RBSE Solutions for Class 11 Physical Geography Chapter 19 Ocean: Relief, Temperature and Salinity

RBSE Solutions for Class 11 Physical Geography Chapter 19 Ocean: Relief, Temperature and Salinity

Rajasthan Board RBSE Class 11 Physical Geography Chapter 19 Ocean: Relief, Temperature and Salinity

RBSE Class 11 Physical Geography Chapter 19 Text Book Questions

RBSE Class 11 Physical Geography Chapter 19 Multiple Choice Questions

Question 1.
On what percent part of the earth is water present?
(a) 29
(b) 67
(c) 71
(d) 81
Answer:
(c) 71

Question 2.
The average height of the continents is:
(a) 10 meters
(b) 400 meters
(c) 840 meters
(d) 1000 meters
Answer:
(c) 840 meters

Question 3.
In one kg. of the oceanic water, the salinity is:
(a) 35 grams
(b) 45 grams
(c) 15 grams
(d) 25 grams
Answer:
(a) 35 grams

Question 4.
Where is the Mariana Trench located?
(a) Pacific Ocean
(b) Indian Ocean
(d) Mediterranean Sea
(c) Atlantic Ocean
Answer:
(a) Pacific Ocean

Question 5.
The oceanic water receives heat from:
(a) from sun
(c) from warm currents
(b) from moon
(d) from self
Answer:
(a) from sun

RBSE Class 11 Physical Geography Chapter 19 Very Short Answer Type Questions

Question 1.
In which ocean is the Mariana Trench situated?
Answer:
The Mariana Trench is in the Pacific Ocean. It is the deepest trench of the world.

Question 2.
What is meant by Land form?
Answer:
A land form is a feature on the earth’s surface that is a part of the terrain. The surface physical shapes are studied under the land forms.

Question 3.
What is meant by Relief?
Answer:
The physical forms of the upper surface of the earth is called the Relief. In this, parts of the earth’s surface with heights and depths: mountain, valley, plain, plateau etc. physical landscapes are included. The word relief is used to express the inequalities and variations in the physical profile of the earth’s surface.

Question 4.
What is the average salinity of the oceanic water?
Answer:
The average salinity of oceanic water is 35 per thousand grams that is, 35 grams of salts are found dissolved in 1 kg. of water.

Question 5.
From where is salinity obtained in ocean water?
Answer:
Salinity is obtained in ocean water mainly from the rivers, which carry 16 million tonnes of salt from the terrestrial regions every year and deposit them in the oceans. Salinity is also obtained from waves, winds and volcanic eruptions.

RBSE Class 11 Physical Geography Chapter 19 Short Answer Type Questions

Question 1.
Describe the land forms of the Pacific Ocean.
Answer:
Pacific Ocean is the largest ocean of the world which covers about 1/3rd part of the earth. In the triangular shape, it is 18000 km. wide from east to west, and 16740 km. long from north to south. Different types of land forms are found in this ocean, like: volcanic mountain ranges, earthquake affected areas and group of islands are found on its coast. More than 20000 islands found in the Pacific Ocean are classified into three parts: Melanesia, Micronesia and Polynesia. Many*troughs, long ridges, plateaus, scarps are found in the Pacific Ocean.

Question 2.
Into how many relief features is the Ocean Bottom classified?
Answer:
The Ocean Bottom is classified mainly into four relief features:

1. Continental Shelf:
It refers to the submerged coast. Thus, those parts of the continents which remain submerged in ocean are called the Continental Shelf and whose maximum depth is considered to be 100 fathom.

2. Continental Slope:
Ahead of the continental shelf, the slope of ocean floor becomes abruptly steep. It extends upto a depth of 3600 to 9100 meters.

3. Deep Sea Plain:
The slope becomes very gentle on the end of the continental slope and the marine plain starts, which is called the Deep Sea Plain.

4. Oceanic Deeps:
The deeps with the maximum depth found on the ocean floor are called the Oceanic Deeps.

Question 3.
What is the Continental Slope?
Answer:
Ahead of the continental shelf, the slope of ocean floor becomes abruptly steep. The biggest feature of these slopes is that they may extend upto a depth of 3600 to 9100 meters. Here, the deposit of alluvial soil is found very less. Due to the lack of light and nutritional substances, the amount of vegetation and sea creatures is found to be less. These slopes are found on 8.5 % part of the total area of oceans. Their slope is between 2 degree to 5 degree.

