DAY – 10 : Insta 75 Days Revision Plan-2026 : GEOGRAPHY

Answer: (a)

Explanation:

Both statements are correct, and Statement-II provides the correct reasoning for Statement-I.

Ocean surface temperatures are highest near the equator and gradually decrease towards the poles. This latitudinal variation is primarily driven by differences in solar energy received at the Earth’s surface. Equatorial regions receive more direct and concentrated sunlight, whereas polar regions receive oblique rays that spread over a larger area, reducing heating efficiency.

As a result, the amount of insolation declines with increasing latitude, which directly leads to lower ocean surface temperatures in higher latitudes. Hence, Statement-II correctly explains the observed temperature pattern described in Statement-I.

Answer: (c)

Explanation

The drainage pattern of Peninsular India is primarily determined by the Western Ghats, which act as a water divide. While most large peninsular rivers (like the Godavari, Krishna, and Kaveri) flow eastward into the Bay of Bengal, there are several significant rivers that flow westward into the Arabian Sea due to specific geological features.

• 1. Narmada: Originating near the Amarkantak plateau in Madhya Pradesh, it flows through a rift valley formed between the Vindhya and Satpura ranges. It is the largest west-flowing river of Peninsular India.
• 2. Tapi: It originates in the Multai reserve forest in Madhya Pradesh and flows parallel to the Narmada in a rift valley to the south of the Satpura range.
• 3. Periyar: This is the longest river in Kerala. It originates in the Western Ghats and flows westward, serving as a lifeline for the state before draining into the Arabian Sea.
• 4. Sabarmati: Originating in the Aravalli Range (Udaipur, Rajasthan), it flows southwest through Gujarat and drains into the Gulf of Khambhat in the Arabian Sea.

Answer: (c)

Explanation

Most Indian soils share a common deficiency: they are generally poor in nitrogen, phosphorus, and humus (with a few exceptions).

• Pair 1 is correctly matched: Black Soil (Regur) is derived from the weathering of basaltic rocks. It is chemically rich in lime, iron, magnesia, and alumina. It also contains potash. However, it is significantly deficient in phosphorous, nitrogen, and organic matter.
• Pair 2 is correctly matched: Alluvial Soil is the most fertile and widespread soil in India. While its composition varies based on the parent rock of the river basin, it is generally rich in potash but poor in phosphorous and nitrogen.
• Pair 3 is correctly matched: Peaty Soils are found in areas of heavy rainfall and high humidity, where there is a good growth of vegetation. The accumulation of dead organic matter is high, giving the soil a high organic matter content (up to 40–50%). Due to the high organic content and lack of drainage, these soils are typically heavy, black, and highly acidic.
• Pair 4 is incorrectly matched: Red Soil develops on crystalline igneous rocks in areas of low rainfall. Its red colour comes from the wide diffusion of iron. Chemically, Red Soil is extremely poor in nitrogen, phosphorus, and humus. This is a common trait across most peninsular soils.

Answer: (a)

Explanation

• Pair 1 is incorrectly matched: While the description for Plutonic Rocks is correct (they are intrusive igneous rocks that solidify deep within the crust), the example is wrong. Basalt is an extrusive rock. The classic example of a Plutonic rock is Granite. Because plutonic rocks cool slowly underground, they develop large, visible mineral crystals.
• Pair 2 is incorrectly matched: The description for Extrusive Igneous Rocks is correct (solidifying at the surface), but the example provided, Granite, is a plutonic (intrusive) rock. The correct example here would be Basalt. When magma reaches the surface (as lava), it cools very rapidly, resulting in a fine-grained or glassy texture because crystals don’t have time to grow.
• Pair 3 is correctly matched: Sedimentary Rocks are formed through lithification—a process involving the compaction and cementation of sediments (organic matter or mineral particles) over long periods. Limestone is a perfect example, often formed from the accumulation of shell, coral, and algal debris

Answer: (c)

Explanation:

Statement I is correct:
Although warm ocean waters (generally above 26.5°C) provide the necessary energy for tropical cyclone formation, cyclones rarely originate or move across the equatorial region (0°–5° latitude). Even though sea surface temperatures are highest near the Equator, this region is not favourable for cyclone development.

