Duncan Passage is located bet- ween—

1. Introduction to India's Island Geography (basic)

India’s island geography is defined by two major archipelagos that extend the country's reach deep into the Indian Ocean: the Andaman and Nicobar Islands in the Bay of Bengal and the Lakshadweep Islands in the Arabian Sea. While both are stunningly beautiful, they have vastly different geological origins. The Andaman and Nicobar group consists of over 500 islands that are actually the peaks of a submerged mountain range (an extension of the Arakan Yoma range in Myanmar), with some being volcanic in origin Exploring Society: India and Beyond, NCERT Class VII (2025 ed.), Geographical Diversity of India, p.21. In contrast, the Lakshadweep islands are coral islands, built by the skeletons of tiny marine organisms called polyps INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.15.

The Andaman and Nicobar chain is geographically divided into two distinct clusters. The Ten Degree Channel, a wide stretch of water roughly 150 km across, separates the Andaman group in the north from the Nicobar group in the south Geography of India, Majid Husain (McGrawHill 9th ed.), Regional Development and Planning, p.90. Within the Andaman group itself, there is a further subdivision. The Great Andaman chain (which includes North, Middle, and South Andaman) is separated from Little Andaman by a specific maritime passage known as the Duncan Passage. Understanding these specific "water gaps" or channels is vital for grasping the maritime navigation and strategic layout of the region.

Feature	Andaman & Nicobar Islands	Lakshadweep Islands
Location	Bay of Bengal	Arabian Sea
Geological Origin	Volcanic and Tectonic (Mountainous)	Coral (Atolls)
Highest Peaks	Saddle Peak (738m), Mt. Thuiller (642m)	Generally low-lying
Key Volcanoes	Barren Island (India's only active volcano)	None

Ecologically, these islands are treasures. They experience an equatorial climate with convectional rainfall, leading to thick tropical rainforests INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.15. They are also home to several ancient tribes and a southern extreme known as Indira Point on the Great Nicobar Island, which is the southernmost point of the Indian Union Geography of India, Majid Husain (McGrawHill 9th ed.), Physiography, p.66.

Sources: Exploring Society: India and Beyond, NCERT Class VII (2025 ed.), Geographical Diversity of India, p.21; INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.15; Geography of India, Majid Husain (McGrawHill 9th ed.), Regional Development and Planning, p.90; Geography of India, Majid Husain (McGrawHill 9th ed.), Physiography, p.66

2. Internal Divisions of the Andaman Archipelago (intermediate)

The Andaman archipelago is not a single contiguous landmass but a complex chain of over 500 islands, primarily representing the elevated peaks of submerged mountain ranges that extend from the Arakan Yoma in Myanmar CONTEMPORARY INDIA-I, Geography Class IX, p.14. To master the geography of this region, we must distinguish between its two primary internal divisions: the Great Andaman group and Little Andaman. The Great Andaman is a dense cluster in the north, further subdivided into North, Middle, and South Andaman islands. These are the most significant landmasses and contain the majority of the archipelago's inhabited areas Geography of India, Majid Husain, p.90. Separating the southern tip of the Great Andaman chain from Little Andaman is a critical maritime gateway known as the Duncan Passage. This strait is roughly 48 km (30 miles) wide and is of immense strategic and navigational importance. It is specifically located between South Andaman (specifically Rutland Island) to its north and Little Andaman to its south. Within the broader Andaman group, you will also find smaller specialized clusters like the Ritchie’s Archipelago and the Labyrinth Islands, which add to the region's geographical diversity INDIA PHYSICAL ENVIRONMENT, Geography Class XI, p.15.

To help you visualize the hierarchy of these divisions, consider this comparison:

Feature	Great Andaman	Little Andaman
Composition	North, Middle, and South Andaman islands.	A single large island to the south.
Key Separator	Separated from Little Andaman by the Duncan Passage.	Separated from the Nicobar group by the Ten Degree Channel.
Notable Clusters	Includes Ritchie’s Archipelago and Labyrinth Islands.	Stands as the southernmost island of the Andaman group.

Sources: CONTEMPORARY INDIA-I, Geography Class IX, Physical Features of India, p.14; Geography of India, Majid Husain, Regional Development and Planning, p.90; INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Structure and Physiography, p.15

3. Major Latitudinal Channels (10 Degree Channel) (basic)

In the vast expanse of the Bay of Bengal lies a critical maritime feature known as the Ten Degree Channel. In geography, a 'channel' is a wide waterway that passes between two landmasses. The name 'Ten Degree' is not arbitrary; it refers to the fact that this body of water lies directly on the 10°N latitude line. Its primary geographical role is to act as a physical divider between the Andaman Islands to the north and the Nicobar Islands to the south India Physical Environment, NCERT Class XI, Structure and Physiography, p.16.

