Geography: UPSC Previous Year Questions (Prelims)

Explanation

The Earth’s rotation affects ocean currents through the Coriolis effect, which causes moving fluids like air and water to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection influences the direction of ocean currents.

Option 2 is correct: Wind patterns which are driven by differences in air pressure, are primary drivers of surface ocean currents. The friction between the wind and the ocean surface pushes water, creating currents.

Option 3 is correct: Differences in water density, which are caused by variations in salinity and temperature, influence vertical ocean currents. Cold water is denser and tends to sink, while warm water is lighter and tends to rise. This process contributes to the thermohaline circulation.

Option 4 is incorrect: The revolution of the Earth does not directly influence ocean currents. While the revolution of Earth impacts seasons and sunlight distribution, it is not a direct cause of ocean current movement.

Explanation

Statement 1 is correct: Ocean acidification reduces the ability of calcareous phytoplankton (such as coccolithophores) to form their calcium carbonate shells. As the ocean becomes more acidic, the process of calcification is impaired, adversely affecting their growth and survival.

Statement 2 is correct: Coral reefs rely on the ability of coral polyps to produce calcium carbonate skeletons. As ocean acidity increases, it becomes more difficult for corals to build and maintain their skeletons, making them more vulnerable. This not only threatens corals themselves but also the ecosystems that depend on them.

Statement 3 is correct: The larvae of some marine organisms, particularly those with phytoplanktonic larvae, rely on calcium carbonate for protection and growth. As the ocean becomes more acidic, these organisms may face difficulties in developing their shells, which could disrupt marine food webs.

Statement 4 is incorrect: While phytoplankton contribute to the release of dimethyl sulfide (DMS), which is linked to cloud formation, ocean acidification does not have a direct and large-scale impact on cloud formation. The reduction in phytoplankton due to ocean acidification may lead to lower DMS emissions, but this effect is relatively minor and unlikely to significantly affect cloud seeding and formation.

Explanation

Mixed farming is an agricultural system where crop cultivation and livestock rearing are carried out on the same farm. Mixed farming integrates crop production and animal husbandry, balancing risks while recycling nutrients through manure and crop residues. It diversifies income and enhances sustainability. This practice is designed to maximize the use of available resources and diversify the income sources for the farmer. The integration of crops and animals is a key feature that distinguishes mixed farming from other farming systems.

Option (a) is incorrect: It involves crop diversification typical of commercial farming, not mixed farming with livestock.

Option (b) is incorrect: describes intercropping, which lacks the animal component essential to mixed farming.

Explanation

The crops which are predominantly rainfed in India are Groundnut, Sesamum and Pearl millets. Groundnut is a drought-tolerant crop that requires moderate rainfall for its growth and development. Rainfall for cultivation - 500 to 600 mm per annum, distributed rainfall pattern throughout the growing season. Groundnut can withstand a dry spell of 15-20 days during its vegetative stage, but it requires adequate moisture during the flowering and pod formation stages. Sesamum requires temperature is 25°C to 30°C, can tolerate up to 40°C, sensitive to frost required rainfall is 500-600 mm, its drought-tolerant, excessive rainfall during flowering can cause lower yields. It requires well-drained Soil type, rich in organic matter, pH range of 5.5 to 8.0. Pearl millet is a hardy crop that can grow in semi-arid regions. The ideal rainfall for pearl millet cultivation is between 400 to 600 mm per annum, with a well-distributed rainfall pattern throughout the growing season. Pearl millet can tolerate drought conditions and requires moisture during the early growth stages, especially during germination and tillering. Rainfed agriculture is carried out in a wide range of soil types, agro-climatic conditions, and annual rainfall ranges from 400 mm to 1600 mm. Rainfed areas account for percent of millet production, 88 percent of pulses, 73 percent of cotton, 69 percent of oilseeds including groundnut and Sesame.

Explanation

The Himalayas are the youngest fold mountains in the world. They exhibit dynamic geological features shaped by tectonic activity. These features provide evidence of their youthful and evolving nature, making them a fascinating subject for geologists and travelers alike. All the given features--deep gorges, U-turn river courses, parallel mountain ranges, and steep gradients causing landslides--are evidence of the Himalayas being young fold mountains. These characteristics result from ongoing tectonic uplift, erosion, and the mountains’ relatively recent formation (around 50 million years ago).

