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Limnic eruptions

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Ned Dempsey

on 26 May 2015

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Transcript of Limnic eruptions

Limnic Eruptions

A limnic eruption is when a series of toxic gases are expelled from a lake. They are extremely rare but are fatal. Most limnic eruptions happen in a lake where an extinct volcano remains. There is mostly magma chamber under the river bed.There have only ever been two of these rare disasters recorded in history. One in 1984 and another in 1986. There are only 3 lakes that produce limnic eruptions known on earth: Lake Nyos, Lake Monoun and Lake Kivu
What are limnic eruptions
On August 21 1986, in Camaroon Africa, one of the most deadly natural disasters occurred. It was a limnic eruption. A magma chamber had been leaking CO2 into the lake for some time. Since CO2 is 1.5 times denser then air, it can't rise to the surface unless it is disturbed. All of a sudden some thing went off that triggered a limnic eruption.Lots of CO2 was sent into the air and water was blasted over 18 meters into the air, creating a small tsunami. The gases were spread over 24km, killing between 1,700-1,800 people and 3,500 livestock in minutes.6 people survived of the 800 in the nearby village.
Lake Nyos
Lake Monoun
In 1984 a lake called Monoun had a limnic eruption. This eruption was not as bad as Lake Nyos, but it still caused a lot of damage. A tsunami 9.5 meters high flattened crops 100 meters inland around the eastern end of the lake. The eruption killed 37 people in total. The gas cloud disappeared after 4 hours. Lake Monoun is also in Cameroon and not far from Lake Nyos. People near the river reported the gas smelling acidic and bitter. The gas cloud was about 3 meters high.
How we can prevent limnic eruptions
There is only really one way to prevent limnic eruption and that is by pumping the CO2 out of the lake. They put pipes at the bottom of the lake near the magma chamber so it can suck all the CO2 out of the water at a safe rate. Now the process happens most of the time. The first use of this procedure was used at Lake Nyos in 2001. They named this procedure degassing. Some one thought that bombing Lake Nyos would get rid of the gas, but that might break the lake's walls and cause a flood.
This is what a limnic eruption might look and sound like
Other lakes that might have a limnic eruption
The only other lake that scientists think might have a limnic eruption is Lake Kivu. It has started to shown signs of erupting so people are keeping an eye on it. It is 2,700 km2 and lies on the border of Rwanda and the Democratic Republic of the Congo. If Kivu were to have an eruption, it would be much bigger then Nyos and cause a lot more damage because it is a much bigger lake. The lake has been producing a lot more methane and CO2 so it might not be long before it erupts.
Facts about limnic eruptions

A limnic eruption is also called a lake over turn.
People used to think that limnic eruptions were a sign from the gods
and were terrified of them!
There may have been more limnic eruptions when humans were not around
Some scientists think that a limnic eruption might have killed the dinosaurs.
Limnic comes from the Greek word limne meaning lake turnover
All the limnic lakes are in extinct volcano craters

A diagram of how people pump CO2 of Lake Nyos
CO2: A toxic gas also known as carbon dioxide.
Magma chamber: A chamber underneath the earth's crust where magma can reside for a moment.
Lakes walls: the land around a lake that keeps the water in.
Methane : A flammable gas that is also called CH4.

Effects on people
After the eruption, people suffered great losses. Crops were flattened and there was no fresh water. The people who survived suffered breathing problems and brain damage. There was hardly any stock to eat and people were afraid that an eruption might occur any time.
Before and after the eruption at lake Nyos
Sheep after the limnic eruption at Nyos
By Ned Dempsey
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