermosphere, have decreasing air density and play roles in meteor burning and auroras.
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• Atmosphere is mainly nitrogen (78%) and oxygen (21%).
• Smaller amounts of argon, CO2, water vapour exist.
• The troposphere is closest to Earth.
• Weather occurs in the troposphere.
• The stratosphere contains the ozone layer.
• Ozone absorbs harmful UV radiation.
• Higher layers include mesosphere, thermosphere.
• These have decreasing air density.