The Blanket of Air
Surrounding our planet is a layer of gases called the atmosphere. This blanket of air is essential for life. It provides us with oxygen to breathe, protects us from harmful solar radiation, and helps to keep the planet at a livable temperature.
The atmosphere is not uniform; it is divided into several distinct layers based on how the temperature changes with altitude.
The Layers of the Atmosphere (from the ground up)
1.Troposphere:
This is the lowest layer and the one where we live. It extends from the ground up to about 12 km (7.5 miles).
Key Feature: This is where all weather occurs. Clouds, rain, wind, and storms are all contained within the troposphere.
Temperature decreases as you go higher in this layer. Think about how it's colder at the top of a mountain than at the bottom.
2.Stratosphere:
This layer sits on top of the troposphere, extending up to about 50 km (31 miles).
Key Feature: The stratosphere contains the ozone layer. Ozone is a molecule (O₃) that absorbs most of the Sun's harmful ultraviolet (UV) radiation. Without the ozone layer, life on the surface would be exposed to dangerous levels of UV rays.
Temperature increases as you go higher in this layer, because the ozone layer is absorbing energy from the sun.
3.Mesosphere:
This layer extends from about 50 km to 85 km (53 miles).
Key Feature: This is the layer that protects the Earth from meteors. When meteoroids enter the atmosphere, friction with the gas particles in the mesosphere causes them to burn up, creating the streaks of light we call 'shooting stars'.
Temperature decreases as you go higher, and this is the coldest layer of the atmosphere.
4.Thermosphere:
This is the uppermost layer, extending to about 600 km (372 miles). The air here is extremely thin.
Key Feature: The aurora (Northern and Southern Lights) occurs in this layer. It is also where the International Space Station orbits.
Temperature increases dramatically in this layer because it absorbs high-energy X-rays and UV radiation from the Sun. Despite the high temperature, it would feel very cold because the molecules are so far apart.
What's in the Air We Breathe?
The air in our atmosphere is a mixture of many different gases.
Nitrogen (N₂): About 78%
Oxygen (O₂): About 21%
Argon (Ar): About 0.9%
Carbon Dioxide (CO₂), Neon, and others: Trace amounts.