UPSC Physical Geography – Chapter 17: Ocean Relief, Temperature and Salinity (22 MCQs)

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UPSC Physical Geography – Chapter 17: Ocean Relief, Temperature and Salinity (22 MCQs) – 22 questions, subject: Geography. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  

The shallowest part of the ocean floor, with an average gradient of 1° or less, is the:

Correct Answer: D [continental shelf]

Explanation:

NCERT describes the continental shelf as the shallowest part of the ocean, with an average gradient of 1° or even less.

2.  

A flat-topped seamount is called a:

Correct Answer: C [guyot]

Explanation:

A guyot is a seamount whose top has been flattened, so it is called a flat-topped seamount.

3.  

Oceanic trenches are generally associated with:

Correct Answer: D [convergent plate margins with earthquakes and volcanoes]

Explanation:

Trenches form where one plate subducts beneath another, so they lie along convergent margins with strong earthquakes and active volcanoes.

4.  

The deepest known point of the oceans lies in the:

Correct Answer: B [Mariana Trench]

Explanation:

The Challenger Deep, nearly 11,000 m below sea level, lies in the Mariana Trench of the western Pacific.

5.  

Iceland is an example of:

Correct Answer: B [the peak of a mid-oceanic ridge rising above the sea]

Explanation:

Iceland is a part of the Mid-Atlantic Ridge whose volcanic peaks rise above sea level as an island.

6.  

The layer in which ocean temperature decreases rapidly with depth is the:

Correct Answer: A [thermocline]

Explanation:

In the thermocline, about 500–1,000 m thick, temperature falls rapidly with increasing depth.

7.  

According to NCERT, the average temperature of the surface water of the oceans is about:

Correct Answer: C [27 °C]

Explanation:

NCERT gives the average temperature of ocean surface water as about 27 °C, decreasing towards the poles.

8.  

Salinity is expressed as the grams of salt dissolved in:

Correct Answer: D [1,000 g of sea water]

Explanation:

Salinity is the grams of dissolved salt in 1,000 g (1 kg) of sea water, expressed in parts per thousand.

9.  

The Bay of Bengal has lower salinity than the Arabian Sea mainly because of:

Correct Answer: B [the influx of river water]

Explanation:

The Ganga, Brahmaputra and other rivers pour huge volumes of fresh water into the Bay, diluting its salinity.

10.  

Consider the following statements:

1. Salinity of normal open ocean ranges between 33‰ and 37‰.
2. The Baltic Sea has low salinity because of large river inflow.
3. The Dead Sea has lower salinity than the open ocean.

Which of the statements given above is/are correct?

Correct Answer: B [1 and 2 only]

Explanation:

Statements 1 and 2 match NCERT; statement 3 is false because the Dead Sea is far saltier than the open ocean.

11.  

Assertion (A): Salinity near the equator is lower than in the subtropics.

Reason (R): Heavy rainfall at the equator dilutes the surface water.

Correct Answer: A [Both A and R are true, and R is the correct explanation of A]

Explanation:

Heavy convectional rain at the equator dilutes surface water, while the dry subtropics lose water by evaporation, so R explains A.

12.  

According to NCERT, which inland water body has the highest salinity?

Correct Answer: D [Lake Van]

Explanation:

330‰.

13.  

A zone where salinity increases sharply with depth is called the:

Correct Answer: D [halocline]

Explanation:

The halocline is the layer in which salinity changes sharply with depth, stratifying the water by salinity.

14.  

Freezing of sea water in polar regions:

Correct Answer: A [increases the salinity of the water below]

Explanation:

Sea ice forms mostly from fresh water and leaves its salt behind, so the water beneath becomes saltier.

15.  

The continental slope has a gradient of about:

Correct Answer: D [2°–5°]

Explanation:

NCERT gives the continental slope a gradient of 2°–5°, steeper than the shelf's 1° or less.

16.  

In the temperate zone, the eastern sections of the oceans are warmer than the western mainly because of:

Correct Answer: B [the westerlies driving warm currents eastward]

Explanation:

In mid-latitudes the westerlies drive warm currents such as the North Atlantic Drift towards the eastern sides of oceans.

17.  

Arrange the following in chronological order:

1. Trieste dives to the Challenger Deep
2. HMS Challenger expedition begins
3. India's Deep Ocean Mission approved
4. UNCLOS adopted

Select the correct answer using the code given below:

Correct Answer: C [2-1-4-3]

Explanation:

1872, 1960, 1982, 2021.

18.  

The deep sea (abyssal) plains lie at depths of about:

Correct Answer: A [3,000–6,000 m]

Explanation:

NCERT places the deep sea plains at depths of about 3,000–6,000 m, covered with fine clay and silt.

19.  

The maximum surface temperature of the oceans is recorded:

Correct Answer: C [slightly north of the equator]

Explanation:

NCERT notes that the highest ocean surface temperatures occur slightly north of the equator, not exactly at it.

20.  

The crewed submersible Matsya 6000 is being developed by:

Correct Answer: B [NIOT, Chennai]

Explanation:

The National Institute of Ocean Technology, Chennai, is developing Matsya 6000 under the Deep Ocean Mission's Samudrayaan.

21.  
UPSC Prelims 2024

Consider the following statements:

1. The Red Sea receives very little precipitation in any form.
2. No water enters the Red Sea from rivers.

Which of the statements given above is/are correct?

Correct Answer: C [Both 1 and 2]

Explanation:

the Red Sea lies in a hot desert belt and no permanent river flows into it.

22.  
UPSC Prelims 2021

Consider the following statements:

1. In the tropical zone, the western sections of the oceans are warmer than the eastern sections owing to the influence of trade winds.
2. In the temperate zone, westerlies make the eastern sections of oceans warmer than the western sections.

Which of the statements given above is/are correct?

Correct Answer: C [Both 1 and 2]

Explanation:

trade winds pile warm water in the west in the tropics; westerlies push warm water east in the temperate zone.

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