Maarg Manthan · Topic 12.4

Ocean Deposits and Mineral Resources

Geography › Coral Reefs, Ocean Resources and Law of the Sea · Topic 12.4

Ocean deposits are the sediments that cover the sea floor, classified as terrigenous from land, biogenic oozes from dead plankton, and authigenic or hydrogenous deposits formed in the water. The ocean's mineral resources include offshore oil and gas, placer minerals, polymetallic nodules, cobalt-rich crusts, polymetallic sulphides, gas hydrates and dissolved minerals, and the seabed beyond national limits is governed by the International Seabed Authority.

6 min read · UPSC Prelims · Geography · Coral Reefs, Ocean Resources and Law of the Sea

At a Glance

Sediments Terrigenous, biogenic, authigenic, volcanic
Biogenic oozes Calcareous and siliceous
Nodules Manganese, nickel, copper, cobalt
Regulator International Seabed Authority, Kingston
India Central Indian Ocean Basin and Indian Ridge contracts
Exam link UPSC Prelims, Geography: Coral Reefs, Ocean Resources and Law of the Sea

Where Does It Fit?

This is the fourth topic of the category on coral reefs, ocean resources and the law of the sea. The previous topics covered reefs, and this topic begins the study of the resources of the oceans with the non-living ones. The next topic covers energy and biotic resources. Previous topic: Coral Bleaching and Zooxanthellae. Next topic: Energy and Biotic Resources of the Oceans.

What Are Ocean Deposits?

In short: the sea floor is covered by sediment that comes from the land, from dead sea life, and from chemical processes in the water.

Type	Source	Where found
Terrigenous deposits	Rock fragments carried from the land by rivers, wind and glaciers: sand, silt, mud	Continental shelf and slope, deltas; also the Bengal Fan
Calcareous ooze	Shells of tiny animals and plants such as foraminifera and coccolithophores, mainly calcium carbonate	Warm, shallower open ocean floors, above about 4,000 to 5,000 m
Siliceous ooze	Remains of diatoms and radiolaria, mainly silica	Cold, productive waters of the Southern Ocean and the North Pacific, and the equatorial Pacific
Red clay	Fine windblown dust and volcanic ash, red from iron oxide	Deepest ocean basins, where calcium carbonate dissolves below the carbonate compensation depth; the slowest to accumulate
Authigenic (hydrogenous) deposits	Chemical precipitation from sea water: manganese nodules, phosphorites, glauconite	Abyssal plains, shelves with slow deposition
Volcanic and cosmogenic deposits	Ash and lava; extraterrestrial dust and microscopic meteorites	Near volcanic arcs and ridges; everywhere in small amounts

The sediments are a record of the history of the Earth. Cores from the sea floor reveal the climate over millions of years, and the age of the sea floor sediment helped prove sea-floor spreading, as in Seafloor Spreading and Paleomagnetism.

What Mineral Resources Does the Ocean Hold?

Offshore oil and gas: about a third of the world’s oil and gas now comes from the continental shelf, such as the North Sea, the Gulf of Mexico, the Persian Gulf and Bombay High, as in Major Ocean Relief Features.
Placer deposits: heavy minerals, including ilmenite, rutile, zircon, monazite and garnet, concentrated by waves and currents on beaches and the shelf. The beach sands of Kerala, Tamil Nadu and Odisha are among the richest in the world and are a source of titanium and thorium.
Polymetallic or manganese nodules: potato-sized lumps on abyssal plains at 4,000 to 6,000 m, formed over millions of years around a core, rich in manganese, nickel, copper and cobalt. The Clarion-Clipperton Zone in the Pacific and the Central Indian Ocean Basin are the main fields.
Cobalt-rich ferromanganese crusts: layers on the slopes of seamounts, with cobalt, nickel and platinum.
Polymetallic sulphides: deposits of copper, zinc, gold and silver around hydrothermal vents on mid-oceanic ridges, as in Minor Ocean Relief Features.
Gas hydrates: ice-like solids of methane and water in cold, high-pressure sediments of the slope, a potential energy source. They are found in the Krishna-Godavari and Mahanadi basins and the Andaman area of India, but a method of safe extraction is not yet commercial. Methane is a strong greenhouse gas, so a release would be risky.
Dissolved minerals and others: common salt, magnesium, bromine, potash, fresh water by desalination, phosphorite nodules and sand and gravel for construction.

Who Governs the Seabed, and What Is India Doing?

