This sounds crazy, but it’s true. There are lakes in the world that randomly explode, and it works in much the same way as soda cans, but on a massive scale, and cause massive death and destruction. They’re called limnic eruptions, and they’re super weird.


Maybe I should do the whole Mentos in a Diet Coke bottle thing in my carport and then explain why it does this. Something about how the chemicals in mentos rapidly pull CO2 out of the carbonated water.

I’ve never actually done this…

Well that made a mess. And it’s like a hundred degrees out here so… I’m going to do the explanation part of this inside.

After I clean this up.

Carbonation happens when carbon dioxide dissolves in water to make carbonic acid, and it does this through pressure. Reason number 1001 that pressure changes everything.

There’s a couple of different ways to do this. Beer makers for thousands of years would add sugar and yeast into a sealed container – the yeast eats the sugar and produces CO2, which with no place to go builds up pressure and dissolves into the water.

This… can go badly.

Today, soda companies add fizz to drinks by injecting carbon dioxide into water and pressurizing it.
To get a little nerdier, the chemical reaction looks like this: H2O plus CO2 produces H2CO3 in dynamic equilibrium. The “dynamic equilibrium” part means the reaction can go left-to-right or right-to-left.
Add pressure, and the reaction goes to the right. Release that pressure, and the process reverses.

So when you open a soda can…

That sound is water and CO2 breaking up. Still a better love story than Twilight.

That’s the sound of water crying.

But why does Mentos make it so explosive? Well the surface of the Mentos is rough, and that rough surface which creates millions of tiny spots where the water and CO2 can break apart, and because they’re heavy, they sink to the bottom, allowing more of the surface to be in contact with the water.

Now this is just a fun little science experiment that might help teach about how soda works but mostly it’s just fun blowing stuff up.

But it turns out, this can happen in nature, on a massive scale. And it’s not quite so fun.

The Lake Monoun Disaster

Late in the evening of August 15, 1984, an explosion rocked the residents of the village of Njindoun in Cameroon. They told police the next morning the sound had come from the direction of Lake Monoun, 5 kilometers to the south.

A policeman went to the lake to investigate, and he brought a doctor with him just in case anybody was hurt. And before they even reached the lake, they came across a strange cloud.

It looked like pale smoke and kind-of hovered near the ground, only reaching a height of about 3 meters. But before they got a chance to really investigate it, they both started feeling sick, so they got out of there.

Once the cloud dispersed, they came back to the area and discovered that whatever that cloud was… it killed everything.

Strewn all over the place were bodies of animals and birds… and 37 people. All of them asphyxiated, and many had strange blisters all over their skin.

The investigators were baffled. There was flattened vegetation around the lake that suggested a 5-meter high wave had crashed at the shore, and there was a sulfurous odor in the area.

As time went on and no answers were found, rumors started to spread that the deaths had been deliberate. Maybe even some kind of biological weapon.

Why Did it Happen?

This, of course, got the attention of the U. S. government. Because weapons… That’s OUR thing.

So they asked Professor Haraldur Sigurdsson to investigate. He is not only the most Icelandic sounding human being alive, he is also an expert volcanologist and geochemist. Which… being from Iceland would make sense.

In fact I believe he popped up in my supervolcanoes video.

And he’s the right person for the job because Lake Monoun was created by a volcanic eruption way back in the day, and it’s actually one of 38 lakes that lie on a chain of volcanoes called the Cameroon Line.

As part of his investigation, he interviewed locals went went out into the lake on a boat to take samples.

It turned out finding the right spot was easy because bubbles were still breaking the surface.

And what he figured out was that these bubbles were carbon dioxide. The lake had become saturated with it and these bubbles were the lake literally fizzing just like a carbonated soda.

Only something caused this lake to erupt. Something was the Mentos that caused this lake to explode. And in the process released so much carbon dioxide gas that everything and everyone in the area choked to death.

After two years of studying this eruption, Haraldur published his theory and gave the phenomenon a name. Limnic eruptions.

Danger at Depth

Well how does a lake get saturated with CO2? It’s the same as with the beer and soda examples earlier – you add pressure.

And it turns out an easy way to add more pressure is just add more water.

If a lake is deep enough, water at the bottom will be under so much pressure from the weight of the water above that water will bond with carbon dioxide, just like in soda.

Now, most lakes absorb CO2 from the air, but since the source of the CO2 is at the top where the pressure is low, it doesn’t become carbonated.

So for that water down at the bottom to become saturated, there has to be a source of carbon dioxide down at the bottom of that lake.

And there are two sources that fit that bill – volcanic gas vents and decomposing plant or animal matter. Both of which create methane, too, which also can dissolve under pressure.
And what happens when lake water combines with CO2 or methane at depth? Well, nothing, so long as the pressure stays high. But if pressure drops….

Imagine fifty billion Mentos falling into a hundred billion liters of Diet Coke. This is a phenomenon that Haraldur Sigurdsson called Lake Overturn.

And Lake Monoun isn’t the only lake to experience this, or the deadliest. Actually, not even close.

The Lake Nyos Disaster

Literally 2 months after Haraldur Sigurdsson published his findings, a second event occurred only 100km away at Lake Nyos.

Around 9 PM on August 21, 1986, people living near the lake heard a rumble. A wind caused some to pass out.

