Geography: UPSC Previous Year Questions (Prelims)

Explanation

Black cotton soil, also known as regur soil, is highly valued in India because of its excellent moisture-retaining properties and suitability for cotton cultivation. Black cotton soil is primarily formed from the weathering of basaltic rocks, which are a type of fissure volcanic rock. These basaltic rocks were originally erupted during the Cretaceous period as part of the Deccan Traps in the northwest Deccan plateau. The weathering process of these volcanic rocks releases minerals that, combined with climatic factors, result in the formation of the distinctive black soil. The high clay content of black cotton soil enables it to retain moisture efficiently. Its properties make it particularly suitable for cotton cultivation, hence the alternative name "black cotton soil."

Explanation

Option (a) is correct: Sugarcane is the least water-ef-ficient crop. It requires around 1800 to 2200 mm of water, making it a water-intensive crop. It has high water requirements, primarily because it is grown in tropical climates where irrigation is essential for optimal growth.

Option (b) is incorrect: Major oilseeds like soyabean, castor seeds, cotton seeds, linseed and sunflower, etc. requires around 672.4 mm of water, which is considerably lower than sugarcane’s water needs, making it more water-efficient.

Option (c) is incorrect: Millets can be grown even in dry regions without irrigation facilities. Pearl millet is a drought-resistant crop that requires only 350 mm of water, making it highly water-efficient, especially in dry regions.

Option (d) is incorrect: Red gram (pulses) requires 200-450 mm of water, making it relatively more water-efficient compared to crops like sugarcane. Crop Water Requirement (mm) Crop Water Requirement (mm) Rice 900-2500 Chillies 500 Wheat 450-650 Sunflower 350-500 Sorghum 450-650 Castor 500 Maize 500-800 Bean 300-500 Sugarcane 1500-2500 Cabbage 380-500 Groundnut 500-700 Pea 350-500 Cotton 700-1300 Banana 1200-2200 Soybean 450-700 Citrus 900-1200 Tobacco 400-600 Pineapple 700-1000 Tomato 600-800 Gingelly 350-400 Potato 500-700 Ragi 400-450 Onion 350-550 Grape 500-1200

Explanation

Option (a) is incorrect: Chenab River originates from Bara Lacha Pass in Himachal Pradesh. It is formed by the confluence of Chandra and Bhaga rivers in Himachal Pradesh, flows through Jammu and Kashmir and enters Pakistan. The Chenab does not join the Indus directly. It merges with the Sutlej River in Pakistan.

Option (b) is incorrect: Jhelum River originates from Verinag Spring in Jammu and Kashmir. It flows through the Kashmir Valley and enters Pakistan. Jhelum joins Chenab, which later merges with Sutlej before reaching the Indus. Jhelum does not directly join Indus.

Option (c) is incorrect: Ravi River originates from Bara Bhan-gal in Himachal Pradesh. It flows through Punjab before entering Pakistan. Ravi joins the Chenab River, which later merges with the Sutlej before meeting the Indus.

Option (d) is correct: Sutlej River originates from Rakshastal, near Lake Mansarovar, Tibet. It flows through Himachal Pradesh and Punjab before entering Pakistan. Sutlej is the only river that directly joins the Indus River at Mithankot, Pakistan. Thus, it is the only Satluj river in the Indus valley system which receives water from three rivers of the system and joins Indus directly. The Indus River System:

Fig: Map of the Indus River System

Explanation

A salt lake or saline lake is a landlocked body of water that has a concentration of salts and other dissolved minerals significantly higher than most lakes. These lakes are characterized by their high salt content, often due to the arid or semi-arid climate and the lack of outflowing rivers leading to the evaporation of water and the concentration of salts. Didwana, Kuchaman, Sargol and Khatu are saline lakes of Rajasthan.

Explanation

Option 1 is incorrect: The Brahmani River does not originate in the Eastern Ghats. The Brahmani River is formed by the confluence of the South Koel and Sankh rivers in Jharkhand. The South Koel originates near Nagri in Jharkhand, while the Sankh River originates in the Chotanagpur Plateau. After the confluence, it flows through the Eastern Ghats in Sundar-garh, Deogarh, Dhenkanal, and Jajpur districts.

Option 2 is correct: The Nagavali River originates in the Eastern Ghats near Lakhbahal in the Kalahandi district of Odisha. It flows through Odisha and Andhra Pradesh before draining into the Bay of Bengal.

Option 3 is incorrect: The Subarnarekha River originates near Nagri in the Chotanagpur Plateau of Jharkhand. It flows through Jharkhand, West Bengal, and Odisha before emptying into the Bay of Bengal. The Chotanagpur Plateau is part of the Deccan Plateau, not the Eastern Ghats.

Option 4 is correct: The Vamsadhara River rises in the Durgakangar Hills of the Eastern Ghats in the Kalahandi district of Odisha. It flows through Odisha and Andhra Pradesh before draining into the Bay of Bengal.

