02 Atmospheric Layers

The atmosphere that surrounds Earth is made up of several layers of gas mixtures. The most common gases in our atmosphere are nitrogen, oxygen, and carbon dioxide.

The atmosphere puts pressure on the planet. However, the further away from Earth's surface we get, the lower the pressure gets. The overall condition of Earth's atmosphere is called weather. Of course, weather frequently changes. That is because the conditions of the atmosphere can change.

There are four main layers in the Earth's atmosphere. These layers are: the troposphere, the stratosphere, the mesosphere, and the thermosphere. The layer closest to the Earth's surface is the troposphere. It extends from the Earth's surface to a height of about 1 1 kilometres. This is the layer where airplanes fly and where most weather comes from. About 75% of Earth's air is in this layer.

Above the troposphere is the stratosphere, which extends to about 50 kilometres above the Earth's surface. Most ozone is in this cold, dry layer. Ozone is very important because it stops some of the Sun's dangerous radiation from reaching the Earth's surface.

The next layer is the mesosphere, which goes up to about 80 kilometres above Earth's surface. This layer is extremely cold. Meteors are most often found in this layer, but most of them burn up before reaching Earth's surface.

The fi nal layer is the thermosphere, which is closest to the Sun. The temperature in this layer can be over 1500 degrees Celsius!

Together, the layers of our atmosphere protect the Earth. The atmosphere provides the conditions needed to support life.

Word List

frequently : very often

radiation : harmful rays from the Sun

You Practice

I. Tell about it—For each atmospheric layer, tell what is special about it.

1) the troposphere:________________________________________

2) the stratosphere:________________________________________

3) the mesosphere:________________________________________

4) the thermosphere:______________________________________

II. Answer the following questions.

1) In which layer of the atmosphere do people live? Why?

2) Where is most of Earth's air found?

3) Why is ozone important?

4) What is the highest layer of atmosphere?

5) Which layer of the atmosphere is the hottest?

III. Word power—Use each of these words from the reading in sentences of your own.

1) weather ______________________________________________

2) extend _______________________________________________

3) protect _______________________________________________

4) layer _________________________________________________

5) surface _______________________________________________