There is a small country in western central Africa, Cameroon, which has a picturesque lake, Lake Nyos. However, such a beautiful scenery has been strictly prohibited as a tourist attraction by the local government, and even nearby residents have been forcibly removed by the government.
In fact, at the end of the last century, it was not deserted, but a peaceful and peaceful place, and the villagers lived a happy life.
Whenever I look at Lake Nyos in the distance, the thoughts of some elderly residents are dragged back to that night more than thirty years ago.
"It was a nightmare, and it still feels terrible when I think about it, when Death stood in front of me."
"For more than thirty years, no one has dared to go near that lake. Until now, I close my eyes and think about what happened that night. ”
What really happened more than thirty years ago? Why did this become a nightmare that changed the lives of villagers near Lake Nyos?
Picturesque Lake Nyos
Although cameroon's land area is only more than 470,000 square kilometers, due to its geographical and cultural diversity, the local natural geography is very rich, known as "Little Africa", tourism resources are very rich, and the annual tourism revenue accounts for 5.3% of Cameroon's GDP.
Lake Nyos is actually the most characteristic lake in Cameroon, and some people say that the scenery here will even be admired by God. But Lake Nyos is the world's famous "killing lake", which once took more than 1,700 lives overnight. Although people are not allowed to approach the lake now, in fact forty years ago, there were a lot of residents living around Lake Nyos.
The formation of Lake Nyos was associated with a volcanic eruption after which a large amount of pumice erupted from the crust, volatile material dissipated into the air, and the neck of the crater collapsed, forming a funnel-shaped depression.
Cameroon has a tropical climate, with a dry and hot climate in the north and a rainy and rainy region in the volcanic foothills in the south, with an annual precipitation of up to 10,000 millimeters, making it one of the rainiest regions in the world.
The formation of Lake Nyos, after this repeated precipitation, gradually hoarded to form a lake, and has become one of the most representative lakes in Cameroon.
In addition to rainfall, snow melting, groundwater and other reasons are the reasons why the crater gradually stores a lot of water and forms a volcanic lake. Like the Changbai Mountain Tianchi in the territory of the mainland, it is also a volcanic lake.
Not far from Lake Nyos, there are a few scattered small villages. Because of the abundance of water resources and the temperature suitable for vegetation, there are many animals living around the lake.
Many years ago, nearby villagers discovered something strange, that is, every once in a while, when they went to the vicinity of Lake Nyos, they might encounter some animal carcasses.
At first, they thought that the animals had encountered predators or died of old age, but soon found that there were no wounds on the carcasses of these animals, and the "expressions" of the dead animals looked very painful.
The inhabitants here do not have a particularly high culture, so when these animals died inexplicably, they thought that the gods of the lake wanted them to sacrifice.
Because there have been no accidents in the family's livestock, everyone has not paid attention to this matter. It wasn't until that night in 1986 that people suddenly reacted that the strange death of animals by the lake was actually a warning from nature.
A night of horror
On August 21, 1986, as usual, the weather was sweltering and hot, and in the evening, many villagers washed up and went to bed.
At about nine o'clock in the evening, the sleeping Alhaji Magaghi Jani was awakened by a loud noise, much like the whistle of a steam train, and like thunder, Alhaji got up and looked out the window, and a huge column of water rose in the air, right in Lake Nyos.
Immediately after, Alhaji smelled a pungent smell of rotten eggs, and he choked on the smell, but the next second he opened his eyes in horror and desperately tugged at his neck.
He felt a pair of invisible hands pinching his neck deadly, unable to take a breath. In just a few seconds, Alhaji lost consciousness in front of his eyes.
When he woke up again, it was already the next morning, and he hurried to get up, only to find that all the people in the family had lost their breath. Overnight, Alhaji lost 31 loved ones. Holding his young daughter, he cried bitterly and desperately shouted her daughter's name, but he did not get a response.
Alhaji walked out the door and saw all the cattle and sheep in the house fall to the ground and die. Shocked by the scene in front of him, he panicked for a moment, and had to knock on the door door to door, hoping that someone would help him, but he found that almost every household had no response, all the livestock raised by the villagers were dead, and the silence around them was chilling.
When the local government learned of this, they sent someone to investigate, and at first their guess was that it was a poisoning incident, but when the investigation team arrived at Lake Nyos, they found that things were not as simple as they thought.
Investigators found that the survivors were almost all villages like Alhaji, slightly further from Lake Nyos, and the closer they got to Lake Nyos, the more human and animal carcasses died. The most frightening thing is that the blue waters of Lake Nyos also turned blood orange overnight.
According to preliminary statistics, the death toll has exceeded 1,700, and the number of dead livestock has exceeded 4,000.
What really happened that night? Why could more than 1,700 lives be claimed overnight?
