Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Social Science Guide Pdf Geography Chapter 4 Hydrosphere Text Book Back Questions and Answers, Important Questions, Notes.

Tamilnadu Samacheer Kalvi 9th Social Science Solutions Geography Chapter 4 Hydrosphere

Samacheer Kalvi 9th Social Science Hydrosphere Text Book Back Questions and Answers

I. Choose the correct answer

Question 1.
The Sunda Trench lies in the ______ ocean.
(a) Atlantic
(b) Pacific
(c) Indian
(d) Antarctic
Answer:
(c) Indian

Question 2.
The temperature of the ocean waters generally ______ at greater depth.
(a) increases
(b) decreases
(c) remains constant
(d) none of the above
Answer:
(b) decreases

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 3.
Ocean currents are produced due to ______
a) due to rotation of earth
b) due to variation in temperature
c) due to earth’s movement
d) all the above
Answer:
(d) all the above

Question 4.
Consider the following statements.
1. Most of the fishing grounds occur in areas where the continental shelf is wide.
2. Fishing is well developed in warm tropical waters.
3. Mixing of warm and cold currents facilitates plant nutrients for fish.
4. Inland fishing became significant in India.
(a) 1 and 2 are correct
(b) 1 and 3 are correct
(c) 2,3 and 4 are correct
(d) 1,2 and 3 are correct
Answer:
(b) 1 and 3 are correct

Question 5.
The oceanic ridge comes into existence due to
(a) convergence of tectonic plates
(b) divergence of tectonic plates
(c) lateral movements of plates
(d) stearing of plates.
Answer:
(b) divergence of tectonic plates

Question 6.
Which of the following indicates the correct sequence of the topography beneath the surface of the sea?
(a) Continental shelf-Continental slope-Sea plain-Sea trench.
(b) Continental slope-Continental shelf-Sea plain-Sea trench.
(c) Sea plain-Continental slope-Continental shelf-Sea trench.
(d) Continental slope-Sea plain-Continental shelf-Sea trench.
Answer:
(a) Continental shelf-Continental slope-Sea plain-Sea trench.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 7.
Which of the following is not correctly matched?
(a) Gulf Stream – Pacific Ocean
(b) Labrador current – North Atlantic Ocean
(c) Canary current – Mediterranean sea
(d) Mozambique current – Indian Ocean
Answer:
(a) and (c)

Question 8.
The amount of planktons to be found in the ocean is determined by
1. Depth of the water.
2. Ocean currents.
3. Temperature and Salinity.
4. Length of day and night.
(a) 1 and 2 are correct
(b) 1,2 and 3 are correct
(c) 1,3 and 4 are correct
(d) All are correct.
Answer:
(b) 1,2 and 3 are correct

II. Questions are of Assertion (A), Reason (R) type.

(A) both A and R are correct and R explains A.
(B) both A and R are correct but R does not explain A.
(C) A is correct but R is false.
(D) A is false R is correct

Question 1.
Assertion (A) : Oceans are always shown in blue in maps.
Reason(R) : It indicates the natural colour of the oceans.
Answer:
(A) both A and R are correct and R explains A.

Question 2.
Assertion(A) : Flat topped seamounts are known as Guyots.
Reason(R) : All guyot features are of volcanic origin.
Answer:
(A) both A and R are correct and R explains A.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 3.
Assertion(A) : Submarine canyons are deep gorges on the ocean floor.
Reason(R) : They are mainly restricted to continental shelf, slope and rise
Answer:
(B) both A and R are correct but R does not explain A.

