Layers of the Atmosphere

First Layer  Scientists divide the atmosphere into four main layers based on the changes in temperature.  The Troposphere (“tropo” = changing) –Where Earth’s weather takes place, where we live. –Lowest layer, extends from Earth’s surface to ~12 kilometers. –Temperature decreases as altitude increases  -60°C at top. –Contains almost all of the mass in the atmosphere.

Stratosphere  The Stratosphere (“strato” = layer)  second layer, above the troposphere  ranges from ~12 - ~50 km above Earth’s surface  It contains the ozone layer.  The ozone layer is important because it protects us from dangerous UV radiation from the sun.  lower stratosphere is –60°C, but middle is warmer because of high amount of ozone, which absorbs heat from the sun.

Mesosphere  The Mesosphere (“meso” = middle) –above the stratosphere and it protects Earth from being hit by meteoroids. –ranges from ~50 - ~80 km above Earth. –Temperatures as cold as –90°C. –As altitude increases in the mesosphere, temperature decreases.

Thermosphere  The Thermosphere (“thermo” = heat) –it is the outermost layer and it extends from ~80 km to outer space. This layer is very hot since it is the first layer exposed to sunlight. –air in this layer is very thin, 0.001% as dense as the air at sea level. –air here is up to 1,800°C because it absorbs heat from the sun first. As altitude increases, temperature increases. –QUESTION: Would you feel warm or cold if you were in the thermosphere?

Two Layers of the Thermosphere  1. The ionosphere is the lower layer (~80- ~400 km) and it contains gas molecules that are electrically charged due to the sun’s energy. Radio waves bounce back from the ionosphere to Earth’s surface. These bright light displays are called auroras.  2. The exosphere is the outer layer and it extends from 400 km outward for thousands of kilometers.

Ozone  While ozone plays an important role in the stratosphere, it can be harmful in the troposphere. Why? –Ozone is a pollutant that can form over cities from sun interacting with smoke and CO 2, and can cause irritation to the lungs and eyes.

1.List the four main layers of Earth ’ s atmosphere, starting with the layer closest to Earth ’ s surface, AND give one important characteristic of each layer. 2. What property is used to distinguish between the different layers of the atmosphere? 3. In what layers of our atmosphere does temperature decrease with altitude? Where does temperature increase with altitude? Why does the temperature in the stratosphere increase with altitude?

4. Which layer of the atmosphere is the outermost layer? Why does this layer have no definite depth? 5. Why would you not feel warm in the thermosphere, even though temperatures can be as high as 1,800 degrees Celsius?