Joyce Willacy, age 8, of Pinawa, Manitoba, Canada, for her question:
What makes the Dead Sea so salty?
Most lakes are filled with fresh water and the world's salty waters belong in the deep, wide seas. But the Dead Sea has a mind of its own. It is a lake, a rather smallish lake. And its waters are about nine times as salty as the salty seas. What's more, it is getting saltier day by day. And scientists suspect that the size of this strange little lake is slowly shrinking year by year.
The geography of the earth is always changing. The ups and downs usually change slowly, too slowly to be noticed in a human lifetime. The creation of the Dead Sea began many millions of years ago which is a mere blink in the earth's history. A long saggy dent began to dip between the countries of Jordan and Israel. Rivers and merry streams ran down its sides and collected in the bottom of what is now the Jordan Valley. This water filled an ancient lake that was at least four times as big as the Dead Sea. The old lake covered the little Sea of Galilee and miles of the present¬ day Jordan River.
We say that rivers and most lakes are filled with fresh water. But this is not quite true. As streams flow along, they wash around pebbles and gravel and seep into rocky minerals. Water, especially running water, dissolves chemicals from different minerals and carries them away. There are always traces of various chemicals, even in so called fresh water lakes and rivers. In the Jordan Valley, there are deep layers of rocks that contain bromines and other salty chemicals. The ancient sag in the earth's crust created deep underground springs. They still bring lots of dissolved salts to the surface.
After many long ages, dirt and debris sifted down into the long valley. But clear, blue water stayed in the Sea of Gallilee. And the River Jordan flowed down and emptied into the deep Dead Sea. Every day, six million tons of water still flow down the Jordan into the Dead Sea. But there is no way out, for the salty salty lake has no outlet. You would think that all this water would make the Dead Sea overflow and grow bigger. But it does not do this because of the hot desert sun.
Every day the warm sunbeams evaporate six million tons of water, just plain water, from the surface. But the salty chemicals dissolved in the water cannot evaporate into the air. So they stay behind. Meantime, each day, the Jordan dumps in more water with more dissolved chemicals. This river rises far north of the Dead Sea and flows right through the sparkling little Lake of Galilee. Its waters gather salty chemicals all along the way. In the floor of Lake Galilee there are springs that well up with salty bromines from far below. The Jordan gathers these salty chemicals also and flows along to dump them all into the Dead Sea. During a sunny day, a filmy haze hangs over the Dead Sea, forming clouds that drift away and disappear in the bright desert sky. This is moisture evaporating from the water and leaving the salty chemicals behind.
Some of the salty chemicals in the water form hard crusts on the rocks around the edges of the Dead Sea. No plants can grow in or around them and the banks are bare. No fish can live in the salty salty water. But they can live in the waters of the Jordan River. Every day a number of unlucky fish are washed down by the river into the salty lake where they soon perish. A few hungry sea gulls hover above in the hazy air waiting to grab the unfortunate fish when they float to the surface.