DAY – 48 : Insta 75 Days Revision Plan-2026 : GEOGRAPHY

Answer: (a)

Explanation

The Polar Vortex is a large-scale cyclonic circulation of cold air centered around the Earth’s poles, most prominently developed over the Arctic during winter in the stratosphere.

Statement I is correct as it accurately defines the Polar Vortex as a region of low pressure containing extremely cold air surrounding the polar regions.

Statement II is also correct. A strong and stable Polar Vortex keeps the cold air tightly confined within the Arctic due to strong westerly winds. However, when the vortex weakens or becomes disturbed, these winds slacken or meander, allowing cold Arctic air to spill southward into the mid-latitudes, often leading to severe winter conditions in regions like North America, Europe, and parts of Asia.

Statement III is incorrect because the Polar Vortex is primarily a stratospheric phenomenon, though it has a weaker counterpart in the troposphere. It is not driven by trade winds; rather, it is maintained by the sharp temperature gradient between the cold polar region and relatively warmer mid-latitudes, along with planetary (Rossby) wave interactions.

Statement IV is incorrect. Sudden Stratospheric Warming (SSW) refers to a rapid rise in temperatures in the polar stratosphere, which disrupts and weakens the Polar Vortex. This weakening can even cause the vortex to split into multiple lobes, increasing the likelihood of cold air outbreaks in lower latitudes.

Answer: (a)

Explanation

The western tropical Pacific is generally warmer than the eastern tropical Pacific due to large-scale ocean-atmosphere interactions. This region, often referred to as the “Western Pacific Warm Pool,” records some of the highest sea surface temperatures on Earth.

Statement I is correct because observations consistently show higher sea surface temperatures in the western Pacific compared to the eastern Pacific. In contrast, the eastern Pacific, especially along the coasts of South America, is relatively cooler due to upwelling of cold, nutrient-rich waters.

Statement II is also correct and provides the underlying mechanism. The trade winds, which blow from east to west along the equator, push warm surface waters westward. This continuous movement leads to the accumulation or “piling up” of warm water in the western Pacific. As a result, sea levels are slightly higher and temperatures significantly warmer in this region.

This westward displacement of warm water also facilitates upwelling in the eastern Pacific, where cooler water rises to the surface, reinforcing the temperature contrast between the two regions.

Answer: (b)

Explanation

The description refers to a glacial depositional landform formed by meltwater activity within or beneath glaciers.

An esker is a long, narrow, sinuous (winding) ridge composed of sand and gravel, deposited by streams flowing through subglacial tunnels in a retreating glacier. As the glacier melts, the sediments carried by these streams are left behind, forming elevated ridges that often stretch for several kilometers.

A drumlin is a smooth, elongated hill formed by glacial till, typically aligned with ice movement, but it is not formed by meltwater streams.

A kame is an irregularly shaped mound or hill of sand and gravel deposited by meltwater, but it is not narrow and winding.

A moraine is an accumulation of unsorted glacial debris (till) deposited directly by ice, not by meltwater streams, and does not form a sinuous ridge.

Answer: (a)

Explanation

The Black Sea is bordered by six countries: Turkey, Bulgaria, Romania, Ukraine, Russia, and Georgia.

In the given list, Georgia and Turkey have coastlines along the Black Sea. Azerbaijan and Iran border the Caspian Sea, while Armenia is a landlocked country and does not have access to any sea.

Answer: (d)

Explanation

The length of a day (LOD), defined as the time taken by the Earth to complete one rotation, is not perfectly constant and can vary on a millisecond scale due to several geophysical and atmospheric factors.

Statement I is correct. The melting of polar ice sheets redistributes mass from high latitudes toward the oceans. This alters the Earth’s moment of inertia, leading to slight changes in rotational speed and thus affecting LOD.

Statement II is correct. Tidal friction, caused primarily by the gravitational interaction with the Moon, transfers angular momentum from the Earth to the Moon. This results in a gradual slowing of Earth’s rotation, contributing to variations in LOD.

Statement III is correct. Changes in the flow and dynamics of the Earth’s molten outer core can alter the distribution of mass within the planet. These internal processes influence angular momentum and can cause short-term fluctuations in rotational speed.

Statement IV is correct. Variations in atmospheric pressure and large-scale wind patterns redistribute mass in the atmosphere. This exchange of angular momentum between the atmosphere and the solid Earth can produce measurable millisecond-level changes in LOD.

Answer: (a)

Explanation

The Prime Meridian (0° longitude) runs from the North Pole to the Equator passing through the eastern Atlantic region and parts of Europe and Africa.

Starting from the North Pole and moving southward:

The first major water body encountered is the Norwegian Sea, located between Greenland and Scandinavia.

Further south, the meridian passes through the North Sea and then reaches the English Channel, which lies between the United Kingdom and France.

Continuing southward into southern Europe, it crosses the Mediterranean Sea.

Finally, after traversing North Africa, the meridian reaches the Gulf of Guinea near the Equator along the west coast of Africa.

Answer: (a)

Explanation

Statement I is incorrect. The Mekong River flows through Southeast Asia and ultimately drains into the South China Sea via a vast delta in Vietnam. It does not drain into the Andaman Sea.

Statement II is correct. The Zambezi River, one of the major rivers of southern Africa, flows eastward and drains into the Mozambique Channel, which is a part of the Indian Ocean between Mozambique and Madagascar.

Statement III is incorrect. The Danube River flows across Central and Eastern Europe and empties into the Black Sea through a large delta in Romania and Ukraine. It does not drain into the Caspian Sea.

