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The Blue Planet: How Many Oceans are There in the World?

How Many Oceans are There in the World?
There are five oceans in the world. However, if the Atlantic and Pacific Oceans are divided into two separate water bodies each; namely, the North Atlantic, South Atlantic, the North Pacific, and the South Pacific, the number of oceans in the world comes to seven. Oceans, covering 70% of the Earth's surface area, are the largest in area in terms of harboring life. Ironically, they are also the least explored. This ScienceStruck post tells you about the major oceans of the world.
Ningthoujam Sandhyarani
Last Updated: Feb 28, 2018
Did You Know?
Ever since exploration started, which was many centuries ago, ocean exploration has been quite less as compared to space exploration, which began just about 50 years ago. It is true and ironic that we know more about the moon than the depths of our oceans.
Previously, there were only four officially recognized oceans in the world; the Pacific, Atlantic, Indian, and Arctic. Later, by the year 2000, a new ocean body was named and declared by the International Hydrographic Organization (IHO). It is called the Southern or Antarctic Ocean. It extends from the southern parts of the Pacific, Atlantic, and Indian Ocean bodies. Thus, the names of the five oceans in the world are Pacific, Atlantic, Indian, Arctic, and the Antarctic.

Thus, strictly speaking, there are five oceans on our planet. But, as the Pacific and Atlantic oceans are quite vast, they are sometimes divided into two separate water bodies each. Their names are: North Atlantic and South Atlantic oceans, and the North Pacific and South Pacific oceans. By this convention, there are seven oceans on our planet. For simplicity though, the universal convention of five major water bodies is followed. The sections below shall brief you about these areas along with their basic information such as location, size, extent, depth, etc.
Oceans on Earth
The image below shows the locations of all five oceans with respect to the positioning of the continental landmasses.
Main oceans of the earth
Pacific Ocean
Pacific Ocean
Pacific ocean is the largest, as well as the deepest one in the world, extending over a vast area of about 63.78 million square miles, i.e., at least 45% of the Earth's surface area. Its boundaries extend from the North and South American landmasses on the east, and Russia, Japan, Australia, and various groups of island nations on the west. Towards the northern and southern boundaries lie the Arctic and Southern/Antarctic Oceans, respectively.
Mariana trench is the deepest trench of our planet, and it lies in the Pacific ocean. The Challenger Deep point of this trench (10,900 meters depth) is the deepest part of the Earth. In this ocean, almost all boundaries are marked by subduction zones.
Atlantic Ocean
Atlantic Ocean
Extending over an area of 41,100,000 square miles, it is estimated that 20 percent of the Earth's surface area is occupied by the Atlantic ocean. This second-largest ocean demarcates the boundary of North America from Africa and Eurasia. It is basically S-shaped and is bordered by both the American landmasses on the west, and Eurasia and the African continents on the east. The northern boundary lies below the Arctic Ocean, whereas the southern boundary lies near the Antarctic Ocean.
The Puerto Rico trench is the deepest point of the Atlantic, and measures about 8,648 meters deep. One of the main features of this water body is the mid-oceanic ridge, which runs almost along its entire length.
Indian Ocean
Indian Ocean
Recorded as the third-largest ocean on the planet, the Indian Ocean covers approximately 20 percent of the Earth's water surface, covering an area of about 28,350,000 sq. miles. This ocean is surrounded by the Indian subcontinent on the northern side and the Antarctic Ocean on the southern side. Towards the west lies the African subcontinent, and the eastern side is bordered by Australia and Southeast Asia.
Among the five such water bodies in oceanography, it is the only one that is named after a country. The deepest point is identified to be the Java trench, which has a depth of 7,125 meters.
Southern Ocean
Southern Ocean
Also known as the Antarctic ocean, it has been recently added in the world's oceans' list. As the name signifies, it surrounds the southern portion of the continent of Antarctica. Dimension-wise, it is the fourth-largest one, which covers an area greater than the Arctic ocean (about 78,48,298 square miles). The ocean is bordered by three oceans: Indian, Atlantic, and Pacific.
There is less information about the deepest point of this marine body. However, it is claimed to be the South Sandwich trench, measuring at a depth of approximately 7,235 meters. This water body is considered to be covering the Earth's surface below the sixty degrees southern latitude (approximately).
Arctic Ocean
Arctic Ocean
The smallest of the five oceans, it lies in the northern hemisphere surrounding the Arctic landmass and covers an area of 5.427 million sq miles. Depth-wise, this ocean comes at the last position. This water body is said to exist above the sixty degrees northern latitude (approximately). The Arctic Ocean is surrounded by Greenland, Russia, Siberia, parts of Europe, and North America. At the boundary of this marine body lies North America and Eurasia.
Arctic's deepest point (Eurasia basin) is recorded to be about 5,450 meters. Situated in the polar region, part of the Arctic ocean remains covered by ice all the year round. Consequently, it is less salty as compared to other oceans.
Oceans are known to have formed and existed on our planet since the Hadean Eon (the first major geological time span since the formation of our planet), although not in the present state. They are one of the greatest and the most dynamic parameters of our planet. Also, they are known for being the regions where life first emerged.
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