The oceans are unique to our planet. No other planet in our solar system has liquid water. The oceans cover about 70% of the earth’s surface. They contain about 97% of the earth's water supply. Life on earth originated in the seas. The oceans continue to be home to an incredible number of plants and animals.

We know very little about the oceans. Because they are so deep and dark, they are hard to study. But scientists are discovering new strange creatures all the time. We are learning more by using satellites to look at the oceans’ surfaces and by using buoys to measure temperature and saltiness. Special vehicles can now travel deep into the dark oceans to see what mysteries can be discovered.

Difference between oceans and seas?

An ocean is a large body of water that is a main part of the hydrosphere (liquid part of the earth). Oceans are the largest division of open water (water that is not blocked by any land).

A sea can be one part of an ocean or a large body of saltwater. It is partially enclosed by land.

Oceans and the weather

More of the sun’s heat is absorbed by water along the equator (middle of the earth) than at the poles (top and bottom of the earth). This means the water at the equator is warmer than water at the poles. These different water temperatures (warm at the equator, cold at the poles) cause the water in the oceans to move. This is called an ocean current.

The air above ocean currents also moves. The warm or cold ocean air moves over the land as wind. Oceans are also a really important part of the water cycle. Evaporation from oceans creates most of the world’s rainfall. Plants on land need the rain to absorb nutrients from the soil.

Oceans and animals

The oceans are also home to all kinds of sea life. These include fish, whales, dolphins, octopi, lobsters, crabs and shrimps. There are also jellyfish and starfish. Many kinds of plants, such as plankton, kelp and sea grass are part of the “forest of the seafloor.”

Oceans and the air

Carbon dioxide in—oxygen out! Oceans help to capture and store carbon dioxide (CO2). They are the largest natural “carbon sinks” in the world. Oceans trap about ¼ of the CO2 that humans put into the air. Oceans also release oxygen. During photosynthesis, plankton (tiny plant-like organisms) release oxygen. Half of the world's oxygen is produced by these tiny plants!

How many oceans are there?

There are five oceans on the earth. The oceans from largest to smallest are: the Pacific, Atlantic, Indian, Southern and Arctic.

Why are oceans important?

1.    Control the weather and temperature of the planet

2.    Are home to over 200,000 (or more!) species of plants and sea life

3.    Capture and store carbon dioxide (CO2)

4.    Release ½ the world’s oxygen.