Maarg Manthan · Topic 8.17

Coastal Plains, Coral Reefs and Islands of India (Andaman and Nicobar Islands, Lakshadweep)

Geography › Physical Geography of India · Topic 8.17

India's coast has two coastal plains and two island groups. The Western Coastal Plain, between the Western Ghats and the Arabian Sea, is narrow and divided into the Konkan, Kanara and Malabar coasts, with backwaters in Keralam. The Eastern Coastal Plain, between the Eastern Ghats and the Bay of Bengal, is wider, with the Utkal, Northern Circars and Coromandel coasts, and large deltas. Coral reefs occur in the Gulf of Kachchh, the Gulf of Mannar, Lakshadweep and the Andaman and Nicobar Islands. Lakshadweep is a group of coral atolls in the Arabian Sea, and the Andaman and Nicobar Islands are an extension of a mountain arc in the Bay of Bengal.

11 min read · UPSC Prelims · Geography · Physical Geography of India

At a Glance

West coast Konkan, Kanara, Malabar
East coast Utkal, Northern Circars, Coromandel
Coral reef areas Kachchh, Mannar, Lakshadweep, Andaman and Nicobar
Lakshadweep Coral atolls
Andaman and Nicobar Mountain arc extension
Exam link UPSC Prelims, Geography: Physical Geography of India

Where Does It Fit?

This topic follows the topics on mountain passes and straits and completes the account of the relief of India with its coasts and islands. Together with the earlier topics on the Himalaya, plains and plateau, it covers all six physical divisions of the country. Previous topic: Sutlej; Himachal Pradesh and Punjab Hirakud Mahanadi; Odisha Tehri Bhagirathi; Uttarakhand; 260.5 m Sardar Sarovar Narmada; Gujarat…">Multipurpose River Valley Projects and Major Dams of India (Bhakra Nangal, Hirakud, Tehri, Sardar Sarovar). Next topic: Indian Standard Meridian and Indian Standard Time.

What Is the Nature of India’s Coastline?

In short: India has a long, smooth coast with few bays and few natural harbours, shaped mostly by faulting and by rivers.

India’s coastline is 7,516.6 km long, including about 6,100 km of mainland coast and the coasts of the islands, and touches 13 states and Union Territories, as in Geographical Location of India and Its Geopolitical Importance. It is largely straight and unindented, unlike the deeply indented coasts of Europe, because it is the result of the faulting and breaking of the Gondwanaland in the Cretaceous period, when the Arabian Sea and the Bay of Bengal came into being. As a result, the coast has few natural harbours, and several ports, such as Mumbai in the creek of Thane, Kochi on a lagoon, and Visakhapatnam in a bay with a rocky headland, are exceptions. Many ports need dredging, because rivers deposit silt. The coast is divided by the Peninsula into the east coast, between the Eastern Ghats and the Bay of Bengal, and the west coast, between the Western Ghats and the Arabian Sea.

What Are the Regional Names and Features of the Coast?

Konkan Coast: Maharashtra and Goa, submerged, with creeks and islands; Mumbai’s Thane creek.
Malabar Coast: Karnataka and Keralam (Kerala), with lagoons and backwaters called kayals; Vembanad is the largest. The northern coast of Karnataka is sometimes called the Kanara coast.
Utkal Coast: the coast of Odisha, with the Mahanadi delta and Chilika, the largest brackish lagoon in the country.
Andhra Coast and Northern Circars: between the Mahanadi and the Krishna, with the merged Godavari and Krishna deltas and the Kolleru lake, once a lagoon on the shore and now far inland because the delta has advanced.
Coromandel Coast: Tamil Nadu and the southern part of Andhra Pradesh, also known as the Carnatic, and with the Pulicat lagoon barred by the Sriharikota sand spit, where the ISRO launch site is located.
Gujarat coast: includes the Gulf of Kachchh and the Gulf of Khambhat with large tides, and the Rann of Kachchh, a former sea arm filled by silt.