Question 4.
Assertion (A) : Atolls are more common in the Atlantic ocean.
Reason(R) :The marine population at the depth is less.
Answer:
A is false R is correct

III. Match the following

  1. Mariana trench – (i) Decreases salinity in the oceans
  2. Great Barrier Reef – (ii) Along the coast of Japan
  3. Sargasso sea – (iii) Deepest point in the Pacific
  4. Spring tides – (iv) Australia
  5. Heavy rains – (v) Second order landform
  6. Kuroshio current – (vi) North Atlantic Ocean
  7. Continental slope – (vii) On full and new moon days

Answer:

  1. – (iii)
  2. – (iv)
  3. – (vi)
  4.  – (vii)
  5. – (i)
  6. – (ii)
  7. – (v)

IV. Answer the following in brief

Question 1.
What do you mean by the term Hydrosphere?
Answer:

  1. Hydrosphere consists of water in various forms found on the earth.
  2. Over 97% of the water on the Earth’s surface is confined to oceans.
  3. Less than 3% of water is held on land as glaciers, ice caps, groundwater, rivers, lakes, and also as the water vapour in air.

Question 2.
What is hydrological cycle?
Answer:

  1. The Earth’s water is not static.
  2. It is always in motion.
  3. This continuous movement of water on, above and below the earth’s surface is called the Hydrological Cycle.

Question 3.
Mention the various relief features of ocean floor.
Answer:
The ocean basins are characterised by the following major relief features:

  1. Continental shelf
  2. Continental slope
  3. Continental rise
  4. Deep sea plain or Abyssal plain
  5. Oceanic deep
  6. Oceanic ridge

Question 4.
What are the factors that generate the ocean currents?
Answer:
The factors that generate ocean currents are:

  1. Earth’s rotation
  2. Prevailing winds and
  3. Differences in temperature and salinity of ocean water.

Question 5.
Write a brief note on sea waves.
Answer:

  1. Of all the movements of the oceans, sea waves are considered to be the strongest.
  2. Sea waves are ripples on water caused when winds blow over the sea.
  3. The height of these waves depends on the speed of wind, its duration and the direction from which they blow.
  4. Sometimes waves are also caused by tremors felt on the ocean floor.
  5. Such waves are quite destructive and called Tsunami.

V. Give reasons for the following

Question 1.
The northern hemisphere and the southern hemisphere are called land and water hemispheres respectively.
Answer:

  1. The Northern Hemisphere holds 61 % of land.
  2. The Southern Hemisphere holds 81% of water.
  3. It is because of this pattern of land and water distribution, the Northern hemisphere is called as the land hemisphere and the Southern hemisphere is called as the water hemisphere.

Question 2.
Continental shelf provides good Ashing ground.
Answer:

  1. The continental shelf is shallower, thus enables sunlight to penetrate through the water.
  2. This encourages abundant growth of grass, sea weeds and plankton.
  3. Hence these zones become the richest fishing grounds in the world.
  4. Example: The Grand bank of New foundland

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

VI. Distinguish the following

Question 1.
Spring tide and Neap tide.
Answer:
Spring tide:

  1. When the Sun, Moon and Earth are aligned in the same line, the collective gravitation pull of the sun and moon on earth’s water strengthens to form a high tide known as spring tide.
  2. Such tides always occur on full moon and new moon days.

Neap tide:

  1. When the sun and the moon are at right angles, their gravitational forces work against each other, causing a low tide called neap tide.
  2. A neap tide occurs between two spring tides i.e., twice a month, when the first and last quarter moon appears.

Question 2.
Abyssal plains and Ocean deeps.
Answer:
Abyssal plains:

  1. The deep sea plains or abyssal plains are underwater plains found on the deep ocean floor.
  2. These plains are usually covered by the thick layer of sediments composed of clay, silt and sand, brought by the rivers.
  3. These are often characterized by features like abyssal hills, sea mounts, guyots, coral, atoll etc.

Ocean deeps:

  1. Trenches are the deepest part of the oceans and occupy about 7% of the total relief of the ocean floor.
  2. Ocean deep are sediment free, most trenches are V-shaped with steep sides.
  3. Epicentre of the great earthquakes are all found in the trenches.