Question 4.
Which are the factors affecting the oceanic temperature?
Answer:
The factors affecting the oceanic temperature are as follows:

1. Latitude.
2. Inequality in the distribution of water and land.
3. Duration of day.
4. Clear atmosphere.
5. Distance of the earth from the sun.
6. Number of sunspots.
7. Ocean Currents.

Among all these factors, in context to the latitudinal status, the temperature decreases on moving towards the poles from the equator. Inequality in the distribution of water and land also affects the temperature, length (duration) of the day (sunshine hours) is also a temperature controller.

The increase or decrease in the amount of dust particles and water vapour in the atmosphere also plays an important role in the temperature distribution. The more or less distance of the earth from the sun, the increase or decrease in the number of sunspots, the ocean currents being cold or warm, also affect the temperature of the ocean water.

Question 5.
What are the factors affecting oceanic salinity?
Answer:
The factors affecting oceanic salinity are as follows:

1. Evaporation.
2. Water availability through rainfall.
3. Arrival of river water.
4. Prevailing winds.
5. Oceanic currents.
6. Transmission of oceanic water.

The increase or decrease in the amount of evaporation affects oceanic salinity. The more the availability of rain water, the less is the salinity. Salinity is more when less pure water comes into the ocean. Likewise, the more or less amount of river water joining the sea is a salinity controller. In the same way, the conditions of prevailing winds and oceanic currents play an important role in increasing or decreasing the salinity. Transmission occurring in oceanic water plays an important role in determining the salinity.

RBSE Class 11 Physical Geography Chapter 19 Essay Type Questions

Question 1.
Explaining the relief, describe the relief features of oceanic bottom.
Answer:
Physical Land forms of the Earth’s Surface:
Mountain, plateau and plain, that is, the surface landscapes are called the Relief. The word relief is used to express the inequalities and variations in the physical profiles of the earth’s surface.

Relief Features of oceanic Bottom:
Like the continents, the oceans are also the First Order Relief. The relief features found in the oceanic regions are classified as follows:

1. Continental Shelf
2. Continental Slope
3. Deep Sea Plain
4. Oceanic Deeps

1. Continental Shelf:
It refers to the sub-merged coast. Thus, those parts of the continents which remain sub-merged in ocean are called Continental Shelf. Their maximum depth is usually 100 fathom and slope is between 1 degree to 3 degree. The continental shelf with gentle slope has more width, and the continental shelf with steep slope has less width.

The average width is 75 km. They are extended on 7.6 % part of the total area of the oceans. The vegetation and living creatures increase on the entrance of sun rays in this part. Sediments carried by rivers accumulate here. Thus, this part of the ocean is very beneficial for the humans. Many minerals, food materials, fishing zones, mineral oil, gases are primarily found here.

2. Continental Slope:
Ahead of the continental shelf, the slope of ocean floor becomes abruptly steep. The greatest feature of these slopes is that they extend upto a depth of 3600 to 9100 meters. Here, the deposit of alluvial soil is found to be very less. Due to the lack of light and nutritional substances, the amount of vegetation and sea creatures is found to be less. These slopes are found on 8.5 % part of the total area of oceans. Their slope is between 2 degree to 5 degree.

3. Deep Sea Plain:
The slope becomes very gentle on the end of the continental slope and the marine plain starts, which is called the Deep Sea Plain. It is an extensive flat area of the oceans, whose slope is very gentle. Lack of erosional process is found here.

4. Oceanic Deeps:
The deeps with the maximum depth found on the ocean floor are called the Oceanic Deeps. On the basis of the shape, they are classified into two parts:

1. Trenches
2. Troughs

Long, thin and deep depressions with steep slope located on the ocean floor are called the trenches or deeps. They are originated by fault or folding. Their average depth is 5500 meters. They are also called the Ocean Canyon.

Question 2.
Describe the factors affecting the temperature of ocean water.
Answer:
The temperature of ocean water is controlled by many factors. The factors affecting the temperature of ocean water are as follows:

1. Latitude.
2. Inequality in the distribution of water and land.
3. Duration of day.
4. Clear atmosphere.
5. Distance of the earth from the sun.
6. Number of sunspots.
7. Oceanic Currents.

