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Why is it Called the Dead Sea?

Satellite view of the Dead Sea. NASA.

Sounds kinda creepy, doesn't it? It's called the Dead Sea because nothing lives in it. 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's no seaweed or plants of any kind in or around the water. There are no fish or any kind of swimming, squirming creatures living in or near the water. As a matter of fact, 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 way 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 kinda 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 (go look at the map). 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 left 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?

Anyway, back to the formation of the Dead Sea. 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 get 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.

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