VII. Answer in a paragraph

Question 1.
Write a paragraph on the origin of oceans.
Answer:

  1. The ocean is a continuous body of salt water that forms the major part of hydrosphere.
  2. Geoscientists believe that the oceans were formed on Earth nearly three billion years ago.
  3. It is difficult to believe that in the beginning there was no water on our planet.
  4. In due course of time, when the Earth started cooling, steam escaped from the interior and entered the atmosphere to form clouds.
  5. At first, the clouds brought incessant rains.
  6. The rain water filled the depressions for tens of thousands of years and eventually a super ocean was formed.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 2.
Write a note on continental shelf and continental slope.
Answer:
(A) Continental Shelf:

  1. A shallow and gently sloping platform extending out from the adjoining continental land mass into the sea is called Continental Shelf.
  2. It i-s almost a uniform zone of sea bed with a gentle gradient.
  3. It is significant in promoting richest fishing grounds.
  4. Since the continental shelf in shallower, thus enables sunlight to penetrate through the water. This encourages abundant growth of grass, sea weeds and plankton to feed fishes.
  5. The continental shelves have extensive deposits of minerals and mineral fuels.
  6. Hence, this zone becomes accessible for oil drilling and mining activities.
    E.g. The Grand Banks of Newfoundland.

(B) Continental Slope

  1. A steep siope which descends from the edge of the continental shelf to the deep ocean-bed is called continental slope.
  2. It forms a boundary between the Continental Crust and the oceanic crust.
  3. This zone is free from deposits as they are steep.
  4. The most important characteristic of continental slope is the presence of deep canyons and trenches.
  5. Due to the low penetration of sunlight, the slope has nearly freezing temperature.
  6. Hence aquatic life has very slow rate of metabolism.

Question 3.
What do you mean by ocean currents? Explain its types.
Answer:

  1. The movement of oceanic water on the surface and at the depths in a definite direction is called ocean current.
  2. Ocean currents are in clockwise motion in the northern hemisphere and in the anti-clockwise motion in the southern hemisphere.
  3. The factors that generate ocean currents are:
    Earth’s rotation, Prevailing winds and Differences in temperature and salinity of ocean water.
  4. On the basis of temperature, ocean currents are classified as warm currents and cold currents.
  5. The movement of ocean currents from the low latitudes (tropical zones) towards high latitudes (temperate and polar zones) is called warm current. Example Gulf Stream in Atlantic Ocean, North Equatorial Current in Pacific Ocean.

Question 4.
Explain the influences of the marine resources on mankind.
Answer:

  1. The biotic and abiotic resources found in the oceanic water and at the bottoms are called marine resources.
  2. The ocean’s resources play a vital role in sustaining the needs of society.
  3. A diverse array of marine organisms is used for food, medicine, cosmetics, and a wealth of industrial applications.
  4. The world’s demand for energy, minerals and water have become increasingly dependent on non-living marine resources.
  5. Fishes, plankton, sea grass, Coral etc. are biological resources.
  6. Petroleum, Naturalgas, Metallic Minerals, sand, gravel etc. are mineral resources.
  7. Energy fuels, Tidal energy, wave Energy etc. are energy resources.

Intext Hots

Question 1.
71% of the earth is covered by water, but very little can be used by humans. Why?
Answer:
Though 71% of the Earth is covered by water, 97.5% of the Earth’s water is in the oceans in the form of saltwater that cannot be used. About 2% of the water is found in the form of glaciers and ice sheets. Thus, only 0.5% of Earth’s water is available for human use. It makes fresh water a critical resource.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 2.
The oceans are salty. Why?
Answer:

  1. Salt in the ocean comes from rocks on land.
  2. The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid (which forms from carbon dioxide and water).
  3. As the rain erodes the rock, acids in the rainwater break down the rock. This process creates ions, or electrically charged atomic particles. These ions are carried away in runoff to streams and rivers and ultimately to the ocean.
  4. Many of the dissolved ions are used by organisms in the ocean and are removed from the water. Others are not used up and are left for long periods of time where their concentrations increase over time.
  5. Two of the most prevalent ions in seawater are chloride and sodium. Together, they make up over 90 percent of all dissolved ions in the ocean. Sodium and Chloride are ‘salty’. So, the oceans are salty.

