Cold Open

It’s August 22nd, 1986, in Subum, a village in northwest Cameroon.

Joseph Nkwain opens his eyes a crack and peers around. It takes him a moment to realize exactly where he is. He’s lying on the floor of his hut.

And someone is hammering on the door. But Joseph doesn’t move. Instead, he just stares up at the ceiling while fragments of the previous night drift back into his memory.

He woke in the early hours to a strange smell and the sound of his daughter struggling to breathe. He rose from his bed to check on her, but his legs suddenly felt weak. And then, everything went black.

From the bright light seeping around the doorframe, Joseph can tell it’s mid-morning. He must have been unconscious for hours.

The knocking comes again. Joseph tries to answer, but his voice is only a croak. Slowly, he clambers to his feet. The movement sends a burning pain across his arms. And looking down, he sees angry red sores covering his skin—marks that definitely weren’t there when he went to bed.

Joseph staggers to the door and opens it. He sees it was his neighbor who was knocking. But the man is already shuffling toward the next hut, moving slowly, as though every step hurts. Joseph tries to call out, but again, his voice fails him.

He looks around. Apart from the neighbor, there’s not a soul to be seen. Subum is a cattle village. Most residents are herders like Joseph. And usually, they’re up and about early to tend to their livestock. But not this morning. Today, the village is deserted.

Suddenly, the world begins to spin. Sensing he’s about to faint, Joseph stumbles back inside, past his daughter lying motionless on her bed…and collapses unconscious again.

When Joseph Nkwain wakes hours later, he makes a horrifying discovery. His daughter is dead, apparently suffocated in her sleep. And she’s not the only sudden, unexpected fatality in the village. Entire families in Subum have perished overnight, leaving just a handful of bewildered survivors—the victims of an invisible natural disaster which swept through this isolated region of Cameroon on August 21st, 1986.

Introduction

From Noiser and Airship, I’m Lindsay Graham, and this is History Daily.

History is made every day. On this podcast—every day—we tell the true stories of the people and events that shaped our world.

Today is August 21st, 1986: The Lake Nyos Disaster.

Act One: The Power of the Lake

It’s the evening of August 21st, 1986, in the mountains of northwest Cameroon, a few hours before villagers in the region succumb to a mysterious illness.

Kalus Ketu feels his calves burn as he climbs the steep path toward Lake Nyos. It's a route he knows well. He lives in a tiny settlement nearby, a village so small that it doesn’t appear on most maps. Like many of his neighbors, Kalus keeps cattle and farms the fertile volcanic soil. But whenever he can, he hikes up to the lake to cast nets for fish and crabs. The catches are usually poor. Lake Nyos fills the crater of an ancient volcano, and its water has an unusual taste, and few creatures seem to be able to survive in it.

But tonight, Kalus isn’t here to fish. Earlier this evening, strange noises echoed down the valley—sharp pops and muffled explosions coming from the direction of the lake. At first, people thought they were gunshots. And as worried neighbors gathered outside their homes, Kalus volunteered to climb the mountain and investigate.

But the hike is harder than usual. The air is still and humid, and Kalus is soon breathing heavily. The forest seems unusually quiet too. Normally, insects buzz in the undergrowth, and frogs call from nearby streams. But tonight, only the crunch of Kalus's footsteps breaks the silence.

As he reaches the crest of the slope, he crouches low and peers over the ridge, expecting to see the nomadic raiders who occasionally trouble the area. Thankfully, there’s no one else here—although the scene is far from tranquil. The water of Lake Nyos, normally a deep blue, is now a murky blood red. Near the center, a towering column of water shoots into the air. It sinks almost back to the surface before erupting once again. This plume rises hundreds of feet before crashing back down, sending waves racing across the lake.

And there's also a low mist hanging just above the water, and a stench that reminds Kalus of rotten eggs and gunpowder. Clusters of dead fish float on the surface, and strange noises seem to echo from the lakebed. Every instinct tells Kalus that something is terribly wrong, but he has no idea what’s caused the sudden change. He can only stand and watch as the waterspout rises and falls.

