DAY – 9 : Insta 75 Days Revision Plan-2026 : GEOGRAPHY

Answer: (b)

Explanation

Statement I – Correct:
The Himalayas originated due to the continental collision between the Indian Plate (often referred to in textbooks as part of the Indo-Australian Plate) and the Eurasian Plate around 50 million years ago during the Cenozoic Era. The northward movement of the Indian Plate compressed the Tethys Sea sediments, leading to intense folding, faulting and uplift, which produced the Himalayan mountain system. This collision continues today, making the Himalayas geologically young and tectonically active.

Statement II – Incorrect:
The Trans-Himalayan ranges lie to the north of the Great Himalayas, not to the south. These ranges developed along the Indus–Tsangpo suture zone, which marks the zone of collision between the Indian and Eurasian plates. Important ranges of this region include the Karakoram, Ladakh and Zanskar ranges. In contrast, the Pir Panjal range belongs to the Lesser Himalayas (Himachal Himalaya) and lies south of the Great Himalayas, not in the Trans-Himalayan system.

Statement III – Correct:
The Siwalik (Outer Himalayas) represent the youngest Himalayan ranges and are mainly composed of unconsolidated or weakly consolidated sediments such as sandstone, shale, gravel and conglomerates. These deposits were formed from erosional debris carried by Himalayan rivers and accumulated in foreland basins during the later stages of Himalayan uplift, particularly in the Miocene–Pleistocene period.

Therefore, only two statements are correct.

Answer: (a)

Explanation

• Aravalli Range is the northernmost, extending from Delhi–Haryana to Gujarat and representing one of the oldest fold mountains of the Peninsular block.
• Satpura Range lies south of the Vindhyan system in central India and runs east–west between the Narmada and Tapti valleys.
• Mahadeo Hills are part of the Satpura system, located mainly in Madhya Pradesh around Pachmarhi, and lie south of the main Satpura ridge in the regional physiographic arrangement.
• Nilgiri Hills occur much further south, at the junction of the Western Ghats and Eastern Ghats in Tamil Nadu–Karnataka–Kerala.

Thus the correct sequence is: Aravalli → Satpura → Mahadeo Hills → Nilgiri Hills.

Answer: (c)

Explanation

Pair I – Correct:
Duns are structural valleys situated between the Lesser Himalayas (Himachal Himalaya) and the Siwalik ranges. They are formed due to tectonic subsidence and subsequent sediment deposition along the Himalayan foothills. These valleys are elongated and longitudinal in orientation. Well-known examples include Dehradun, Kotli Dun and Patli Dun.

Pair II – Incorrect:
Karewas are lacustrine deposits found in the Kashmir Valley, formed from sediments deposited in an ancient lake that once occupied the valley during the Pleistocene period. They consist mainly of clays, silts and sands and form elevated table-land like terraces. Karewas are agriculturally important and are particularly known for saffron cultivation near Pampore. They are not fluvio-glacial terraces associated with the Indus valley.

Pair III – Correct:
Patlands refer to flat-topped upland surfaces of the Chotanagpur Plateau, especially in Jharkhand. These surfaces represent old erosion surfaces formed due to prolonged denudation, and they are often covered with lateritic soils. Patlands represent remnants of the ancient plateau surface preserved at higher elevations.

Pair IV – Correct:
An intermontane basin is a basin or depression located between mountain ranges. Such basins typically form due to tectonic movements such as faulting or folding, and they may accumulate thick sedimentary deposits over time. These basins are characteristic of mountain systems formed through active tectonic processes.

Therefore, three pairs are correctly matched.

Answer: (a)

Explanation

Statement I – Correct:
The Eastern Coastal Plains are wider than the Western Coastal Plains. Major east-flowing rivers such as the Mahanadi, Godavari, Krishna and Cauvery carry large sediment loads. Continuous delta formation and alluvial deposition along the Bay of Bengal have broadened the coastal plains.

