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No place on Earth is like the Dead Sea in the Middle East. Not really a sea but a large salt water lake, the Dead Sea is 47 miles (76 km) long and up to 11 miles (18 km) wide. The name "Dead Sea" was attributed by Christian monks when they noticed the absence of any form of life in the salty water.
It is located in the deepest part of the valley that comprises the great Syrian-African rift valley fault. The surface is about 1,300 feet (430 meters) below sea level, the lowest point on Earth, and varies with each season. It is also very deep, with a depth of around 1,300 feet (430 meters).
Fresh water can only flow into the Dead Sea and not out. The only way for water to escape the region is through evaporation. It is estimated that up to seven million tons of water (840,000 gallons) evaporates each day due to the arid climate. Average annual rain fall is only two to four inches (50-100 mm).
When water evaporates, it leaves any impurities behind. As a result, the Dead Sea has the saltiest and most mineral-laden natural water in the world. Its surface water has a salinity of about five to nine times that found in the oceans, and the salinity increases with depth. As a result, the water has a greasy feel, stings cuts, and causes pain if it comes in contact with the eyes.
At a depth of about 130 feet (40 meters), salinity approaches 300ppt, nearly ten times the salinity of the oceans. Below 300 feet (100 meters), though, the water has a salinity of 332ppt and is saturated. This means that the water can not hold any more salt in solution; the rest precipitates out and piles up on the bottom.
The high salinity increases the density of the water, making objects in the water more buoyant. This increased buoancy actually makes it hard to swim in the Dead Sea. All someone needs to do is recline and float.
Mark Twain (1835 - 1910) best described swimming the Dead Sea as he traveled through the Middle East in 1867...
"My face smarted for a couple of hours, but it was partly because I got it badly sun-burned while I was bathing, and staid [sic] in so long that it became plastered over with salt.
It was a funny bath. We could not sink. One could stretch himself at full length on his back, with his arms on his breast, and all of his body above a line drawn from the corner of his jaw past the middle of his side, the middle of his leg and through his ancle [sic] bone, would remain out of water. He could lift his head clear out, if he chose."
"No position can be retained long; you lose your balance and whirl over, first on your back and then on your face, and so on. You can lie comfortably, on your back, with your head out, and your legs out from your knees down, by steadying yourself with your hands. You can sit, with your knees drawn up to your chin and your arms clasped around them, but you are bound to turn over presently, because you are top-heavy in that position."
"You can stand up straight in water that is over your head, and from the middle of your breast upward you will not be wet. But you can not remain so. The water will soon float your feet to the surface. You can not swim on your back and make any progress of any consequence, because your feet stick away above the surface, and there is nothing to propel yourself with but your heels. If you swim on your face, you kick up the water like a stern-wheel boat. You make no headway."
"A horse is so top-heavy that he can neither swim nor stand up in the Dead Sea. He turns over on his side at once."
(Photo courtesy of Ben Weiger))
"Some of us bathed for more than an hour, and then came out coated with salt till we shone like icicles. We scrubbed it off with a coarse towel and rode off with a splendid brand-new smell, though it was one which was not any more disagreeable than those we have been for several weeks enjoying.
It was the variegated villainy and novelty of it that charmed us. Salt crystals glitter in the sun about the shores of the lake. In places they coat the ground like a brilliant crust of ice."
M. Twain, The Innocents Abroad