Question 3.
What will happen if the seas and oceans contain only fresh water?
Answer:

  1. All of the organisms in the sea are adapted to salt water. If they were suddenly immersed in fresh water, too much water would diffuse into their bodies and they would die.
  2. The global ecosystem would collapse, and the oceans and atmosphere would eventually revert to their composition before the evolution of photosynthesis: Almost no oxygen and lots of carbon dioxide.
  3. The ocean currents will be completely disturbed. Hence it will trigger profound climatic changes at the global scale.

Samacheer Kalvi 9th Social Science Hydrosphere Additional Important Questions and Answers

I. Choose the correct answer

Question 1.
The deepest point in the Arctic ocean is _____
(a) Java Trench
(b) Fram basin
(c) Puerto Rico
(d) South Sandwich Trench
Answer:
(b) Fram basin

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 2.
Hawaii islands are located on the ocean.
(a) Pacific
(b) Indian
(c) Atlantic
(d) Arctic
Answer:
(a) Pacific

Question 3.
The height of the waves depends on _____
(a) speed of wind
(b) Its duration
(c) the direction
(d) All of the above
Answer:
(d) All of the above

Question 4.
Marine resources consists of resources.
(a) Biological
(b) Mineral
(c) Energy
(d) All of the above
Answer:
(d) All of the above

Question 5.
A very long narrow depression on the ocean floor is called _____
(a) Guyot
(b) Ridge
(c) Trench
(d) atoll
Answer:
c) Trench

Question 6.
Consider the following statements.
1. There are four major processes involved in the water cycle.
2. The ground water gets collected below the earth’s surface
3. The Northern hemisphere holds 81% of land
4. The ocean floor is flat.
(a) 1 and 2 are correct
(b) 2 and 3 are correct
(c) 2 is correct
(d) 2,3 and 4 are correct
Answer:
(c) 2 is correct

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 7.
Consider the following statements.
1. Sylvia Earle is a famous American oceano-grapher
2. The continental shelves have extensive deposits of mineral fuels.
3. Submarine fans are located in continental slope.
4. Abyssal plains are otherwise called shallow sea plains
(a) 1 and 2 are correct
(b) 2 and 4 are correct
(c) 3 and 4 are correct
(d) 1,2, and 3 are correct
Answer:
(a) 1 and 2 are correct

Question 8.
Consider the following statements.
1. Dragon Hole is the deepest known underwater sink hole in the world.
2. Epicentre of the great earthquakes are found in Aby ssal plains.
3. Fathom means an imaginary line joining the points of equal salinity.
4. Salinity’ is maximum at the poles.
(a) 1 is correct
(b) 1 and 2 are correct
(c) 4 is correct
(d) 2 and 3 correct
Answer:
(a) 1 is correct

Question 9.
Assertion (A) : The Ocean water is dynamic
Reason (R) : Waves and currents are in horizontal motion w hile tides have vertical motion.
(a) Both A and R are correct
(b) Both A and R are wrong
(c) A is correct and R gives the explanation of A
(d) A is correct but R is wrong
Answer:
(c) A is correct and R gives the explanation of A

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 10.
Assertion (A) : The gravitational pull of the sun and moon on earth cause tides on sea water.
Reason (R) : Neap tides are caused when the first and last quarter moon appears.
(a) Both A and B are wrong
(b) A is correct, R gives the correct explanation of A
(c) A is false R is correct
(d) A is correct R does not give correct explanation of A
Answer:
(b) A is correct, R gives the correct explanation of A

Question 11.
Assertion (A) : The energy of the falling wave water is used to turn hydro turbines to generate power.
Reason (R) : Gulf of Khambat is one of the potential Tidal energy Zones.
(a) A and R are correct, but R does not explain A
(b) A and B are false
(c) A is correct R gives correct explanation of A
(d) A is false, R is correct
Answer:
(a) A and R are correct, but R does not explain A

