Q3721. Chlorofluorocarbons (CFCs) cause ozone depletion primarily because:
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Q3722. The "ozone hole" refers to a region of exceptionally depleted ozone primarily observed over:
Explanation
Every year, a dramatic thinning of the ozone layer occurs over a specific polar region during the late winter and spring. This phenomenon is driven by unique atmospheric conditions and the presence of man-made chemicals. The extreme cold in the area leads to the formation of special clouds that provide a surface for the chemical reactions that destroy ozone molecules, resulting in the well-known depletion zone.
Q3723. Match List I with List II regarding ozone protection agreements:
| International Protocol/Amendment | Key Focus |
|---|---|
| A. Vienna Convention | i. Phase-down of Hydrofluorocarbons (HFCs) |
| B. Montreal Protocol | ii. Framework for protection of the ozone layer |
| C. Kigali Amendment | iii. Phase-out of ozone-depleting substances (ODS) |
Explanation
International efforts to protect the atmosphere have evolved through several key agreements. The initial framework established a commitment to cooperation and research. This was followed by a binding treaty to phase out the production of substances that directly destroy ozone molecules. More recently, an amendment was added to target other chemicals that, while safe for ozone, contribute significantly to the global warming problem.
Q3724. Why was the Kigali Amendment to the Montreal Protocol deemed necessary?
Explanation
While the original agreement successfully addressed chemicals that were destroying the ozone layer, their replacements turned out to be extremely potent greenhouse gases. To prevent these substitutes from contributing to rapid global warming, an international amendment was adopted. This new regulation requires a gradual reduction in the use of these heat-trapping substances, helping to protect both the ozone layer and the global climate system.
Q3725. Polar Stratospheric Clouds (PSCs) play a crucial role in ozone depletion over Antarctica by:
Explanation
During the dark polar winter, the temperature in the upper atmosphere can drop low enough for clouds to form in a region that is usually very dry. These clouds provide a solid surface where chemical reactions occur between stable reservoir molecules. When the sun returns in the spring, these reactions release highly reactive forms of chlorine, which then rapidly destroy ozone in a catastrophic cycle.
Q3726. The thickness of the ozone layer is measured in which of the following units?
Explanation
Scientists use a specific unit to represent the total amount of ozone in a vertical column of air above a given location. It is defined as the thickness that the ozone would have if it were compressed into a pure layer at standard temperature and pressure. This measure allows for easy comparison of ozone levels across the globe and helps track the recovery of the protective layer.
Q3727. Which of the following is an expected health consequence of a significantly depleted ozone layer?
Explanation
A significant decrease in the concentration of ozone in the upper atmosphere allows more high-energy radiation to reach the Earth’s surface. This increased exposure is directly linked to several serious human health issues. Most notably, it leads to higher incidences of DNA damage in skin cells and clouding of the lens in the eye. These conditions can result in chronic illness and loss of vision over time.
Q3728. Desertification is formally defined by the UNCCD as land degradation in which specific areas?
Explanation
Land degradation in specific climate zones is a major global environmental challenge. This process occurs in regions where the amount of water lost through evaporation and plant usage exceeds the amount of rainfall received. These dry areas are particularly vulnerable to over-exploitation and shifting weather patterns. When the soil in these zones loses its productivity and biological potential, it is formally described as a type of desertification.
Q3729. Which anthropogenic activity is the leading cause of desertification globally?
Explanation
Several human activities contribute to the loss of productive land in dry regions. The most significant factor worldwide is the pressure placed on vegetation by large numbers of domestic animals. When livestock eat more plants than can naturally regrow, the soil is left exposed to wind and water erosion. This disruption of the natural plant cover is the primary driver of the degradation seen in many arid lands.
Q3730. The "Great Green Wall" is a monumental project aimed at combating desertification in which region?
Explanation
An ambitious project aims to restore millions of hectares of degraded land by planting a massive belt of trees and vegetation across a wide geographical area. This initiative is focused on a transition zone south of a major desert, where environmental conditions are increasingly harsh. By creating a living barrier, the project helps to improve soil health, provide local resources, and combat the southward expansion of drylands.Answer key for these questions
| Q | Correct answer |
|---|---|
| 3721 | (d) They release ozone-destroying chlorine |
| 3722 | (a) Antarctica |
| 3723 | (c) A-ii, B-iii, C-i |
| 3724 | (a) To target HFCs, which are potent GHGs |
| 3725 | (d) Providing surfaces for chlorine release |
| 3726 | (b) Dobson Units (DU) |
| 3727 | (c) Higher rates of skin cancer and cataracts |
| 3728 | (a) Arid, semi-arid, and dry sub-humid areas |
| 3729 | (b) Overgrazing by livestock |
| 3730 | (b) The Sahel region, Africa |
Frequently asked questions
How many RAS Prelims practice MCQs are there on RAS Prelims?
This page has 9654 practice MCQs on the RAS Prelims syllabus. Each has the correct answer, and most have an explanation.
How should I practise MCQs for RAS Prelims?
Attempt each question first, then open the answer and read the explanation. Practise one chapter at a time, note the facts you got wrong and revise them. Repeat the chapter after a few days.
Are these actual RAS Prelims past-paper questions?
No. These are practice questions written for the RAS Prelims syllabus. They follow the pattern the exam uses: factual questions, statement-based questions, match-the-list and assertion-reason.