Preliminary speculation: poison gas leak
As a survivor, Alhaji's words became the most important reference in the investigation. Experts believe that Alhaji mentioned that he smelled a pungent smell of rotten eggs that night, followed by suffocation and fainting, so this pungent smell may be poisonous gas, which is the cause of people's deaths.
Generally speaking, when the sulfide gas is volatilized, it will emit the smell of rotten eggs, and this smell is toxic. Considering that Lake Nyos is a volcanic lake, it is very likely that a large amount of sulfide gas is released during the eruption of the volcano, and the loud noise is the sound of the volcanic eruption.
The death of people due to volcanic gas eruptions has long occurred, and Indonesia's Shilila Volcano was originally an extinct volcano, and on January 20, 1979, due to the movement of the Earth's crust, it suddenly erupted without warning and released a large amount of toxic gases. The disaster claimed the lives of hundreds of residents and thousands more were injured by inhaling poison gas.
Moving forward, in 1902, the Pere Volcano on Martinique also erupted suddenly, killing more than 30,000 residents of the nearby town, only 2 people survived, and all the others were gassed.
The volcano below Lake Nyos is also an extinct volcano that has not erupted for many years, and experts believe that it is very likely that this sudden eruption carried a large amount of toxic gases and led to the tragedy.
However, during the investigation, experts found that the plants around Lake Nyos were safe and sound, and the houses showed no signs of corrosion. If people and animals are poisoned by poisonous gases, there are requirements for the concentration of toxic gases in the air, and in such cases, vegetation cannot survive.
In this way, it contradicts the speculation that poison gas kills. So what is the truth?
Caldera Lake National Park
At this time, some experts thought of Crater Lake National Park in Oregon, and perhaps some of its data could bring some new hints to this survey.
Crater Lake was formed 7,700 years ago during a massive volcanic eruption, and Mezama Volcano sank 1,524 meters directly because of this eruption, creating a crater with a diameter of 9.66 kilometers.
Although the current Mezzama volcano no longer erupts, after investigation, it has been found that the magma under the volcano has not solidified and is still flowing. This is also why around the crater lake can still see a lot of "fairy gas floating" scene, in fact, is the carbon dioxide released during the magma movement, sulfur dioxide, along with water vapor drilled out of the ground.
Due to the high pressure of the rocks underground, the gases in the magma cannot be volatilized. However, as the magma flows, the weight of the upper magma decreases, and the gas can leave the magma and slowly seep into the lake.
According to relevant statistics, 1,000 tons of carbon dioxide are injected into the crater lake from underground magma every year.
This study has also been verified on other volcanic lakes, and almost every volcanic lake has a large amount of carbon dioxide gas under the quiet water of the lake.
But since it is a gas, lighter than the weight of water, why is it dissolved in water instead of emitting into the air?
Lakes like Crater Lake are deeper, so the water pressure is enormous. The bottom of the lake is affected by magma, and the water temperature is also higher, so the density is lower. In this way, the surface of the lake is like a huge bottle cap, and the lake full of carbon dioxide is like a bottle of Coke, and the gas can't go out until the lid is opened.
Under the dome
The local government intervened strongly, experts tested Lake Nyos, pumped out the water deep under the lake, and found that carbon dioxide did volatilize every day, so they made a bold speculation that it was this carbon dioxide that killed people.
But carbon dioxide is one of the important components in the air, the gas we exhale every day is carbon dioxide, this gas is non-toxic, why does it become a deadly "poisonous gas"?
Although carbon dioxide itself is non-toxic, it accounts for only 0.031% of the air; Once more than 1%, the human body will feel obvious discomfort, dizziness; More than 17% will make people feel weak and gradually lose consciousness until they die.
Simply put, too high a concentration of carbon dioxide can cause us to be unable to exhale enough oxygen, and once a person lacks oxygen, it will lead to suffocation and death.
It also explains how Alhaji said he felt unable to breathe that night, as if an invisible hand had choked his neck deadly.
So there are so many volcanic lakes in the world, why are other volcanic lakes all right?
This has a lot to do with the climate of Lake Nyos, usually, in the area with four distinct seasons, because the summer temperature is relatively high, the surface temperature of the lake is much higher than the lower water temperature, under such an action, the gas in the lake water is heated up, leaving the lake in the form of bubbles and emitting into the air.
In winter, the surface water cools faster than the bottom water, and a circulation is formed inside the lake. When the water at the bottom of the lake is circulated to the surface, the gas is released rapidly due to the cooling. Although there are a large number of carbon dioxide and other gases in the lake water, because of the change of the climate in the four seasons, there are opportunities to release gases, which avoids the possibility of a large amount of gas accumulation.
Lake Nyos is located in the tropics, hot and humid all year round, there is no winter, so it cannot form a cycle, so a large amount of gas can only accumulate at the bottom of the lake, becoming a time bomb.
So how powerful are these carbon dioxide eruptions? We've seen a video of Throwing Mantos into Coke online, and in just a split second, Coke spews out a jet of water.