While the entire archipelago is often mentioned as a single unit (Andaman & Nicobar), they are distinct clusters separated by this channel, which is approximately 150 km wide Geography of India, Majid Husain, Regional Development and Planning, p.90. Specifically, the channel flows between Little Andaman (the southernmost of the Andaman group) and Car Nicobar (the northernmost of the Nicobar group). This separation is not just a line on a map; it represents a significant deep-sea passage that allows for international shipping and navigation in the Indian Ocean.

To master this region, it is also essential to distinguish the Ten Degree Channel from the Duncan Passage. While the Ten Degree Channel separates the two major island groups, the Duncan Passage is a narrower strait (about 48 km wide) located further north. It separates South Andaman from Little Andaman. Understanding these specific water bodies helps you visualize the fragmented nature of India's island territories, which are home to dense tropical rainforests and unique floral strains from India, Malaysia, and Myanmar Geography of India, Majid Husain, Regional Development and Planning, p.90.

Feature	Ten Degree Channel	Duncan Passage
Separates...	Andaman Group from Nicobar Group	South Andaman from Little Andaman
Width	~150 km	~48 km
Latitude	10° N	Between 11° N and 12° N

Sources: India Physical Environment, NCERT Class XI, Structure and Physiography, p.16; Geography of India, Majid Husain, Regional Development and Planning, p.90

4. Volcanic Features and High Peaks of the Region (intermediate)

To understand the volcanic and mountainous landscape of India, we must look beyond the mainland. While the Indian Peninsula and the Himalayas are devoid of active volcanoes today, the Andaman and Nicobar Islands tell a different story. These islands are actually the visible summits of a submerged mountain range that extends from the Arakan Yoma in Myanmar. Within this chain, Barren Island stands out as India's only active volcano. After a long period of dormancy, it became active again in the 1990s and most recently spewed lava and ash in 2017 Physical Geography by PMF IAS, Volcanism, p.157. Its counterpart, Narcondam Island, located to the northeast, is classified as an extinct volcano with a significantly eroded crater wall Physical Geography by PMF IAS, Volcanism, p.156.

Moving to the high peaks, the topography of the archipelago varies significantly from north to south. The highest point in the entire island chain is Saddle Peak (738 m), located in North Andaman. As we move south, other notable heights include Mount Diavolo in Middle Andaman and Mount Koyob in South Andaman. In the southern Nicobar group, the most prominent elevation is Mount Thuiller (642 m) on Great Nicobar Island INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Structure and Physiography, p.15. These peaks are essential landmarks for understanding the structural layout of the islands, which are often separated by strategic water bodies like the Duncan Passage (separating South Andaman from Little Andaman) and the Ten Degree Channel (separating the Andaman group from the Nicobar group).

On the mainland, volcanic history is largely ancient (like the Deccan Traps), but the high peaks of the Central Highlands remain vital geographic markers. For instance, the Aravalli Range, one of the world's oldest fold mountain systems, culminates at Guru Shikhar (1722 m) near Mount Abu Geography of India, Majid Husain, Physiography, p.54. This peak is separated from the main Mount Abu highlands by the Goranghat Pass, illustrating how tectonic and erosional forces have shaped India's diverse vertical relief over millions of years.

Region	Highest Peak	Elevation (Approx)
North Andaman	Saddle Peak	738 m
Great Nicobar	Mount Thuiller	642 m
Aravalli Range	Guru Shikhar	1722 m

Sources: Physical Geography by PMF IAS, Volcanism, p.156-157; INDIA PHYSICAL ENVIRONMENT, Geography Class XI, Structure and Physiography, p.15; Geography of India, Majid Husain, Physiography, p.54

5. Strategic Passages and International Borders (exam-level)

To understand India's geography, we must look beyond its landmass and appreciate the maritime gateways and land frontiers that define its geopolitical reach. In the Indian Ocean, the Andaman and Nicobar Islands act as a strategic sentinel. While most students know the Ten Degree Channel separates the Andaman group from the Nicobar group NCERT Class XI, Structure and Physiography, p.16, a more specific and vital maritime passage is the Duncan Passage. This strait is roughly 48 km wide and serves as the primary separator between South Andaman and Little Andaman. Navigating this passage requires precision, as it is flanked by the Sisters Islands and North Brother Island. Just north of it lies Rutland Island, which is separated from the Cinque Islands by the Manners Strait, a smaller branch of the Duncan system.

Moving to the northeast land frontier, the India-Myanmar border represents a complex physical and political boundary. Stretching approximately 1,458 km, this border is not merely a line on a map but follows the natural watershed between the Brahmaputra and the Ayeyarwady (Irrawaddy) river systems Majid Husain, India–Political Aspects, p.48. It traverses dense, forested hills across Mizoram, Manipur, Nagaland, and Arunachal Pradesh. A critical point of interest here is the Diphu Pass, which serves as the tri-junction between India, Myanmar, and China. Understanding these specific narrow points—whether water channels or mountain passes—is crucial because they dictate trade routes, security protocols, and international diplomacy.

