Oceans

Plankton Plankton are some of the most important life forms in the ocean. © Choksawatdikorn

Oceans are large bodies of saltwater. Oceans cover more than 70 percent of Earth’s surface. They hold about 97 percent of all the water on Earth.

People need oceans. They eat plants and animals from the ocean. People also travel on oceans. Oceans also affect weather and climate.

Earth has five oceans. The largest is the Pacific Ocean. The smallest is the Arctic Ocean. The other oceans are the Atlantic Ocean, the Indian Ocean, and the Southern Ocean.

The Pacific Ocean is located between North and South America and Asia. It covers about 60 million square miles (155 million square kilometers). This area is 30 percent of Earth’s surface.

The Arctic Ocean is located above the Arctic Circle. It covers about 5 million square miles (13 million square kilometers).

The Atlantic Ocean is located between North and South America and Europe and Africa. It covers about 41 million square miles (106 million square kilometers).

The Indian Ocean is located between Africa and Australia. It covers 26 million square miles (67 million square kilometers).

The Southern Ocean surrounds Antarctica. It covers 8 million square miles (21 million square kilometers).

The average depth of the oceans is about 12,100 feet (3,688 meters). The deepest place in the oceans is the Mariana Trench in the Pacific Ocean. It is about 35,750 feet (10,897 meters) deep. People cannot travel to the bottom of the trench because it is too deep.

Oceans affect Earth’s weather. In the summer, oceans absorb, or take in, heat from the sun. In winter, oceans release this heat into the air.

When the sun heats the oceans’ surface, water evaporates. It turns into vapor and rises into the air. The vapor then forms clouds.

The clouds cool off and release rain. Almost all the rain that falls on Earth comes from water that was in the oceans.

Ocean water moves in patterns called currents. Some currents carry warm water from the equator toward the North or South Pole. (The equator is an imaginary line that circles Earth halfway between the North and South Pole.)

Other currents carry cold water from the poles toward the equator. As these currents flow along the edges of landmasses, they affect the temperature on land.

Many types of animals and plants live in the oceans. These living things are important to humans and the rest of the world. People use some of the animals and plants for medicine and food.

Plankton are tiny organisms that live in the ocean. They drift on ocean currents. Some plankton are plants. Some are animals. Many other ocean animals eat plankton.

Many kinds of fish live in oceans. They include eels, sharks, swordfish, and tuna. Shellfish live in oceans, too. They include shrimp, crabs, and lobsters.

Mammals also live in oceans. Mammals are warm-blooded animals that give birth to live babies instead of laying eggs. Some ocean mammals are manatees, dolphins, seals, walruses, and whales.