IAS Prelims Geography Q.2–2025 | Equator & World Water Bodies

Authentic Classroom Explanation by IAS Monk

📌 Question

Consider the following water bodies:
I. Lake Tanganyika
II. Lake Tonlé Sap
III. Patos Lagoon

Through how many of them does the Equator pass?
(a) Only one
(b) Only two
(c) All the three
(d) None

✅ Correct Answer: (d) None

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🎯 Theme of the Question

World Geography | Latitudinal Position | Equator | Lakes & Lagoons

UPSC here is testing map sense + latitude awareness, not memory of sizes or fame.

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🧠 Classroom Explanation

Let’s locate each water body strictly with respect to latitude.

I. Lake Tanganyika

• Location: East Africa
• Countries: Tanzania, DRC, Burundi, Zambia
• Latitude span: ~3°S to 9°S
• 👉 Entirely south of the Equator

❌ Equator does not pass through it

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II. Tonlé Sap

• Location: Central Cambodia
• Latitude: ~12°N to 13°N
• Famous for: Seasonal reversal of flow with Mekong
• 👉 Completely north of the Equator

❌ Equator does not pass through it

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III. Patos Lagoon

• Location: Rio Grande do Sul, southern Brazil
• Latitude: ~30°S
• Largest lagoon in Brazil
• 👉 Deep in the Southern Hemisphere

❌ Equator does not pass through it

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🧮 UPSC Elimination Logic

• Lake Tanganyika → Southern Hemisphere ❌
• Tonlé Sap → Northern Hemisphere ❌
• Patos Lagoon → Far Southern Hemisphere ❌

✔️ None lie on the Equator → Option (d)

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🧠 Memory Hook

“Tanganyika dips south, Tonlé Sap sits north, Patos sinks deep south”

If it’s Africa Rift / Cambodia / South Brazil → Think away from Equator

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🔍 Curiosity Corner

Despite being near the Equator:

• Lake Victoria lies just south of it
• Lake Tanganyika lies much farther south than many assume

UPSC loves exploiting this false proximity bias.

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📘 Enrichment Note

Water bodies actually crossed by the Equator (for contrast):

• Lake Victoria ❌ (close but not crossed)
• Congo Basin rivers ❌
• Indonesian seas ✔️ (key equatorial zone)

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🎯 Prelims Strategy Insight

• UPSC increasingly asks “through how many” questions
• Do not rely on size or fame
• Always apply latitude first, facts second

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🧩 One-Line Ready Recall

No major lake among Tanganyika, Tonlé Sap, and Patos lies on the Equator.

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🧭 IAS Monk Whisper
In geography, the map never lies—but memory often does. Trust latitude.