What are the oceans of the world?

The largest water bodies

Seen from space, the Earth looks blue because almost three-fourths of its surface is water. The largest water bodies on the globe are the oceans. Their smaller extensions have other names, such as a sea, a bay or a gulf.

The five oceans

The world map shows five oceans: the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Arctic Ocean and the Southern (or Antarctic) Ocean. By size:

1. Pacific, the largest
2. Atlantic
3. Indian
4. Southern
5. Arctic, the smallest

Oceans and hemispheres

The Equator divides the Earth into the Northern and Southern Hemispheres. Some oceans lie in both:

Ocean	Northern Hemisphere	Southern Hemisphere
Pacific	Yes	Yes
Atlantic	Yes	Yes
Indian	Yes (a smaller part)	Yes (most of it)
Southern	No	Yes
Arctic	Yes	No

The Southern Hemisphere holds much more water than the Northern, which has more land.

One connected ocean

Although we list five oceans, they are not really separate. The lines dividing them on the map are conventions, and the natural world does not follow such boundaries. Seawater constantly flows from one ocean into another, carrying nutrients and warmth, and many plant and animal species are found across several oceans.

Life in the oceans

Marine means related to or found in the oceans and seas. The marine flora includes tiny plants called algae and all kinds of seaweeds; the marine fauna includes thousands of kinds of colourful fish, dolphins, whales, sharks, sea turtles, starfish and countless mysterious deep-sea creatures. Coral reefs are home to tropical fish, and emperor penguins live along the icy Southern Ocean. Each part of the ocean, from the sunlit surface to the dark depths, has its own life forms.

The Indian Ocean and India

The Indian Ocean is bounded by Asia to the north, Africa to the west and Australia to the east, with the Southern Ocean to the south. On either side of India lie two of its parts: the Arabian Sea to the west and the Bay of Bengal to the east. India’s two major island groups lie in them: the Lakshadweep Islands in the Arabian Sea and the Andaman and Nicobar Islands in the Bay of Bengal.

Salty water

The oceans hold most of the water on the planet, but it is salty and cannot be drunk by humans or most land animals. Freshwater, found in glaciers, rivers, lakes, the air and underground, is only a very small share. That is why saving water is important even on a ‘blue planet’.

Oceans, rain and disasters

Clouds that form over the oceans bring rain to the land; the monsoon rains India waits for every summer come from the ocean. But oceans also produce cyclones, violent storms with extreme rain or very strong winds that can damage coasts, and tsunamis, huge waves usually caused by an earthquake or a volcanic eruption under the ocean floor.

On 26 December 2004, a tsunami set off by an earthquake in Indonesia struck India and 13 other countries, and more than two lakh people lost their lives. Early warning systems, such as the Indian Ocean Tsunami Warning System, now help protect lives.

Why oceans need protection

Oceans give rain, make more than half of the world’s oxygen and feed millions of people, yet we throw millions of tonnes of plastic into them every year, and overfishing reduces marine life. Read about the land in continents of the world, or see the whole chapter in the Chapter 2 notes.