Statement II – Incorrect:
Chilika Lake on the Odisha coast is the largest brackish water lagoon in India, not a saltwater lake. It formed due to deposition of sandbars that separated part of the Bay of Bengal from the mainland, creating a shallow lagoon system.

Statement III – Incorrect:
The Eastern Coast is mainly an emergent coast. Large rivers deposit huge quantities of silt and sediments, forming deltas and shallow coastal waters. Because of this heavy siltation, natural deep-water harbors are rare. In contrast, the Western Coast is more submergent, allowing natural harbors such as Mumbai and Kochi to develop.

Therefore, only Statement I is correct.

Answer: (a)

Explanation

Statement I is correct: Black soils contain montmorillonite clay minerals, which have strong swelling and shrinking properties. These clay minerals enable the soil to retain moisture for long periods, making black soils suitable for crops like cotton.

Statement II is correct: Laterite soils develop under conditions of high temperature and heavy rainfall. Intense leaching removes silica and soluble bases, while iron and aluminium oxides accumulate, giving the soil its characteristic reddish colour.

Statement III is incorrect: Alluvial soils are generally deficient in nitrogen and humus, though they are relatively rich in potash and lime. Their fertility is maintained mainly through periodic deposition of fresh sediments by rivers, rather than inherent nutrient richness.

Answer: (c)

Explanation

Statement I is correct: Western Disturbances are mid-latitude (extratropical) cyclonic systems that originate in the Mediterranean–West Asian region. They move eastward towards the Indian subcontinent under the influence of prevailing westerly winds.

Statement II is correct and explains Statement I: These systems are embedded in the subtropical westerly jet stream, which carries them eastward. As they reach the Indian region during winter, they cause rainfall over north-western plains and snowfall in the western Himalayas, influencing states such as Punjab, Haryana, Himachal Pradesh and Jammu & Kashmir.

Statement III is incorrect: Western Disturbances mainly affect north-western India during winter. The northeast monsoon rainfall over peninsular India is primarily associated with tropical cyclones and depressions forming over the Bay of Bengal, rather than with Western Disturbances.

Therefore, only Statement II is correct and it explains Statement I.

Answer: (b)

Explanation

Ken – Correct
Ken is a right-bank tributary of the Yamuna River. Since the Yamuna is the largest tributary of the Ganga, the Ken ultimately forms part of the Ganga River system. It originates near Ahirgawan in Madhya Pradesh and joins the Yamuna near Chilla (UP).

Tons – Correct
The Tons River originates from the Garhwal Himalayas (Uttarakhand) and joins the Yamuna near Dehradun/Kalsi region. As a tributary of the Yamuna, it is also part of the Ganga river basin.

Banas – Correct
The Banas River rises in the Aravalli Range (Rajasthan) and flows into the Chambal River. The Chambal is a major tributary of the Yamuna, which ultimately drains into the Ganga, making Banas part of the Ganga river system.

Sharda – Correct
The Sharda (Mahakali) River originates in the Himalayas near the India–Nepal border and later joins the Ghaghara River, which is a major left-bank tributary of the Ganga.

Subarnarekha – Incorrect
The Subarnarekha River originates near Ranchi Plateau (Jharkhand) and drains directly into the Bay of Bengal near Odisha, forming an independent east-flowing river system, not part of the Ganga basin.

Vamsadhara – Incorrect
The Vamsadhara River rises in the Eastern Ghats (Odisha) and flows through Odisha and Andhra Pradesh before draining directly into the Bay of Bengal, independent of the Ganga system.

Answer: (a)

Explanation

Statement I is correct: National Waterway-1 (NW-1) runs along the Ganga–Bhagirathi–Hooghly river system from Prayagraj to Haldia, covering about 1620 km. It passes through Uttar Pradesh, Bihar, Jharkhand and West Bengal, making it the longest operational national waterway in India and an important inland transport corridor in the Ganga basin.

Statement II is incorrect: National Waterway-2 (NW-2) is located on the Brahmaputra river and extends from Dhubri to Sadiya in Assam. It does not extend up to Pasighat in Arunachal Pradesh, as mentioned in the statement.

