﻿Mother nature wants to kill you.
You already know many of the ways that can happen. Earthquakes, hurricanes, tornadoes, volcanoes, and
avalanches are common enough. But with a little warning and preparation, you can survive those.
Tsunamis are certainly among the worst as they can inflict mass casualties and
there is little defense against it. Even so, it usually doesn’t kill everybody.
What if I told you there was a rare type of natural disaster that killed nearly
everything in the immediate area? There is no chance to run and nowhere to hide. Death
arrives silently and without warning. Unfortunately, it is very real.
Surprise! You’re Dead On August 15, 1984 in Cameroon,
Africa some people driving on a road near Lake Monoun made a horrifying discovery. They found
thirty-seven people lying on or near the road and all of them were dead.
When authorities began investigating, they suspected a massacre.
After realizing the victims weren’t murdered, they next suspected an infectious disease.
Witnesses informed investigators that they heard rumbling noises then saw a white cloud
rise from the lake. They also claimed to smell sulfur. The authorities thought that perhaps a
volcanic eruption happened. The gases from that eruption could have suffocated the victims.
The truth may never be known for certain. But some scientists have made an educated guess.
Lake Monoun is in a volcanic crater, and it is very deep.
On the day of the disaster part of the crater collapsed and caused a landslide. When the
landslide hit the bottom, it forced carbon dioxide to be released from the surface of the lake.
The gas is heavier than oxygen, so it sinks to the ground and displaces it. It is also odorless.
The thirty-seven people who died suffocated without warning.
Lake Nyos is another deep lake located in a volcanic crater. It is also in Cameroon,
though over two hundred miles from Lake Monoun. On the night of August 21, 1986 Lake Nyos
experienced a landslide. It released thousands of tons of carbon dioxide into nearby areas.
The gas suffocated over 1,700 people and it reached as far as sixteen miles.
Wildlife, cattle, and even insects were killed in large numbers.
Even plants on the edge of the lake were destroyed. The landslide caused a tsunami which
ripped vegetation from the ground. Survivors
Although most people died, some did survive. And as you might expect natural disasters
can cause mental health issues. When people experience a traumatic natural event their first
reaction is a combination of fear and distress. Even after the event has passed it isn’t uncommon
for those who lived through it to experience extreme stress and anxiety. Unsurprisingly,
alcohol and drug abuse is a common response too. It isn’t hard to see why. Can you imagine
falling unconscious unexpectedly only to awake and find that your child has died?
It happened to Joseph Nkwain. He survived the event at Lake Nyos and explained what happened.
I could not speak. I became unconscious. I could not open my mouth because then I smelled something
terrible ... I heard my daughter snoring in a terrible way, very abnormal ... When crossing to
my daughter's bed ... I collapsed and fell. I was there till nine o'clock in the morning ... until
a friend of mine came and knocked at my door ... I was surprised to see that my trousers were red,
had some stains like honey. I saw some ... starchy mess on my body. My arms had some wounds ... I
didn't really know how I got these wounds ... I opened the door ... I wanted to speak,
my breath would not come out ... My daughter was already dead ... I went into my daughter's bed,
thinking that she was still sleeping. I slept till it was 4.30 in the afternoon. (Then) I
managed to go over to my neighbours' houses. They were all dead ... I decided to leave ... I got my
motorcycle ... A friend whose father had died left with me ... As I rode ... through Nyos I
didn't see any sign of any living thing ...." Many of the survivors described smelling sulfur
and had lesions on their skin. The victims insisted they were exposed to dangerous gases
other than carbon dioxide. The doctors who treated them thought the smells might have been imagined.
Apparently, carbon dioxide poisoning can cause hallucinations. The lesions appeared
to be pressure sores which occur when the body is deprived of oxygen. Furthermore, if the victims
were really exposed to hydrogen or sulfur, they would have had burning pains in the eyes or nose.
So, in addition to finding all their friends and family dead,
the survivors couldn’t even trust their memories. What is this cruel natural disaster that strikes
without warning? How does it happen? And can anything be done about it?
Limnic Eruptions A limnic eruption is
a natural disaster which occurs when dissolved carbon dioxide erupts from a lake. It forms a
gas cloud that sinks over the surrounding area killing everything which breathes.
Lakes are a common but very temporary feature geologically speaking. Most of them only last
a few thousand years, whereas rivers and oceans can measure their life spans in the millions.
This is due to the way lakes form. Compared to rivers and oceans their waters are relatively
calm. Sediments in the water eventually fall to the bottom and are deposited there.
Over time the bottom of the lake rises as sediments are deposited.
If this follows its natural course, then within a few thousand years the lake may be gone entirely.
Mostly it depends on how deep the lake is.
Some lakes that are near volcanoes form in craters that are very deep.
And because they form in a crater the lowest parts of the lake are under high pressure.