The coast is under pressure. A national assessment of the shoreline change of the Indian coast over several decades found that about a third of it is eroding, mostly the stretches of West Bengal, Odisha, Andhra Pradesh, Tamil Nadu, Keralam and Gujarat, due to sea-level rise, storms, sand mining, ports and sea walls, with about a quarter growing by accretion; the figures should be treated as approximate. The Coastal Regulation Zone notification regulates construction near the shore, and mangroves, dunes and coral reefs are protected as natural defences, as in Tropical Cyclones: Formation Conditions, Paths, Naming Conventions, Early Warning Systems. As an analytical point, the Indian coast is almost smooth and has few sheltered bays, which is why India has built artificial ports and why its low-lying deltas and lagoons are the most exposed to the sea-level rise discussed in Temperature of Ocean Water: Vertical and Spatial Variations, the Thermocline.

What Are the Divisions of the Western Coastal Plain?

Division	Extent and width	Features
Kachchh and Kathiawar	Gujarat; an extension of the Peninsula, but levelled and treated as part of the plain	Kachchh was once an island, later filled by sediments, and is now arid; the Great Rann to the north and the Little Rann to the south-east are salt flats; Kathiawar has the Mandav hills with radial drainage, Mount Girnar (1,117 m) of volcanic origin, and the Gir range, home of the Asiatic lion
Gujarat Plain	East of Kachchh and Kathiawar; South Gujarat and the Gulf of Khambhat	Formed by the Narmada, Tapti, Mahi and Sabarmati; fertile in the east, with sand and loess near the coast; large tides in the Gulf of Khambhat
Konkan Plain	Daman to Goa; 50 to 80 km wide	Submerged, with cliffs, shoals, reefs and islands; the Thane creek forms the natural harbour of Mumbai; rocky, with laterite
Karnataka (Kanara) Plain	Goa to Mangalore; 30 to 50 km wide, up to about 70 km	Narrow, with steep streams from the Ghats forming waterfalls such as the Jog (Gersoppa) Falls on the Sharavati, about 250 m high; sea cliffs and small estuaries
Keralam (Malabar) Plain	Mangalore to Kanyakumari	The Malabar Plain is wider and low-lying; lagoons, lakes, backwaters called kayals, spits and sandbars; Vembanad is the largest lake; monazite-bearing sands

The western plain is made of the alluvium brought down by short, fast streams from the Western Ghats, and the sea has cut the coast with coves and creeks. The plain is narrow because the Ghats stand close to the sea, and it widens only in Gujarat and Keralam, where the slope of the land is gentler and the rivers have brought more sediment. Only the Narmada and the Tapti form large estuaries, since they flow in rift valleys, and the other rivers, such as the Mandovi, Zuari, Sharavati and Periyar, are short and steep and cannot build deltas because the tides and waves remove the sediment.

What Are the Divisions of the Eastern Coastal Plain?

In short: the east coast is wide, delta-rich and low, and it faces the cyclones of the Bay of Bengal.

Division	Extent	Features
Utkal Plain	Coastal Odisha, from the Subarnarekha to south of Chilika	The Mahanadi delta; Chilika Lake, the largest brackish water lagoon in the country, whose area varies from about 780 sq km in winter to about 1,144 sq km in the monsoon, and which is about 64 km long; low hills to the south of the lake
Andhra Plain	South of the Utkal plain up to Pulicat Lake; the Northern Circars between the Mahanadi and Krishna	The Godavari and Krishna deltas have merged into one physiographic unit and have advanced by about 35 km, leaving Kolleru Lake, once a lagoon, far inland; a straight coast with few harbours except Visakhapatnam and Machilipatnam
Tamil Nadu Plain	From Pulicat Lake to Kanyakumari, about 675 km, average width about 100 km; the Carnatic between the Krishna and Kaveri	The Kaveri delta, 130 km wide, is the granary of South India; Pulicat Lake is barred by the Sriharikota sand spit, the site of the ISRO launch centre

Between the Mahanadi and the Krishna the region is called the Northern Circars, and between the Krishna and the Kaveri, the Carnatic. Tamil Nadu and part of Andhra Pradesh together are also known as the Coromandel Coast or the Payan Ghat.