The seabed beyond the national jurisdiction is called the Area. Under the United Nations Convention on the Law of the Sea, the Area and its resources are the common heritage of mankind, as in UNCLOS, Territorial Waters and Exclusive Economic Zone. The International Seabed Authority, ISA, based in Kingston, Jamaica, grants exploration contracts and is meant to frame the rules, the mining code, for commercial exploitation. India was an early pioneer investor: it received the first registration as a pioneer investor in 1987, and has an ISA contract of 2002 for polymetallic nodules over 75,000 square kilometres in the Central Indian Ocean Basin, and a 2016 contract for polymetallic sulphides over 10,000 square kilometres on the Central Indian Ridge and the Carlsberg Ridge. India’s Deep Ocean Mission, approved in 2021 with an outlay of about 4,000 crore rupees for five years, includes the development of technology for deep-sea mining and a crewed submersible, Matsya 6000, to go to 6,000 m.

Commercial deep-sea mining has not yet started. The ISA council’s talks in March 2026 ended without an agreed mining code, and more than 30 countries have called for a pause or a moratorium, because the effects on deep-sea ecosystems are poorly known. Meanwhile, the United States has opened its own domestic permitting route for companies, which many countries see as outside the UNCLOS system, and the status of the first application is still unsettled. As an analytical point, the debate sets the demand for nickel, cobalt and copper, needed for batteries and the energy transition, against the risk to some of the least-known habitats on Earth, and the recycling of metals and the technologies that use less cobalt can reduce the pressure.

Why Is This Topic Important?

Facts Sediments and nodules asked
India Deep Ocean Mission and ISA contracts
Debate Mining versus conservation

What Came Next?

The next topic describes the energy and biotic resources of the oceans. Next topic: Energy and Biotic Resources of the Oceans.

Key People and Terms

Ooze Fine sediment made of plankton remains
Placer deposit Heavy minerals concentrated by water
Polymetallic nodule Metal-rich lump on the sea floor
Gas hydrate Methane locked in ice
The Area Seabed beyond national jurisdiction
Mining code Rules for commercial seabed mining

Exam Corner

Points to Remember

Calcareous oozes lie above the carbonate compensation depth.
Red clay is the deepest deposit.
Kerala and Odisha have rich beach sands.
The ISA sits in Kingston.
India holds two ISA contracts: nodules and sulphides.

Do Not Confuse With

Terrigenous and biogenic deposits From land versus from living organisms
Nodules and sulphides Abyssal plains versus ridge vents
Placer and nodule Shore concentration versus deep-sea precipitate

Memory Hook

Land mud on the shelf, ooze in the open, clay in the deep; nodules on the plain, sulphides at the vent.

Mains Angle

Questions ask for resources and the policy debate. These points add depth.

Resources Nodules, sulphides, hydrates
Governance Common heritage and ISA
Trade-off Energy transition versus habitats

A Question You May Face

An original practice question, not a past paper question.

“Discuss the mineral resources of the oceans and evaluate the issues involved in deep-sea mining, with reference to India’s Deep Ocean Mission.”

How to Answer

Deposits Types of sediment.
Resources Nodules to hydrates.
Governance ISA and common heritage.
India Contracts and mission.

GS Relevance

Prelims: types of sediments, nodules, sulphides, ISA, India's contracts. GS Paper 3: mineral resources, blue economy, Deep Ocean Mission.

Frequently Asked Questions

What are marine sediments?

Marine sediments are the deposits on the ocean floor. They are divided into terrigenous sediments from land, biogenic oozes from the remains of plankton, authigenic deposits that form by chemical precipitation in the sea water, and volcanic and extraterrestrial material.

What are polymetallic nodules?

Polymetallic nodules are potato-sized lumps of manganese, iron, nickel, copper and cobalt that form very slowly on the deep abyssal plains, around a small core such as a shark tooth. The Clarion-Clipperton Zone in the Pacific and the Central Indian Ocean Basin have large fields.

What are placer deposits?

Placer deposits are concentrations of heavy and valuable minerals, such as ilmenite, rutile, zircon and monazite, separated from sand by waves and currents. The beaches of Kerala, Tamil Nadu and Odisha have rich placer deposits, used for titanium, thorium and other materials.

What is the International Seabed Authority?

The International Seabed Authority is an organisation set up under the UN Convention on the Law of the Sea, located in Kingston, Jamaica. It organises and controls activities in the international seabed area, which is the common heritage of mankind, and it grants exploration contracts and is developing mining rules.

What is India's Deep Ocean Mission?

The Deep Ocean Mission is an Indian programme, approved in 2021 with an outlay of about 4,000 crore rupees over five years, to develop technology for deep-sea exploration and mining, a crewed submersible called Matsya 6000, ocean climate services and marine biodiversity studies.

PYQ Practice — Statement Analysis

1 Red clay is found in the deepest parts of the ocean.

True

Calcium carbonate dissolves below the compensation depth.

2 Biogenic oozes are formed from the remains of land rocks.

False

They come from marine organisms.

3 The ISA is located in Kingston, Jamaica.