The Andaman and Nicobar Islands are an elevated, partially submerged extension of the tertiary fold mountain chain of the Arakan Yoma (Myanmar) to the north and the Mentawai Ridge (Sumatra, Indonesia) to the south. Formed primarily due to the tectonic collision between the Indo-Australian Plate and the Eurasian (Sundal) Plate, this archipelago sits along a highly active subduction zone. This tectonic positioning makes the entire region highly seismically active, classifying it under Seismic Zone V of India.
Topographical Configuration
The archipelago consists of roughly 572 islands, islets, and rocks, stretching linearly from 6°45′ N to 13°45′ N latitude and 92°10′ E to 94°15′ E longitude. The chain is broadly divided into two distinct groups separated by the 10 Degree Channel: the Andaman Group to the north and the Nicobar Group to the south.
- The Andaman Group: Characterized by rugged, non-volcanic topography with narrow valleys and steep hills made of sandstone, limestone, and shale.
- The Nicobar Group: Features relatively flatter terrain compared to the Andamans, coral platforms, and elevated alluvial terraces.
Detailed Classification of Islands and Sub-Groups
The Andaman Sub-Clusters
The Andaman chain is divided geographically into distinct subdivisions, each possessing unique geomorphological identities:
- North Andaman: Home to Saddle Peak, the highest point of the entire archipelago (732 meters), surrounded by dense tropical rainforests.
- Middle Andaman: The largest island in terms of land area within the entire archipelago, characterized by broad valleys and extensive mangrove networks.
- South Andaman: Contains the administrative capital, Port Blair. It features deep natural harbors and jagged coastlines.
- Ritchie’s Archipelago: A cluster of smaller islands located east of Great Andaman, which includes popular destinations like Havelock Island (Swaraj Dweep) and Neil Island (Shaheed Dweep).
- Little Andaman: Positioned at the southern tip of the Andaman group, separated from South Andaman by the Duncan Passage.
The Nicobar Sub-Clusters
The Nicobar group contains fewer islands, which are divided into northern, central, and southern units:
- Car Nicobar: The northernmost island of the Nicobar group, largely flat and highly fertile with thriving coconut plantations.
- Central Nicobar Group: Includes Camorta, Katchal, Nancowry, and Trinket islands. Nancowry boasts an exceptional landlocked natural harbor.
- Great Nicobar: The largest and southernmost island of the Nicobar group. It hosts the Galathea National Park and terminates at Indira Point (6°45’ N), the southernmost point of India’s territory.
Volcanic and Coral Features of the Archipelago
Active and Extinct Volcanism
The region marks the only area in India exhibiting active subaerial volcanism, driven by the subduction tectonic processes along the Andaman Sea edge.
- Barren Island: Situated east of the Middle Andaman, it is India’s only active volcano. It lay dormant for over a century before erupting in 1991, with subsequent low-intensity eruptive phases recorded into the mid-2010s and 2020s.
- Narcondam Island: Located northeast of Barren Island, it is a dormant/extinct volcanic island composed primarily of andesite lava plugs.
Coral Reef Ecosystems
The islands are surrounded by extensive fringing coral reefs. These reefs act as natural barriers against wave erosion and provide critical habitats for marine biodiversity, including the endangered Dugong (sea cow), which is the state animal of the Andaman and Nicobar Islands.
Crucial Maritime Channels, Straits, and Passages
The safe navigation and strategic control of the eastern Indian Ocean depend heavily on several natural channels and straits cutting through the archipelago:
| Channel / Strait | Spatial Location | Strategic and Geographical Significance |
| Coco Channel | Between Landfall Island (Northernmost Andaman) and Coco Islands (Myanmar). | Marks the international maritime boundary between India and Myanmar; highly monitored for maritime surveillance. |
| Duncan Passage | Between South Andaman and Little Andaman. | A critical navigable waterway separating the main northern settlement clusters from the isolated southern Andaman island. |
| 10 Degree Channel | Between Little Andaman (Andaman Group) and Car Nicobar (Nicobar Group). | A 150 km wide, deep oceanic channel that forms a major global shipping artery connecting the western Indian Ocean to the Straits of Malacca. |
| Sombrero Channel | Between Little Nicobar and Car Nicobar clusters. | Provides local navigation routing through the central Nicobar islands. |
| Great Channel (Six Degree Channel) | Between Great Nicobar Island and Sumatra Island (Indonesia). | Located at the base of the Andaman Sea, it acts as the primary approach lane for all global maritime traffic heading toward the Malacca Strait from the west. |
Strategic, Geopolitical, and Ecological Importance
Strategic Security Outpost
The Andaman and Nicobar Islands give India a massive geopolitical advantage by commanding the western approaches to the Strait of Malacca, a critical global choke point through which a significant portion of world trade and energy supplies pass. To secure this maritime space, India established the Andaman and Nicobar Command (ANC) in 2001 at Port Blair—the country’s first and only operational tri-services theater command, integrating the Army, Navy, and Air Force.
Blue Economy and Exclusive Economic Zone (EEZ)
Though the islands account for less than 0.3% of India’s total landmass, their geographical spread across the Bay of Bengal and Andaman Sea generates nearly 30% of India’s total Exclusive Economic Zone (EEZ). This provides exclusive sovereign rights over massive marine fisheries, deep-sea mineral exploration, and potential offshore energy blocks.
Ecologically Protected Areas
The archipelago is home to exceptional biodiversity, featuring tropical wet evergreen, semi-evergreen, and extensive mangrove forests.
- Biosphere Reserve: The Great Nicobar Biosphere Reserve is recognized under UNESCO’s Man and the Biosphere (MAB) program, housing endemic species like the Nicobar Megapode and the giant robber crab.
- Tribal Reserves: Large portions of the islands are designated as Tribal Reserves to protect Particularly Vulnerable Tribal Groups (PVTGs), including the Sentinelese, Jarawas, Onge, and Great Andamanese (of Negrito origin in the Andamans) and the Shompen and Nicobarese (of Mongoloid origin in the Nicobars).
Key Facts and Trivia for Civil Services Prelims
- Renamed Islands: In December 2018, three prominent islands in the Andaman regular cluster were officially renamed to honor Netaji Subhas Chandra Bose and the Indian National Army: Ross Island became Netaji Subhas Chandra Bose Dweep, Havelock Island became Swaraj Dweep, and Neil Island became Shaheed Dweep.
- The 2004 Tectonic Impact: The massive 9.1 magnitude Indian Ocean earthquake in December 2004 caused significant permanent geological shifts; parts of the North Andaman island tilted upward by over 1 meter, exposing coral reefs, while parts of the southern Nicobar group subsided, permanently submerging Indira Point’s lower lighthouse platform under water.
- Saddle Peak National Park: It features the unique Kalpong River, which stands out as the only perennial river in the entire Andaman archipelago, hosting the region’s solo hydro-electric project.
- Chatham Island: Located near Port Blair, it is home to one of Asia’s oldest and largest sawmills, established by the British in 1883 to process the abundant local timber reserves like Padauk and Gurjan.