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The carbon dioxide vent in an African village lake killed every living
thing for miles around
The carbon dioxide vent in an African village lake and killed every
living thing for miles around
ø I posted a brief article on this topic in 1996
before they had designed a relief mechanism. For
those idiots who think CO2 can be collecting in the
atmosphere for years, read it and weep~~ fools
~~~~~~ o0o~~~~~~
The carbon dioxide vent in a African village pond
killed every living thing for miles around
The Strangest Disaster of the 20th Century.
Here’s the story of how scientists unlocked the secrets of the worst
natural disaster in the history of the West African nation of
Cameroon… and what they’re doing to try and stop it from happening
again.
THE DISCOVERY
On the morning of August 22, 1986, a man hopped onto his bicycle and
began riding from Wum, a village in Cameroon, towards the village of
Nyos. On the way he noticed an antelope lying dead next to the road.
Why let it go to waste? The man tied the antelope onto his bicycle and
continued on. A short distance later he noticed two dead rats, and
further on, a dead dog and other dead animals. He wondered if they’d
all been killed by a lightening lightning strike – when lightening
lightning hits the ground it’s not unusual for animals nearby to be
killed by the shock.
Soon the man came upon a group of huts. He decided to see if anyone
there knew what had happened to the animals. But as he walked up to
the huts he was stunned to see dead bodies strewn everywhere. He
didn’t find a single person still alive—everyone in the huts was dead.
The man threw down his bicycle and ran all the way back to Wum.
By the time the man got back to the village, the first survivors of
whatever it was that had struck Nyos and other nearby villages were
already stumbling into Wum. Many told tales of hearing an explosion or
rumbling noise in the distance, then smelling strange smells and
passing out for as long as 36 hours before waking up to discover that
everyone around them was dead.
Wum is in a remote part of Cameroon, so it took two days for a medical
team to arrive in the area after local officials called the governor
to report the strange occurrence. The doctors found a catastrophe far
greater than they could have imagined: Overnight, something had killed
nearly 1,800 people. Plus more than 3,000 cattle and countless wild
animals, birds and insects—in short every living creature for miles
around.
The official death toll was recorded as 1,746 people, but that was
only an estimate, because the survivors had already begun to bury
victims in mass graves, and many terrified survivors had fled corpse-
filled villages and were hiding in the forest. Whatever it was that
killed so many people seemed to have disappeared without a trace just
as quickly as it had come.
LOOKING FOR CLUES
What could have caused so many deaths in such a short span of time?
When word of the disaster reached the outside world, scientists from
France (Cameroon is a former French colony), the United States, and
other countries arrived to help the country’s own scientists figure
out what had happened. The remains if the victims offered few clues.
There was no evidence of bleeding, physical trauma, or disease, and no
sign of exposure to radiation, chemical weapons, or poison gas. And
there was no evidence of suffering or “death agony”: The victims
apparently just blacked out, fell over, and died.
One of the first important clues was the distribution of the victims
across the landscape: The deaths had all occurred within about 12
miles of Lake Nyos, which some local tribes called the “bad lake.”
Legend had that long ago, evil spirits had risen out of the lake and
killed all the people living in a village at the water’s edge.
Both the number of victims and the presence of fatalities increased as
the scientists got closer to the lake: In the outlying villages many
people, especially those who had remained inside their homes, had
survived, while in Nyos, which is less than two miles away was the
closest village to the lake, only 6 of more than 800 villagers were
still alive.
But it was the lake itself that provided the biggest and strangest
clue of all: its normally clear blue waters has turned a deep, murky
red. The scientists began to wonder if there was more to the legend of
the “bad lake” than anyone had realized.
STILL LIFE
Lake Nyos is roughly one square mile in surface area and has a maximum
depth of 690 feet. It’s what’s known as a “crater lake”—it formed when
the crater of a long-extinct volcano filled with water. But was the
volcano really extinct? Maybe an eruption was the culprit: Maybe the
volcano beneath the lake had come back to life and in the process
suddenly released enough poison gas to kill every living creature over
a very wide area.
The theory was compelling but problematic: An eruption capable of
releasing enough poison gas to kill that many people over that wide an
area would have been very violent and accompanied by plenty of seismic
activity. None of the eyewitnesses had mentioned earthquakes, and when
the scientists checked with seismic recording station 140 miles away,
it showed no evidence of unusual activity on the evening of August 21.
This was backed up by the fact that even in the hardest-hit villages,
goods were still piled high on shelves in homes where every member of
the house-hold had been killed. And the scientists noticed another
mysterious clue: The oil lamps in these homes had all been
extinguished even the ones still filled with plenty of oil.
TESTING THE WATERS
The scientists began to test water samples taken from various depths
in the lake. The red on the surface turned out to be dissolved iron—
normally found on the bottom of the lake, not the top. Somehow the
sediment at the bottom had been stirred up and the iron brought to the
surface, where it turned the color of rust after coming into contact
with oxygen.