Explanation

The Jet Stream is a geostrophic wind that generally blows from west to east across the upper layers of the troposphere at an altitude of 20,000 to 50,000 feet. Air masses with different temperatures collide to form jet streams. Thus, the location of the Jet Stream’s formation is normally characterized by surface temperatures.

Statement 1 is incorrect: Jet streams exist in both the Northern and Southern Hemispheres. They typically form near the boundaries of major air masses and are driven by temperature differences and the Earth’s rotation. The Polar Jet Stream and Subtropical Jet Stream are present in both hemispheres.

Statement 2 is correct: Not all cyclones form an eye. The eye is a distinct feature of well-developed, intense tropical cyclones. In contrast, temperate cyclones do not have an eye because there is no central area where winds and rainfall are calm or inactive.

Statement 3 is incorrect: The eye of a tropical cyclone is the calm center with the lowest surface pressure and the warmest air above it. At about 12 km high, the air in the eye can be 10°C or more warmer than the surrounding air, while at the surface, it’s only 0-2°C warmer.

Explanation

Ocean Mean Temperature (OMT) represents the thermal energy in the upper layer of the ocean. It is measured up to the 26°C isotherm, which represents the depth where water temperature is consistently 26°C. OMT is a more reliable indicator than Sea Surface Temperature (SST) for predicting the Indian monsoon rainfall, as it reflects the ocean’s thermal energy more comprehensively.

Statement 1 is incorrect: OMT is measured up to the 26°C isotherm. In the southwestern Indian Ocean during January-March, the depth of the 26°C isotherm is approximately 59 meters, not 129 meters.

Statement 2 is correct: OMT, especially during the January-March period (pre-monsoon season) has been found to be a useful indicator for forecasting the Indian Summer Monsoon rainfall. Warmer OMT in this period can suggest a stronger monsoon and potentially higher rainfall, while cooler OMT may indicate a weaker monsoon. This is because the ocean’s temperature influences the amount of moisture available for the monsoon winds. Studies by the Indian Institute of Tropical Meteorology (IITM) and other scientific bodies have shown a strong correlation between OMT and monsoon performance.

Explanation

Statement 1 is correct: In India, the important pulse crops grown in winter (rabi) are chickpea, lentil, lathyrus, field pea and kidney bean. However, green gram, black gram and cowpea are grown in both spring and rainy season. Black gram (Urad dal) can be cultivated in both kharif (monsoon) and rabi (winter) seasons in India, making it a versatile crop in the country’s agricultural cycle.

Statement 2 is incorrect: According to the Directorate of Economics and Statistics (DES), the share of pulse production in 2018-19 was as follows: Tur (15.34%), Gram (43.29%), Moong (Green gram, 10.04%), Urad (Black gram, 13.93%), Lentil (6.67%), and other pulses (10%). Green gram alone does not account for nearly half of India’s total pulse production.

Statement 3 is incorrect: Over the past three decades, both kharif pulses and rabi pulses have experienced increased production due to improved agricultural practices, increased area under cultivation, and better support for pulse farming.

Explanation

Option (a) is correct: Cotton is India’s most important fiber crop, accounting for about 25% of the world’s cotton production. Cotton growing condition requirements:

Temperature and climate: Cotton flourishes in a subtropical climate with optimal temperatures ranging from 21°C to 30°C. Rainfall: Cotton needs 50 to 100 cm of rainfall during its growing period, but excessive or waterlogged conditions can negatively affect its growth. Soil Type: Cotton grows best in light, well-drained, moisture-retaining soils, especially the black cotton soil of the Deccan Plateau, which has high moisture-retention capacity. Frost-Free Days: Requires at least 210 frost-free days and bright sunshine to complete its life cycle. Growing Season: It is a kharif crop and typically takes 6 to 8 months to mature Top Cotton Producing States: Gujarat > Maharashtra > Telangana > Andhra Pradesh > Rajasthan. Options (b), (c) and (d) are incorrect:

Jute: Requires high rainfall (150-200 cm) and humid weather, not subtropical conditions. Sugarcane: Requires higher rainfall (75-200 cm) and thrives mainly in tropical regions. Tea: Requires cool, humid conditions, heavy rainfall (150-300 cm), and acidic soils, unlike the drier conditions needed for cotton.

Explanation

In India, minerals are classified as major minerals and minor minerals under the Mines and Minerals (Development and Regulation) Act, 1957. Major minerals are those specified in the First Schedule of the Act and are under the regulatory control of the central government. Minor minerals are defined under Section 3(e) of the Act and are regulated by state governments.

Option (d) is correct: The following are Major minerals:

Chromite is an oxide mineral of chromium and iron and is the primary source for chromium. It is extensively used in metallurgy, refractory materials, and chemicals. Kyanite is a typically blue silicate mineral used in refractory and ceramic products. Sillimanite is an alumino-silicate mineral used in high-temperature ceramics and refractories. Bentonite is a type of clay formed from volcanic ash and is primarily used in drilling mud, binder, purifier, and absorbent applications. In India, bentonite is officially classified as a minor mineral.