India possesses a prominent maritime position in the Indian Ocean region. With a coastline stretching over thousands of kilometers, the coastal and marine geography of India plays a critical role in its climate, economy, biodiversity, and strategic geopolitics.
Maritime Boundaries and Coastline Statistics
India’s total coastline measures 7,516.6 km, which includes 5,422.6 km of mainland coastline and 2,094 km of island territories. The coastal zone spans 9 coastal States and 4 Union Territories (UTs).
| State/UT | Coastline Length (in km) | Features / Significance |
| Gujarat | 1,214.7 | Longest mainland coastline; characterized by creeks and gulfs. |
| Andhra Pradesh | 973.7 | Longest coastline in South India; dominated by the Krishna-Godavari deltas. |
| Tamil Nadu | 906.9 | Features the Coromandel Coast; prone to North-East monsoon cyclones. |
| Maharashtra | 652.6 | Rocky Konkan coast with numerous ria estuaries and structural bays. |
| Kerala | 569.7 | Characterized by lagoons, backwaters (Kayals), and barrier islands. |
| Odisha | 476.4 | Utkal plains; features Chilika Lake and Wheeler Island (Abdul Kalam Island). |
| Karnataka | 300.0 | Canara coast; features a mix of sandy beaches and rocky cliffs. |
| West Bengal | 157.5 | Dominated by the active deltaic system of the Sundarbans mangrove forest. |
| Goa | 101.0 | Shortest mainland coastline state; rich in pocket beaches and estuaries. |
| Andaman & Nicobar Islands | 1,962.0 | Longest coastline among all absolute territories/UTs; volcanic and coral origins. |
| Lakshadweep Islands | 132.0 | Coral atoll formations in the Arabian Sea. |
| Puducherry | 47.6 | Fragmented coastal pockets along the East and West coasts. |
| Daman & Diu and Dadra & Nagar Haveli | 42.5 | Located around the Gulf of Khambhat. |
Geomorphological Classification of Indian Coastal Plains
The Indian coastal plains are broadly divided into the Western Coastal Plains and the Eastern Coastal Plains. They represent a stark contrast in terms of tectonic origin, wave action, and depositional features.
The Western Coastal Plains
The Western Coastal Plain is a narrow strip of land sandwiched between the Western Ghats and the Arabian Sea. It is an example of a submerged coastal plain, except for the Malabar stretch which shows signs of emergence.
- Kachchh and Kathiawar Peninsula: Formed by the deposition of silt by the Indus River in geological times. Kachchh features the Great Rann (salt marsh) and Little Rann. Kathiawar lies south of Kachchh, marked by the Mandav Hills and Mount Girnar.
- Gujarat Plain: Formed by the rivers Narmada, Tapi, Mahi, and Sabarmati. It slopes towards the Gulf of Khambhat.
- Konkan Coast: Extends from Daman to Goa. It is a highly dissected, rocky coast featuring cliffs, caves, and ria (drowned river valleys) estuaries.
- Kannada/Canara Coast: Extends from Goa to Mangalore. It is a transitional zone with narrow plains and steep streams originating from the Western Ghats.
- Malabar Coast: Extends from Mangalore to Kanyakumari. It is relatively wider and characterized by Kayals (backwaters) and lagoons. Vembanad Lake is the largest lagoon here.
The Eastern Coastal Plains
The Eastern Coastal Plain lies between the Eastern Ghats and the Bay of Bengal. It is an example of an emergent coastal plain, making it broader and less suitable for deep natural harbors compared to the west.
- Utkal Plain: Extends along the Odisha coast. It includes the Mahanadi delta and features Chilika Lake, the largest brackish water lagoon in India.
- Andhra Plain: Extends from the south of Utkal plain to Pulicat Lake. It is dominated by the massive deltas of the Godavari and Krishna rivers. Kolleru Lake, a freshwater lake, lies between these two deltas.
- Coromandel Coast / Tamil Nadu Plain: Extends from Pulicat Lake to Kanyakumari. It features the Cauvery delta, often called the “Granary of South India.” This coast receives winter rainfall from the North-East monsoon.
Comparative Geomorphology: West vs. East Coasts
| Parameter | Western Coastal Plains | Eastern Coastal Plains |
| Tectonic Nature | Submerged coast (faulting/subsidence). | Emergent coast (upliftment/deposition). |
| Width | Narrow (average 50-65 km). | Wide (average 80-120 km). |
| River Features | Short, fast-flowing rivers forming estuaries (no deltas). | Long, meandering rivers forming extensive deltas. |
| Ports & Harbors | Highly favorable for natural ports due to deep waters near the coast. | Requires dredging; mostly artificial ports due to shallow, gently sloping continental shelves. |
| Sand Dunes & Lagoons | Abundant sand dunes and unique Kayals (backwaters). | Marked by large coastal lagoons like Chilika and Pulicat. |
Indian Island Ecosystems
India possesses two major island groups located in distinct marine environments, alongside numerous offshore islands.