The scientists also discovered unusually high levels of carbon dioxide
(CO2) dissolved or “in solution” in the water. Samples from a as
shallow as 50 feet deep contained so much CO2 that when they were
pulled to the surface, where the water pressure was lower, the
dissolved CO2 came bubbling out of solution—just as if someone had
unscrewed the cap on a bottle of soda.
CONTENTS UNDER PRESSURE
As the scientists took samples from deeper and deeper in Lake Nyos,
the already high carbon dioxide (CO2) levels climbed steadily higher.
At the 600 foot depth, the levels suddenly shot off the charts. Beyond
that depth, the CO2 levels were so high that when the scientists tried
to pull the samples to the surface, the containers burst from the
pressure of all the gas that came out of solution. The scientists had
to switch to pressurized containers to collect their samples, and when
they did they were stunned to find that the water at the bottom of the
lake contained five gallons of dissolved CO2 for every gallon of
water.
As the scientists pieced together the evidence, they began to form a
theory that centered around the large amount of CO2 in the lake. The
volcano that formed Lake Nyos may have been long extinct, but the
magma chamber that fed it was still active deep below the surface of
the Earth. And it was still releasing carbon dioxide gas—not just into
Lake Nyos, but into the surrounding environment as well. In fact, it’s
not uncommon in Cameroon to find frogs and other small animals
suffocated in CO2 “puddles” that have formed in low points along the
ground. (CO2 is heavier than air and can pool in low spots until the
wind blows it away.)
But what was unusual about Lake Nyos wasn’t that there was CO2 in the
lake; that happens in lakes all over the world. What was unusual was
that the CO2 had apparently never left—instead of bubbling to the
surface and dissipating into the air, the CO2 was accumulating at the
bottom of the lake.
UPS AND DOWNS
In most lakes CO2 escaped because the water is continually
circulating, thanks to a process known as convection: Rain, cold
weather or even just wind blowing across the surface of the lake can
cause the topmost layer of water to cool, making it denser and
therefore heavier than the warmer layer below. The cool water sinks to
the bottom of the lake, displacing the warmer, CO2 rich water and
pushing it higher enough for the CO2 to come out of the solution,
bubble to the surface, and escape into the air.
STILL WATERS RUN DEEP
That’s what usually happens, but the water at the bottom of Lake Nyos
was so saturated with CO2 that it was clear that something was
interfering with the convection process. As the scientists soon
discovered, the waters of Lake Nyos are among the most still in the
world: Tall hills surround the lake, blocking the wind and causing the
lake to be unusually consistent in temperature from the surface to the
bottom. And because Lake Nyos is in a tropical climate that remains
hot all year round, the water temperature doesn’t vary much from
season to season, either. Lastly, because the lake is so deep, even
when the surface is disturbed, very little of the agitation finds its
way to the lake floor. The unusual stillness of the lake is what made
it so deadly.
FULL TO BURSTING
There is a physical limit to how much CO2 water can absorb, even under
the tremendous pressured that exist at the bottom of a 690 foot deep
lake. As the bottom layers become saturated, the CO2 is pushed up to
where the pressure is low enough for it to start coming out of
solution. At this point any little disturbance—a landslide, stormy
weather, or even high winds or just a cold snap—can cause the CO2 to
begin bubbling to the surface. And when the bubbles start rising, they
can cause a siphoning or “chimney” effect, triggering a chain reaction
that in one giant upheaval can cause the lake to disgorge CO2 that has
been accumulating in the lake for decades.
CO2 is odorless, colorless, and non-toxic; your body produces it and
you exhale some every time you breathe. Even the air you inhale
consists of about 0.05% CO2. What makes it a killer in certain
circumstances is that fact that it’s heavier than air: If enough
escapes into the environment at once, it displaces the air on the
ground, making breathing impossible. A mixture of as little as 10% CO2
in the air can be fatal: even 5% can smother a flame…which explained
why the oil lamps went out.
SNUFFED OUT
The scientists figured that if their theory was correct, there might
be other instances of similar eruptions in the past. It didn’t take
very long to find one, and they didn’t have to look very far, either:
Two years earlier, on August 15, 1984, a loud boom was heard coming
from Lake Monoun, a crater lake just 59 miles southeast of Lake Nyos.
In the hours that followed, 37 people died mysteriously, including a
group of 17 people who died while walking to work when the came to a
low point in the road—just the place where CO2 would have settled
after being released from the lake. The incident was small enough that
it hadn’t attracted much attention from the outside world…until now.
THE BIG BANG
In the months following the disaster at Lake Nyos, the scientists
continued to monitor the lake’s CO2 levels. When the levels began to
increase again, they concluded that their theory was correct.