And soon, he notices that he’s no longer alone. Others from nearby villages have climbed to the lakeside too, all drawn by the same unsettling sounds. Some whisper prayers. Others declare that the volcano must have reawakened.

As the villagers debate what’s going on, the low-hanging mist begins to drift away from the water and slide down the mountain. A friend from a neighboring village decides he’s seen enough and turns toward home. Kalus watches the glow of his lamp slowly descend before vanishing into the eerie mist.

Kalus refuses to follow. Because something about this mist feels wrong. Instead, he settles in and waits. For hours, he watches the cloud ebb and flow in the moonlight. And eventually, the wind shifts, carrying the mist away from the path to his village.

Only then does Kalus make his way home, and by the time he reaches his house, it’s the middle of the night. He bolts the door behind him and climbs into bed, hoping that the mist won’t return.

The following morning, the mist is gone, but something still isn’t right. The mountain remains eerily silent—no birdsong, no chirruping insects, and even the dogs have stopped barking. Kalus sets out to check on the friend he watched disappear into the cloud the night before.

And when he reaches the neighboring village, he finds a scene of devastation. Many people are dead, apparently suffocated in their sleep. Kalus's friend is one of the few survivors. But he sits alone, his eyes raw with tears. His daughter is among the dead.

Kalus stays to help bury this man’s child, then helps other families with their dead as well. As the morning wears on, word arrives from other villages across the region. And everywhere, the story is the same. Sometime during the night, a strange mist drifted through their homes and cattle pens, silently killing people and livestock alike.

It will take days for the news of these deaths to escape this remote corner of Cameroon. And when it does, scientists around the world will be confronted with one of the deadliest and most baffling natural disasters in African history.

Act Two: The Response

It’s August 24th, 1986, in Cha, a village near Lake Nyos, three days after the disaster.

A humanitarian worker walks along the dirt road into the village. He’s been here before—but it barely resembles the place he remembers. Cha is usually full of life: children playing, women pounding grain, cattle lowing. But now, the only sounds are muffled voices, the scrape of shovels, and the buzzing of flies.

Everywhere he looks, there are bodies. Birds lie scattered beneath trees as though they simply dropped from the sky. Goats and sheep sprawl across footpaths. Cattle remain where they collapsed inside their pens. And even stray dogs lie motionless beside the road.

Then he sees the people. Some have been wrapped in blankets by grieving relatives. Others still lie in their beds, in doorways, or on the earthen floors of their homes.

The survivors are doing everything they can to bury their loved ones. But there are too many dead, and too few people left alive to dig the graves.

When word reached the outside world of mysterious deaths around Lake Nyos, this aid worker was one of the first on the scene. Early reports had suggested that 40 people suffocated in one night, but the aid worker can already tell that those early estimates are horribly inaccurate. More than that have died in this one village alone.

Stunned by the scale of the tragedy in Cha, the worker walks on to nearby Nyos Village. But nothing he has witnessed so far prepares him for the devastation there. Almost everyone in this village of more than 1,000 people is dead. Only six men are still alive. And they stand around in a daze of confusion and grief. The aid worker gently questions them and discovers that they only survived through good fortune. They’d been tending cattle on the hillside on the night the mist rolled through. When they returned the following morning, not a single person in the village was left alive.

The aid worker does what he can to help the weak, dehydrated, and traumatized. Before leaving the village, he stops at the small post office to use the telephone. And in a call to his headquarters, he explains that the situation is far worse than initial reports suggested. Medical teams, food, and clean water are all needed—but more than anything, they desperately require hundreds of body bags.

As the true scale of the catastrophe becomes clear, the remote mountains surrounding Lake Nyos are transformed into the center of a huge international relief operation.

