Back to Oceans



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Earth is known as the " Blue planet " due to abundant water present in it. Oceans are the storehouse of water. There is approximately 320,000,000 litres of water present in the Ocean. But from where does all this water come from?

It is the result of the continuous water cycle which provides water to earth and to oceans. Over a short period of time the amount of water in the ocean doesn't change but in a longer span it does have an impact. Let's have a look at the water cycle which keeps on circulating huge amounts of water from the ocean and then gives back to oceans.

The Water Cycle

Evaporation, cooling, freezing condensation, melting are all important processes that drive the hydrological cycle which is a never-ending process of water circulation from oceans to clouds and rivers and back to oceans. The steps involved in cycling of huge amount of water are - 

  • Evaporation - The sun which is the primary source of energy heats up the large surface area of oceans and causes the water from oceans to evaporate. This large amount of water constitutes the atmospheric water vapour. Warm water vapour rises up thereby cooling the surface of water. Huge amount of heat is absorbed by the ocean for the heating up of water from the surface of Ocean continuously. 

  • Condensation - the water vapour rises up continuously and is carried away by the atmospheric air currents where it cools and condenses to form the clouds. Condensing water vapour releases latent heat and this latent heat plays an important role in Earth's heat balance.The clouds are accumulation of fine droplets of water at extremely low temperature and remain suspended at high altitudes.

  • Precipitation - the clouds collide and their the electrical discharge which results in the precipitation of water droplets to the ground. The precipitation may be in the form of rain, snow, hail etc. Most precipitation falls on water bodies or on land.

  • Surface runoff - The water that falls on land meets a different fate. A portion of water flows over the ground as runoff and due to gravity it eventually is discharged into rivers and other water bodies.

  • Stream flow - The water accumulated from surface runoff and drainage flows into streams, lakes and rivers which travel along the surface of earth to reach sea and finally meet the oceans.

  • Soil moisture - Some water infiltrates into the soil which is utilised by plants and returns to the atmosphere by evapotranspiration.

  • Groundwater - Deep infiltration of water results in replenishing ground water table which then later emerges as springs or is taken by humans for their use.

Over time all this water keeps circulating through various channels, but ultimately it is poured back to the oceans from where it's journey started.

Significance of Water Cycle

1.The cycling of water is related to energy exchange between ocean, atmosphere and land.

2.It influences Earth's climatic conditions and climate change to a great extent.

3. Large amounts of heat absorbed by the ocean helps in buffering the green house effect from increasing carbon dioxide and other gases.

4.Condensed water vapour releases latent heat which drives atmospheric circulation in the tropical regions.

FAQ (Frequently Asked Questions)

1. What are Aquifers?

Ans- Groundwater which is stored beneath the rocks as a reservoir of water is known as aquifers. They provide 98% of groundwater. Wells can be drilled to draw water out of aquifers which recharge naturally through precipitation.

2. Explain Role of Plants in Water Cycle.

Ans- Plants play a major role in attracting atmospheric moisture in the form of clouds and humidity. Condensation on plants provides additional moisture. The groundwater or deep percolated water is harnessed by the plants, which is later evapo-transpirated by the plants upto 99%. Hence plants play a major role in atmospheric circulation and water cycle.

3. What is the Driving Energy of a Water-Cycle?

Ans- The sun which is the ultimate source of energy for earth drives all the physical reactions. It provides heat energy which is used for the evaporation of large amounts of ocean water.

4. What Do You Mean By Precipitation? Explain Different Types of Precipitation.

Ans-. Precipitation is the falling of water particles in different forms from higher altitudes to the surface of earth. It occurs when the atmosphere becomes saturated with water vapour which condenses and falls to the ground by the action of gravitational pull of earth. Due to the variation in climatic regimes, there are different types of precipitation. They are-

  • Rain- When precipitation occurs in the form of water droplets of size not less than 0.5mm. It occurs when clouds of opposite charge collide. It is the most common form of precipitation and source of freshwater.

  • Drizzle- Water droplets less than 0.5 mm are called drizzle. It is a mild form of precipitation but stronger than mist. A persistent drizzle is found in cold atmospheric temperatures.

  • Snow-  Every time there is production of snow but most of it melts on reaching near the surface of the earth and occurs in the form of rain. But in places where there is low temperature snow is often seen. Snow is characterized by the presence of cirrus clouds and occurs in sub freezing temperatures. Snow has a fluffy,white and soft structure and occurs in different shapes in the form of plates or needles.

  • Snow grains- They are very small, white opaque grains of ice which are flat in shape and have diameter less than 1 millimeter. They are almost similar to drizzle except the fact that they are in hard form.

  • Diamond dust- it is extremely small crystals of ice formed at low temperature below minus 30 degree Celsius.

  • Sleet- Also known as ice pellets, are formed in freezing atmospheric conditions. The raindrops falling from the sky freeze into ice pellets and precipitation of small semi-transparent balls of ice occurs.

  • Hail- Hail is the big irregular form of ice that falls during thunderstorms. Hail is predominant in winter or cold weather. The size of particles varies from 5 millimetres to 15 cm and diameter. Hence, it causes large damage to crops.

5. What Do You Mean by Sea Breeze and Land Breeze?

Ans-  Sea breeze- when water moves from sea to land due to the difference in air pressure created by heating of the water and land it is called sea breeze. Because land gets heated faster than sea, this breeze occurs after sunrise and during the day. It creates a cooling effect, as the sea breeze is laden with water vapour.

Land breeze- when water moves from land to sea it is referred to as land breeze. This is because the land dissipates heat faster than water. This moment of wind is during night. The land breeze does not contain any moisture until and unless there are water bodies on the land.