What Is the Ocean?

The Ocean is a vast, salt water body that covers three fourths of the Earth’s surface. Oceans are so large and powerful that they influence every other Earth system, including climate and weather. The constant transfer of heat from the equator to the poles drives oceanic and atmospheric circulation—winds, waves, currents, eddies, and more. It’s also home to life: the ocean produces most of the world’s oxygen and holds 50 times more carbon than the atmosphere.

The ocean is a vital resource for humans. It provides food, jobs, recreation, and many other important services. But it’s also being damaged by human activity. From overfishing to plastic pollution, the ocean needs our help. National Geographic supports ocean exploration, conservation, and education through our work with preeminent scientists and explorers.

We use the terms sea and ocean interchangeably, but they have different meanings. When we refer to the whole ocean, it is often called a world ocean or global ocean. This is because it is one body of water that connects all continents. We further divide the world ocean into sections based on their location: the Pacific Ocean (from the east coasts of Asia and Australia to the west coasts of North America), the Atlantic Ocean (from the east coasts of Africa and Europe to the west coasts of Asia and the Americas), the Indian Ocean (from the east coasts of Africa, India, and Australia to the west coasts of Europe and Asia), and the Arctic Ocean (in the extreme global north).

Oceans form when tectonic plates move slowly along a layer of hot, semi-liquid rock beneath Earth’s surface. As the plates separate, they create vast underwater mountain ranges known as mid-ocean ridges. These ridges provide a route for magma to rise up from deep within the Earth to form new seafloor. Over time, the new seafloor spreads out and forms an ocean basin.

From a biological perspective, oceans are rich in biodiversity: they contain a great diversity of living things. Coral reefs, salt marshes, mangroves, and sea grass beds are examples of ocean habitats that support many species of plants and animals. They also support a great diversity of fish species—fish make up 16% of the animal protein consumed by people worldwide.

Sea grass beds, for example, are a great source of food for marine animals and birds. They also have the ability to absorb and store carbon from the atmosphere, which helps offset some of the effects of human-caused climate change.

The ocean is a major player in the global economy. It provides clean drinking water, generates electricity, regulates the climate, and supports billions of people with food, jobs, recreation, and more. The ocean is an incredible source of beauty, too: beaches, whales, dolphins, and other sea creatures delight us with their majestic displays.

We rely on the ocean for transportation, too. Ships transport billions of tons of goods and people across the globe each year. From a planetary perspective, shipping freight by sea is better than flying because it uses less fuel per load.

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