In the meantime, they had also come up with an estimate of just how
much CO2 had escaped from the lake on August 22—and were stunned by
what they found. Eyewitness accounts from people who were high enough
in the hills above the lake to survive the eruption described how the
lake began bubbling strangely on August 17, causing a misty cloud to
form above the surface of the water. Then without warning, on August
22, the lake suddenly exploded; water and gas shot a couple of hundred
feet into the air. The CO2 had taken up so much space in the lake that
when it was finally released 1.2 cubic kilometers of CO2—enough to
fill 10 football stadiums—in as little as 20 seconds. (Are you old
enough to remember the huge volume of ash that Mt. Saint Helens
released when it erupted in 1980? That eruption released only 1/3 of
one cubic kilometer of ash—a quarter of Lake Nyos’s emission.)
CLOUD OF DOOM
Grazing cattle killed in the 1986 Lake Nyos disaster (Image Credit:
Water Encyclopedia)
Cattle herders graze their animals on the hills above Lake Nyos, and
after the lake disgorged as much as 80% of its massive store of CO2 in
one big burst, dead cattle were found as high as 300 feet above the
lake, indicating that the suffocating cloud shot at least that high
before settling back onto the surface. Then the gas poured over the
crater’s edge into the valley below, traveling at an estimated 45
miles per hour.
For people living in the village closest to the lake, death was almost
inevitable. A few people on hillsides had the presence of mind to
climb to higher ground; one man who saw his neighbors drop like flies
jumped on his motorcycle and managed to keep ahead of the gas as he
sped to safety. There were the lucky few. Most people didn’t realize
the danger until they were being overcome by the gas. Even if they
had, it would have been impossible to outrun such a fast-moving cloud.
CURIOSITY KILLED THE CAT
In villages father away from the lake, people had a better chance of
survival, especially if they ignored the noise the lake made as it
disgorged its CO2. Some survivors said it sounded like a gunshot or an
explosion; others described it as a rumble. But people who stepped
outside their homes to see where the noise had come from, or to see
what had caused the rotten egg smell (a common smell “hallucination”
associated with CO2 poisoning) quickly collapsed and died right on
their own doorsteps. The sight of these first victims passing out
often brought other members of the household to the door, where they,
too, were overcome…and killed.
People who were inside with their windows and doors shut had a better
chance of surviving. There were even cases where enough CO2 seeped
into homes to smother people who were lying down asleep, but not
enough to kill the people who were standing up and had their heads
above the gas. Some of these survivors did not even realize anything
unusual had happened until they checked on their sleeping loved ones
and discovered they were already dead.
AN OUNCE OF PREVENTION
The disaster at Lake Nyos was only the second such incident in the
recorded history—the 1984 incident at Lake Monoun was the first. To
date, scientists believe that only three lakes in the entire world,
Nyos, Monoun, and a third lake called Lake Kivu on the border of Congo
and Rwanda, accumulate deadly amounts of dissolved CO2 at great
depths.
It had taken about a year to figure out what had happened at Nyos.
Then, when it became clear that the lake was filling with CO2 again,
the government of Cameroon evacuated all the villages within 18 miles
of the lake and razed them to prevent their inhabitants from coming
back until the lake could be made safe.
Scientists spent the next decade trying to figure out a way to safely
release the gas before disaster struck again. They eventually settled
on a plan to sink a 51/2-inch diameter tube down more than 600 feet,
to just above the floor of the lake. Then when some of the water from
the bottom was up to the top of the tube, it would rise high enough in
the tube for the CO2 to come out of solution and form bubbles, which
would cause it to shoot out the top of the tube, blasting water and
gas more than 150 feet into the sky. Once it got started, the siphon
effect would cause the reaction to continue indefinitely, or at least
until the CO2 ran out. A prototype was installed and tested in 1995,
and after it proved to be safe, a permanent tube was installed in
2001.
RACE AGAINST TIME
As of the fall of 2006 the tube was still in place releasing more than
700 million cubic feet of CO2 into the air each year. That’s a little
bit more than enters the lake in the same amount of time. Between 2001
and 2006, the CO2 levels in Lake Nyos dropped 13%.
But the scientists who study the lake are concerned that 13% is still
too small an amount. The lake still contains more CO2 than was
released in the 1986 disaster, and as if that’s not bad enough, a
natural dam on the north side of the lake is eroding and could fail in
as little as five years. If the dam collapses, the disaster of 1986
may prove to be just a small taste of things to come: In the event of
a dam failure, 50 million cubic meters of water could pour out of the
lake, drowning as many as 10,000 as it washed through the valleys
below. That’s only the beginning—releasing that much water from the
lake would cause the level of the lake to drop as much as 130 feet,
removing the water pressure that keeps the CO2 at the bottom of the
lake and causing a release of gas even more catastrophic than the
devastation of 1986.
Scientists and engineers have devised a plan for shoring up the
natural dam with concrete, and it’s believed that the installation of
as few as for more siphon tubes could reduce the CO2 in the lake to
safe levels in as little as four years. The scientists are hard at
work trying to find the funding to do it, and there’s no time to
waste: “We could have a gas burst tomorrow that is bigger than either
(the Lake Monoun or Lake Nyos) disaster,“ says Dr. George Kling, a
University of Michigan ecologist who has been studying the lake for 20
years. “Every day we wait is just an accumulation of the probability
that something bad is going to happen.