Some of the Earth’s water supply is temporarily locked up within the many life forms found across the Earth’s biosphere. This water makes up a majority of most organisms, and is a critical component, making the processes of life possible. Some organisms are made up of 95% water, while almost all are more than half water.
Why is water so important to life? It all has to do with the unique properties that water exhibits. Firstly, it is the only substance on Earth that is in liquid form at the temperatures commonly found on the Surface of our planet. Secondly, it is a superb solvent, meaning that other substances regularly and easily dissolve into it. This allows water to carry nutrients to cells, and carry waste away from them.
In addition, water has the unique property of expanding as it freezes. Because water expands becoming less dense, frozen water, or ice floats. This is very important, because it protects the water underneath, insolating it from freezing.
Imagine what would happen if water became more dense? It would sink, allowing another layer of water to freeze. Eventually all the water across the entire surface of our planet would freeze, making life impossible.
The Hydrologic Cycle
While the total amount of water on Earth remains relatively constant, the disbursement of this water changes from moment to moment. Water is constantly in motion. The chief process responsible for moving water around the Earth is the hydrologic cycle.
We examine this cycle in much greater detail in chapter six. Essentially, water is carried from the oceans, lakes, and streams via evaporation upward into the atmosphere. It is then returned in the form of rain.
The Earth’s Oceans
Because most of the Earth’s water is found in the oceans, in order to understand the hydrosphere, we must understand these massive bodies of water. Fortunately, this is easier today, than it has ever been. Modern technologies allow scientists to study the oceans in much greater detail than was possible to previous generations. You are fortunate to live in a time when this detailed knowledge is available to you.
Oceans Divided
In order to aid scientists in studying and understanding the vast seas of the Earth, researchers generally divide them into four distinct oceans. These oceans are the Pacific Ocean, the Atlantic Ocean, The Indian Ocean, and the Arctic Ocean.
As you can see in this image, these oceans are connected, forming one large ocean. Water from one of the four oceans is free to move into another ocean. Whales, fish, and other life forms from one ocean are free to travel to another.
In addition to these four oceans, a number of seas, bays, and gulfs have also been designated. These are generally just smaller portions of one of the larger oceans, though in some cases, such as the Mediterranean Sea, they are almost completely cut off.
to be continued....
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