Based on this information, we can make a rough guess about that night. Under the action of some unknown factor, Lake Nyos is like a bottle of cola that has just been opened, and suddenly it is thrown into a "Mantos", and then the carbon dioxide in the lake water forms a huge impact under the action of this small factor, rushing out of the 90-meter-high column of water.
But carbon dioxide is a gas that shouldn't rise into the air after breaking free of the shackles of the lake' waters?
Glaciers melt
The carbon dioxide in Lake Nyos, according to common sense, should also rise to the air, so why did it become a murderer?
To unravel the answer to this question, you need to refer to an experiment. Ohio State University once did a demonstration experiment in which a ladder was placed in a glass jar, followed by a burning candle, and finally dry ice at the top of the ladder.
As the dry ice continues to volatilize, the candles on the stairs are extinguished from top to bottom.
Dry ice is actually solid carbon dioxide, placed in a room temperature environment, which will soon volatilize into carbon dioxide gas. Carbon dioxide is 1.5 times denser than air, so it squeezes out nearby air.
Ohio State University
Lake Nyos is higher than the surrounding villages, and at the moment of eruption, it is like the dry ice in the experiment, spreading very quickly to the surrounding area, and the surrounding 25 kilometers of villages are all covered with carbon dioxide, as if an invisible dome shrouds the area centered on Lake Nyos.
In terms of image points, this distance is equivalent to a circle from the center of Beijing to the fifth and sixth rings, and the people living in such a large range were almost all taken away that night.
Eerie Lake of Blood
After finding the cause of the death of people and livestock, there is still a mystery that haunts people, that is, why on the second day of the incident, Lake Nyos turns a terrible blood orange color.
After expert investigation, it was found that there was a large amount of rhombite at the bottom of Lake Nyos, and when the dioxide pond at the bottom of the lake was affected by external forces, some of the rhodochroite was also washed out of the lake.
Iron reacts chemically after encountering oxygen and becomes a red substance. At the moment of the explosion, other materials at the bottom of the lake were also stirred and brought to the surface of the lake, and under the combined action, the lake water turned blood orange.
siderite
The cause of the explosion
Although the murderer was found, the cause of the sudden explosion in Lake Nyos has never been found.
Some experts believe that there may have been a landslide at the time of the incident, and a stone fell into Lake Nyos, which is the "Mantos", which triggered a huge catastrophic event in just a moment.
However, although experts found a large number of evidence of landslides in Lake Nyos, they could not prove that the landslide occurred first and then caused the explosion. Or did it explode for some other reason, and the mountain went down a landslide because of the explosion. This chicken-and-egg question has become a problem that plagues experts.
Some experts believe that although Lake Nyos is an extinct volcano, the underground magma has not been solidified, and this force from the underground has been stirring, perhaps a small eruption brought about by a small magma upwelling, which has led to the formation of carbon dioxide at the bottom of Lake Nyos to erupt.
Survivors smelled pungent rotten eggs, most likely hydrogen sulfide and carbon dioxide released during the eruption.
Some experts believe that there may have been an earthquake at that time, and after Lake Nyos was affected by the wave force of the earth's crust impact, it was like a constantly shaking Coke bottle, which would gush out at once. However, the nearby residents did not feel any earthquakes, and there was no recorded data on earthquakes.
Until today, more than thirty years later, the cause of the eruption of Lake Nyos has not been found. However, with the continuous efforts of experts, they found an appropriate solution to the potential huge bomb of Lake Nyos.
In 2001, the local government installed a specialized carbon dioxide release system around the lake district. With this equipment, carbon dioxide can be pumped up from the bottom of the lake through pipes, which is gradually emitted into the air.
In order to ensure that nothing is lost, an alarm device has been installed at the bottom of Lake Nyos, and once the concentration of carbon dioxide in the lake water exceeds a certain value, the alarm will be alarmed to warn people of the danger.
Now all the inhabitants of lake Nyos have left their ancestral homes and moved to safety.
postscript
The horror of the Lake Nyos incident is that when the carbon dioxide erupted, it was like a raging flood, which gave people no chance to react and instantly devoured the lives of more than 1,700 people. It is also because of this incident that people first realized the terrible nature of carbon dioxide.
Until today, 2022, more than thirty years later, Lake Nyos is as quiet as ever. Under the intervention of science and technology, the "Killing Lake" killing people has never happened again.
This tragedy is also a reminder that in the face of nature, in fact, we humans are very small, in the vast universe, human beings are very small, like a grain of dust. We should always maintain a reverence for life, a reverence for nature.
Bibliography:
[1] Geography China Program 201110 - "Murder Lake" Exploration
Zhao Xiyang. Lake Nyos explosion explains extinction[J].Science World, 2005(03):60-64.
Chen Shun. The bottom of the lake subdues the "Killing Lake"[N].Xinhua Daily Telegraph, 2001-06-21