Coastline of India – Emergence and Submergence

At a Glance

• Length 7,516.6 km; 13 states and Union Territories
• Origin Faulting of Gondwanaland
• West coast Konkan and Malabar; mixed
• East coast Utkal, Andhra and Coromandel; emergent
• Concern Erosion and sea-level rise
• Exam link UPSC Prelims, Geography: India: Plains, Plateau, Coasts and Islands

Where Does It Fit?

This is the fourth topic of the macro on India’s plains, plateau, coasts and islands. The previous topic described the hills of the plateau, and this one begins the study of the coasts. The next two topics describe the western and eastern coastal plains in detail. Previous topic: Hill Ranges of the Peninsular Plateau. Next topic: Western Coastal Plains of India.

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 India as a Geographical Unit and Its Frontiers. 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 Coastlines of Emergence and Submergence?

Geographers describe the east coast, especially the south-eastern Tamil Nadu coast, as emergent, with lagoons such as Chilika and Pulicat, spits and sandbars. The west coast is both: the northern part, the Konkan coast of Maharashtra and Goa, is submerged as a result of faulting, with creeks and estuaries and the natural harbour at Mumbai; and the southern part, the Kerala or Malabar coast, is emergent, with lagoons and backwaters. The classification is simplified, because most coasts show features of both, and changes in sea level during the ice ages have left both raised and drowned features. The ancient city of Dwarka, now partly under water off Gujarat, and the shore temples of Mahabalipuram are cited as evidence of changes in the coastline.

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 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, Kerala 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 Naming, Warning and Effects of Tropical Cyclones. 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 Distribution of Oceans.

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 describes the western coastal plains of India. Next topic: Western Coastal Plains of India.

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 Kerala
• Spit Sand ridge extending into the sea
• Coromandel Tamil Nadu and south Andhra coast

Exam Corner

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