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More than 70 percent of the Earth’s surface is covered by water, and our oceans make up a lot of that. You might’ve heard ocean or sea used interchangeably, but a sea is smaller than an ocean and is often partly enclosed by land. The oceans are interconnected; all of the planet’s oceans make up the World Ocean.
The largest ocean on Earth takes up one-third of the planet’s surface, but can you name which one that is? Below, we break down the world’s largest oceans and seas as well as offer a few runners-up.
Top 10 of the World’s Largest Oceans and Seas
With blue water that stretches to the horizon, the globe’s largest oceans and seas can feel infinite:
10. Arabian Sea
The Arabian Sea, in the Indian Ocean, is almost 1.5 million square miles in area. It only gets up to 15,262 feet deep. This sea has been an essential trade route since ancient times. In fact, the Arabian sea is named after the merchants that controlled it for centuries.
The Arabian Sea is exceptionally salty because of its high evaporation rate and the lack of rivers feeding it. Still, it is home to many species, including a type of algae that is only found in its waters.
9. Coral Sea
Many people are unfamiliar with the Coral Sea. This body of water lies in the southwestern Pacific Ocean. It is about 1.8 million square miles in area and merges with the Tasman and Solomon Seas. The deepest part of this sea reaches more than 25,000 feet below sea level.
The sea gets its name from its coral formations. The Coral Sea is home to the Great Barrier Reef, which is the largest reef system in the world. The sea sits off the coast of Australia, and its coastline is mainly sand. This area is an ecological wonder. It’s home to 200 bird species and many types of sharks.
8. Caribbean Sea
The Caribbean Sea spans just over 1 million square miles. Unlike the Mediterranean, the Caribbean is part of the Atlantic Ocean. Twenty-eight nations and more than 7,000 islands border the Caribbean Sea.
The deepest part of the Caribbean lies in the Cayman Trench, which is 22,500 feet below the surface of the sea. The average depth is closer to 2,200 feet, though.
The Caribbean isn’t just one of the largest seas. It’s one of the biggest oil-producing areas in the world. Although many people associate coral reefs with Australia, 14 percent of the world’s reefs lie in the Caribbean. However, those reefs, which bring in millions of dollars from tourists, are threatened by global warming.
The Caribbean is a popular vacation destination. It has a beautiful climate, and the water temperature doesn’t vary by more than 3 degrees.
7. Mediterranean Sea
The Mediterranean Sea has a steady inflow of water from the Atlantic Ocean because the rivers that feed it can’t keep up with the evaporation. Some people believe that the Mediterranean is part of the Atlantic Ocean, but it is a separate body of water.
The Mediterranean spans approximately 965,000 square miles, with an average depth of 4,900 feet. The deepest spot in this sea is at 17,280 feet.
The Mediterranean has always been an important transportation route. Its lush, fertile soil was ideal for supporting agriculture, and many ancient civilizations formed along its coast. Today, it remains a significant transportation route for people and goods.
6. South China Sea
The South China Sea is a 1.4-million square mile area within the Pacific Ocean. It’s the largest sea in the world and is bordered by several countries, including Indonesia, China, Taiwan, and Malaysia. More than 250 tiny islands and sandbars are hidden under the South China Sea. They are usually only visible at low tide.
5. Arctic Ocean
The Arctic Ocean is the smallest of the world’s oceans, and it’s also the shallowest. It takes up an area of about 5.4 million square miles and is roughly the size of Russia.
(You might be interested in reading about the other Smallest Oceans and Seas)
The Arctic Ocean is practically surrounded by land and covered by ice. The polar ice, which doesn’t melt, can be as thin as 6 feet in the summer and 150 feet in the winter. But the pack ice, at the edges of the polar ice, only freezes completely in the winter.
With all that ice, you might think that the region has limited animal life. However, many fish, whales, seals, walruses, polar bears, and jellyfish live here. In fact, there are more fish species in the Arctic Ocean than any other ocean in the world.