Controllers of the Oceanic Temperature:
The description of all these factors is as follows:

1. Latitude:
The temperature of the surface water of ocean decreases on moving towards the poles from the north or south of equator because the sun – rays get slanted towards the poles. Consequently, the amount of insolation also decreases towards the poles. The temperature of ocean water is lower than the temperature of air between 40 degrees north and south latitudes from the equator, but the temperature of ocean water is more than that of ambient air latitudes between 40 degrees from the poles.

2. Inequality in the Distribution of Water and Land:
There is more of the land in the Northern Hemisphere, and more of the water in the Southern Hemisphere. For this reason, inequality is found in the distribution of water and land. Oceanic surface water temperatures are found to be higher in the northern hemisphere than in the southern hemisphere.

3. Duration of Day:
In condition of longer duration of the day, the oceanic water is relatively more warm by attaining more amount of insolation. In condition of shorter duration of the day, the amount of insolation is less in the oceanic water and hence, it is colder.

4. Clear Atmosphere:
On the atmosphere being clear, the insolation reaches to the bottom of water in more amount, thereby making the oceanic water more warm. Due to impure atmosphere, the oceanic water becomes less warm by receiving less of the insolation because a large amount of insolation is absorbed by the dust particles, which increase the impurity of the atmosphere.

5. Distance of the Earth from the Sun:
On the earth being closer to the sun, the oceanic water becomes warmer by receiving more insolation.

6. Number of Sunspots:
The insolation is more with the increased number of sunspots towards the earth and the insolation is less with the reduced number of sunspots. Sunspots are related to the sun’s magnetic field.

7. Oceanic Currents:
Oceanic currents affect the oceanic temperature of their flow area. Cold currents reduce the temperature of oceanic water of their flow area and the warm currents increase the temperature.

Question 3.
Explaining oceanic salinity, describe the factors affecting the salinity in oceanic water.
Answer:
The ratio of the weight of oceanic water and the weight of the substances dissolved in it is called Oceanic Salinity. It is expressed in the form of total amount of solid substances dissolved in one kg. of the oceanic water. Oceanic salinity is expressed in the form of amount of salt present in per thousand grams of water. Among oceanic salts, sodium chloride is found in the maximum amount.

Factors Affecting Oceanic Salinity:
Oceanic salinity is not found in the same amount in all the oceans of the world. It varies according to the prevailing conditions. The factors controlling the extent of oceanic salinity are as follows:

1. Evaporation.
2. Water availability through rainfall.
3. Arrival of river water.
4. Prevailing winds.
5. Oceanic Currents.
6. Transmission of oceanic water.

The description of all these factors is as follows:

1. Evaporation:
There is a direct relation between the amount of salinity and evaporation. The more and rapid the evaporation, the more rise in salinity: Lack of humidity in the winds is necessary along with the evaporation. Salinity is more the regions where the temperature is high and the evaporation is more, like – near to the Tropic of Cancer and the Tropic of Capricorn.

2. Water Availability through Rainfall:
Salinity reduces due to more availability of clean water. Salinity decreases in the regions where excessive rainfall occurs. Despite of the high temperatures in the equatorial regions, salinity is found to be low due to excessive rainfall.

On the other hand, despite of the low rainfall in tropical parts, salinity is found to be more due to high temperature. In the polar and sub – polar parts, the glaciers formed by excessive snowfall bring snow in the oceans, which reduces the salinity of ocean by melting on reaching the temperate regions.

3. Arrival of River Water:
Although the rivers bring salts to the oceans, yet they have so much amount of clean water that they lack salinity near their basin. For example, low salinity is found in the parts of the river basins of the Ganga, Congo, Niger, Amazon, St. Lawrence, etc.

4. Prevailing Winds:
In warm and dry regions, evaporation occurs more due to the rapid winds moving towards the oceans. Thus, salinity is found to be more in such parts of the oceans. On the other hand, evaporation occurs less by flow of cold, humid and slow winds.

5. Oceanic Currents:
Currents flowing from the regions with low oceanic salinity bring with them the water of low salinity and reduce the amount of salinity on their flow path. On the other hand, salinity is found to be more on the path of the currents flowing from the regions with high oceanic salinity.

6. Transmission of Oceanic Water:
Distribution of salinity in the high seas becomes normal by the transmission of ocean water. More saline water gets heavier and settles down and moves in the depth towards low saline water. To take its place, the low saline water moves in the form of surface flow. In this way, the balance of the salinity of ocean water is maintained by this transmission.

