Straits & Choke Points — UPSC Mapping Reference

Straits and choke points are one of the most heavily and consistently tested topics in UPSC Prelims (Geography + International Relations). Questions appear almost every year — either direct identification or reasoning about strategic importance.

1. Main Straits of the World

2. Canals — Strategic Waterways

3. Choke Points — Strategic Analysis

4. India's Island Channels (Prelims Trap)

These channels are among the most frequently confused topics in UPSC Prelims. The degree of latitude gives the channel its name.

Memory Aid:

• 8 Degree: Minicoy — Maldives (international)
• 9 Degree: Minicoy — Rest of Lakshadweep (internal)
• 10 Degree: Andaman — Nicobar (separates the two island groups)
• Duncan: South Andaman — Little Andaman
• Coco: North Andaman — Myanmar (Coco Islands)

Exam Strategy

This is THE most PYQ-rich topic in UPSC Geography. Expect 1–3 questions every Prelims.

Key Prelims traps to memorize:

Trap 1 — Bab-el-Mandeb vs Bosphorus vs Dardanelles:

• Bab-el-Mandeb: Red Sea to Gulf of Aden (Africa/Yemen) — Suez route entry
• Dardanelles: Aegean to Sea of Marmara (Turkey) — first Turkish strait from Mediterranean side
• Bosphorus: Sea of Marmara to Black Sea (Turkey, Istanbul) — second Turkish strait, leads to Black Sea
• Memory: "D before B" — Dardanelles is south (Aegean end), Bosphorus is north (Black Sea end); Sea of Marmara sits between them

Trap 2 — Malacca vs Lombok vs Sunda:

• Malacca: Between Malaysia/Thailand and Indonesia (Sumatra) — busiest, shallowest for large ships
• Lombok: Between Bali and Lombok (Indonesia) — deeper, preferred by Chinese submarines and large vessels
• Sunda: Between Java and Sumatra (Indonesia) — narrower and shallower than Lombok; Krakatoa is here
• Memory: "Malacca is the main highway; Lombok is the deep bypass; Sunda is the narrow back road with a volcano"

Trap 3 — Which sea/ocean connects to what:

• Hormuz connects Persian Gulf, NOT Red Sea
• Bab-el-Mandeb connects Red Sea (not Persian Gulf) to Gulf of Aden
• Palk Strait connects Bay of Bengal (northeast) to Gulf of Mannar (southwest) — does NOT connect to Arabian Sea directly
• Ten Degree Channel connects Andaman Sea to Indian Ocean proper

Trap 4 — Indian channels degrees:

• 8° = Minicoy to Maldives; 9° = Minicoy to rest of Lakshadweep; 10° = Andaman to Nicobar
• Duncan Passage is NOT a "degree channel" — it separates South Andaman from Little Andaman

Trap 5 — Montreux Convention:

• Governs BOTH Dardanelles AND Bosphorus (together called "Turkish Straits")
• Signed in 1936; guarantees civilian passage; restricts warship tonnage/duration
• Became highly relevant during Russia-Ukraine war (2022+): Turkey invoked it to block warships

Trap 6 — Busiest vs Most Important:

• Dover Strait: busiest by number of ships per day (~400–500 ships/day)
• Strait of Malacca: busiest by annual vessel count (~94,000 vessels/year) and trade volume
• Strait of Hormuz: most important for energy (20% of global oil)

Previous Year Questions

Prelims:

1. Consider the following pairs — Strait : Connects:
   

   1. Bab-el-Mandeb : Red Sea and Persian Gulf
      
   2. Strait of Malacca : Indian Ocean and South China Sea
      
   3. Dardanelles : Aegean Sea and Sea of Marmara
      
   4. Lombok Strait : Java Sea and Indian Ocean
      How many of the above pairs are correctly matched?
      (a) One
      (b) Two
      (c) Three
      (d) Four
      Answer: (b) — Pairs 3 (Dardanelles) and 4 (Lombok) are correct; Bab-el-Mandeb connects Red Sea to Gulf of Aden, not Persian Gulf.

2. With reference to India's island territories, consider the following statements:
   

   1. The Ten Degree Channel separates the Andaman Islands from the Nicobar Islands.
      
   2. The Nine Degree Channel separates Minicoy from the Maldives.
      
   3. The Eight Degree Channel separates Minicoy from the rest of the Lakshadweep group.
      Which of the statements given above is/are correct?
      (a) 1 only
      (b) 2 and 3 only
      (c) 1 and 3 only
      (d) 1, 2 and 3
      Answer: (a) — Only statement 1 is correct; 9° separates Minicoy from rest of Lakshadweep, and 8° separates Minicoy from Maldives.

3. The Montreux Convention of 1936 is associated with which of the following?
   (a) Freedom of navigation in the Strait of Malacca
   (b) Regime of passage through the Turkish Straits (Bosphorus and Dardanelles)
   (c) Demilitarization of the Suez Canal zone
   (d) Transit rights through the Panama Canal
   Answer: (b) — Montreux Convention (1936) governs warship passage through both the Bosphorus and Dardanelles (Turkish Straits).

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