What's the difference between a sea and an ocean?

The terms 'sea' and 'ocean' are often used interchangeably, but they are not the same thing. In this article, we expore the differences.

Ste Wright | 2 min read

While both 'sea' and 'ocean' refer to large bodies of saltwater that cover most of the Earth's surface, there are significant differences between the two.

An ocean is a vast body of salt water that covers more than 70% of the Earth's surface. The five major oceans are the Atlantic, Pacific, Indian, Southern, and Arctic Oceans. Oceans are interconnected bodies of water, and they are distinguished by their vast size, depth, and ocean currents.

In contrast, a sea is a smaller body of salt water usually connected to an ocean but partly enclosed by land. Seas are often shallower than oceans and can be found along the coasts of continents and islands. They are also affected by tides and currents, which are often less intense than those in the ocean.

coast with cliffes and shore
Seas tend to partially enclosed by land

Size and depth differences

One of the most significant differences between seas and oceans is their size. Oceans are much larger than seas and cover a significant portion of the Earth's surface. Seas, on the other hand, are smaller and usually have a limited coverage area.

Another difference is the depth of the water. Oceans are much deeper than seas and can reach depths of up to 36,070 feet (10,994 meters) in the Mariana Trench. In contrast, the average depth of a sea is around 200 meters (656 feet).

The salinity level of the water is also another distinguishing factor. Oceans have a higher salinity level than seas because they are larger and have more evaporation and less freshwater inflow. Seas have a lower salinity level because they receive freshwater from rivers and streams that flow into them.

Finally, the wildlife found in oceans and seas is different due to the variations in depth and temperature. Oceans have a more extensive range of marine species, including larger animals such as whales, sharks, and dolphins. In contrast, seas tend to have smaller and fewer marine animals.

In conclusion, while both oceans and seas are bodies of saltwater that cover much of the Earth's surface, they are not the same. Oceans are larger, deeper, and have a higher salinity level, while seas are smaller, shallower, and have a lower salinity level. Knowing the differences between the two can help you better understand the unique characteristics and ecosystems found in these vast bodies of water.

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