Where Are the Coral Reefs of India?

India has four main coral reef areas, in warm shallow seas where the water is clear and temperatures stay above about 18 °C, which are the conditions for reef growth.

Area	Type of reef	Remarks
Gulf of Kachchh	Fringing and patch reefs	The northernmost reefs; in the Marine National Park of Jamnagar; stressed by industry and salinity
Gulf of Mannar and Palk Bay	Fringing reefs and coral islands	A biosphere reserve with rich marine life
Lakshadweep	Atolls	Almost all the islands are coral atolls built on the Chagos-Laccadive Ridge
Andaman and Nicobar Islands	Fringing and barrier reefs	The richest reefs in India

Reefs protect coasts, shelter fish and support tourism, but face bleaching from warm sea water, cyclones and human pressure. Coral bleaching is described with the reef conditions in the macro on oceanography.

What Are the Groups of Islands and Their Features?

Feature	Details
Number	Counts vary by source and by what is included. The archipelago has more than 500 islands, islets and rocks, of which only about 37 are inhabited; older textbooks give 265 for the larger ones, with 203 in the Andaman group and 62 in the Nicobar group
Andaman group	North, Middle and South Andaman form the Great Andaman group, with Little Andaman to the south, separated by the Duncan Passage; Saddle Peak (737 m) in North Andaman is the highest point
Nicobar group	Car Nicobar is the northernmost and Great Nicobar the largest and southernmost; Indira Point on Great Nicobar is the southernmost point of India, only about 150 km from Sumatra; Nancowry is a central group
Ten Degree Channel	Separates the Andaman from the Nicobar group; about 150 km wide
Volcanoes	Barren Island, the only confirmed active volcano in India, which has erupted in recent years; Narcondam, a dormant volcano; mud volcanoes in Baratang
Capital	Port Blair in South Andaman, renamed Sri Vijaya Puram in 2024
Vegetation and coast	Hills with dense tropical evergreen and moist deciduous forest, mangroves and coral reefs

The islands are home to indigenous peoples, including the Great Andamanese, Jarawa, Onge and Sentinelese in the Andamans and the Nicobarese and Shompen in the Nicobars. Several of them are Particularly Vulnerable Tribal Groups, and the Sentinelese on North Sentinel Island live in isolation, protected by law, with entry to the island prohibited.

What Is Lakshadweep and How Did It Form?

In short: Lakshadweep is a string of low coral islands built on the peaks of an undersea ridge.

Lakshadweep, meaning a hundred thousand islands, is the smallest Union Territory of India, in the Arabian Sea off the coast of Keralam. The islands lie on the Chagos-Laccadive Ridge, a submerged volcanic ridge formed as the Indian plate moved north over the Reunion hotspot, and corals built up on its sunken peaks to form atolls and reefs, as in Minor Relief Features: Mid-Oceanic Ridges, Seamounts, Submarine Canyons, Guyots, Atolls. The territory has about 36 islands, which include 12 atolls, three reefs and five submerged banks, of which only 10 are inhabited, and a land area of about 32 sq km. It has a lagoon of around 4,200 sq km and an exclusive economic zone of around 400,000 sq km, as in United Nations Convention on the Law of the Sea (UNCLOS). Most islands are flat and rise no more than about 5 m, and have no hills, streams or valleys.

What Are the Groups and Channels of Lakshadweep?

Group or feature	Details
Amindivi Islands	The northern group, including Bitra, Chetlat, Kiltan, Kadmat and Amini
Laccadive (Cannanore) Islands	The central group, with Kavaratti, the capital, Agatti, which has an airport, Androth, Kalpeni and Kadmat; Androth is the largest island, about 4.9 sq km
Minicoy	The southernmost, second largest island, about 4.5 sq km, with its own culture and language, Mahl, which is related to Divehi of the Maldives
Nine Degree Channel	Separates Minicoy from the main Laccadive group
Eight Degree Channel	Separates Minicoy from the Maldives
Coral features	Fringing reefs around the islands and lagoons on the western or leeward side; Pitti is a small uninhabited bird sanctuary

The economy relies on coconut, tuna fishing and tourism; fresh water is scarce, being obtained from shallow groundwater lenses and desalination, as in Resources from the Ocean: Mineral Resources on the Deep Sea Floor, Energy Resources, Biotic Resources. Lakshadweep became a Union Territory in 1956 and took its present name in 1973. The Indian Navy commissioned a base at Minicoy named INS Jatayu in 2024, which adds to the strategic value of the islands near the busy east-west shipping route.