Statement II is correct and explains Statement I:
For a cyclone to develop, it must acquire a rotational motion (vortex). This rotation is generated by the Coriolis force, which deflects moving air. However, the Coriolis force is absent at the Equator (0° latitude).
As a result, air flowing towards a low-pressure centre does not acquire the necessary spin and instead converges directly, preventing cyclone formation. Typically, a minimum latitude of about 5°–10° is required for sufficient Coriolis effect to initiate and sustain rotation.

Statement III is incorrect:
High vertical wind shear is actually unfavourable for cyclone development. It disrupts the vertical structure of the storm by displacing heat and moisture away from the centre, thereby weakening or preventing intensification. In contrast, low vertical wind shear is essential for the formation and strengthening of cyclones.

Answer: (c)

Explanation:

The description refers to the Kikori River Basin, also known as part of the Great Papuan Plateau in Papua New Guinea. This region is ecologically significant due to its vast and largely intact forest cover, making it one of the most important biodiversity-rich landscapes in the Southern Hemisphere.

It spans a wide range of ecological zones—from high-altitude alpine and montane forests to dense tropical lowland forests and extensive mangrove ecosystems along the coast. The area is also notable for its unique geological features, including limestone karst formations, deep gorges, waterfalls, and extinct volcanic structures such as Mount Bosavi.

In addition to its ecological importance, the basin supports exceptional biodiversity, including numerous endemic species. It is especially renowned for its rich bird diversity, including several species of birds-of-paradise, and even hosts rare ecological phenomena such as underground roosting birds.

Answer: (a)

Explanation

Katabatic winds (from the Greek word katabatikos, meaning “going downhill”) are downslope winds driven by the difference in air density.

• Statement 1 is correct: These winds are created by radiational cooling of the air at high altitudes (like a mountain plateau or glacier) during the night. The air becomes cold, heavy, and dense. Under the force of gravity, this dense air “spills” over the edges and rushes down the slopes into the valleys below.
• Statement 2 is correct: The Mistral (flowing from the Alps down to the Mediterranean coast of France) and the Bora (flowing from the Julian Alps down to the Adriatic coast) are famous examples of cold, intense katabatic winds. In Antarctica and Greenland, katabatic winds can reach hurricane speeds (over 200 km/h).
• Statement 3 is incorrect: Katabatic winds occur primarily at night (when the ground cools rapidly) and are most common and powerful during the winter, when the temperature difference between the high-altitude ice/snow and the lower valleys is at its peak. They are not restricted to summer; in fact, they are a defining feature of winter weather in polar and alpine regions.

Answer: (a)

Explanation

• Statement 1 is correct: The Central Highlands lie to the north of the Deccan Plateau and are bounded on the western side by the Aravalli Range. They form the northern boundary of the Peninsular Plateau system.
• Statement 2 is incorrect: The general elevation of the Central Highlands ranges between 700–1000 metres, not uniformly above 1000 metres. The region slopes towards the north and northeast, draining into the Yamuna and Ganga river systems.
• Statement 3 is also incorrect: The eastern extension of the Central Highlands is represented by the Rajmahal Hills. The Satpura Range, however, lies to the south of the Central Highlands and forms part of the Deccan Plateau system, not its eastern extension.

Value Addition

• The Great Boundary Fault (GBF): This is a major geological fault that separates the Aravalli Range from the Vindhyan sediments of the Central Highlands.
• Mineral Wealth: The eastern part of this region, particularly the Chotanagpur Plateau, is often called the “Ruhr of India” due to its massive deposits of coal, iron ore, and manganese.

Answer: (C)

Explanation:
The Organisation for Economic Co-operation and Development (OECD) released the “Global Drought Outlook 2025”, offering a comprehensive analysis of drought as a rising global threat. It reports that 40% of the world’s land area faces frequent and severe droughts, with economic losses rising by 3–7.5% per year per drought episode.