Explanation

Monsoon refers to a seasonal change in wind patterns that results in a shift in precipitation patterns over a region. Monsoons occur primarily in tropical and subtropical regions and are characterized by a wet season and a dry season.

Statement 1 is correct: The monsoon duration decreases from southern India (June-September) to northern India (July-August) due to the gradual weakening of monsoon winds as they move inland. Due to its proximity to the sea, India’s southern region has earlier and longer rainy seasons than its northern region.

Statement 2 is correct: The northern plains experience a rainfall gradient, with higher rainfall in the east (Assam, West Bengal) and decreasing towards the west (Punjab, Rajasthan) due to the weakening of monsoon winds. During the southwest monsoon, Kolkata receives 119 cm, Patna 105 cm, Allahabad 76 cm, and Delhi 56 cm.

Explanation

Arunachal Pradesh has the following mentioned characteristics:

Northern Rajasthan lies approximately between 26°N to 27°N latitude. Arunachal Pradesh (27°N-29°N) closely aligns with this latitude range. Assam (24°N-28°N), Himachal Pradesh (30°N-33°N), and Uttarakhand (29°N-31°N) are either too far north or south. As per the India State of Forest Report (ISFR) 2021, Arunachal Pradesh has 82.4% forest cover. While Assam has 35.83%, Himachal Pradesh 27.72%, and Uttarakhand 45.44%. Arunachal Pradesh has over 12% of its forest area designated as Protected Areas, including Namdapha National Park, Pakke Wildlife Sanctuary, and Mouling National Park.

Explanation

Under the text of the Ramsar Convention wetlands are defined as: "areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres". Wetlands in India are vital ecosystems supporting biodiversity, water regulation, and livelihoods. They are classified into coastal and inland wetlands, each with unique ecological and geographical significance.

Statement 1 is correct: Gujarat has the largest area under wetlands in India. It is primarily due to the extensive Rann of Kutch, a seasonal salt marsh, and coastal wetlands like the Gulf of Kutch. According to the National Wetland Inventory and Assessment by the Space Applications Centre (ISRO), Gujarat accounts for ~22.7% of India’s total wetland area.

Statement 2 is incorrect: Inland wetlands (like lakes, rivers, and marshes) cover a larger area than coastal wetlands (like mangroves, estuaries, and lagoons). As per the National Wetland Atlas, inland wetlands constitute ~69% of India’s total wetland area, while coastal wetlands make up ~27%.

Explanation

Statement 1 is correct: The primary reason the westerlies in the Southern Hemisphere are stronger and more persistent than in the Northern Hemisphere is because the Southern Hemisphere has significantly less landmass (about 20% land and 80% water), whereas the Northern Hemisphere has 40% land and 60% water. The vast oceans in the Southern Hemisphere allow westerly winds to move with minimal obstruction, making them stronger and more persistent. In contrast, larger landmasses in the Northern Hemisphere create friction and disrupt wind flow.

Statement 2 is incorrect: The Coriolis force acts equally in both hemispheres at the same latitude as it depends on the Earth’s rotation and the latitude. It does not make the westerlies stronger in one hemisphere over the other. The main reason for the difference is the land-sea distribution. The Coriolis force is stronger near the poles and weaker at the equator, but it does not explain the difference in strength of the westerlies between the two hemispheres.

Explanation

Statement 1 is correct: The African and Eurasian desert belt (Sahara, Arabian, Thar, Gobi) lies in the sub-tropical high-pres-sure zone (20°-30° latitudes). In this region, descending dry air from the Hadley Cell suppresses cloud formation and rainfall, creating arid conditions. This becomes the main reason for the formation of these deserts.

Statement 2 is incorrect: Warm ocean currents increase evaporation followed by humidity, leading to higher rainfall in coastal areas rather than desert formation. Deserts are mainly found near cold ocean currents (e.g., the Atacama Desert near the Peru Current, the Namib Desert near the Benguela Current), which cool the air and reduce its moisture-holding capacity, causing dry conditions. Moreover, many deserts in this belt are landlocked, far from direct oceanic influence.