Samacheer Kalvi 9th Social Science – Geography Unit 4 Book Back Answers:
Samacheer Kalvi 9th Standard New Social Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 9 New Syllabus 2021 to 2022 Book Back Question & Answer available for both English and Tamil Mediums. Class 9 Social Geography Book Unit 4 – Hydrosphere Answers/Solutions are provided on this page. 9th Std Social Science History Book portion consists of 11 units, Geography Book portion consists of 8 units, Civics book portion consists of 6 units, and Economics book portion consists of 5 units, All Social Book Back One, and Two Mark Solutions are given below.
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Samacheer Kalvi 9th Social Science Book Back Solutions PDF:
9th Social Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 9th Geography Unit 4 Answers are given below.
Geography Book Back Answers
Unit 4 – Hydrosphere
I. Choose the correct answer.
1. The Sunda Trench lies in the ……………… ocean.
(a) Atlantic
(b) Pacific
(c) Indian
(d) Antarctic
Answer: (c) Indian
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
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
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
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
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.
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 Ocehn.
Answer:
(a) Gulf Stream—Pacific Ocean; (c) Canary current—Mediterranean sea
8. The amount of plankton 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. Assertion (A), Reason (R) type questions.
(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 but R is correct
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.
2. Assertion (A): Flat topped seamounts are known as Guyots.
Reason (R): All guyot features are of volcanic origin.
Answer:
(C) A is correct but R is false.
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.
4. Assertion (A): Atolls are more common in the Atlantic ocean.
Reason (R): The marine population at the depth is less.
Answer:
(A) both A and R are correct and R explains A.
III. Match the following:
1. Mariana trench – (a) Decreases salinity in the oceans
2. Great Barrier Reef – (b) Along the coast of Japan
3. Sargasso sea – (c) deepest point in the Pacific
4. Spring tides – (d) Australia
5. Heavy rains – (e) Second-order landform
6. Kuroshio current – (f) North Atlantic Ocean
7. Continental – (g) slope On full and new moon days
Answer:
1. (c)
2. (d)
3. (f)
4. (g)
5. (a)
6. (b)
7. (e)
I. Answer the following in brief:
1. What do you mean by the term Hydrosphere?
Answer:
The hydrosphere, the third sphere of Earth is a collection of all forms of water on the earth.
2. What is the hydrological cycle?
Answer:
The 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.
Answer:
The ocean basins are characterised by the following major relief features:
- Continental shelf
- Continental slope
- Continental rise
- Deep sea plain or Abyssal plain
- Oceanic deep
- Oceanic ridge.
4. What are the factors that generate ocean currents?
Answer:
The factors that generate ocean currents are:
- Earth’s rotation
- Prevailing winds and
- Differences in temperature and salinity of ocean water.
5. Write a brief note on sea waves.
Answer:
Sea waves are ripples on water caused when winds blow over the sea. The height of these waves depends on the speed of wind, its duration and the direction from which they blow.
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