4. Antarctic/Southern Ocean
Also referred to as the Southern Ocean, the Antarctic Ocean makes up the southern part of the World Ocean, but its boundaries have been delineated several times over the years.
The Antarctic Ocean reaches up to 23,000 feet of depth at the South Sandwich Trench. But it’s not nearly as large as the three largest oceans. The Antarctic Ocean is approximately 7.1 square miles in area.
Although not many fish species live in the Antarctic Ocean, the waters are home to many invertebrates, such as squid. Seals, emperor penguins, and albatross also make their home in the Antarctic Ocean.
3. Indian Ocean
This third-largest ocean covers one-fifth of the Earth’s surface. It covers more than 28 million square miles of area and is surrounded by the coastlines of Asia and Africa. Many small islands dot the Indian Ocean, including Mauritius and Seychelles. The deepest part of the ocean is about 7,200 miles below sea level.
But whereas the Atlantic Ocean has abundant sea life, the Indian Ocean is limited in biodiversity. It has the warmest water of any ocean in the world, and the temperature doesn’t support the growth of plankton and other species.
The composition of the water in the Indian Ocean is also special. Some parts of the Indian Ocean have the lowest levels of marine salinity in the world, while others have the highest. But the water’s oxygen content is low because the ocean evaporates more quickly than it gets replenished.
2. Atlantic Ocean
Perhaps not surprisingly, the Atlantic Ocean is the second-largest in the world. Reaching 27,480 feet below sea level, the Atlantic is not quite as deep as the Pacific. The first human made it to the bottom of the Puerto Rico Trench as recently as 2022.
Almost 6.5 times the size of the U.S., the Atlantic Ocean spans one-fifth of the surface area of the planet. It makes up about 29 percent of the Earth’s water surface area and spreads across 41.1 million square miles. The equator separates the North Atlantic from the South Atlantic.
This is the youngest ocean, even though it took millions of years to develop. The Atlantic Ocean formed when the supercontinent Pangea split, during the Jurassic period. Water from super-ocean Panthalassa filled the void, creating the Atlantic.
The Atlantic has the most abundant fishing of any ocean. Many species that call the Atlantic Ocean their home are endangered, though.
1. Pacific Ocean
You guessed it—the Pacific is the largest ocean in the world. It takes up almost half of the planet’s water surface. The Pacific Ocean covers an area of 70,017,000 square miles.
Although the average depth of all the oceans on the planet is 12,100 feet, the Pacific is home to the deepest trench on Earth. This area, called the Challenger Deep, has a depth of about 36,200 feet.
The ocean is so deep in this area because it is located where two tectonic plates converge. One of the plates plunges into the Earth’s mantle, creating a trench that is deeper than Mount Everest is tall.
The Pacific Ocean surrounds five of the Earth’s seven continents. But the ocean’s ecology varies among locations. You can dip your toes in the chilly waters off of the coast of Canada or bask in the warm humidity along the coast of Central and South America. Or, you can snorkel in the crystal-clear waters around Fiji.
Even though the Pacific Ocean is the largest, it was the last ocean that the Europeans discovered. But, of course, there were plenty of other civilizations along its shores. The name “Pacific” comes from the word “peace.” Magellan, who named the ocean the way that we know it today, thought that it was quite tranquil.
A Few Other Large Oceans and Seas Worth Mentioning
The following bodies of water are also notable for their size:
- Bering Sea: 890,000 square miles
- Sea of Okhotsk: 613,800 square miles
- East China Sea: 482,300 square miles
- Sea of Japan: 389,100 square miles
The world’s largest oceans and seas are responsible for providing us with many natural resources, including minerals, oil, and animals. They also play a large role in controlling the Earth’s climate. Oceans and seas also provide oxygen, absorb carbon dioxide, and offer recreation and economic opportunities. It’s vital that we take care of our bodies of water.
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