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Water and Oceans
Factfile |
 Water and Oceans |
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The Salty Sea |
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So what is it about seawater that makes it seawater?
Sunrise - Joe Arcury
Seawater has many minerals, chemical compounds and gases dissolved within it. Would you believe that about 9 million tons of gold is dissolved in the world's oceans? There are also large qualities of potassium, magnesium and calcium salts. Creatures such as crabs, mussels and barnacles depend upon seawater for calcium carbonate to make their shells. These soft-bodied creatures take calcium carbonate from seawater as they grow, and the resulting shell helps to protect them from predators.
The main mineral dissolved in seawater is sodium chloride or common salt, the same stuff that you put on your food. Salt in the ocean has come from the rocks and soil on land. Rain washes the salt into rivers, which in turn carry it to the sea. Some salt also comes from undersea volcanoes. It is a process that has been happening for millions of years. In some very hot countries, people trap the tide when it comes in. They then wait for the Sun to dry up the water, before collecting the salt that has been left behind.
There are two types of water on Earth: salty seawater and fresh water. Most fresh water is frozen in the ice sheets that cover Antarctica and Greenland.
The saltiness of seawater is called its salinity and a water's salinity level is measured as p.s.u. (practical salinity units). This is achieved by measuring the amount of dissolved salt there is in 1,000 parts of water. In the case of ordinary seawater, it has a salinity level of 35 p.s.u and fresh drinking water has a salinity level of less than 1 p.s.u. Some seawater, like the water found in the Dead Sea has a very high salinity level, which is why swimmers can float in it.
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