Geography: UPSC Previous Year Questions (Prelims)

Explanation

Scientific studies confirm that Earth’s rotation (affecting day length) and axis orientation (causing polar motion) are shifting due to climate-driven factors--notably melting polar ice, glacier retreat, and groundwater depletion. These changes lead to mass redistribution, altering Earth’s moment of inertia, which in turn causes a rotational slowing (e.g., 1.33 milliseconds per century) and polar wander (axis shifts of 10-20 cm/year). Since 1980, Earth’s spin axis has shifted nearly 4 meters. The Chandler wobble, a natural axis oscillation, is also amplified by these mass changes.

Statement I is correct: Mass redistribution--e.g., Greenland losing 4,700 Gt and Antarctica 2,720 Gt (1992-2020), and 1.6 trillion tons of groundwater pumped since 1990--shifts mass toward the equator, slowing rotation and shifting the axis.

Statement II is correct: Solar flares and coronal mass ejections (CMEs) release up to 10° joules of energy, impacting the ionosphere and thermosphere (80-1000 km altitude). These cause geomagnetic storms, disrupting satellites, radio, and triggering auroras. However, per NASA and NOAA, they do not affect rotation or axis shifts, since they alter magnetic fields and atmospheric density, not mass distribution.

Statement III is correct: Climate-driven polar ice melt and groundwater depletion (e.g., Punjab & Haryana in India) shift mass equatorward, increasing moment of inertia, thus slowing rotation and causing axis drift, as confirmed by NASA and Nature Geoscience.

Explanation

Also referred to as "Cordillera de los Andes" in Spanish, the Andes Mountains is the world’s longest mountain range that stretches for more than 6,999km along the western margin of the South American continent. The Andes Mountains have an average height of 4,000m and a maximum width of 200 to 700km, and are considered as the highest mountain range that is situated outside the continent of Asia. This long mountain range extends from the north to south direction straddling the seven South American nations of Argentina, Bolivia, Colombia, Chile, Ecuador, Peru, and Venezuela. The Andes Mountains also form a part of the American Cordillera, which is a continuous series of mountain ranges that stretches across a major part of North, Central and South Americas.

Explanation

Lake Tanganyika: South of Equator.Lake Tanganyika was formed about 9-12 million years ago in the western arm of the East African rift valley. It is located within Burundi (8%), Democratic Republic of the Congo (DRC) (45%), Tanzania (41%), and Zambia (6%). Lake TonleSap: in Cambodia, North of Equator Patos Lagoon: in Brazil, South of Equator

Explanation

Statements 1,2 and 3 are correct: India is the largest producer, consumer and exporter of turmeric in the world. In the year 2022-23, an area of 3.24 lakh ha was under turmeric cultivation in India with a production of 11.61 lakh tonnes (over 75% of global turmeric production). More than 30 varieties of Turmeric are grown in India and it is grown in over 20 states in the country. The largest producing states of Turmeric are Maharashtra, Telangana, Karnataka and Tamil Nadu. India has more than 62% share of world trade in turmeric. During 2022-23, 1.534 lakh tonnes of turmeric and turmeric products valued at 207.45 million USD was exported by more than 380 exporters The leading export markets for Indian Turmeric are Bangladesh, UAE, USA and Malaysia.

Explanation

Statement 1 is correct: Radiometric dating techniques have confirmed that the rock formations along the eastern coast of South America (Brazil) and the western coast of Africa are similar in age, type, and structure. This is one of the most compelling geological evidences supporting the theory of continental drift.

Statement 2 is correct: Ghana, located on the west coast of Africa, has rich gold deposits along its coast, yet there is no local source rock to account for this mineral wealth. The likely explanation is that these gold deposits originated from the Brazil Plateau which, before the continents drifted apart, lay adjacent to what is now Ghana. This is one of the pieces of evidence supporting the theory of continental drift.

Statement 3 is correct: The Gondwana system of sedimentary rocks, particularly tillite deposits (sediments formed from glacial activity), found in India, have strikingly similar counterparts in six different landmasses in Southern Hemisphere namely Africa, Antarctica, Australia, Madagascar, Falkland Islands, and South America. These similarities provide evidence that these landmasses were once part of a supercontinent called Gondwanaland.