Question 12.
Assertion (A) : On the basis of temperature, ocean currents can be classified as warm currents and cold currents.
Reason (R) : The movement of ocean current from the low latitudes towards high latitudes cause cold current.
(a) Both A and R are correct, R gives the correct explanation of A
(b) Both A and R are false
(c) A is correct but R does not explain A
(d) A is correct, R is false.
Answer:
(d) A is correct, R is false

Question 13.
Assertion (A) : The mid ocean ridge is probably the most extensive single feature of the earth’s topography.
Reason (R) : The Mid – Atlantic Ridge is the largest unbroken oceanic ridge,
(a) A is correct, R explains A
(b) A is correct R is wrong
(c) A is false, R is correct
(d) Both A and R are false
Answer:
(a) A is correct, R explains A

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 14.
Assertion(A) : Salinity is higher in closed ocean basins.
Reason(R) : Enclosed ocean bhsins undergo little mixing with the open ocean.
(a) Both A and R are correct, R gives the correct explanation of A
(b) Both A and R are false
(c) A is correct but R does not explain A
(d) A is correct, R is false.
Answer:
(a) Both A and R are correct, R gives the correct explanation of A

II. Match the following

  1. Finland – (i) Atlantic Ocean
  2. Land Hemisphere – (ii) Fishing grounds
  3. Green land – (iii) Equal depths
  4. New foundland – (iv) Kerala
  5. Iso bath – (v) Goa
  6. Vizhinjam – (vi) Land of Thousand Lakes
  7. NIO – (vii) Northern Hemisphere

Answer:

  1. – (vi)
  2. – (vii)
  3. – (i)
  4. – (ii)
  5. – (iii)
  6. – (iv)
  7. – (v)

III. Answer the following in brief:

Question 1.
Mention the four spheres of the earth.
Answer:

  1. The earth consists of four spheres
  2. They are
    1. Lithosphere
    2. Atmosphere
    3. Hydrosphere
    4. Biosphere

Question 2.
Why is earth called a Blue planet?
Answer:

  1. One of the most indispensable natural resources on earth is water.
  2. The Earth is also called the Blue planet, as it holds water in abundance.
  3. Thus stands unique among all other planets.

Question 3.
Mention the three major processes involved in the water cycle.
Answer:

  1. The three major processes involved in the water cycle are evaportation, condensation and precipitation.
  2. Water changes its form constantly i.e. Ice, water and water vapour.

Question 4.
Explain the term
(a) Water Table
(b) Aquifers
Answer:
(a) Water table is a level below the ground, where water is found collected beneath the Earth’s surface.
(b) Aquifers are porous rock strata filled with water, found below the earth’s surface.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 5.
What is Hypsometric curve?
Answer:

  1. Hypsometric curve is a graphic representation which shows the height of a certain place found on land and the height of ocean features at sea.
  2. ‘Hypso’ means height in Greek.

Question 6.
Write a note on ONGC.
Answer:

  1. Oil and Natural Gas Corporation (ONGC) is India’s largest oil and gas exploration and production company.
  2. Its latest estimate is that about 20 million tons of oil reserves are found west of Mumbai High off shore.

Question 7.
Explain the terms
(a) Isobath
(b) Isohaline
Answer:
(a) Isobath – An imaginary line on a map joining the points of equal depths.
(b) Isohaline – An imaginary line on a map joining the points of equal salinity in oceans.

Question 8.
What role is played by NIO (National Institute of Oceanography)
Answer:

  1. National Institute of Oceanography (NIO) was established on 1st January 1966.
  2. The headquarters of NIO is located at Dona paule, Goa.
  3. It conducts research and observations to understand Oceanic features, Ocean engineering, Marine Archaeology etc.,

Question 9.
Where do we see the Great Barrier Reef?
Answer:

  1. The Great Barrier reef is the world’s largest coral reef system composed of2,900 individual reefs and 900 islands stretching for about 2,000 kilometres.
  2. The reef is located in the Coral sea, off the coast of Queensland, Australia.
  3. These coral reefs are built by billions of tiny organisms, known as coral polyps.
  4. This sprawling coral reef system is one of the most biologically diverse places on the planet.

