9th Social Science - Book Back Answers - Geography Unit 4 - English Medium Guides

  

 

9th - Social Science - Book Back Answers - Geography Unit 4 - English Medium

Tamil Nadu Board 9th Standard Social Science - Geography Unit 4: Book Back Answers and Solutions

    This post covers the book back answers and solutions for Unit 4 – Geography from the Tamil Nadu State Board 9th Standard Social Science textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Geography Unit 4 along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 9 students! Prepare well and aim for top scores. Thank you!

Topic: Unit 4. HYDROSPHERE

I. Choose the correct Answer

Question 1.
The temperature of the ocean waters generally ______ at greater depth.
(a) increases
(b) decreases
(c) remains constant
(d) none of the above
Answer Key:
(b) decreases
 
Question 2.
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 Key:
(d) all the above

Question 3.
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 Key:
(b) 1 and 3 are correct

Question 4.
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 Key:
(b) divergence of tectonic plates

Question 5.
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 Key:
(a) Continental shelf-Continental slope-Sea plain-Sea trench.
 
Question 6.
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 Key:
(a) and (c)

II. Assertion (A), Reason (R) type questions

Directions
(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 Key:
(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 Key:
(A) both A and R are correct and R explains A.
 
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 Key:
(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 Key:
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. Spring tides             –  (iii) Deepest point in the Pacific
4. Heavy rains              –  (iv) Australia
5. Kuroshio current      –  (v) Second order landform
6. Continental slope     –  (vi) On full and new moon days

Answer Key:

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

IV. Distinguish Between

Distinguish between:

 

1. SPRING TIDE	NEAP TIDE
* When the Sun, Moon and Earth are aligned in the same line, the collective gravitation causing to form a high tide called Spring tide. * It occurs on full moon and new moon days.	* When the Sun, Moon and Earth are at right angles, their gravitational force causes a low tide is called Neap tide. * It occurs the first and last quarter moon appears.
2. ABYSSAL PLAINS	OCEAN DEEPS
* These plains are underwater plains found on the deep ocean floor. * These are slight slope.	*Trenches are the deepest part of the oceans. * They occupy about 7% of the total relief of the ocean floor.

V. Answer the following briefly

1. What do you mean by the term Hydrosphere?

• Hydrosphere consists of water in various forms found on the Earth.
• It is a collection of all forms of water on the Earth.

 

2. What is Hydrological cycle?

• The Earth's water is always in motion. This continuous movement of water on above and below the Earth's surface is called the hydrological cycle.

3. Mention the various relief features of ocean floor.

• Continental shelf  
• Continental slope
• Continental rise
• Deep sea plain
• Oceanic deep 
• Oceanic ridge.

 

4. What are the factors that generate the oceanic currents?

• Earth' s rotation            
• Prevailing winds
• Difference in temperature
• Salinity of ocean water

 

5. Write a brief note on sea waves.

• Sea waves are ripples on water caused by the winds that blow over the sea.
• The height of these waves depends upon on the speed of wind its duration and the direction

VI. Answer all the questions given under each caption

1. Write a note on Continental Shelf and Continental Slope.

 

Continental Shelf:

• A gently sloping platform extending out from the continental land mass into the sea is called Continental Shelf.
• This type of land is shallower.
• There is abundant growth of grass, sea weeds and plankton. So these zones become the richest fishing ground in the world.

Continental Slope:

• A steep slope which descends from the edge of the continental shelf to the deep ocean bed is called Continental Shelf.
• Deep canyons and trenches are present there.

 

2. What do you mean by ocean currents? Explain its types.

 

Ocean currents:

• The movement of oceanic water on the surface and at the depths in a definite direction is called Ocean currents.

Types of ocean currents

• Warm currents.
• Cold currents

Warm currents:

• The movement of ocean currents from the low latitudes towards high latitudes are called warm currents.
• Ex., Gulf stream in Atlantic ocean.

Cold current:

• The movement of ocean currents from high latitudes to low latitudes are called cold currents.
• Ex., Peruvian current in Pacific ocean.

 

3. Explain the influences of the marine resources on mankind.

• Oceans are the life blood of planet Earth and mankind.
• They are essential for the oceanic prosperity.
• Oceans have extensive deposits of oil reserves.
• Besides a major fishing ground, it helps in the development of many ports for trade activities.
• Coastal tourism also attracts people around the world.