The next day, investigators found the lake transformed. The blue waters had turned red, from iron being dredged from the depths.

They found that a massive wave had struck portions of the lakeshore, with water cresting as high as 100 meters in some places.

It damaged the contours of the lake so much it dried out a waterfall.

But far more disturbing was the death around the lake. It wiped out literally everything.

Eyewitnesses described a chilling silence in the area. No bird calls, no animals moving around. Not even any bugs.

I think the creepiest detail from the eyewitness accounts was the absence of flies. Dead bodies were all over the place and none of them had any flies on them. Because even the flies were dead.

The human death toll in the end came out to 1,746 people. This was a massive disaster. And it brought a lot more experts to Cameroon.

They found blisters on the bodies, as they had at Lake Monoun. This lead some to believe that a volcano had erupted. But volcanoes… let’s just say they aren’t that subtle.

Volcanic eruptions throw out huge quantities of rock and ash, create lava flows, and release sulfur in the air. Now you might remember reports of a sulfur smell at Lake Monoun, well it was also smelled by Nyos survivors, but when investigators couldn’t find evidence of elevated sulfur levels anywhere.

The water was also too cool to have suffered a volcanic eruption. Investigators found that if it was volcanic the water would be 40 degrees Celsius warmer.

It was pretty clear that CO2 was the culprit for the deaths, in fact, one of the key investigators name George Kling took a sample of Lake Nyos water and said it literally exploded from its container.

Unanswered Questions

But there were still some major questions around this. Number one was the smell. CO2 doesn’t smell like sulfur.

On the other hand, it has been known to trigger sensory hallucinations. Maybe the sulfurous odor was an illusion.

Or maybe the survivors did smell sulfur, but at such low doses, it left only traces were found.

What about the blisters? One theory was that it wasn’t carbon dioxide but carbon monoxide, which has been known to cause blisters, by limiting the circulation of blood to a person’s skin.

Or they could have been caused by trace, toxic gases mixed in the CO2 cloud.

Which leaves only the big question. Why, exactly, did the lakes erupt? What caused that pressure drop that set everything in motion?

Lake Monoun and Lake Nyos appear to have been accumulating gases for some time. Both are thought to be fed by “soda springs” that carry gasses from deep underground.

One theory was that a landslide may have broken the lake’s seal. Or a volcanic eruption that was too small to leave direct signs.

Both disasters occurred during monsoon season, so George Kling suggests a rain storm might have cooled the water and allowed the deep water to rise, which would lower the pressure.
We may never have all the answers to these two eruptions. But we do know arguably the most important thing – how to prevent them in the future.

Degassing Efforts

In 1990, a team of engineers added plumbing to the exploding lakes. There were money problems and it took a while to build but they basically installed artificial fountains that let the gassy water escape from the depths.

Nyos was so saturated the fountain shot up to 45 meters high. At first. It’s gone down since then, which is a good thing, that means it’s working.

And yeah, thanks to these efforts, Lake Nyos and Lake Monoun are now considered safe.

But… in the words of the great Master Yoda… There is another.

Lake Kivu’s Danger

About 2000 kilometers west of Lake Monoun lies Lake Kivu. Kivu is not only much larger and considerably deeper than these two lakes, but it’s also sitting on top of volcanic vents that have been releasing gas into it for thousands of years.

Yeah, they estimated in 2021 that the amount of CO2 in Lake Kivu equals as much as 5% of global CO2 emissions. That’s in one lake.

So if Lake Kivu exploded, that would be bad for, like, everyone. But for the people nearby… It would be an absolute disaster.

Actually, no Lake Nyos was a disaster, and that was with a population of 14,000 people living around it. Lake Kivu is on the border of Rwanda and the Democratic Republic of Congo. And there are nearly 2 million people living around it.

And it’s also bordered by an active volcano, Mount Nyiragongo, which actually erupted in May of 2021. Half a million people had eo evacuate. Luckily Kivu didn’t explode.

Actually the size of Kivu might be its saving grace. It’s just so big and heavy it can keep that pressurized gas trapped down there.

But don’t relax too much because it also contains huge amounts of methane, which is more prone to the overturn effect.

The upside to methane is that it’s a natural gas, so if you can get it out of the lake, you can sell it. And that’s exactly what’s happening.

Power Plant Plans

In 2015 a new power plant came on line called KivuWatt that’s currently delivering 26 MegaWatts of electricity to the Rwandan power grid. I mean talk about a win-win.

Of course every rose has its thorn. Some experts are concerned that methane extraction can destroy the layer of dense water that keeps the gasses trapped.

And if that doesn’t trigger an explosion directly, it could make the lake more sensitive to other triggers, like Mount Nyiragongo.

On top of that, many of the locals make a living by fishing the lake, and there are concerns that the methane extraction could stir up other toxic gasses that the volcanic vents have been releasing.

To be fair, the Rwandan government is monitoring the water and so far, so good.

But KivuWatt isn’t a perfect solution. At their current rate, they will extract less than 5% of the lake’s methane in 25 years. Plans to expand are in place, but they have moved slowly.

Of course, they kind of have to. Lake Kivu is a time bomb.

Except with a time bomb, at least you know how much time is left.

So next time you crack open a soda, just remember you’re flirting with some dangerous chemistry. and don’t get me started on the sugar, it’s bad for you…So bad for you.

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