Only about 3% of Earth’s water is fresh and the rest is salty. The great sea of salt water that encircles the world is divided into four units – the Pacific, Atlantic, Indian and Arctic Ocean. The Antarctic Ocean is generally considered a distinct ocean by some. All the oceans actually consolidate into one great interconnected body of water. About 71% of earth’s surface is covered with water.
With an area of about 64 million squares, Pacific Ocean is the largest, larger than the Atlantic and Indian Ocean together. While the Atlantic Ocean covers about 32 million square miles, Indian Ocean covers about 28 million square miles.
Pacific Ocean lies between the Americas and Asia. Atlantic Ocean lies between the Americas, Europe and Africa. Frozen over for most of the year, this ocean is the smallest. The Antarctic Ocean was only recognized as an ocean only few years back.
Depths of oceans are normally measured by echo soundings. Ultrasonic pulses are transmitted from ships. They travel swiftly to the floor of the sea and then bounce back. By measuring the time echo takes to reach the ship, exact depths are calculated.
The smallest of the oceans is the Arctic Ocean. It is also the shallowest with an average depth of about 5000 feet. The next larger is the Indian Ocean that averages about 13,000 feet. The Atlantic is slightly deeper averaging about 14,000 feet. The largest Pacific Ocean too has an average depth of 14,000 feet but has such a vast expanse that it hides the deepest known scar in the earth’s crust.