The living part of the earth (called the Biosphere) can be put into three parts. They are:
Lithosphere (Solid part of the earth)
Hydrosphere (parts of the earth containing water)
One reason for the existence of life on planet earth is simply because of the nature of its atmospheric composition. The earth’s atmosphere is held close to the earth by the force of gravity. Read our article on gravitational force HERE. The atmosphere consists of gases that surround the entire surface of the spherical shaped earth. The compositions of these gases are as follows:
Nitrogen (N2): 78.09%
Oxygen (O2): 20.95%
Argon (Ar): 0.93%
Carbon(IV)oxide (CO2): 0.036%
Neon (Ne): 0.002%
Krypto (Kr): 0.001%
Helium (He): 0.0005%
Xenon (Xe): 0.00009%
Hydrogen (H2): 0.00005%
Water Vapour: Variable
All of these gases that make up the atmosphere are generally called air.
As we move away from planet earth, the atmosphere becomes thinner until it disappears into the outer space. There is no atmosphere in space and this is why astronauts always carry along their oxygen gas masks and canisters when in space. People living on very high altitudes will have reduced oxygen and this will affect the normal functioning of their body. On mountain Everest for instance, mountain climbers will need to carry oxygen canisters because lesser amount of oxygen are present on this mountain.
Note: The atmospheric composition on the moons and other planets are quite different from that of the earth. Most of them will have lesser percentage of oxygen or even no oxygen at all, thus making life incompatible on them. Some may not even have an atmosphere to begin with.
The only process in nature that actively enriches our atmosphere with oxygen is photosynthesis. Every other process like respiration, burning and combustion takes away oxygen while also introducing carbon(IV)oxide CO2 into the atmosphere. Photosynthesis is also the only process that takes away CO2 from the atmosphere.
Note: Photosynthesis is the process by which green plants manufacture food by utilizing carbon(IV)oxide and water in the presence of sunlight while given off oxygen as a bye product.
Potentially dangerous ultraviolet radiation coming from the space is hindered by the atmosphere from reaching the surface of the earth and that’s a good thing. This is because ultraviolet radiation is harmful to living organisms. On the other hand, the atmosphere allows the sun’s rays to reach the earth, while also preventing it from leaving the earth back into the outer space. One fact concerning life is; “The sun is the ultimate source of energy and without the sun’s rays on earth, life will be non-existent”. The atmosphere is also a major component of water cycle, while also assisting in keeping the climate of the earth stable.
The atmosphere surrounding the earth is layered. Each layer has its own characteristics although the boundaries between them are not clearly defined. Beginning from the layer closest from the earth, they include:
From the surface of the earth, the troposphere is about 0 - 7 miles or 0 -12 kilometers high. It is easily penetrated by the sun’s heat into the surface of the earth while also preventing the escape of heat reflected from the ground of the earth into the outer space. This layer of the atmosphere contains water vapour, making it the point of weather development.
Note: The level of the atmosphere that forms the boundary between two atmospheric layers will always end in a "pause" when named; for instance, tropopause (is the interface or boundary between the troposphere and stratosphere). Other boundaries includes; stratopause, mesopause, ionopause and so on.
This layer of the atmosphere extends from the tropopause and is about 7 - 31 miles or 12 - 50 kilometers high. Because of the reduced atmospheric turbulence in this region, planes prefer to fly here. Some of the oxygen tri-atomic molecule (O3) called ozone is present here. This ozone prevents the harmful ultraviolet radiations from reaching the earth.
Note: The chemical chlorofluorocarbon (CFC) can bring about ozone depletion in the atmosphere.
This layer begins from the stratopause from a height of 31 - 58 miles or 50 - 80 kilometers. It is characterized with the lowest of temperatures when compared with other layers of the atmosphere. The largest amounts of clouds are also present here. Aircraft and Spacecraft do not fly within this region.
Extending from the mesopause at a height of 50 - 440 miles or 80 - 700 kilometers, the thermosphere is the densest layer of the atmosphere. It comprise of the ionosphere, a layer that conducts electricity. These ions in the ionosphere are created from the particles of sunlight and those of the space. Gases like hydrogen, helium and oxygen are found here.
The main gas found here is hydrogen. This layer commences from the thermopause at a height of 440 - 6,200 miles or 700 - 10,000 kilometers. Some of the earth’s artificial satellite can be found in this region of the atmosphere.
The moon has no atmosphere.
All the planets in the solar system have atmospheres although they are quite different in composition from that of the earth.
The atmospheres of the terrestrial planets (Mercury, Venus, Earth and Mars) are somewhat similar to that of the earth but nonetheless they are still not able to support life.
The atmosphere of the gas giants planets (Jupiter, Saturn, Uranus and Neptune) are composed mainly of hydrogen and helium gases. Planets Neptune and Uranus contains an additional gas “methane” in their atmosphere while gives them their prominent bright blue colour.
Although Venus and Mars contain oxygen, the atmosphere of Venus is too thick to support life while that of Mars is too thin to support life.
Earth is the only planet whose atmosphere is compatible with life.
Topics in GeographyTypes of Rocks Types and Branches of Geography Layers and Composition of the Atmosphere The Solar System