Introduction to Oceans


This chapter introduces the oceans which cover a larger part of the earth’s surface. The margins of the ocean are projected into the land in different forms of which seas, gulf, bay, and strait are important.
  1. The hydrosphere constitutes an important component of the earth’s environment. About 71% of the total area of the earth’s surface is covered with water.
  2. It is known as a includes vast stretches of water called oceans like Pacific, Atlantic, Indian, and the Arctic along with a number of seas, bays, and gulfs which have projected far into the landmasses and also there is the innumerable number of lakes, etc.
  3. Of the total area of water bodies, about 57 percent is in the southern hemisphere .so which is known as the water hemisphere, being the major shape of the landmass in the northern hemisphere it is called the land hemisphere.
  4. The scientific study of the ocean is a branch of modern science known as oceanography. The length, width, and area of the ocean are measured by a unit called a nautical mile or geographical mile. Which is the 1-minute distance from one degree of latitude .one nautical mole measured a length of 6080 feet or 1.15 miles.


  1. Oceans are the large expanse of water covering large area of the earth’s surface. There are four major oceans recognized namely the pacific ocean, the Atlantic ocean, the Indian ocean, and the Arctic ocean.
  2. The vast stretch of water around the Antarctic continent south of 60°S is the proposed Southern Ocean.
  3. It is recognized by the International Hydrographic organization but it is not accepted by all the countries.

Pacific Ocean

  1. The Pacific Ocean is the largest and deepest ocean in the world.
  2. The oceans are interconnected and have no marked boundaries.
  3. The Pacific Ocean, the largest of the oceans, also reaches northward from the Southern Ocean to the Arctic Ocean. The deepest known area of the Earth’s oceans is known as the Mariana Trench, which is found in this Ocean.
Pacific ocean

Atlantic Ocean

The Atlantic Ocean, the second-largest, extends from the Southern Ocean.
Atlantic ocean

Indian Ocean

The Indian Ocean, the third-largest, extends northward from the Southern Ocean to India, the Arabian Peninsula, and Southeast Asia in Asia, and between Africa in the west and Australia in the east.
Indian ocean

Arctic Ocean

  1. The Arctic Ocean is the smallest of the five. It joins the Atlantic Ocean near Greenland and Iceland and joins the Pacific Ocean at the Bering Strait.
  2. The Southern Ocean is a proposed ocean surrounding Antarctica, dominated by the Antarctic Circumpolar Current, generally the ocean south of 60 degrees south latitude.
Arctic ocean


  1. A part of the ocean, an arm of the ocean either completely or partially enclosed by land is known as a sea.
  2. The seas are the second largest water bodies next to the ocean.
  3. There are several seas in the world.
  4. Some of the important seas are the Mediterranean sea, the Bering Sea, the sea of Japan, the Arabian sea, the coral sea, the yellow sea, the red sea, the white sea, etc.


  1. A bay is defined as a wide indentation into the land.
  2. The bay has a wide entrance between two headlands.
  3. Some of the important bays are Hudson bay, bay of Biscay, Bay of Bengal, etc.


  1. A gulf is an enlarged bay.
  2. It is extensive and penetrated far into the land.
  3. Some of the important gulfs are the Gulf of Finland, the Persian Gulf, the Gulf of Torrents, the Gulf of Panama, the Gulf of Cambay, the Gulf of Mannar, etc.


A narrow passage of water connecting two large water bodies is called a strait. Thus it separates two landmasses. The well-known straits in the world are:
    1. Gibraltar strait
    2. Palk Strait
    3. Malacca strait
    4. Bering strait
    5. Strait of Magellan
    6. Cook strait
    7. Johor strait
    8. Strait of Hormuz
    9. Bikh -El-Mandeb

1. Gibraltar strait

Between the Atlantic and the Mediterranean sea separates Africa and Europe (Spain and Morocco)

2. Palk Strait

Between the Bay of Bengal and Gulf of Mannar separates India and Sri Lanka.
palk straits

3. Malacca strait

Between Andaman and Java sea separates Sumatra (Indonesia) and Malaysia.
Malacca strait

4. Bering strait

Between Pacific and Arctic oceans, separates Asia and Alaska of north America.

5. Strait of Magellan

Between the Atlantic and the Pacific ocean. Separates Chile and tierra del Fuego.

6. Cook strait

Between the pacific ocean and Tasmanian sea. Separating the northern and southern islands of New Zealand.

7. Johor strait

Between Malaysia and Singapore.

8. Strait of Hormuz

It is between the Persian Gulf and the Gulf of Oman and separates Iran and UAE.

9. Bikh -El-Mandeb

Between the Red sea and the Gulf of Aden of the Arabian sea separates Djibouti and Eritrea (Africa) and Yemen (Asia).

United Nations Convention on the Law of the sea (UNCLOS)

It is an international agreement signed by the members of UNO in 1982. From time to time several treaties were held by different countries adopting various regulations regarding authority on sea waters. UNCLOS III signed in 1982 came into force in 1994. The UNCLOS  replaces all the previous regulations and the much older freedom of the seas. UNCLOS is currently the prevailing law of the sea developed by International Maritime Organisation of UNCLOS. It is ratified by the USA.
UNCLOS has clearly defined the area and components of the sea. It has defined the area and components of the sea. It has divided sea waters into five zones. the following are its major features.

Internal waters

  1. It is the area of waters on which a bordering country will have full authority as on its land area.
  2. A nation’s internal water includes waters on the side of the baseline of the nation’s territorial waters that are facing towards its land except in archipelago states. It means in an indented coast if the most projected parts are joined by a straight line, it is called the baseline.
  3. It includes water bodies such as streams, rivers, canals, and small bays.
  4. The state can enact laws relating to its internal waters and regulate their use.
  5. Foreign vessels can enter the internal waters only with permission.
  6. In the case of an Archipelago, the entire group of Islands is treated as a unit and the outer boundary is treated as the boundary of the internal waters.

Territorial waters

  1. It extends up to 12 nautical miles from the baseline. The state can enact laws regulating the use of territorial waters.
  2. Illegal activities are controlled by the states.
  3. Fishing, pollution, weapon practice, and spying are not innocent actions and these are not permitted.
  4. Ships and Submarines should navigate on water surface with flag.

Contiguous zone

Beyond the 12 nautical miles (22km) limit extending further 12 nautical miles, from the baseline lies the contiguous zone. In this zone, the state can enforce laws related to customs, taxation, immigration, and pollution

Extrusive economic zone

This zone extends up to 200 nautical miles(370 k) from the baseline. the coastal state has sole rights over the exploitation of the resources of the region. fishing and oil exportation in this zone has been debated by many states. Foreign countries may lay submarine pipelines.

High seas

It is the open area of the ocean.