Question 10.
What do you mean by the ocean salinity?
Answer:

  1. The degree of concentration of salts in the sea water is called salinity.
  2. It is usually expressed in terms of parts per thousand (ppt or %o).
  3. Salinity varies both horizontally and vertically.
  4. The influence of temperature on ocean salinity depends upon the heating up of the surface water, which varies from tropics to polar regions.

IV. Distinguish the following

Question 1.
Pacific ocean and Atlantic ocean.
Answer:
Pacific ocean:

  1. Pacific ocean is spread between the western coast of America to the fareast coast (China)
  2. It has less sea traffic
  3. It is larger in Size.
  4. Deepest point – Mariana Trench (10,924 m)

Atlantic ocean:

  1. Atlantic ocean is spread between Europe and eastern coast of America.
  2. It has served as an important sea route for trade in the earlier countries and has contributed to the discovery of America.
  3. It has stronger ocean currents.
  4. Deepest point – Puerto Rico Trench (8,605 m)

V. Give reasons for the following

Question 1.
Abyssal plains in the Atlantic and Indian Oceans tend to be extensive than the Pacific
Ocean. Why?
Answer:

  1. Abyssal plains in the Atlantic and Indian Oceans tend to be extensive than the Pacific Ocean.
  2. Because, majority of the world’s largest rivers empty their sediments into either Atlantic or Indian Ocean.
  3. E.g. Amazon, Ganga and Brahmaputra rivers.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 2.
The ocean waters are saline in nature.
Answer:

  1. After years and years of river inflow and evaporation, the salt content of the lake water built up to the present levels.
  2. The same process made the seas salty.
  3. Rivers carry dissolved salts to the ocean.
  4. Water evaporates from the oceans to fall again as rain and to feed the rivers, but the salt remains in the oceans. Therefore the ocean waters are saline in nature.

VI. Answer in a paragraph

Question 1.
Write a note on Fresh Water.
Answer:

  1. Rain water is considered to be the purest form of water, as it contains very less proportion of salts when compared to the oceans and seas.
  2. Hence it is called fresh water.
  3. A major part of fresh water is found in the frozen state in the form of ice caps and glaciers.
  4. Around 0.5 tol% of it, is found in the liquid state as rivers, streams, lakes, ponds etc.
  5. Surface water may also penetrate through porous rocks and gets collected beneath the Earth’s surface.
  6. This is called groundwater.

Question 2.
Explain the terms
(a) Continental Rise
(b) Oceanic ridge
Answer:
(a) Continental Rise

  1. At the base of the continental slope is a gently sloping layer of sediments which merge into the deep-sea floor.
  2. This underwater feature found between continental slope and abyssal plains is called the continental rise.
  3. It consists of submarine fans which are similar to the alluvial fans found on land.

(b) Oceanic Ridge

  1. Oceanic ridge is a continuous submarine mountain chain.
  2. They are made of young basaltic rock formed when two tectonic plates moves apart.
  3. The mid-ocean ridge is probably the most extensive single feature of the earth’s topography.
  4. Two of the most well laiown mid- ocean ridges are the Mid-Atlantic Ridge and the East Pacific Ridge.
  5. The Mid-Atlantic Ridge is the largest unbroken oceanic ridge.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 4 Hydrosphere

Question 3.
Why should we conserve marine resourses?
Answer:

  1. Oceans are the life blood of planet earth and mankind.
  2. The humankind depends on the marine resources for its survival.
  3. They are also essential for the economic prosperity, social well-being and quality of life.
  4. Oceans have extensive deposits of oil reserves.
  5. Besides a major fishing ground, it helps in generating non-conventional energy, development of many ports and harbours for trade activities.
  6. Coastal tourism also attracts people around the world.
  7. Loss of biodiversity, loss of habitats, contamination through dangerous substances, and the impacts of climate change – all these are a threat to the marine environment.

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