Natural Resources

Atmosphere

• The multilayered gaseous envelope surrounding the planet Earth is called atmosphere.
• It extends from the ground to about 11 km into space.
• It gets denser due to the gravity as we approach the ground.
• It has the right amount of pressure and composition to sustain life.
• It is a mixture of gases such as nitrogen, oxygen and carbon dioxide.
• Atmosphere is divided into five distinct layers or zones:
  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere (ionosphere) and
  • Exosphere.
• The atmosphere above the earth’s surface forms a blanket of gases protecting us from many harmful radiations that come from outer space.
• The three important roles of air are discussed below:

Air for Breathing

• Except a few species of bacteria, all life on land require air to survive because it contains two essential components: Oxygen and Carbon dioxide.
  • Respiration: Animals use oxygen to convert the chemical energy stored in food into energy that they can use for all activities. So, they take in oxygen and it reacts with molecules from food to produce energy. Carbon dioxide and water along with usable energy are released.
  • Photosynthesis: Plants also breathe in carbon dioxide in the presence of sunlight to store the energy of light as chemical energy in food. They convert the carbon dioxide molecule into glucose (food) molecules using sunlight. Oxygen is released as a byproduct.
• Thus air is required by animals to gain energy from food and by plants to store energy in form of food.
• This balance sustains all life forms on earth.

Air for Combustion

• Fuel combines with oxygen to release energy in the form of heat and light by the process known as combustion.
• The heat released can be used to produce electricity, run cars and cook food.
• During the process of combustion, oxygen in the atmosphere combines with carbon atoms to produce carbon dioxide and hydrogen atoms to produce water.
• Without oxygen one cannot use these fuels for our daily needs.
• But, too much oxygen can cause uncontrolled burning and explosions.
• Fire can be caused by the tiniest uncontrolled spark.
• But this phenomenon is not observed in the atmosphere even though oxygen is present in the air around us.
• This is because of the presence of 78% nitrogen gas in air.
• Nitrogen does not support combustion and thus prevents the excess reactivity of oxygen.
• Thus these two components are essential to ensure that energy from the fuel can be used in a controlled manner.

Air for regulating temperatures or climate control

• The air moderates the temperature on earth for life to exist.
• Without the atmosphere, the daytime temperatures on earth would be as very high and at night it would be as cold as -30⁰ C which would make it very difficult for life to survive.
• The density of air reduces on heating and it rises upwards.
• Similarly, cold air is denser than the hot air which sinks towards the ground.
• As the hot air rises, it creates a space of low pressure where the cold air rushes in and occupies this space. This results in the movement of air called wind.
• As the hot region heats up the air and gets raised, the colder air from the surroundings enters into it, get heats up and the cycle repeats.
• The rising of the hot air transfers its heat into outer space and sinks back down.
• In this way, heat is transferred from hotter regions to colder regions. This is known as temperature regulation and the process of transferring heat is called convection.
• Moon has no atmosphere. Hence the temperature varies from 190°C to 110°C.

Other natural resources like water, land, plants, rivers, mountains, etc. play a vital role in sustaining life on earth by complementing each other. But one must not take these resources for granted. Due to population outburst, these resources are under great stress and measures need to be taken so that the future generation can also enjoy the luxury of nature like us.

WIND: THE MOVEMENT OF AIR

Air movement in coastal areas: In coastal areas, at daytime, there is a regular flow of cool air from the sea towards the land, whereas at night, there is a reverse flow of air from land to sea.

• DURING DAY: This happens because during the daytime, land gets heated faster than water. The hot air rises from the land and creates an area of low pressure. Whereas sea water does not get heated so rapidly. That means air above the sea is relatively cool and creates a high pressure as compared the air over land. Therefore, cooler air over the sea, flows toward the area where low pressure exists. The movement of air from one region to the other creates winds.
• DURING NIGHT: Reverse flow of air occurs at night. Land cools down rapidly making the air above the land cooler. This gives high pressure over the land. Sea water cools down slowly. The air above the sea is hotter and has a lower air pressure as compared to air pressure above the land. Therefore, cooler air present over land flows towards sea.

Factors Influencing Movements of Air

The following factors influence the movement of air:

• Uneven heating of land at different parts of Earth.
• Rotation of Earth.
• Presence of high mountain ranges in the path of winds.
• Vaporization and condensation of water vapors.
• Difference in topography over which the wind passes.
• Differences in heating and cooling of land and water bodies.

RAIN

• When water bodies get heated by solar radiations during the day, a large amount of water evaporates and goes into the air.
• Various biological activities such as transpiration by plants leads to amount of water vapour also goes into the atmosphere.
• This hot air rises up, carrying water vapours with it.
• As the air rises, the air expands and cools.
• This cooling causes the water vapour in the air to condense in the form of tiny droplets around dust particles.
• An enormous collection of tiny droplets of water appear in the form of clouds.
• When the droplets become big and heavy, they fall down in the form of rain.
• Occasionally, when the temperature of air is very low, precipitation then may occur in the form of snow, sheet or hail.
• Rainfall patterns are decided by the prevailing wind pattern.
• In large part of India, rains are mostly brought by the South-west or North-east monsoons.