Convoys of trucks crawl along rough dirt roads carrying doctors, nurses, engineers, and relief supplies. Soldiers establish checkpoints and help evacuate survivors. International aid organizations dispatch medical specialists and disaster experts. And temporary camps are set up for the thousands of villagers who can no longer return to their homes. Eventually, investigators conclude that more than 1,700 people died in a single night, with another 800 left requiring medical treatment.

So scientists race to establish the exact cause of these deaths, and their investigations are not simply a matter of scientific curiosity. There are 39 other crater lakes like Nyos in Cameroon. Unless they can figure out what happened, a similar disaster could occur elsewhere.

In March 1987, seven months after the disaster, scientists gather for a conference in the capital of Cameroon. This meeting is dominated by two competing explanations for what happened. One group believes that the dormant volcano underneath Lake Nyos briefly reawakened, releasing toxic gases from deep underground. Others suggest a different, rarer kind of eruption—one never seen before by scientists. According to this theory, carbon dioxide seeped naturally into the lake from the magma in the volcano below. Over time, enormous quantities of CO2 accumulated in the lake’s deep water. The pressure grew, until the gas was suddenly released in what scientists term a “limnic eruption.” A deadly cloud of carbon dioxide then rolled silently down into the valleys and villages beneath the lake.

Eventually, this limnic eruption theory will be accepted by most scientists. But simply discovering the cause of the Lake Nyos Disaster will not solve the problem. If carbon dioxide can build silently beneath one crater lake, it can accumulate beneath others as well. So somewhere in the mountains of Cameroon, another disaster may occur—unless scientists can find a way to defuse these time bombs before they go off.

Act Three: Crisis Averted

It’s March 1995 on Lake Nyos, more than eight years after the disaster which claimed nearly 2,000 lives.

French scientist Michel Halbwachs pushes a raft into the water and watches it float across the deep blue surface. A team of scientists and engineers pulls on ropes to guide the raft into position in the center of the lake. Michel checks the remote control he holds in his hand, making sure that he’s still getting a strong signal from the raft. Because this is the moment of truth—the end of an experiment years in the making.

On the raft is a device that Michel has been working on ever since scientists concluded that the Lake Nyos Disaster was the result of a limnic eruption. The machine is relatively simple, just a pipe attached to a pump, but it could save thousands of lives. If all goes to plan, the pipe will be lowered into the depths of Lake Nyos, where carbon dioxide is already building up again. But the pump will draw this gas-infused water up through the pipe, allowing the CO2 to disperse into the atmosphere safely. But Michel has to test his invention in the field.

An engineer signals that the raft is in position. Using his remote control, Michel activates the pump. And for a few seconds, nothing happens. Michel begins to worry that the long journey to this moment is about to end in failure. But then, a jet of water suddenly shoots more than 20 yards into the air, casting a rainbow as it sprays back down onto the lake.

Michel allows the pump to run for several minutes. And then comes the crucial test. He turns the pump off, but the waterspout doesn’t drop. Now that the gas has started escaping, its own pressure keeps the water flowing. The process is effectively self-sustaining. As long as there’s carbon dioxide at the bottom of Lake Nyos, this machine will remove it from the water.

Over the next few hours, Michel and his team take recordings and make observations. Because this is just a proof of concept—now they can seek funding for a larger pump. That will be installed six years later in 2001—and with it in place, scientists will be confident that there will be no repeat of the Lake Nyos Disaster, which killed more than 1,700 people on August 21st, 1986.

Outro

Next on History Daily. August 24th, 1572. Religious tensions between Catholics and Protestants explode into violence in Paris on St. Bartholomew’s Day.

From Noiser and Airship, this is History Daily, hosted, edited, and executive produced by me, Lindsay Graham.

Audio editing by Muhammad Shahzaib.

Sound design by Mollie Baack.

Music by Thrumm.

This episode is written and researched by Samuel Hume.

Edited by Scott Reeves.

Managing producer Emily Burke.

Executive Producers are William Simpson for Airship and Pascal Hughes for Noiser.