Statement IV is incorrect. The Volga River, the longest river in Europe, flows entirely within Russia and drains into the Caspian Sea, which is an inland water body, not the Black Sea.

Answer: (c)

Explanation

Statement I is correct. Khamsin is a hot, dry, dust-laden wind that blows across Egypt from the Sahara Desert, typically during spring, significantly raising temperatures and reducing visibility.

Statement II is incorrect. The Mistral is a cold, dry, northerly wind that blows through the Rhone Valley in southern France towards the Mediterranean Sea. It is not associated with the Adriatic Sea region.

Statement III is correct. The Zonda wind occurs on the leeward side of the Andes in Argentina and is a warm, dry downslope wind similar to the foehn. It is often termed a “snow-eater” due to its ability to rapidly melt snow.

Statement IV is correct. The Berg Wind in South Africa is a hot, dry wind that blows from the interior plateau toward the coast, often leading to sharp temperature increases and dry conditions.

Answer: (b)

Explanation

The Indian Ocean Dipole (IOD) is an ocean-atmosphere phenomenon characterized by differential sea surface temperatures between the western and eastern parts of the Indian Ocean.

Statement I is correct. A positive IOD is marked by cooler-than-normal sea surface temperatures in the eastern Indian Ocean (near Indonesia) and warmer conditions in the western Indian Ocean. This temperature gradient influences atmospheric circulation.

Statement II is incorrect. A negative IOD generally leads to suppressed or below-normal rainfall over the Indian subcontinent, as warmer waters near Indonesia enhance convection away from India. In contrast, a positive IOD is often associated with enhanced monsoon rainfall.

Statement III is incorrect. While the IOD is an independent mode of variability, it is not entirely independent of ENSO. There are known interactions between the IOD and the El Niño Southern Oscillation, and their combined effects can influence global and Indian monsoon patterns.

Answer: (b)

Explanation

The Walvis Ridge is a prominent submarine feature in the South Atlantic Ocean, extending westward from the coast of southwestern Africa (Namibia) towards the Mid-Atlantic Ridge. It is classified as an aseismic ridge, meaning it is not associated with significant seismic activity.

Geologically, it is believed to have formed due to hotspot activity, specifically linked to the Tristan da Cunha hotspot, which led to volcanic buildup on the ocean floor. The ridge represents a trail of volcanic activity as the African Plate moved over this hotspot.

Other options are incorrect as they describe different geomorphological features. Option (a) refers to Arctic oceanic ridges, option (c) describes a trench associated with subduction zones, and option (d) relates to transform fault boundaries, none of which correspond to the Walvis Ridge.

Answer: (c) 24

Explanation:
When a cube is painted on all faces and then cut into smaller equal cubes, different types of smaller cubes are formed:

• Corner cubes → 3 faces painted
• Edge cubes (excluding corners) → 2 faces painted
• Face center cubes → 1 face painted
• Inner cubes → 0 faces painted

We are asked about cubes with exactly two faces painted, which lie along the edges but not at the corners.

A cube has 12 edges.
Each edge contains smaller cubes, but the 2 corner cubes on each edge are excluded.

Number of small cubes along one edge = 4
Excluding corners → 4 − 2 = 2 cubes per edge

Total such cubes = 12 × 2 = 24

Answer: (a) 1

Explanation:
In dice problems, when two positions have two common faces, the third (different) faces are opposite to each other.

Step 1: Compare Position 1 and Position 2

• Common faces: 1 and 3
• Remaining faces: 2 and 5
  → Therefore, 2 is opposite 5

Step 2: Compare Position 1 and Position 3

• Common faces: 2 and 3
• Remaining faces: 1 and 4
  → Therefore, 1 is opposite 4

Hence, the number opposite to 4 is 1

Answer: (a) Only 3 and 4

Explanation:

Conclusion 1: Some thinkers are day-dreamers

• We know:
  All thinkers → poets
  Some poets → day-dreamers
• But there is no direct connection that ensures thinkers fall into the “some poets” category
  → Therefore, this does not definitely follow

Conclusion 2: All poets are thinkers

• Given: All thinkers are poets
• This does NOT imply the reverse
  → This is false

Conclusion 3: No scientist is a day-dreamer

• Given: No day-dreamer is a scientist
• This type of statement is reversible
  → Therefore, this follows

Conclusion 4: Some poets are thinkers

• Since all thinkers are poets, at least some poets must be thinkers
  → Therefore, this follows

Correct conclusions → 3 and 4

Answer: (b) Only 2 and 3

Explanation:

First, understand the phrase:
“Only a few workers are managers” means:

• Some workers are managers
• Some workers are NOT managers

Now evaluate each conclusion:

Conclusion 1: All workers being managers is a possibility

• This is impossible because we already know some workers are not managers
  → Therefore, this does not follow

Conclusion 2: Some managers are not directors

• All managers are executives
• No executive is a director
  → Therefore, no manager is a director
  → This implies some managers are not directors
  → This follows

Conclusion 3: Some workers are executives

• Some workers are managers
• All managers are executives
  → Therefore, some workers are executives
  → This follows

Correct conclusions → 2 and 3

Answer: (d)

Explanation:
The passage presents a balanced argument:

• It acknowledges that nature provides essential services
• It warns against treating nature purely as a commodity
• Most importantly, it highlights that these services are ignored in current economic systems, leading to their overuse and degradation

Option (d) captures this central idea precisely.
Other options either take extreme positions or focus on secondary points.