The risk of recurring Lake Nyos disaster killed 1,700 people

Twenty-five years ago a cloud of carbon dioxide (CO ₂ ) spread from Lake Nyos in Cameroon suddenly crashed into villages around the lake, killing more than 1,700 people. Until today, scientists have not yet explained why poison gas escapes from the lake.

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Deadly clouds

For Nyos villagers, the fifth day is an important day because of the fair. Thousands of people flock here to buy and sell and meet relatives and friends.

August 21, 1986 is also the fifth day. The atmosphere in Nyos village is very bustling because this year the whole village gets corn season. No one in the village noticed just 3km away from the village, something strange was going on. Until 8.30 am they suddenly heard a screeching sound.

Later the witnesses said, the roar lasted for several tens of seconds, everyone rushed out of the cottages and stared at the lake. In front of them was a giant pillar of water, smoke-like smoke-like clouds puckering from the lake. Thousands of cows died. The sudden natural event at Lake Nyos took only a few minutes but the consequences were immeasurable.

At that time the wind blew quite strong, about 70 km / hour, the cloud from the lake spread out very quickly and covered many peaceful villages. These clouds are dense CO ₂ , heavier than air so people living on the lakeside have absolutely no chance of escaping. The men who had recently talked happily and now collapsed, many felt that there were no limbs, children were stopped breathing, birds fell from the sky to the ground.

1,700 people and 8,000 cattle died in the Lake Nyos disaster.

Within a few hours there were over 1,700 people suffocated. Ten days later, dead bodies were still found within 10 kilometers of the lake. Thousands of cattle died. Some people suffer from prolonged coma, some people only recover after 36 hours.

The Lake Nyos disaster shocked the world and remembered a similar event two years earlier in Lake Monoun, also in Cameroon, which killed 37 people. The case of Lake Nyos is much larger - many villages like Nyos, Father and Subum are almost wiped out without anyone.

The majority of survivors all told of a very similar symptom like being frowning away, dizzy after the explosion. Many people feel confused and dizzy then faint. Everyone smelled like a smell of rotten eggs or gunpowder, showing that this is a symptom of CO ₂ poisoning.

The button came out

Immediately after the disaster, a Cameroonian geologist found water levels in Lake Nyos dropping by about 1 meter and arrived at the loss of Lake Nyos water equivalent to the weight of about 1.7 million tons of CO2.

Lake Nyos is located on the crater, formed during the cooling of volcanoes and by the accumulation of rainwater. The amount of CO2 released from volcanoes accumulates for hundreds of years in the bottom of the lake without escaping. The year-round warm temperatures in Lake Nyos and surrounding areas are the reason why CO2 cannot escape. This warm temperature makes the water layer on the surface of the lake have a higher temperature than the bottom lake CO ₂ and the surface water layer forms a "button " that keeps the CO2 from escaping. there, the button is broken, causing the deadly poisonous gas to explode and shoot into the sky.

So what is that 'button'?

This is the question scientists have been studying since the summer of 1986. Initially it was suspected that CO2 was pushed up by volcanic eruption at the lake. However, geological experts concluded that due to landslides, the warm water layer was turned downwards, and water from the bottom was pushed up. CO ₂ from the dissolved state will escape like bubbles bubbling from a bottle of water that has been opened. Those air bubbles attract water up and when they come out of the water they flare up into a giant pillar of water and explode, from which the CO ₂ escapes like clouds.

Script for the next disaster

Since then Lake Nyos has been dubbed "Killersee" (killer lake), the government has forced people in villages around the lake to leave. The houses of the people here were even dismantled so no one would dare to think about returning. But the land south of Lake Nyos is very fertile, so people are ignoring the disaster and the government's prohibition: The crowded cows are grazing, the cornfields grow green and the wings fly. . Since the 90s people have released fish in the lake and they grow very well, before this lake has almost no fish.

But since 2001, the amount of toxic CO2 in the lake bottom has doubled compared to 1986, when the disaster occurred. In order to avoid catastrophe, since 2001, it has been carried out degassing in control. However, to do this, a system of 5 toxic gas drains must be built, but now there is only one pipeline going into operation.

The situation is quite urgent. According to the UN mandate, a group of Dutch experts conducted research here. And there is a risk of a catastrophe bigger than the previous CO ₂ explosion. A volcanic rock dike to the north of Lake Nyos is at risk. If dike breaks occur, the water at Lake Nyos in the highlands will fall downstream of over 60km long to the Nigerian border and can drown thousands of lives.