The Atmosphere

The Atmosphere

The earth is surrounded by all kind of gases. This layer is called the earth's Atmosphere. Without this atmosphere life on earth isn't possible. It gives us air, water, heat, and protects us against harmful rays of the sun and against meteorites.

This layer around the earth is a colorless, odorless, tasteless 'sea' of gases, water and fine dust. The atmosphere is made up of different layers with different qualities. It consists of 78 percent nitrogen, 21 percent oxygen, 0,93 percent argon, 0,03 percent carbon dioxide and 0,04 percent of other gases.

The Troposphere is the layer where the weather happens. Above this layer is the Stratosphere and in between them is the Ozone layer, that absorbs the sun's harmful ultraviolet rays. Above the Stratosphere is the Mesosphere, the Thermosphere including the Ionosphere - and the Exosphere. The atmosphere measures about 500 miles (700km).

Where does the Atmosphere consist of?

The atmosphere has at the upper side no clear boundary, because higher in the atmosphere, the layer becomes thinner and thinner. It constantly loses molecules of lighter gases such as helium and hydrogen. The further we get from the earth, the atmosphere is divided in thin layers, based on changes in the temperature.

The Troposphere
The Troposphere is the lowest layer of the atmosphere and measures about 7 miles(12 km). It contains over 75 percent of all the atmosphere's gases and vast quantities of water and dust. As the sun heats the ground, it keeps this thick mixture churning. The weather is caused by these churnings of the mass. The troposphere is normally warmest at ground level and cools higher up where it reaches its upper boundary (the tropopause). The tropopause varies in height. At the equator it is at 11,2 miles(8 km) high, at 50 N and 50 S, 5,6 miles(9 km) and at the poles 3,7 miles(6 km) high.

Stratosphere:
The Stratosphere extends from the tropopause up to its boundary (the Stratopause), 31 miles(50 km) above the Earth's surface. In this layer there is 19 percent of the atmosphere's gases and it contains little water vapour. Compared to the troposphere it is calm in this layer. The movements of the gases are slow. Within the stratosphere is the ozone layer, a band of ozone gas, that absorbs harmful ultraviolet rays of the sun. The higher you get in the atmosphere, the warmer the air gets. The temperature rises from -76 ºF(-60 ºC) at the bottom to a maximum of about 5 ºF(10 ºC) at the stratopause.

Mesosphere:
The mesosphere is the next layer above the stratopause and extends to its upper boundary (the Mesopause), at 50 miles(80 km) above the ground. The gases in the mesosphere are too thin to absorb much of the sun's heat. Although the air is still thick enough to slow down meteorites hurtling into the atmosphere. They burn up, leaving fiery trails in the night sky. The temperatures in the mesosphere drop to -184 ºF(-120 ºC) at the mesopause.

Full size

Layers of the atmosphere
The atmosphere is divided into five main layers plus the ionosphere. It extends over 430 miles (700 km) into the sky.

Image by:
Roy Flookes,
Dorling Kindersley

Thermosphere:
The Thermosphere is the layer above the mesopause. The gases of the thermosphere are even thinner than those in the mesosphere, but they absorb ultraviolet light from the sun. Because of this, the temperatures rise to 3,600 ºF (2,000 ºC) at the top. This is at a height of 430 miles (700 km) of the earth's surface. In the thermosphere is a separate layer, the Ionosphere. This layer extends of 62 miles(100 km) to 190 miles(300 km) of the earth's surface.

Ionosphere:
The ionosphere is part of the thermosphere. It is made of electrically charged gas particles (ionised). The particles get this electric charge by ultraviolet rays of the sun. The ionosphere has the important quality of bouncing radio signals, transmitted from the earth. That’s why places all over the world can be reached via radio.

Exosphere:
The Exosphere is the outermost layer of the atmosphere and extends from 430 miles(700 km) to 500 miles(800 km) above the ground. In this layer gases get thinner and thinner and drift off into space.

What influence does the Atmosphere have?

The atmosphere is of vital importance for life on earth. Without atmosphere life would be impossible. It gives us air to breathe and protects us from meteorites and ultraviolet rays from the sun. The atmosphere absorbs so much heat that temperatures on earth are such that life is possible. The weather, that exists by constant circulation of water to water vapor, to rain to water. This cycle causes, together with the differences in temperature and circulation of air (wind), erosion of the earth's surface. By erosion the outside of the earth changes through the years.

Relative sites

Home | Formation of the Earth | Earth's Structure | Life on Earth

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