Atmosphere
Topic: Atmosphere: Composition, Structure and Elements of Weather · NCERT: Class 11, Ch 7 "Composition and Structure of Atmosphere"
Meaning
The atmosphere is a blanket of gases, water vapour and dust that wraps around the Earth. Gravity holds it in place. It is thickest near the ground and thins out with height: 99 per cent of its mass lies within 32 km of the surface. It gives oxygen to animals and carbon dioxide to plants. It blocks harmful ultraviolet (UV) rays and keeps the Earth warm by trapping part of the Sun's energy.
Example
Air presses down hardest at sea level, at about 1,013 millibars (mb) in places like Mumbai. At Khardung La in Ladakh, high in the mountains, it is only about 650 mb. There is much less air above the pass, so visitors there often feel short of breath.
Don't confuse with
- Air pollution: the atmosphere is the natural layer of gases around the Earth. Pollution is the harmful matter that people add to it, such as smoke and PM2.5.