Guide to Oceans
The Earth's oceans are a dramatic part of what makes our planet very special and unique in our solar system. Not only are they alive with sea life but they are constantly changing. If you were to travel to outer space so that you could view the earth from space, in the same way we view other planets, you would discover something very unique about Earth. Its water.
That's right, water. The earth which is often referred to as the Blue Planet is covered with water unlike other known planets. Because we inhabit the Earth's land mass, we often think of the earth in relation to land size. The truth is that there is much more water on the surface of the earth than there is land. Only about 29% of the earth's surface is covered with land while 71% is covered with the Earth's salt water oceans. This unique fact has also earned our planet the label, The Water Planet.
The great oceans of the Earth are much like the surface above water, including underwater mountains, called ocean ridges. Active volcanoes have formed islands, plateaus and trenches which make up the deepest places on earth. More than half of the ocean's water is over 9,000 feet deep.
The vast ocean waters are often thought of in four different sections or oceans. Actually the water that covers the planet is one large body of water but we have named the different geographic locations based on the way they are roughly divided by land.
The largest ocean is the Pacific which makes up 48% of the world's ocean. Covering almost half of the earth, it extends from the Americas to Asia and from near the Arctic to Antarctica . The Pacific is not only the largest, but the deepest as well, measuring at 36,200 feet deep in the Mariana Trench.
The second largest of Earth's oceans is the Atlantic which is 28% of the total ocean water. The deepest place in the Atlantic is the Puerto Rico Trench at 28,374 feet. The average depth of the Atlantic is much shallower than the Pacific but the Atlantic has a very unique feature called a mid-water ridge. This is an under water mountain range that runs the entire length of the ocean. The Island of Iceland is part of this "S" shaped ridge that appears above the surface.
The third largest of Earth's oceans is the Indian which makes up 20%. Located between Southern Asia and Africa, it covers the surface to Antarctica in the south to Australia in the east. The deepest point in the Indian Ocean is 25,344 feet in the bottom of the Java Trench. But what makes up the most impressive feature of the ocean is a vast two part underwater ridge that extends around both the African and Australian continents.
The fourth and smallest of Earth's oceans is the Arctic which includes only 4%. This ocean is where the polar ice cap is located. The Pacific Ocean is more than 13 times larger than the Arctic and the deepest point in the Arctic is 17,881 feet at the Eurasian basin.
Have you ever left a container of water outdoors? After a short time, the water evaporates and disappears. Why doesn't the ocean ever go dry? While the ocean is always loosing water, it is also always gaining water. This process is called the Hydrologic cycle. While loosing water to evaporation, it also is replenished by the moisture condensing and returning through rain. Some falls directly into the ocean, while other water returns to the ocean by rivers which keeps the world's ocean from going dry.
Scientists guess that 230,000 forms of life live in the ocean. This number is just a guess as many forms of marine life are constantly being discovered. There are also many types of plants that live in the ocean. Many of the most common are sea grass, kelp, seaweed and rockweed. Plants are a very important part of ocean life. They are food for many fish as well as a good hiding place for smaller fish to hide from their predators.