Authentic Classroom Explanation by IAS Monk

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📍 The Question

Which of the following is/are correct inference/inferences from isothermal maps in the month of January?

1. The isotherms deviate to the north over the ocean and to the south over the continent.
2. The presence of cold ocean currents, Gulf Stream and North Atlantic Drift, make the North Atlantic Ocean colder and the isotherms bend towards the north.

Select the correct answer using the code given below:

(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Correct Answer: (a) 1 only

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🎯 Theme of the Question

Physical Geography | Climatology | Isotherms | Ocean–Land Contrast

This question tests the ability to interpret isothermal maps, especially the seasonal influence of landmasses and ocean currents in January.

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🧠 Classroom Explanation

First, recall a key concept.

Isotherms are lines joining places of equal temperature.
In theory, they run parallel to latitudes, but land–sea contrast and ocean currents distort them.

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🔹 Statement 1: Isotherms deviate northward over oceans and southward over continents in January. ✅

• January is winter in the Northern Hemisphere
• Land cools faster and more intensely than oceans
• Oceans retain heat longer due to:
  • High specific heat
  • Vertical mixing
• As a result:
  • Over oceans, temperatures remain relatively higher → isotherms bend northward
  • Over continents, temperatures drop sharply → isotherms bend southward

✔️ Statement 1 is correct

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🔹 Statement 2: Gulf Stream and North Atlantic Drift are cold currents that make the North Atlantic colder. ❌

• Gulf Stream and North Atlantic Drift are warm ocean currents
• They:
  • Warm the North Atlantic region
  • Cause isotherms to bend northward, not because of cold, but because of warmth
• The statement incorrectly labels them as cold currents

✘ Statement 2 is incorrect

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📊 Final Assessment

Statement	Status
Isotherm deviation over ocean & land (January)	✅ Correct
Gulf Stream & North Atlantic Drift as cold currents	❌ Incorrect

👉 Only Statement 1 is correct

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❌ UPSC Elimination Logic

• UPSC uses:
  • Incorrect qualifiers (“cold currents”) as traps
• Gulf Stream and North Atlantic Drift are standard warm-current facts
• Even if the bending direction is right, wrong cause = wrong statement

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🧩 Memory Hook

“In January, oceans comfort the cold — continents exaggerate it.”

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🧠 Prelims Strategy Insight

For isotherm questions:

• January = maximum land–sea contrast
• Always check:
  • Nature of ocean current (warm vs cold)
  • Hemisphere-specific effects

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🧭 IAS Monk Whisper

Maps speak softly, but only to those who know why lines bend.