Jamie Lunceford, age 10, of Spokane, Washington, for his question

How did salt get into the ocean

It seems that the world of nature is getting harder to understand. This is partly because we didn't know as much about it as we thought we did. Also, there is a news explosion in the world of science. To keep up with things, we must exchange many old ideas for new ones. What's more, modern scientists tend to suspect easy one two three explanations. For example, they view the salty content of the sea as a complicated global system of give and take. Naturally a wide awake student prefers the up to date explanation, even though it may strain the brain somewhat.

For generations we said that the sea steals its salt from the land. It was a true statement and it still is    but modern scientists tell us that there is more to the story. As you know, they take a global view of everything that occurs in nature. Whatever happens involves complicated exchanges that cause other changes, on and on around the world. Basically, the sea gets its salt from the land    and the two of them cover the entire globe. But the airy atmosphere also enters the picture and stirs a lot of changes into our salty story.

The so called salt in the sea is, of course, a mixture of dozens of dissolved chemicals. Some seas are many times saltier than others. But a cubic mile of average seawater contains about 166 million tons of salty chemicals. The ingredients dissolved in the world wide ocean are estimated to weigh about 50 quadrillion tons. The ancient seas were much fresher. But rains and rivers dissolved soft salty chemicals and other minerals from the rocks. The busy streams carried the loot along and dumped it with their waters into the seas. The oceans got saltier and every year the rivers still add billions of tons of more dissolved chemicals.

At this point the atmosphere plays a very complicated role in the story. Warm dry air evaporates water from the surface of the seas. But it leaves most of the dissolved chemicals behind. However, it carries aloft countless fragments of ordinary table salt. Misty clouds use them to form drops of rain    and this salt falls back to the earth. Dry ocean winds also carry air borne sea salt and return millions of tons of it to the land. The main salty story is a never ending cycle of land, water and  air on a global scale. But most of the salt is shifted from land to sea which is why the seas get a little saltier every year.

Other events play minor roles in the story. Countless ocean dwellers extract salty chemicals from the water to build shells and bones. Their remains sink and sometimes the restless earth lifts a slab of the seabed above the waves. The sunken chemical deposits then become dry land. The salty ocean is mixed and mingled by restless winds, tides and currents. Sometimes deep water wells up, bearing rich minerals dissolved from the seabed. These events sift salty chemicals to the surface  ¬where the atmosphere can carry them back to the land.