Statement III is incorrect: National Waterway-3 (NW-3) lies entirely in Kerala. It consists of the West Coast Canal along with the Champakara and Udyogmandal canals, connecting Kollam and Kottapuram through the Kerala backwaters. It does not form a navigation corridor from Mangaluru to Kanyakumari.

Therefore, only Statement I is correct.

Answer: (c)

Explanation

I is correct: The rules require district authorities to submit biannual reports identifying suspected contaminated sites. This helps establish a systematic monitoring framework for early identification.

II is correct: Once a site is reported, the State Pollution Control Board (SPCB) or designated authority must conduct a preliminary assessment within 90 days to determine the level and nature of contamination.

III is correct: The rules mandate the creation of a national inventory of contaminated sites, which will track the status of identification, assessment, and remediation across the country.

This inventory improves transparency and helps guide policy decisions related to environmental risk management.

Thus, all three provisions are included in the Rules.

Answer: (c)

Explanation

Biostimulants are substances or microorganisms applied to plants or soil to stimulate natural plant processes. They improve nutrient uptake, growth, yield, and tolerance to environmental stresses such as drought or salinity.

They do not act as fertilisers, because they do not primarily supply essential nutrients like nitrogen, phosphorus or potassium. They also do not control pests or diseases, which distinguishes them from pesticides.

Most biostimulants are derived from natural sources such as seaweed extracts, plant residues, amino acids, or beneficial microorganisms.

In India, bio stimulants are regulated under the Fertiliser Control Order (FCO), 1985, following an amendment introduced in 2021, which requires toxicity tests, eco-safety studies and bio-efficacy trials before approval.

Answer: (C)

Explanation:

Let the present ages be:

A = 5x
B = 7x

Five years ago:

A = 5x − 5
B = 7x − 5

According to the question:

(5x − 5) / (7x − 5) = 2 / 3

Cross multiplying:

3(5x − 5) = 2(7x − 5)

15x − 15 = 14x − 10

15x − 14x = 15 − 10

x = 5

Present age of B:

7x = 7 × 5 = 35

Answer: (C)

Explanation:

Let the incomes be:

A = 3x
B = 4x
C = 5x

Let the expenditures be:

A = 2y
B = 3y
C = 4y

Savings = Income − Expenditure

For A:

3x − 2y = 2000

For B:

4x − 3y = 2000

Subtracting the first equation from the second:

(4x − 3y) − (3x − 2y) = 0

x − y = 0

x = y

Substitute in the first equation:

3x − 2x = 2000

x = 2000

Income of C:

5x = 5 × 2000 = ₹10,000

Answer: (B)

Explanation:

Initial quantity = 40 L
Quantity removed each time = 10 L

Remaining fraction after each operation:

(40 − 10) / 40 = 30 / 40 = 3 / 4

Number of operations = 3

Milk remaining:

40 × (3/4) × (3/4) × (3/4)

= 40 × 27 / 64

= 1080 / 64

= 16.875 litres

Answer: (B)

Solution:

Cost of cheaper rice = 40
Cost of dearer rice = 60
Mean price = 48

Difference between dearer price and mean price:

60 − 48 = 12

Difference between mean price and cheaper price:

48 − 40 = 8

Ratio of cheaper to dearer rice:

12 : 8

Simplified ratio:

3 : 2

Answer: (C) 

Explanation:

The passage emphasizes that dissent plays a crucial role in strengthening democratic systems. It explains that democracy does not rely on the absence of disagreement but on the ability to accommodate diverse viewpoints. Constructive criticism allows governments to review policies, identify mistakes, and implement necessary reforms. Suppressing dissent can hinder progress because innovation and societal improvement often emerge from questioning established ideas and practices.

Therefore, dissent should not be viewed as a threat to national unity but as an essential mechanism that promotes accountability, reform, and democratic growth. Among the given options, only option (C) accurately captures this central idea.