Marilyn Haynes, age 13, of Kingston Mines, I11. for her question:
Why isn't lake water salty like the sea?
The water in Lake Erie is clean and clear as crystal. On a calm day it breaks in little ripples on the shores of this Great Lake. And it is fresh water not salty like the sea.
The water on the beach at Santa Monica is greenish blue and tipped with white. On the calmest days, the water from the vast Pacific Ocean heaves onto the beach in giant rollers, clutching at the sand and pebbles with foamy white fingers. And the water is salty ¬loaded with the salts and chemicals which the sea has been stealing from the land through countless ages.
The Pacific Ocean is one with the great seas that cover almost three quarters of the earth. It is millions and millions of years old. All that time the sun has been stealing its surface waters by evaporation. Lake Erie, one of the five Great Lakes, is a new comer to the world’s water supply maybe less than a million years old. Less water has evaporated from its surface. Whats more, it is con¬stantly on the move, collecting fresh rain water from other lakes and s thousand little streams which drain a great land area.
This rain water started out clean and pure. Some of it seeped through the ground to trickle towards the lakes in underground springs and streams. As it went, it lapped at the earth and rocks, dissolving and carrying away salts and chemicals. Some of the water rippled through stony streams, stealing salts and chemicals as it came. All the water arrived at the lake carrying small loads of salts and chemicals. But not enough to spoil the freshness of the Great Lake.
The lake water flows gently down to thunder over Niagara, along the river and into lake Ontario. There it flows along the river St. Lawrence and finally, bearing its light loads of chemicals, it joins the mighty Atlantic.
There, the tides, the currents and the storms churn up this almost fresh water with the salty ocean. Year by gear, the warm sun evaporates more fresh water from the surface of the seas. Very little, if any, of the salts and chemicals, are clriawn up with the fine particles of water vapor These sre left behind. Day by day, year by year the rivers lakes and streams are busy robbing the land of more and more chemicals and carrying them along to the sea.
The water in the lakes carries only small doses of these chemicals at any time. But the sea adds to its hoards of plunder every day. It is estimated that right now the ocean contains about 20,000 billion tons of salt. That is a pinch of salt as large as our continent and one and a half miles deep.