Why Is This Topic Important?

Concepts Emergence and submergence asked
Names Regional coast names
Risk Erosion and sea level

What Came Next?

The next topic explains the Indian Standard Meridian and Indian Standard Time. Next topic: Indian Standard Meridian and Indian Standard Time.

Key People and Terms

Emergent coast Coast raised from the sea
Submergent coast Coast drowned by the sea
Lagoon Shallow water behind a bar
Kayal Backwater of Keralam
Spit Sand ridge extending into the sea
Coromandel Tamil Nadu and south Andhra coast

Exam Corner

Points to Remember

Coast is 7,516.6 km with few natural harbours.
Konkan is submerged; Malabar is emergent.
Chilika is the largest brackish lagoon.
Sriharikota is a sand spit.
Faulting of Gondwanaland made the coast straight.

Do Not Confuse With

Emergence and submergence Land rising versus land sinking
Konkan and Malabar Maharashtra-Goa versus Karnataka-Keralam
Coromandel and Northern Circars Tamil Nadu coast versus Mahanadi-Krishna coast

Memory Hook

Faulted, smooth, short of harbours: Konkan sinks, Malabar rises, the east coast lifts.

Mains Angle

Questions ask why Indian ports are few and which segments are emergent. These points add depth.

Origin Gondwana faulting
Types Mixed coast
Hazard Erosion and rise in sea level

A Question You May Face

An original practice question, not a past paper question.

“Distinguish between coastlines of emergence and submergence with examples from India and explain why India has few natural harbours.”

How to Answer

Origin Fault coast.
Types Emergence and submergence.
Examples Konkan, Malabar, Coromandel.
Harbours Few; dredged ports.

GS Relevance

Prelims: coastal divisions, coral reef areas, island groups and channels. GS Paper 1: physical geography of India.

Frequently Asked Questions

Why is India's coastline straight?

India's coastline is straight and regular because it was formed by the faulting and breaking up of the Gondwanaland in the Cretaceous period. As a result there are few deep inlets and bays, and the country has few natural harbours compared with Europe, which has an indented coastline.

What is a coastline of emergence?

A coastline of emergence is formed when land rises or the sea level falls, exposing former sea floor. It is typically smooth with bars, spits, lagoons and salt marshes, and poor natural harbours. The Tamil Nadu coast and the Keralam coast with their lagoons are considered to be emergent.

What is a coastline of submergence?

A coastline of submergence forms when the land sinks or the sea level rises, drowning the lower ends of valleys. It has creeks, estuaries and indentations and offers good harbours. The Konkan coast of Maharashtra, with the harbour of Mumbai, is an example of a submerged coast.

What are the Keralam backwaters?

The Keralam backwaters are a network of lagoons, lakes, canals and inlets running parallel to the coast and separated from the sea by sandbars. They are called kayals, and the Vembanad Lake is the largest. They support fishing, rice cultivation, inland navigation and tourism.

How were the Andaman and Nicobar Islands formed?

The Andaman and Nicobar Islands are the tops of a submerged mountain range that continues the Arakan Yoma of Myanmar. They form an island arc at the subduction zone where the Indian plate dives under the Burma plate, and are made of Tertiary sedimentary rocks over volcanic rocks.

PYQ Practice — Statement Analysis

1 The Konkan coast is a coast of submergence.

True

It has creeks and a natural harbour at Mumbai.

2 The Indian coastline is deeply indented like that of Europe.

False

It is straight and regular.

3 The Andaman and Nicobar Islands are an extension of the Arakan Yoma.