RBSE Class 11 Physical Geography Chapter 19 Other Important Questions

RBSE Class 11 Physical Geography Chapter 19 Multiple Choice Questions

Question 1.
The only planet of the solar system on which water is present:
(a) Earth
(b) Mercury
(c) Jupiter
(d) Saturn
Answer:
(a) Earth

Question 2.
What is the height of Mt. Everest?
(a) 6000 meters
(b) 7000 meters
(c) 8200 meters
(d) 8848 meters
Answer:
(d) 8848 meters

Question 3.
What is the depth of Mariana Trench?
(a) 9990 meters
(b) 10430 meters
(c) 11033 meters
(d) 12315 meters
Answer:
(c) 11033 meters

Question 4.
What is the average depth of the oceans?
(a) 2808 meters
(b) 3808 meters
(c) 4808 meters
(d) 5808 meters
Answer:
(b) 3808 meters

Question 5.
Which is the largest ocean of the world?
(a) Pacific Ocean
(b) Atlantic Ocean
(c) Indian Ocean
(d) Arctic Ocean
Answer:
(a) Pacific Ocean

Question 6.
The depth of the oceans is measured in:
(a) Nautical Mile
(b) Fathom
(c) Meter
(d) Barrel
Answer:
(b) Fathom

Question 7.
Which saline material is found in the highest amount in the oceanic water?
(a) Magnesium Sulphate
(b) Calcium Sulphate
(c) Sodium Chloride
(d) Magnesium Chloride
Answer:
(c) Sodium Chloride

Question 8.
Where is the highest salinity found in the world?
(a) Mediterranean Sea
(b) Dead Sea
(c) Lake Van
(d) Baltic Sea
Answer:
(c) Lake Van

Matching Type Questions

Question A.
Match the contents of column A with column B:

Column A (Name of Relief)	Column B (Ocean)
(i) Mariana	(a) Atlantic Ocean
(ii) Romanche	(b) Indian Ocean
(iii) Sunda	(c) Arctic Ocean
(iv) Norway Sea	(d) Pacific Ocean

Answers:

1. (d)
2. (a)
3. (b)
4. (c)

Question B.
Match the contents of column A with those of column B:

Column A (Name of Sea)	Column B (Salinity in %)
(i) Black Sea	(a) 37.5%
(ii) Baltic Sea	(b) 40%
(iii) Red Sea	(c) 238%
(iv) Dead Sea	(d) 15%
(v) Mediterranean Sea	(e) 18%

Answers:

1. (e)
2. (d)
3. (a)
4. (c)
5. (b)

RBSE Class 11 Physical Geography Chapter 19 Very Short Answer Type Questions

Question 1.
Which planet is known as the Aquatic Planet and why?
Answer:
Earth is known as the Aquatic Planet because it is the only planet of the solar system on which such huge reservoirs of water are found so far.

Question 2.
Name the highest and the deppest place on the earth’s surface.
Answer:
The highest place on the earth is Mt. Everest (8848 meters) and the deppest place is Mariana Trench (11033 meters).

Question 3.
Name the oceans in descending order as per area.
Answer:
The oceans in descending order as per their area are Pacific Ocean, Atlantic Ocean, Indian Ocean and Arctic Ocean.

Question 4.
What is the length and width of the Pacific Ocean?
Answer:
Pacific Ocean extends over 18000 km. in width from east to west, and 16740 km in length from north to south.

Question 5.
Into which parts are the islands of the Pacific Ocean classified?
Answer:
About 20000 islands found in the Pacific Ocean are classified into three parts:
Melanesia, Micronesia and Polynesia.

Question 6.
What is the main feature of the Atlantic Ocean?
Answer:
Atlantic Ocean is the world’s most busy ocean, on both the sides of which, the developed countries of the world are located.

Question 7.
Name the seas and gulfs included in the Atlantic Ocean.
Answer:
Mediterranean Sea, North Sea, Baltic Sea, Caribbean Sea, Black Sea, Gulf of Mexico, Biscay Bay, etc. are included in the seas and gulf of the Atlantic Ocean.

Question 8.
How wide is the north and south part of the Atlantic Ocean?
Answer:
The north part of the Atlantic Ocean is 5400 km. wide and the south part is 9600 km. wide.