Explanation

Statement I is correct: Dust particles are more concentrated in subtropical and temperate regions due to the presence of dry winds. These regions often experience arid and semi-arid climates, where the lack of vegetation and strong winds promote the suspension of dust particles in the atmosphere. Deserts such as the Sahara, Thar, and Arabian Desert, all located in subtropical zones, are prime examples of major dust sources. Equatorial regions are humid and vegetated, which suppresses dust through rainfall and plant cover, while polar regions are cold and icy, limiting dust production.

Statement II is incorrect: Dry winds are prevalent in subtropical and temperate regions, and these winds are precisely the reason dust concentration is higher in these areas. In the subtropics, for example, descending air from the subtropical high-pressure belts results in dry and stable conditions, which are associated with low humidity and dusty environments.

Explanation

Statement I is correct: In January, the Northern Hemisphere’s large landmasses cool down rapidly, leading to lower temperatures. Isotherms shift southward (towards the equator) over the continents. In contrast, oceans retain heat longer, so the isotherms bend northward (poleward) when passing over oceans like the North Atlantic, where warm currents like the Gulf Stream increase the surrounding air temperature.

Statement II is correct and explains statement I: Due to the high specific heat capacity of water, oceans cool down more slowly than land. Therefore, in winter (January), the marine areas remain warmer than the adjacent continental interiors. Because of this temperature contrast the isotherms bend equatorward while crossing the landmasses and poleward while crossing the oceans in the month of January in the northern hemisphere.

Explanation

Statement II is correct: Chalk is porous, meaning it contains numerous small holes or voids that can absorb water. This porosity contributes to its high permeability, as the interconnected pores facilitate water movement through the rock. Hence, it explains Statement I.

Statement III is Incorrect: Clay is not completely non-porous. It possesses a high porosity due to its fine-grained structure; however, the pores are so small and poorly connected that they prevent significant water flow, resulting in low permeability. Hence, only one of the Statements II and III is correct and that explains Statement I.

Explanation

Statement I is correct: You may recall that the earth’s atmosphere is a dynamic mixture of gases that envelops the planet. It plays a great role in making the planet livable for different life forms. It provides us air to breathe, protects us from harmful ultraviolet (UV) radiation coming from the sun, traps the heat and creates a warming effect on the planet making it conducive to live by preventing extremes of temperatures. Without the atmosphere, temperatures would be well below freezing everywhere on earth’s surface.

Statement II is correct: The atmosphere helps regulate the Earth’s temperature by absorbing heat from the Sun during the day and slowing its escape at night. This heat-trapping ability is what keeps the planet’s average surface temperature around 15°C, making it suitable for life. Without this natural insulation, Earth would experience harsh temperature fluctuations between day and night, similar to what occurs on planets and moons with thin or no atmospheres.

Statement III is correct: Certain gases in the Earth’s atmosphere, particularly greenhouse gases like carbon dioxide (CO₂), methane, and water vapor, have the unique ability to absorb and trap radiation. This property makes them especially effective in trapping heat within the atmosphere, contributing significantly to the greenhouse effect.

Explanation

Pair 1 is correct: Arunachal Pradesh’s capital is Itanagar, which is named after the historical Ita Fort ("Ita" means brick). Additionally, the state has two National Parks -- Namdapha National Park and Mouling National Park --confirming the accuracy of the description.

Pair 2 is correct. Nagaland became a full-fledged state of India on 1st December 1963 through the 13th Constitutional Amendment Act, 1962, which also inserted Article 371A into the Constitution. This article provides special provisions for the state, confirming that Nagaland came into existence via a constitutional amendment.

Pair 3 is correct. Tripura initially became a Part ‘C’ State after its merger with the Indian Union on 15 October 1949. Following the States Reorganisation Act, 1956, it was converted into a Union Territory (centrally administered). Later, it attained full statehood on 21 January 1972 under the North Eastern Areas (Reorganisation) Act, 1971, as confirmed by official sources such as the Tripura Legislative Assembly website and Sepahijala District website.