The bottom part of the lake is also very cold. This allows carbon dioxide, and possibly other
volcanic gases, to build up in the bottom layers. Lake Nyos, for instance, is 311 feet deep or
about 95 meters. Lake Monoun is 682 feet deep or 208 meters.
Sometimes a tsunami can arise from the violence of gas escaping.
As the carbon dioxide escapes the water is lifted which in turn allows more gas to escape. When the
water returns to the lake it does so with enough force to create destructive waves.
One feature of lakes that possess the ability to kill in this manner is they must be meromictic.
This means that the lake has stratified layers of water that do not mix. When something happens
that causes the layers to mix that is when dissolved gas can be suddenly released.
The triggers which can cause this are numerous. Landslides, as mentioned previously, are one way
to force this to happen. Earthquakes can cause it too, as well as rainstorms and strong wind.
Once the layers of water start to mix and the carbon dioxide begins to escape it becomes a
runaway reaction that can’t be stopped. The good news is most lakes on Earth are
holomictic. This means that the top and bottom layers of water mix regularly.
Now there are three known lakes that can generate limnic eruptions and
all three are in Africa. These are Lake Nyos and Lake Monoun, and Lake Kivu.
Lake Kivu is on the border of Rwanda and Democratic Republic of The Congo.
Studies of the sediments have shown that it has an eruption
roughly every one thousand years and kills everything around it.
Of course, since lakes come and go all the time they have appeared elsewhere throughout
Earth’s history. In Messel, Germany for instance fossils were discovered which seemed to have been
created by a degassing event. The event was far in the past so Germans don’t have to be worried.
It last happened fifty-six million years ago. Scientists were still learning about this
phenomenon in the 1980s. Today it may be possible to prevent lakes from degassing.
Solutions
When a limnic eruption does occur, the process is very similar to what happens
when you open a carbonated beverage. Until you open the bottle, carbon dioxide is dissolved
in the liquid under high pressure. When the container is opened it suddenly releases.
Of course, soft drink bottles only contain a small amount of carbon dioxide. The eruption at Lake
Nyos released about 1.6 million tons of it. Although this may seem like a lot,
it is only a problem because it arrives suddenly in a low-lying area. The United
States alone released 5.27 billion tons of carbon dioxide into the atmosphere in 2017.
Clearly people around the world aren’t suffocating to death because of it.
Are they suffocating slowly instead? We’ll cover that in a future episode.
The good news is since scientists now understand limnic eruptions they can do
something to help prevent them. They can’t stop carbon dioxide from coming out of the lake bottom.
But they can engineer a solution that does it in a controlled manner.
In 1990 a team led by French scientist Michel Halbwachs (ALB-vacks) began
experimenting at Lake Nyos and Lake Monoun. They installed pipes pointing
down into the lake with the top of the pipe rising a few feet above the surface.
This allowed gas to escape continuously without turning into a runaway event.
In January 2001 a single pipe was installed in Lake Nyos. In 2011 United Nations funding
allowed for the installation of two more. By 2006 Lake Monoun also had
three pipes. The three pipes were thought to be enough to prevent the lakes from erupting again.
Installing a few pipes helps but as a long-term solution it has downsides.
At the lowest levels of the lakes the high levels of carbon dioxide also mean the water is acidic.
So, pipes and other equipment degrade quickly and require constant maintenance.
It isn’t cheap to keep the systems running. In 2003 a project was approved to fully degas
Lake Monoun. Within eighteen months the project was complete. So, it is possible to eliminate the
danger of limnic eruptions. But it is costly too. Lake Kivu and Lake Nyos have not been completely
degassed. But thanks to the pipes they are probably safe. More accurately, they are safe
as long as the systems are maintained. Also, are the Great Lakes a danger?
Lake Superior is 1,332 feet or 406 meters deep. Lake Michigan is 925 feet or 282 meters. That’s
deeper than Lake Nyos, Lake Monoun, or Lake Kiva. Could they suddenly experience a degassing event?
For the moment scientists think not. For one thing, the lakes are spread over a greater area.
Furthermore, they are not located near volcanoes. And it appears to some extent their waters do
mix. Lake Michigan, for instance, seems to “burp” carbon dioxide every fall.
If scientists are wrong though and the Great Lakes ever did experience a limnic eruption the results
would be catastrophic. Around thirty-two million people currently live in the Great Lakes Basin.
Although limnic eruptions are rare and the odds are you will never be near one there is
a more important lesson to be learned from them. Even with modern technology and all
the wonders of science we still can’t know what the next disaster will be.
Should you be constantly worried because you can’t know when it will
come or defend against it? Or is there no point worrying since you can’t do anything about it?
We can’t tell you how to feel. But we can point out that if you survive a horrible natural
disaster you will probably be scarred for life and become a raging alcoholic or drug addict.
The good news is scientists are smart and can probably figure out
how to keep you from going through it again. Is this a happy ending? By our standards yes.
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