The ocean covers 71% of the earth's surface. Due to the known diameter of the earth, it is not difficult to calculate that the ocean area is approximately 360 million square kilometers. However, the volume of the ocean is much more difficult to estimate because of the varying depths of water and the inaccuracy of early sounding techniques. With modern acoustic technology, people discovered that the average depth of the global ocean is 3680 meters, and the total volume of seawater is estimated to be about 1.3 billion cubic kilometers. Imagine if the earth's surface was a smooth, flat spherical surface, so much water would be enough to submerge the entire surface under a water depth of about 2600 meters.
The earth is a planet of water. More than 97% of the earth's water is in the sea, and fresh water accounts for less than 3%. Most of it is stored in the north and south poles in the form of ice. Although the most common rivers and lakes traverse the earth, they only account for 0.036% of the earth's water. Compared with the ocean, it is really a tiny bit! The vast ocean divides the land into large and small land masses and islands, but the ocean itself is interconnected and integrated. However, people are accustomed to dividing the world's oceans into the Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean and Southern Ocean with land or submarine ridge as the boundary. Five oceans: the Arctic Ocean and the Southern Ocean. Among them, the Pacific Ocean is the largest and deepest, accounting for 46% of the total ocean area and larger than all the land combined! The Atlantic Ocean is located between the Americas, Europe and Africa, accounting for 23%. The Indian Ocean stretches between Africa and Australia-Southeast Asia, accounting for 21%. The Southern Ocean was later separated from the Pacific, Atlantic and Indian Oceans and surrounded Antarctica. In contrast, the smallest, shallowest and coldest Arctic Ocean is almost surrounded by land.
Take a look at a globe and you will notice how uneven the distribution of ocean and land between the northern and southern hemispheres is! The ocean area in the northern hemisphere accounts for 61%, while the ocean area in the southern hemisphere is as high as 81%. Especially between 56° and 65° south latitude, the Southern Ocean forms a 360° circle. If you sail along this latitude line, you will never see the land and can only sigh at the vastness of the ocean.