Question 9.
By which terrestrial parts is the Indian Ocean surrounded?
Answer:
Terrestrial parts are found in the form of India in the north of the Indian Ocean, Africa in its west and Australia in its south – east.

Question 10.
Why is adequate information not available about the Arctic Ocean?
Answer:
Adequate information is not available about the Arctic Ocean located on the North Pole because most of its part remains covered with snow for most of the year.

Question 11.
What is meant by oceanic bottom?
Answer:
The oceanic bottom means the expanse of land surface under water in the oceans, that is the expansion of the heights and depths on the sea level.

Question 12.
Over how much part of the oceans do the continental shelfes extend?
Answer:
The continental shelfes extends over 7.6 % part of the total area of the oceans.

Question 13.
Over how much part of the oceans does the continental slope extend?
Answer:
The continental slope extends over 8.5 % part of the total area of the oceans.

Question 14.
What is meant by Oceanic Deep?
Answer:
The deeps with the maximum depth found on the ocean floor are called the Oceanic Deeps.

Question 15.
Why does the temperature of surface water decrease on moving from the equator towards the poles?
Answer:
The temperature of surface water decreases on moving from the equator towards the poles because the sun – rays get slanted towards the poles.

Question 16.
What does the term insolation mean?
Answer:
The energy or heat received on earth or any other planet from the sun is called insolation.

Question 17.
What is the meaning of Horizontal Distribution of Ocean Temperature?
Answer:
When the temperature of oceanic water is studied on the latitudinal basis, it is considered as the Horizontal Distribution of Ocean Temperature.

Question 18.
How much salt is there in one cubic km. of sea water?
Answer:
There is about 4.10 million tonnes of salt in one cubic km. of sea water.

Question 19.
Name the main salts found in the sea water.
Answer:
In the main salts found in the sea water, sodium chloride, magnesium chloride, magnesium sulphate, calcium sulphate, potassium sulphate, calcium carbonate and t magnesium bromide are included.

Question 20.
Why is the amount of salinity found to be the highest in tropical regions?
Answer:
The salinity is found to be the highest in tropical regions due to the high temperature, prevailing warm and dry winds, excessive evaporation, lack of rainfall and lesser availability of clean water.

Question 21.
Why is high salinity found in the Sargasso Sea?
Answer:
The main reason for the high salinity found in the Sargasso Sea is that the cyclic flow of ocean currents found here does not mix the intermediate water with the water of other areas.

Question 22.
What is Isohaline?
Answer:
Lines joining the places with similar salinity in the oceanic regions on the map, are called Isohalines.

Question 23.
Why is high salinity found in the Persian Gulf?
Answer:
High salinity is found in the Persian Gulf due to the lack of rainfall, lesser availability of clean water, high temperature, excessive evaporation, etc.

Question 33.
Why is the salinity found to be low on the surface of polar region?
Answer:
The salinity is found to be low on the surface of polar region due to the availability of clean water by the melting snow.

RBSE Class 11 Physical Geography Chapter 19 Short Answer Type Questions (SA-I)

Question 1.
Describe the land forms of the Atlantic Ocean.
Or
Which land forms are found in the Atlantic Ocean?
Answer:
Atlantic Ocean is extended in the shape of letter ‘S’ of English. Many seas and gulfs are found in this ocean. In this ocean, the Gulf of Mexico, Mediterranean Sea, North Sea, Biscayne Bay, Baltic Sea, Caribbean Sea, Black Sea, etc. are found. The equator divides the ocean into two parts. The North Atlantic Ocean located in its northern part is 5400 km. wide, and the South Atlantic Ocean located in the southern part is 9600 km. wide.

Many troughs are found in this ocean, in which the Brazil Trough, Canary Trough, Guinea Trough and North America Trough are the major ones. Many deeps are also found in this ocean, in which Puerto Rico, Romanche Trench, Naresh Trench, Bhosle Trench, Chun and Buchanan Trench etc. are prominent. In this ocean, various ridges such as Walvis Ridge, South – Mid Atlantic Ridge, North – Mid Atlantic Ridge, Wiville Thomson Ridge are also found.

