Navigation
An introduction to the five layers of the atmosphere and how they protect life on Earth.
Imagine you are on a rocket ship blasting off into space. As you climb, the air doesn't just get thinner—it acts like a giant, invisible layer cake where the temperature swings from freezing to boiling hot! Why does our 'shield' behave this way?
The Earth is wrapped in a blanket of gases called the atmosphere, held in place by gravity. This blanket isn't uniform; it is divided into five distinct layers based on how temperature changes with height. From the ground up, these layers are the Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere. Each layer serves as a specific line of defense, filtering out dangerous radiation and keeping our planet at a livable temperature. Think of it like a multi-layered suit of armor that protects us from the harsh environment of space.
Quick Check
Which force keeps our atmosphere from floating away into deep space?
Answer
Gravity.
The Troposphere is the lowest layer, extending from the surface to about km high. This is where we live, breathe, and where all weather occurs. Interestingly, in this layer, the temperature decreases as you go higher. This is because the Troposphere is primarily heated by the Earth's surface, not the sun directly. As you move away from the warm ground, the air gets colder at a rate called the environmental lapse rate, which is approximately for every meters of altitude.
If the temperature at sea level ( m) is , let's calculate the temperature at the top of a m mountain. 1. Identify the lapse rate: per m. 2. Calculate the total drop: . 3. Subtract from the starting temperature: . Result: It is much chillier at the peak!
Above the troposphere lies the Stratosphere ( to km). Unlike the layer below, the temperature here actually increases with altitude. Why? Because of the Ozone Layer. Ozone () molecules absorb the sun's high-energy ultraviolet (UV) radiation, converting it into heat. This layer is vital for life; without the ozone shield, UV rays would cause severe burns and damage the DNA of all living organisms. Commercial jets often fly in the lower stratosphere because it is stable and above the turbulent weather of the troposphere.
Quick Check
Why does the temperature increase as you go higher in the Stratosphere?
Answer
Because the Ozone Layer absorbs UV radiation and converts it into heat.
Beyond the Stratosphere, we find the Mesosphere, the coldest layer where temperatures drop to . This is where most meteors burn up, protecting us from space rocks. Next is the Thermosphere, which can reach because it absorbs high-energy X-rays from the sun. However, because the air is so thin, it wouldn't feel hot to your skin! Finally, the Exosphere is the outermost edge where the atmosphere fades into the vacuum of space. This is where most satellites orbit the Earth.
In the Thermosphere, the temperature is extremely high (), but an astronaut would freeze to death without a suit. 1. Temperature measures the average speed of molecules. 2. Heat measures the transfer of energy. 3. Because the molecules in the Thermosphere are so far apart, they rarely hit you to transfer their energy. Even though they move fast (high temperature), there aren't enough of them to keep you warm (low heat).
In which layer does all of Earth's weather occur?
What is the primary function of the Ozone Layer?
The temperature consistently gets colder the higher you go through all five layers of the atmosphere.
Review Tomorrow
In 24 hours, try to list the five layers of the atmosphere in order from the ground up and recall which one contains the Ozone Layer.
Practice Activity
Draw a diagram of the five layers. Label each layer and draw one object found in each (like a cloud, a plane, a meteor, or a satellite).