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Transcript
Lowest Elevation....
DEAD SEA
Why is it called the Dead Sea?
Satellite view of the Dead Sea. NASA.
Sounds creepy, doesn't it? The name 'Dead Sea' is
actually a kinder, gentler translation from the
Hebrew name 'Yam ha Maved', which means,
'Killer Sea'. It is some of the saltiest water
anywhere in the world, almost six times as salty as
the ocean! The Dead Sea is completely landlocked
and it gets saltier with increasing depth. The
surface, fed by the River Jordan, is the least
saline. Down to about 130 feet (40 meters), the
seawater comprises about 300 grams of salt per
kilogram of seawater. That's about ten times the
salinity of the oceans. Below 300 feet, though, the
sea has 332 grams of salt per kilogram of seawater
and is saturated. Salt precipitates out and piles up
on the bottom of the sea.
There are no fish or any kind of swimming, squirming creatures living in or near the water.
There are, however, several types of bacteria and one type of algae that have adapted to harsh
life in the waters of the Dead Sea. What you'll see on the shores of the Sea is white, crystals of
salt covering EVERYTHING. And this is no ordinary table salt, either. The salts found in the
Dead Sea are mineral salts, just like you find in the oceans of the world, only in extreme
concentrations. The water in the Dead Sea is deadly to living things. Fish accidentally swimming
into the waters from one of the several freshwater streams that feed the Sea are killed instantly,
their bodies quickly coated with a preserving layer of salt crystals and then tossed onto shore by
the wind and waves. Brutal!
The guy to the left is actually floating in the Dead Sea. "But,
hey, I thought you said the Dead Sea was DEADLY!" Not to
us. Humans are remarkably adaptable. We can swim in the
Dead Sea, just like we can swim in the ocean. Well, people
don't really "swim" in the Dead Sea - they just "hang out".
That's what's so cool about the Dead Sea. Because of the
extremely high concentration of dissolved mineral salts in the
water its density is much more than that of plain old fresh
water. What this means is our bodies are more buoyant in the
Dead Sea - so you bob like a cork. In fact, people are so buoyant in this water it makes it tough to
actually swim. Most people like to just kick back in the water and read. It almost looks as though
this guy is sitting on an air mattress that has sunk below the surface, but he's not. He's really just
floating, without having to hold is feet in that position! If you think this is easy, try floating like
this in a freshwater swimming pool.
What Caused the Dead Sea to Form?
This lesson takes us back to the subject of plate tectonics. In this part of the world there is a rift
forming where two crustal plates are spreading apart. The East Rift Valley runs through most of
Africa, but it starts north of the Dead Sea and runs south
along the eastern side of the continent. The Sea is located
right along the Rift Valley where the earth's crust is being
stretched thin. To get an idea of how this "crustal spreading"
thing works, take a bar of taffy, or taffy-like candy and try to
pull it apart. You'll see where the candy starts to come apart
it gets really thin just before it breaks. That's what is
happening to the earth's crust in the Rift Valley. Where the
earth's crust gets thin, that part of the surface sinks
downward. Look at the picture at right to see how the rift
forms, sinking downward where the crust is stretched thin. You know what? The Dead Sea is
still sinking lower, even today. Scientists figure that the Dead Sea lowers by as much as 13
inches per year. On a geologic time scale that's incredibly fast!
Why is the Dead Sea so Salty?
We talked about how the surface of the Sea got down so low in elevation, but why is it so salty?
All roads lead to the Sea when it comes to the rivers in the area. The Dead Sea is continually fed
water from the rivers and streams coming down off the mountains that surround it. But the kicker
is this....no rivers drain out of the Dead Sea. The only way water gets out of the Sea is through
evaporation. And boy does it evaporate! This part of the world gets plenty hot. When the water
evaporates, it leaves behind all the dissolved minerals in the Sea, just making it saltier. In fact,
it's through the dual action of; 1) continuing evaporation and 2) minerals salts carried into the
Sea from the local rivers that makes the Sea so salty. The fact that the water doesn't escape the
Sea just traps the salts within its shores. There's nothing living in the Dead Sea because it got so
salty, so quickly, that evolution has not had a chance to produce any creatures that could adapt to
such brutal conditions.
http://www.extremescience.com/DeadSea.htm
accessed Feb. 9, 2010