Chapter - 13
Ocean Water
Why is the Earth called the Blue Planet?
The oceans cover 71 percent of the Earth's total area. It appears blue when viewed from space, hence it is called blue planet.
️ Water cycle :-
The water cycle is a cycle operating on the earth for millions of years. In this, the water changes its state and place continuously and in the form of a cycle it reaches from the ocean to the surface and from the surface back to the ocean.
Water evaporates from the bottom of the oceans, which leads to the formation of clouds. The water vapor present in the atmosphere condenses and comes to the earth in the form of precipitation.
This water reaches back into the ocean through rivers. This cycle of water is called the water cycle. In this way, the water cycle keeps the lithosphere, hydrosphere and atmosphere connected to each other.
️ Mathematical method of water cycle :-
RF = RO + ET, here RF – all types of rain water, RO = Run off which is not absorbed by the earth, ET = Estimated Time
️ Ocean trenches or troughs :-
The long, thin and deep depression with a sharp slope located on the ocean floor is called trench or trough. The name of the deepest trench in the world is Mariana Trench, its depth is 11033 meters. Which is in the Pacific Ocean.
️ Continental Frontier :-
The outer boundary of the continents submerged in the sea is called continental frontier.
Sub Sublimation: -
The direct change of a substance from solid state to gaseous state is called sublimation. Like the direct conversion of water vapor into snowflakes.
️ Continental Shelf :-
Magnets are those parts of the continents, which are submerged in the sea, are called continental magnets. Its maximum depth is generally 200 m and slope is normal, its width depends on its slope. As a result, its width varies from a few kilometers to 1000 km. m. can happen till . Yet its average width is 80 km. m. it occurs . The continental shelf ends at a steep slope called a shelf recess.
️ Severe oceanic plain :-
As soon as the continental slope ends, the slope slows down and a deep oceanic plain begins which is called the Nital Plain. It is a wide flat area whose slope is less than 1° degree. About 40 percent of the ocean floor is covered by these plains. They are present in almost all oceans and many seas. Their depth is 3000-6000 m. Happens till then . These plains are covered with fine-grained sediments such as clay and silt.
️ Nital Hills (Sea Mount) :-
Thousands of such hills are found on the ocean floor, which are submerged in sea water, whose peak is raised more than 1000 meters above the bottom, they are called sea mountains or Nital hills.
While the flat-topped mountains are called Guyot Guyot, all these shapes are formed by the volcanic process, most of the low hills are in the Pacific Ocean.
️ Submerged Canyon Sub – marine Canyon :-
Deep and narrow or deep gorges with steep slopes submerged on the ocean floor are called submerged canyons, they are found more on the continental sloping and deep oceanic plains.
According to Shared and Baird, there are 102 Kenyans in the world. Most canyons are found in the Pacific Ocean. The world's longest submerged canyon, Bering, Privilaf and Gemchug are found in the Bering Sea. The world's most famous canyon is the Hudson Canyon, which starts from the mouth of the Hudson River and runs to the Atlantic Ocean.
️ Continental Slop
The part situated between the ocean basins and the continental submerged coast is called the continental slope. Its slope is between 2-5 and its depth is between 200 to 300 meters.
️ Marine Mound :-
The sea mound is a mountain with pointed peaks that rises above the sea level. But it does not reach the ocean surface. Its height can range from 3000 m to 4500 m above sea level, for example - Emperor is a sea mound which is an extension of the Hawaiian Islands in the Pacific Ocean.
️ Salinity of ocean water :-
The water of the sea is salty, this is due to the salinity present in it. Its calculation is expressed by the amount (in grams) of salt dissolved in 1000 grams (1 kg) of sea water. It is usually given per 1000 grams or pp. Tea . is expressed as.
️ Factors affecting the salinity of ocean water :-
Different amounts of salinity are found at different places. Following are the factors affecting it:-
Supply of water: Cold water has less salinity than hot water. Salinity is low at the mouths of rivers.
The amount of evaporation: - Less at the poles and higher latitudes, while more evaporation occurs at the Tropic of Cancer and Capricorn. Where evaporation is high, the salinity will be high.
Ocean currents: Salinity is low in cold currents and high in warm currents.
Horizontal distribution of salinity of ocean water :-
The distribution of salinity in the water of different oceans of the world is of different types, it can be described as follows:-
Salinity of open oceans :-
The amount of salinity is highest on the Tropic of Cancer and Capricorn. (due to excessive evaporation)
Due to the high rainfall, the amount of salinity is less near the equator.
The amount of salinity is found to be less near the poles, (due to the mixing of ice in the sea)
️ Factors affecting the temperature distribution of oceans :-
Like all other things present on the earth, ocean water gets its heat from the sun. The water of the sea is heated by receiving heat from solar radiation, due to which its temperature increases. The temperature of sea water is not always the same. It varies with time and place.
What layers of temperature will you face when you go down from the sea? Why does temperature vary with depth?
There are thousands of types of animals and other elements in the sea, which are affected by the sea temperature, as we increase towards the depth of the sea, the sea temperature keeps on varying. On going down in the sea the following layers are encountered.
First Level: - It represents the highest, warmest level of ocean water. Its thickness is about 500 meters, the temperature here ranges from 20 ° C to -25 ° C.
Second Level: - This is called thermocline or heat gradient. Its characteristic is that the temperature decreases rapidly with increasing depth. Its thickness is up to 500-1000 meters.
Third Level: - This level is very cold and extends to the deep ocean floor, the temperature of surface water in Antarctica circles is 0 ° C. Which extends from the surface to the deep oceanic plain. In this, the heat is not received directly from the sun, but through circulation, the lower parts get it.
What is the difference between heat gradient (thermocline) and salt gradient (halocline).
The temperature gradient and the salinity gradient denote the level at which the temperature and salinity rise or fall rapidly, respectively. Both these layers are found in the sea at a depth of 500-1000 meters.
The temperature gradient layer shows a rapidly falling temperature while the salinity gradient shows a rapidly increasing salinity. Both temperature and salinity affect the density of sea water. This leads to the stratification of ocean water. Water of higher density moves under water of lower density and causes the birth of water currents in the oceans.
