Major Domains of the Earth

The Northern Hemisphere is called the land hemisphere because the greater part of continental landmass lies in the northern hemisphere while on the other hand large percentage of area in the southern hemisphere is covered with oceans.

Atmosphere acts as a blanket of the earth because it maintains a fairly even temperature both during day and night. Atmosphere also shields the earth from the strong ultraviolet rays of the sun due to the presence of ozone gas. It also protects earth from meteors.

The different layers of the atmosphere are:
1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Exosphere
Closest layer to the earth's surface is the Troposphere.

The major oceans on the earth are:
Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean and Southern Ocean. In 2000, the International Hydrographic Organization created the Southern Ocean extends from the coast of Antarctica north to 60 degrees south latitude with an area of approximately 20.3 million square kilometers.

A strait is a narrow passage of water connecting two large water bodies like seas and oceans. The strait between India and Sri Lanka is Palk Strait.

A plateau is a large area of fairly level land rising much above the surrounding areas. A plateau may have steep slopes on one or more sides. The height of the plateau may range from 400 meters to several thousand meters above sea level. These are almost flat. Deccan Plateau of India and the plateau of Africa are two important examples.

The climbers experience problems in breathing due to decrease in the density of air. They have to carry with them oxygen cylinders to be able to breathe at higher altitude as the density of air keeps on decreasing with increase in altitude.

A mountain is a conical mass of land rising to a much greater height than the surrounding areas. Its uppermost projected area is called peak.

Old mountains have rounded features and are low in height such as Aravallis. It is because they are very old and have been eroded by the forces of nature like wind, water, etc. over a long period. Young mountains have conical features and are greater in height.The best example of young folded mountains is Himalaya.

The major continents of the earth are:

1. Asia
2. Europe
3. North America
4. South America
5. Africa
6. Australia
7. Antarctica

The major constituents of the atmosphere are:

1. Gases
2. Water Vapour
3. Dust Particles

The major effects of water pollution are:

1. The food chain is damaged. When toxins are in water, the toxins travel from the water to the animals and to humans when the animal's meat is eaten.
2. Diseases can spread via polluted water. Infectious diseases such as typhoid and cholera can be extended from drinking contaminated water.
3. Acid rain contains sulfate particles, which can harm fish or plant life in lakes and rivers.
4. Pollutants in the water will alter the overall chemistry of the water, causing changes in acidity, temperature and conductivity. These factors all have an affect on the marine life.
5. Marine food sources are contaminated or eliminated by water pollution.
6. Altered water temperatures (due to human actions) can kill the marine life and affect the delicate ecological balance in bodies of water, especially lakes and rivers.

The three domains of the earth interact with each other and affect each other. For example, the industrial effluents are thrown on the land from where they gradually flow into rivers, lakes and other water bodies. Hence, polluting both land and water. The polluted release of smoke and other gases further pollute the atmosphere. So, all the major domains are affected by one common source.

Global warming is the increase average temperature of the Earth's near-surface air and oceans.

1. Most prominent factor is from the combustion of fossil fuels in cars, factories and electricity production. They produce carbon dioxide, which is the most common gas responsible for the global warming.
2. Other contributors include methane released from landfills and fertilizers.
3. Gases used for refrigeration and industrial processes.
4. The loss of forests that would otherwise store CO2.

Antarctica lies completely in the southern hemisphere. At the centre of the continent is the South Pole. It is permanently covered with thick ice sheets. There are no permanent human settlements here. Many countries have set up there research station here. Maitri and Dakshin Gangotri are Indian research centres.

The earth experiences water shortage because 97% of the earth’s water is found in the oceans and is too salty for human use. Of the remaining 3%, large proportion is in the form of ice sheets, glaciers and under the ground. A very small percentage is available as fresh water.

Ocean currents greatly affect the Earth's climate by transferring heat from the tropics to the Polar Regions, and transferring warm or cold air and precipitation to coastal regions, where winds may carry them inland. The oceans are essential for transportation: Most of the world's goods are exported or imported by ship between the different continents. Oceans are also the major supply source for the fishing industry Offshore Oil, Gas and Mining Recreation and Tourism: Including fishing, boating, swimming etc. Disposal of Waste from Land: Including sewage, non-point sources, CO2 sink.

The level of seawater remains same everywhere. Elevation of land is measured from the level of the sea, which is taken as zero.

The continuous changes of the state and movement of water throughout the Earth system, i.e., the atmosphere, biosphere, lithosphere and hydrosphere is known as the water cycle. The water cycle is driven by energy from the Sun rays, which cause liquid water from Earth's surface to change into gas in a process called evaporation. As gaseous vapour rises and circulates in the atmosphere, it cools and changes back into a liquid, a process known as condensation. When water vapour condenses, tiny droplets form clouds, which return the water to Earth as precipitation.

The outermost layer of Earth's atmosphere extends upward. Here, the particles are so far apart, that they can travel hundreds of km without colliding with one another. Since the particles rarely collide, the atmosphere no longer behaves like a fluid. These free-moving particles follow ballistic trajectories and may migrate into and out of the magnetosphere or the solar wind. The exosphere is mainly composed of hydrogen and helium.

Rain water is naturally acidic due to carbon dioxide, which partially reacts with water to give carbonic acid. When we talk about acid rain, we mean the enhanced effect which is caused by other gases released when fossil fuels are burnt. Two main gases are:Sulphur dioxide and Nitrogen oxide. The dilute acid falls to ground as acid rain.

Ozone depletion occurs when the natural balance between the production and destruction of stratospheric ozone is tipped. Although natural phenomena can cause temporary ozone losses, man-made synthetic compounds such as CFCs are now accepted as the main cause of this depletion. Ozone depletion, in fact, is occurring all over the world due to man-made pollution, at 19 to 30 km above the Earth's surface. However, in certain parts of the world, ozone depletion is particularly severe.