There are four oceans. In order of their size, they are : Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean.

PACIFIC OCEAN

1. The explorer Ferdinand Magellan, who circumnavigated the Earth, named the ocean “Pacific” meaning calm or peaceful.
2. The Pacific Ocean (Area :166,240,000sq.km) is the largest ocean of the world.
3. It is the deepest ocean with an average depth of 4200m.
4. The Marina Trench is the world’s deepest trench with a depth of 11,776 metres.
5. Most of the islands of this ocean are of volcanic or coral origin.

ATLANTIC OCEAN

1. The Atlantic Ocean (Area : 86,560,000 sq.km) is the second largest ocean.
2. Its name is derived from Atlas, a Titan (giant) in Greek mythology.
3. The Atlantic Ocean has the longest coastline.
4. The Atlantic Ocean is the busiest ocean for trade and commerce since its shipping routes connect the two most industrialized regions, namely Western Europe and N.E. United States of America.
5. The Atlantic Ocean was formed millions of years ago when a rift opened up on the Gondwanaland and the continents of South America and Africa separated. The separation continues even today and the Atlantic Ocean is still widening.
6. The continental islands of Newfoundland and British Isles are the major ones.
7. Volcanic islands are fewer and they include those of Cuba, Jamaica and Puerto Rico, Iceland is the largest island of volcanic origin.

INDIAN OCEAN

1. The Indian Ocean (Area : 73,430,000 sq.km) is the only ocean named after a country.
2. The Indian Ocean is deeper than the Atlantic Ocean.
3. It contains numerous continental islands, Madagascar and Sri Lanka being the largest ones.
4. Some of the islands of volcanic origin are those of Mauritius, Andaman and Nicobar, Seychelles, Maldives and Lakshadweep are of coral origin.

SOUTH INDIAN OCEAN

1.      Warm currents :

• South Equatorial
• Mozambique
• Madagascar
• Agulhas

2.      Cool currents :

• Antarctic drift
• West Australian currents

ARCTIC OCEAN

1. The Arctic Ocean (Area :13,230,000 sq.km ) is the smallest of all the oceans.
2. It lies within the Arctic Circle, hence the name Arctic Ocean.
3. The North Pole lies in the middle of the Arctic Ocean.
4. Most of the parts of Arctic Ocean remains frozen with thick ice for most of the days every year.
5. It is the shallowest of all oceans, with an average depth of 1,500 m.
6. It has the least salinity of all the oceans. It has a salinity of 20 unit per thousand.

OCEAN CURRENTS

1. The flow of a large amount of water in a definite direction with a great intensity is known as Ocean Current.
2. Ocean Currents are of two types – Hot and Cold.

HOT CURRENTS

The currents flowing from tropical zones of lower latitudes to higher temperate and sub polar zones are known a hot water currents.

COLD CURRENTS

The currents flowing from higher latitudes to lower latitudes are known as cold water currents.

The only exception to the conduction of ocean currents is found n the Indian Ocean. The flow of currents changes here with a change in the direction of the Monsoon Winds. The hot currents flow towards cooler oceans and the cold currents flow towards the warmer oceans.