Question 2.
Describe the land forms of the Indian Ocean.
Answer:
In the north of the Indian Ocean, part of Gondwana Land, Peninsular India, Plateau of Africa, western part of Australia continental land are present. Many troughs are found in this ocean which include Arabian Trough, Mauritius Trough, Andaman Trough, Oman Trough, Naital Trough, etc. Many ridges are also found in this ocean which include Socotra – Chagos Ridge, Chagos Ridge, Sachlis Ridge, St. Paul Ridge, Amsterdam Ridge, Madagascar Ridge and Indian Antarctica Ridge.

In the gulfs found in this ocean, the Bay of Bengal, Gulf of Aden, Persian Gulf and Gulf of Thailand are the major ones. Many islands are found in this oceanic part in which Lakshadweep Island, Andaman and Nicobar Islands Group,Madagascar Island, Zanzibar and Reunion Islands are included. Sunda is the main deep of this ocean.

Question 3.
Describe the landforms of the Arctic Ocean.
Answer:
Adequate information is not available about this ocean located on the North Pole because most of its part remains covered with snow for most of the year. Its place of submergence is very wide. Many islands are found on this ocean, in which Barents, Hope, Spitsbergen, Novaya, etc. are the major ones. In the seas found in this ocean, the Norway Sea, Laptev Sea, East Siberian Sea and Greenland Sea are the major ones. Many sub-merged ridges are found here.

Question 4.
How does the Continental Shelf prove to be useful for us?
Answer:
The usefulness of the Continental Shelf can be explained in the following points:

1. The vegetation and living creatures sustain and survive by the entrance of sun – rays on the continental shelf.
2. Sediments carried by the rivers accumulates here, thus, this part of the ocean is very beneficial for the humans.
3. Many types of food materials, fishes and creatures are obtained on the continental shelf.
4. Many types of minerals, mineral oil and gases, etc. are found on the continental shelf.

Question 5.
How does the transmission of the temperature of oceanic water occur?
Answer:
In ocean water, the sun – rays provide heat by entering down to 25 meters depth. After this depth, the effect of sun’s radiation becomes negligible. Thus, due to insolation, the surface water of ocean becomes hotter. In polar regions, the cold water being heavy settles down at the bottom. Due to being light, the warm water of the equatorial regions flows towards the polar regions by surface currents. In this way, the transmission of the temperature of oceanic water takes place.

Question 6.
Mention the names of saline substances and their amount found in the oceanic water.
Answer:
Various saline substances are found in the oceanic water. These saline substances, their amount and percentage is being presented through the following table:
Saline Substances Found in the Oceanic Water:

Question 7.
Explain the distribution of salinity in the internal seas.
Answer:
Internal Sea and lake are completely surrounded by the land. The amount of salinity in the Dead Sea is found to be 238 per thousand due to the factors like the high temperature, excessive warm and dry winds, more evaporation and lack of rainfall etc. The amount of salinity in the southern part of the Caspian Sea is 170 per thousand. In the northern part, it is only 14 per thousand. In the northern part of the Caspian Sea, the Ural and Volga Rivers provide the availability of the clean water. The highest salinity in the world is found in the Van Lake of Turkey which is 330 per thousand.

RBSE Class 11 Physical Geography Chapter 19 Short Answer Type Questions (SA-II)

Question 1.
What are the differences between the continental shelf and the Continental Slope?
Answer:
The following differences are found between the continental shelf and the continental slope:

Basis of Difference	Continental Shelf	Continental Slope
Situation	Continental shelf is the submerged part of the continent.	Continental slope is the part that is ahead of the continental shelf.
Depth	Continental shelf is found usually up to the depth of 100 fathoms.	Continental slope extends up to a depth of 3600 to 9100 meters.
Slope	The slope of continental shelf is found* between 1 degree to 3 degree.	Continental slope is usually with 2 degree to 5 degree slope.
Percentage of Oceans	They are extended on 7.6% part of the total area of oceans of the world.	They are extended on 8.5% part of the total area of oceans of the world.
Sun – rays	Sun – rays reach easily on the continental shelf.	Lack of sun – rays is found on these slopes due to greater depth.
Vegetation and Living creatures	Abundance of vegetation and living creatures is found on the continental shelf.	Lack of vegetation and living creatures is found on the continental slope.

