Mains answer practice — GS 1 : Questions on major divisions of the ocean floor and below-normal, normal, and above-normal rainfall (Week 101)

Indian Express

09-05-2025

UPSC Essentials brings to you its initiative for the practice of Mains answer writing. It covers essential topics of static and dynamic parts of the UPSC Civil Services syllabus covered under various GS papers. This answer-writing practice is designed to help you as a value addition to your UPSC CSE Mains. Attempt today's answer writing on questions related to topics of GS-1 to check your progress.
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What is meant by below-normal, normal, and above-normal rainfall? Explain the factors responsible for the distorted distribution of rainfall.
Describe the main divisions of the ocean floor and discuss the characteristics and formation processes of each.
Introduction
— The introduction of the answer is essential and should be restricted to 3-5 lines. Remember, a one-liner is not a standard introduction.
— It may consist of basic information by giving some definitions from the trusted source and authentic facts.
Body
— It is the central part of the answer and one should understand the demand of the question to provide rich content.
— The answer must be preferably written as a mix of points and short paragraphs rather than using long paragraphs or just points.
— Using facts from authentic government sources makes your answer more comprehensive. Analysis is important based on the demand of the question, but do not over analyse.
— Underlining keywords gives you an edge over other candidates and enhances presentation of the answer.
— Using flowcharts/tree-diagram in the answers saves much time and boosts your score. However, it should be used logically and only where it is required.
Way forward/ conclusion
— The ending of the answer should be on a positive note and it should have a forward-looking approach. However, if you feel that an important problem must be highlighted, you may add it in your conclusion. Try not to repeat any point from body or introduction.
— You may use the findings of reports or surveys conducted at national and international levels, quotes etc. in your answers.
Self Evaluation
— It is the most important part of our Mains answer writing practice. UPSC Essentials will provide some guiding points or ideas as a thought process that will help you to evaluate your answers.
QUESTION 1: What is meant by below-normal, normal, and above-normal rainfall? Explain the factors responsible for the distorted distribution of rainfall.
Note: This is not a model answer. It only provides you with thought process which you may incorporate into the answers.
Introduction:
— The total monthly rainfall in India for a given month. Similarly, all-India seasonal rainfall refers to the total amount of rainfall received across India during a certain season.
— The monsoon season begins in June and extends across the southern peninsula, delivering rain to central India. However, rainfall in June was 11% below normal across the country.
Body:
You may incorporate some of the following points in your answer:
Calculation of below-average, normal, and above-normal rainfall
— If 'm' is the mean and 'd' is the standard deviation of any climate variable like rainfall. Assuming the time series is normally distributed, 68 per cent of the observations fall within +/- standard deviation (d) from the mean.
— If the realised value of the variable falls between:
(i) m-d to m+d (Normal rainfall)
(ii) less than m-d (Below normal rainfall)
(iii) more than m+d (Above normal rainfall)
Reasons for distorted rainfall distribution
— The central and southern peninsular regions have received an excess of rainfall, owing primarily to the position of the monsoon trough — a semi-permanent, low-pressure area that extends between Pakistan and the Bay of Bengal during the monsoon season and typically oscillates between north and south throughout the season.
— When it advances south, as it has done in this case, additional rain can fall in central, eastern, and peninsular India. When it changes to the north, the Himalayan foothills are likely to receive more rainfall, while the rest of India would have less rainfall.
— Other rain-bearing weather systems, such as an off-shore trough (a shallow trough of low pressure that forms along India's coast during the monsoon season), have also contributed to excess rainfall in the central and southern peninsular regions.
— Since the monsoon trough has yet to move northward, rainfall has been insufficient in the northwest, extreme north, east, and northeast regions this season. Furthermore, there have been fewer rain-bearing weather systems, and those that formed did not reach or bring rain to these areas.
(Source: How is the rainfall performance during the ongoing monsoon season? by Anjali Marar, mausam.imd.gov.in)
Points to Ponder
Read more about El Nino and La Nina
Read about types of clouds and types of rainfall
Related Previous Year Questions
Why is the South-West Monsoon called 'Purvaiya' (easterly) in Bhojpur Region? How has this directional seasonal wind system influenced the cultured ethos of the region? (2023)
What characteristics can be assigned to monsoon climate that succeeds in feeding more than 50 per cent of the world population residing in Monsoon Asia? (2017)
QUESTION 2: Describe the main divisions of the ocean floor and discuss the characteristics and formation processes of each.
Note: This is not a model answer. It only provides you with thought process which you may incorporate into the answers.
Introduction:
— The oceans are limited to the vast depressions in the earth's outer layer. The waters naturally blend, making it difficult to distinguish between them. Geographers have classified the oceanic portion of the world into five oceans: the Pacific, the Atlantic, the Indian, the Southern, and the Arctic.
— These huge oceans include several seas, bays, gulfs, and inlets. A significant percentage of the ocean floor is located between 3-6 kilometres below sea level. The ocean floors are rough, featuring the world's greatest mountain ranges, deepest trenches, and vast plains.
— As with continents, these features are generated by tectonic, volcanic, and depositional processes.
Body:
You may incorporate some of the following points in your answer:
Major divisions of the oceanic relief
The ocean floors can be divided into four major divisions:
(i) the Continental Shelf
— It is the extended margin of each continent occupied by relatively shallow seas and gulfs.
— It is the shallowest part of the ocean showing an average gradient of 1° or even less.
— The average breadth of continental shelves is around 80 kilometres. Some margins, such as the Chilean coasts and Sumatra's west coast, have essentially no shelves or are extremely thin. On the contrary, the Siberian shelf in the Arctic Ocean, the world's widest, is 1,500 kilometres wide.
— The continental shelves are covered with variable thicknesses of sediments brought down by rivers, glaciers, wind, from the land and distributed by waves and currents.
(ii) the Continental Slope
— The continental slope connects the continental shelf with the ocean basins. It starts at the bottom of the continental shelf and abruptly drops off onto a steep slope.
— The grade of the slope region varies from 2 to 5 degrees.
— The depth of the slope region ranges from 200 to 3,000 metres. The slope border marks the end of the continents. This region contains canyons and pits.
(iii) the Deep Sea Plain
— Deep sea plains are gently sloping sections inside ocean basins. These are the flattest and smoothest parts of the planet.
— The plains are covered in fine-grained sediments such as clay and silt.
(iv) the Oceanic Deeps
— These are the deepest parts of the ocean. The trenches are steep-sided, narrow basins. They are about 3-5 km deeper than the surrounding ocean floor.
— They occur near the base of continental slopes and along island arcs, and are linked to active volcanoes and powerful earthquakes.
Conclusion:
— The ocean floor holds vast quantities of metals and rare earths. Many countries and corporations are interested in the commercial potential of deep-sea mining.
— The UN's sea convention stipulates that any activities in the high seas must be equitably shared among states, and that would include profits from deep-sea mining.
(Source: Are deep-sea metals a vital resource or an environmental disaster in the making?, ncert.nic.in)
Points to Ponder
Read about deep sea mining
Read about places in news in Ocean
Related Previous Year Questions
What are the forces that influence ocean currents? Describe their role in the fishing industry of the world. (2022)
Explain the factors responsible for the origin of ocean currents? How do they influence regional climates, fishing and navigation? (2015)
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