Andaman and Nicobar Islands (Bay of Bengal)
- Geological Origin: They are the elevated portions of submerged submarine hills, representing the tertiary fold mountain chain extension of the Arakan Yoma (Myanmar).
- Structure and Segregation: The archipelago consists of roughly 572 islands. The 10-Degree Channel (10° N latitude) geographically separates the Andaman group from the Nicobar group.
- Key Features and Trivia:
- Barren Island: India’s only active volcano, located in the Andaman Sea.
- Narcondam Island: An extinct or dormant volcanic island.
- Saddle Peak: The highest peak in the Andaman islands (732 m), located in North Andaman.
- Mount Thullier: The highest peak in the Nicobar islands (642 m), located in Great Nicobar.
- Indira Point: Located on Great Nicobar Island, it is the southernmost point of India’s territory (submerged during the 2004 Tsunami).
Lakshadweep Islands (Arabian Sea)
- Geological Origin: They are entirely of coral origin (atolls and fringing reefs) built on the submerged Laccadive-Chagos submarine ridge.
- Structure and Segregation: The group consists of 36 islands divided into Aminidivi, Laccadive, and Minicoy.
- Key Features and Trivia:
- 9-Degree Channel: Separates the main Lakshadweep archipelago from Minicoy Island.
- 8-Degree Channel: Separates Minicoy Island from the independent Maldives nation.
- Pitti Island: An uninhabited island that serves as a designated bird sanctuary.
- Kavaratti: The administrative capital of the Union Territory.
Significant Offshore and Riverine Islands
- Majuli Island: Located in Assam within the Brahmaputra River, it is the world’s largest fully riverine island and India’s first island district.
- New Moore Island (Purbasha): A disputed, low-lying sandbar island in the estuary of the Hariabhanga river (Sundarbans), which has largely been submerged due to sea-level rise.
- Pamban Island (Rameswaram): Situated between peninsular India and Sri Lanka, forming part of Rama’s Bridge (Adam’s Bridge).
- Sriharikota: A barrier island in Andhra Pradesh separating Pulicat Lake from the Bay of Bengal; houses the Satish Dhawan Space Centre.
- Wheeler Island (Dr. APJ Abdul Kalam Island): Located off the Odisha coast, used as India’s primary missile testing launch facility.
- Sagar Island: Located in the Hooghly delta of West Bengal, it is a major religious pilgrimage site (Ganga Sagar).
Indian Marine Geography and Zones
India’s maritime jurisdiction is governed by the United Nations Convention on the Law of the Sea (UNCLOS). The country claims distinct maritime zones extending from its baselines.
Maritime Zones under UNCLOS
| Zone | Extension from Baseline | Jurisdiction and Rights |
| Territorial Sea | Up to 12 nautical miles (22.2 km) | Sovereignty over the airspace, water column, seabed, and subsoil. Foreign vessels have the right of innocent passage. |
| Contiguous Zone | Up to 24 nautical miles (44.4 km) | Limited enforcement rights to prevent and punish infringements of customs, fiscal, immigration, or sanitary laws. |
| Exclusive Economic Zone (EEZ) | Up to 200 nautical miles (370.4 km) | Sovereign rights for exploring, exploiting, conserving, and managing living and non-living natural resources of the water and seabed. |
Important Marine Gulfs, Straits, and Channels
- Gulf of Kachchh: A shallow water body in Gujarat known for its high tidal range, mangrove vegetation, and India’s first Marine National Park.
- Gulf of Khambhat (Cambay): A funnel-shaped gulf in Gujarat where the Narmada, Tapi, Mahi, and Sabarmati rivers discharge. It experiences the highest tidal bore phenomena in India.
- Gulf of Mannar: Located between southeastern India and western Sri Lanka, it is a globally significant biosphere reserve rich in sea cows (Dugongs) and coral reefs.
- Palk Strait: A narrow strip of water separating Tamil Nadu from the Northern Province of Sri Lanka.
- Coco Channel: Separates the northernmost parts of the Andaman Islands from the Coco Islands of Myanmar.
- Duncan Passage: A strait that separates South Andaman from Little Andaman.
India’s Marine Sediments and Mineral Wealth
The marine geography of India contains critical economic and strategic resources distributed across its continental shelves.
- Poly-Metallic Nodules (PMN): India is a pioneer investor in the Central Indian Ocean Basin (CIOB) under the International Seabed Authority (ISA). The seabed contains potato-sized nodules rich in Manganese, Nickel, Cobalt, and Copper.
- Monazite Sands: Found extensively along the beaches of Kerala, Tamil Nadu, and Odisha; it is a primary source of Thorium, critical for India’s three-stage nuclear power program.
- Offshore Hydrocarbons: Key reserves include Mumbai High, Vasai High (Arabian Sea), and the Krishna-Godavari (KG) Basin (Bay of Bengal) which contains massive deep-water natural gas deposits.
- Heavy Minerals: Coastal placer deposits yield Ilmenite, Rutile, Zircon, and Garnet along the southern coasts.