Question 2.
Explain the distribution of salinity in partially-surrounded oceans.
Answer:
Distribution of salinity depends on the local conditions in partially – surrounded oceans. The distribution of salinity in the Mediterranean Sea is found to be very different. In its north – eastern part, the salinity is 39 per thousand grams, while in its south – eastern part, it is 41 per thousand grams. In the northern part of the Red Sea, the amount of salinity is 41 per thousand grams, and in the southern part, it is 36 per thousand grams.

In the Persian Gulf, the amount of salinity is 48 per thousand grams. High salinity is found here due to the factors like lack of rainfall, lesser availability of clean water, high temperature, more evaporation, etc. The amount of salinity in the Black Sea is about 18 per thousand grams, in the Baltic Sea it is about 15 per thousand, in the Gulf of Bothania it is about 8 per thousand and in the Gulf of Finland, it is only 2 per thousand. The main reasons for this is the extensive clean water supply by rivers, supply of melt water by glaciers, low temperature, low evaporation rate, etc.

Question 3.
Explain the vertical distribution of salinity in oceanic water.
Answer:
There is no definite trend in the distribution of salinity along the depth. However, some trends emerge from the distribution of salinity in the vertical plane:

1. In the polar region, salinity is low on the surface and it increases towards the depth. Salinity remains low on the surface due to the supply of clean melt water from glaciers.

2. In the mid latitudes, salinity increases till the depth of 400 meters. After this, the amount of salinity reduces along with the depth. It happens due to more evaporation and low availability of clean water on the surface.

3. In the equatorial region, salinity is low on the surface, it increases till the depth of one
thousand meters, and after that, it again starts reducing.

RBSE Class 11 Physical Geography Chapter 19 Essay Type Questions

Question 1.
Explain the horizontal and vertical distribution of the temperature of oceanic water.
Answer:
Temperature in oceanic water usually reduces along with the increasing latitudes. An extensive form of the horizontal distribution of the temperature of oceanic water is being presented as follows:


It is clear from the above table, that the temperature generally decreases towards the poles. In the Atlantic Ocean only, after the slightest increase in temperature between 20 degrees and 30 degrees north latitudes, the sequence of decline again continues. Due to less expansion of 20 to 30 degree latitudes in the Indian Ocean, the rate of temperature decline is very low. Thus, the rate of decline in temperature towards the poles is half degree Celsius per latitude.

Vertical Distribution of Temperature:
The vertical distribution of ocean temperature is dependent on the amount of heat absorption, its horizontal displacement by water current and vertical motion of water. In ocean water, the sunrays provide heat by entering down to a depth of 25 meters. After this depth, the effect of sun’s radiation becomes negligible.

Thus, due to insolation, the surface water of ocean becomes hotter. In polar regions, the cold water being heavy settles down at the bottom. Due to being light, the warm water of the equatorial regions flows towards the polar regions by surface currents. In this way, the transmission of the temperature of oceanic water occurs.

From the surface of oceanic water towards the depth, the temperature declines with rapid speed till the depth of 2000 meters. After that depth, the rate of temperature decline becomes very low. This fact is visible in the open seas. In partially surrounded oceans like the Mediterranean Sea and the Red Sea, the decline in temperature is lower than that in the nearby open oceans.

Question 2.
Explain the horizontal distribution of salinity in the open regions.
Answer:
The amount of salinity in tropical regions is found to be the highest (36 per thousand). More salinity is found in this region due to the high temperature, prevailing warm and dry winds, more evaporation, lack of rainfall and lesser availability of clean water. At both the sides of tropical regions, that is, towards the equator and the poles, the amount of salinity reduces. But the amount of salinity is found to be lesser in the polar regions than the equatorial regions.

The reason for this is that there is less evaporation and more supply of melt water by glaciers in the polar regions. In the equatorial regions, both the evaporation and the availability of clean water remain high. There are also local variations in the distribution of salinity in the coastal regions of the ocean. For example, due to the availability of clean water, low salinity is found in the parts of the river basins of the Ganga, Congo, Niger, Amazon, Indus Rivers, etc.

In the Sargasso region of the North Atlantic Ocean, the salinity is 38 per thousand. The main reason for this high salinity is that the cyclic flow of ocean currents found here does not mix the intermediate water with the water of other areas. Lines joining the places with similar salinity in the oceanic regions are called Isohalines.

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सम्पूर्ण व्याकरण

जीवनी

निबंध

टेन्स

सामान्य ज्ञान

Rajasthan Board

NCERT Solutions in Hindi

NCERT Solutions in English