Historically, India's strategic positioning was revolutionized by the opening of the Suez Canal in 1869, which slashed the maritime distance to Europe by nearly 7,000 km NCERT Class IX, India Size and Location, p.2. This connectivity, combined with internal landmarks like the 82°30'E Standard Meridian, ensures that India remains a central hub in global transit. To keep these straight, remember that 'Channels' often refer to latitudinal gaps, while 'Passages' or 'Straits' refer to specific navigable gaps between landmasses.

Feature	Separates / Connects	Significance
Duncan Passage	South Andaman & Little Andaman	Key maritime route in the Great Andaman chain.
Ten Degree Channel	Andaman Group & Nicobar Group	Major latitudinal division in the Bay of Bengal.
Diphu Pass	India, Myanmar, & China	Strategic tri-junction and mountain pass.

Sources: INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.), Structure and Physiography, p.16; Geography of India, Majid Husain (McGrawHill 9th ed.), India–Political Aspects, p.48-49; CONTEMPORARY INDIA-I, Geography, Class IX NCERT (Revised ed 2025), India Size and Location, p.2

6. The Duncan Passage and Manners Strait (exam-level)

The Andaman and Nicobar Islands represent a classic archipelago—a chain or cluster of islands in the ocean Certificate Physical and Human Geography, Islands and Coral Reefs, p.102. Within this vast island chain, maritime 'passages' or 'straits' are the navigable water bodies that separate the landmasses. The Duncan Passage is one of the most strategically significant straits in the Indian Ocean, acting as a gateway between South Andaman Island to the north and Little Andaman Island to the south. It is approximately 48 km (30 miles) wide and facilitates the movement of vessels between the Bay of Bengal and the Andaman Sea.

To understand the Duncan Passage in detail, we must look at the smaller island groups that define its boundaries. To its north lie the Sisters Islands (off South Andaman), and to its south is North Brother Island (off Little Andaman). A critical sub-feature of this area is the Manners Strait. This is essentially a branch or a narrower extension of the Duncan Passage that specifically separates Rutland Island (at the southern tip of the South Andaman group) from North Cinque Island. While the Duncan Passage is the broader waterway, the Manners Strait is the specific channel used for navigation closer to the South Andaman mainland.

It is vital for geography students to distinguish between the various 'channels' in this region. While the Duncan Passage manages the internal division of the Andaman group, the Ten Degree Channel is a much wider separation located further south, which divides the entire Andaman archipelago from the Nicobar archipelago. Mapping these locations requires a clear understanding of cardinal directions and scale to grasp the distances between these critical maritime points Exploring Society: India and Beyond, Locating Places on the Earth, p.11.

Feature	Duncan Passage	Ten Degree Channel
Separates...	South Andaman & Little Andaman	Andaman Group & Nicobar Group
Width	Approx. 48 km	Approx. 150 km
Key Landmark	Manners Strait (Rutland vs Cinque)	Car Nicobar (North of channel)

Sources: Certificate Physical and Human Geography, GC Leong, Islands and Coral Reefs, p.102; Exploring Society: India and Beyond, NCERT, Locating Places on the Earth, p.11; Geography of India, Majid Husain, Regional Development and Planning, p.90

7. Solving the Original PYQ (exam-level)

Now that you have mastered the vertical sequence of the Andaman and Nicobar archipelago, this question tests your ability to pinpoint the precise maritime boundaries within that chain. The Duncan Passage is a critical "building block" in Indian geography because it serves as the primary separator within the Great Andaman group itself. While you previously learned that the Ten Degree Channel acts as the macro-divider between the Andamans and the Nicobars, the Duncan Passage is the specific gateway separating the southern tip of the Great Andaman chain from the outlier island to its south.

To arrive at the correct answer, (A) South and Little Andaman, you must visualize the map from north to south: North, Middle, and South Andaman are clustered together, but Little Andaman sits further south, separated by this 48 km wide stretch of water. Think of it this way: the passage is the final "exit" from the main Great Andaman group before you hit the open water leading toward the Nicobars. As noted in Geography of India by Majid Husain, this passage is bounded by the Sisters Islands and Rutland Island, further confirming its position just below the South Andaman administrative hub.

UPSC designed the other options to exploit common confusion regarding island proximity. Options (C) and (D) are classic traps; while North, Middle, and South Andaman are distinct islands, they are separated by very narrow, shallow creeks rather than a wide "Passage." Option (B) is a spatial trap that moves you too far south into the Nicobar group, which is separated from the Andamans by the much more prominent Ten Degree Channel. By remembering that "Duncan" sits between the southern cluster and the little outlier, you can confidently eliminate the internal northern straits and the southern Nicobar channels.