1 The great oceans of the world cover about 70% of the Earth's surface and are divided by islands we call continents. Each ocean includes smaller bodies of water called seas, bays, and gulfs. The land under the oceans, which is called the "ocean floor," has huge mountain ranges; wide basins and plains; and long, narrow valleys.
2 The Pacific is the largest and deepest ocean. It covers about 64,186,000 square miles, more than 1/3 of the Earth's surface. That's an area large enough to hold all of the continents in the world! The average depth of the Pacific is 15,215 feet. The deepest spot in all the oceans, "Challenger Deep," is 36,198 feet (more than six miles) below the surface of the Pacific. At this depth in the ocean, the water would cause the same amount of pressure as if there were elephants pressing against every square inch of your body! Water pressure in the ocean (the pressure caused by the weight of the water) increases 14.7 pounds per square inch for every 33 feet of depth. North America and South America lie to the east of the Pacific. Asia and Australia are to the west. To the north, Bering Strait links the Pacific with the Arctic Ocean. The word "Pacific" means "peaceful." But some of the most powerful storms on Earth blow out of the Pacific. Thousands of volcanoes rise from the ocean floor, and earthquakes happen often.
3 The Atlantic Ocean is the second largest body of water. Europe and Africa lie to the east; and North America and South America are on the west. The Atlantic meets the Arctic Ocean to the north. It covers about 33,420,000 square miles and has an average depth of 12,881 feet. Major industrial nations are located on the coasts of the Atlantic, making it the most important ocean for trade. Today, large ships are still used to carry heavy machinery and bulky products like grain and oil.
4 The Indian Ocean is smaller than the Atlantic, covering 28,350,000 square miles and averaging 13,000 feet in depth. Africa borders it on the west, and Australia and the East Indies are to the east. Asia lies to the north. Usually the winds that blow across the Indian Ocean are very gentle, but as the winds change with the seasons, violent storms called "typhoons" sometimes occur.
