The Open Door Web Site
Part X : The Environment
Environmental Factors Appropriate for Life
North Sea Coast, Filey, UK
The Earth and Water
One of the characteristics of the planet Earth which makes it unique is the fact that it has liquid water on its surface. Most of the water in the Earth's hydrosphere is found in the oceans (more than 97%). About 2% of the water is frozen as ice and snow, mostly near the North and South Poles. The rest of the water, less than 1 %, is underground, in lakes and reservoirs, rivers and streams, marshes and swamps' and inside the living organisms that make up the biosphere.
The oceans and the seas are vast bodies of water covering over two thirds of the Earth's surface. Rain falls on the Earth's surface and collects in rivers which can eventually enter the seas. It could be thought that water only enters the seas or oceans and never comes out. This idea raises a few questions:
The seas and oceans contain salt water. The water found on land is fresh water. This also raises a certain number of questions:
Water can be found everywhere in the environment: in the atmosphere, in soil, in plants and animals, in the human body. Water is essential to daily living. The water which comes out of the kitchen tap seems never to run out. Where does all that water come from?
The planet Earth may be considered as a closed system where the water within it is continuously recycled. No water enters this recycled on Earth for millions of system from space and no water is lost from it yea's. to space. The water people drink today is millions of years old and it will continue to be recycled for millions of years. This cycle is called the water cycle.
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