• The report also observed declining soil moisture in 37% of global land since 1980, groundwater depletion in 62% of aquifers, and major disruptions to inland water navigation (e.g., Panama Canal), hydropower output, and agriculture.
• This goes beyond environmental indicators—OECD connects droughts to poverty, displacement, and inequality, emphasizing a need for resilience-focused policy frameworks.
• Although WMO and UNEP work on related themes, it is the OECD that provided the economic–ecological lens in this landmark 2025 document, aligning with its expertise in policy analysis across G20 and global South economies.

Answer: (b)

Desalination refers to the process of removing salts and other minerals from saline water to make it suitable for human consumption, agriculture, or industrial use.

• Statement 1 is incorrect. Gas hydrate formation does not involve high-temperature plasma discharge. Instead, it relies on low temperatures and high pressure, where water molecules form crystalline solids (hydrates) by encapsulating gas molecules (like methane or CO₂). This method separates freshwater as hydrates and is still in experimental stages for desalination.
• Statement 2 is correct. Reverse Osmosis (RO) is the most widely used method for desalination globally. It uses semipermeable membranes to remove salts under high pressure. It is relatively cost-effective and scalable for both small- and large-scale operations.
• Statement 3 is correct. Nanofiltration (NF) also uses membranes but operates at lower pressure and targets specific ions or molecules, making it more energy-efficient than RO, especially for brackish water or partial softening.

Hence, the correct answer is (b) 2 and 3 only.

Answer: (b) ₹3.24 lakh

Solution:

Let last year incomes be:
A = 4x, B = 3x

For A:
Last : Current = 3 : 4
Current A = 4x × (4/3) = 16x/3

For B:
Last : Current = 5 : 6
Current B = 3x × (6/5) = 18x/5

Total current income:
16x/3 + 18x/5
= (80x + 54x)/15
= 134x/15

Given:
134x/15 = 8.04
x = 0.9

Current income of B = 18x/5 = ₹3.24 lakh

Answer: (b) ₹2052

Solution:

A : B = 2 : 3
B : C = 1 : 2 → Multiply by 3 → 3 : 6

So:
A : B : C = 2 : 3 : 6

C : D = 3 : 4 → Multiply by 2 → 6 : 8

Final ratio:
A : B : C : D = 2 : 3 : 6 : 8

Difference:
D − A = 8k − 2k = 6k = 648
k = 108

Total sum = (2 + 3 + 6 + 8) × 108
= 19 × 108 = ₹2052

Answer: (d) 7 : 9

Solution:

Spirit fraction:
A = 5/7
B = 7/13
Mean = 8/13

Using alligation:

Difference between A and mean = 9/91
Difference between B and mean = 1/13

Required ratio:
= (1/13) : (9/91)

Multiplying by 91:
= 7 : 9

Answer: (c) 16 litres

Solution:

Let A = 4x, B = x
Total = 5x

From 10 litres removed:
A removed = 10 × (4/5) = 8
B removed = 10 × (1/5) = 2

Remaining:
A = 4x − 8
B = x − 2

After adding 10 litres of B:
B = x − 2 + 10 = x + 8

New ratio:
(4x − 8) / (x + 8) = 2/3

Solving:
12x − 24 = 2x + 16
10x = 40
x = 4

Substituting x = 4:
Initial quantity of A = 4x = 16 litres

Answer: (b)

Solution:

The passage critiques the excessive emphasis on high-stakes testing, arguing that it promotes rote memorization and a culture of compliance rather than inquiry. It explains that such an approach narrows the definition of success to performance in recall-based assessments, thereby neglecting broader competencies like critical thinking, creativity, and emotional intelligence. The issue is attributed to systemic rigidity rather than individual teachers, and no extreme solution such as abolishing testing is proposed. Thus, the most logical inference is that the current system prioritizes narrow, quantifiable performance metrics over holistic development, making option (b) the most appropriate answer.