"They died in the houses, in streets, outside the forest, in the stream."

June 11, 2010 9:43 AM

One of the most dangerous places on Earth, Lake Nyos in northwestern Cameroon sits atop a volcanic source. Early evening Aug. 21, 1986, a cloud of deadly CO2 erupted from the lake surface, killing an estimated 1,700 people and 3,000 cattle.. Now people are trying to tame it (Via NucleophilicAttack via Metachat)
posted by The Whelk (29 comments total)

Wow. I was trying to describe the 1986 event to someone just the other day. I'll have to send them this link.
posted by brundlefly at 9:52 AM on June 11, 2010

I remember freaking out over that story as a kid. I'm glad SCIENCE is on the case.

Also, Valley of Death.
posted by DU at 10:00 AM on June 11, 2010

Wait did you mean 17,000 people.. or 1. Or 7000?
posted by ReeMonster at 10:12 AM on June 11, 2010

Worth repeating.
posted by Bathtub Bobsled at 10:17 AM on June 11, 2010

Wait did you mean 17,000 people.. or 1. Or 7000?

There's an interesting post somewhere that had this in a link:

The U.N. Disaster Relief coordinator in Geneva put the toll at 1,746, but the number may be far higher.
posted by Bathtub Bobsled at 10:19 AM on June 11, 2010

The Lake Nyos incident is precisely why I'm wary of carbon sequestration plans involving gaseous CO₂ storage underground.
posted by dephlogisticated at 10:25 AM on June 11, 2010 [1 favorite]

Yeah, I remember reading about this shortly after it happened. I vaguely recall that scientists believed that the release of CO2 was caused by boats on the surface moving too rapidly, creating a converging wavefront that pushed into deep waters. So it could have happened basically any time, it was just a coincidence that some boats moved at the right distance and speed to cause a compounded wavefront.
posted by charlie don't surf at 10:26 AM on June 11, 2010

CO₂ isn't deadly in and of itself, the only problem is that if the concentration gets to high there's no oxygen left to breath. It can happen with any gas, like when teenagers died after crawling into a huge helium balloon.
posted by delmoi at 10:34 AM on June 11, 2010

CO2 isn't deadly in and of itself

From the NIOSH page on carbon dioxide:

"Basis for original (SCP) IDLH: The chosen IDLH [immediately dangerous to life and health] is based on the statements by ACGIH [1971] that a 30-minute exposure at 50,000 ppm produces signs of intoxication, and a few minutes of exposure at 70,000 ppm and 100,000 ppm produces unconsciousness [Flury and Zernik 1931]. AIHA [1971] reported that 100,000 ppm is the atmospheric concentration immediately dangerous to life. In addition, Hunter [1975] noted that exposure to 100,000 ppm for only a few minutes can cause loss of consciousness."

So at large concentrations it IS deadly. But it is unlikely to find those concentrations in nature, and your point is probably correct that all those people died of lack of oxygen, rather than of CO2 poisoning.
posted by Danf at 10:41 AM on June 11, 2010

I think they ended up identifying a small landslide as the most likely trigger. That's not as fun though.
posted by vapidave at 10:46 AM on June 11, 2010

Worth repeating.

Not really.
posted by applemeat at 10:50 AM on June 11, 2010

...and your point is probably correct that all those people died of lack of oxygen, rather than of CO2 poisoning.

In my opinion, that's partially correct. Between the C02 and the usual Hydrogen Sulfide present in volcanic eruptions, then yes. This would have blocked their bodies ability to absorb oxygen.

However, with the vomiting blood and warm sensations, I believe there was hydrogen chloride present, as well, although I only have the symptoms suggest such is the case. I'm not sure which types of geothermic disturbances cause hydrogen chloride emission.

Perhaps it was a little of both.
posted by Bathtub Bobsled at 10:52 AM on June 11, 2010

Millions of people live around Lake Kivu. If that blew it would be so much worse.
posted by gottabefunky at 11:07 AM on June 11, 2010

Carbon dioxide is more deadly than nitrogen or helium, which merely displace oxygen in the lungs. The binding of carbon dioxide to hemoglobin allosterically displaces oxygen, and vice versa. Therefore a rise in carbon dioxide levels will not only displace oxygen in your lungs, it will also decrease your blood's ability to absorb and transport oxygen. While the end result is the same (hypoxia), carbon dioxide is more efficient at causing this than inert gases, though not as efficient as carbon monoxide.

Also worth noting is that a rise in carbon dioxide levels will usually trigger panic reactions, whereas a drop in oxygen will not. That's ultimately the difference between dying peacefully by falling asleep and dying while staggering around on the floor, gasping.
posted by dephlogisticated at 11:22 AM on June 11, 2010 [1 favorite]

CO2 isn't deadly in and of itself, the only problem is that if the concentration gets to high there's no oxygen left to breath.

This is completely wrong. If CO2 reaches 9% of your atmosphere, you will die even if the other 91% is pure oxygen

Toxic levels of carbon dioxide: at levels above 5%, concentration CO2 is directly toxic. [At lower levels we may be seeing effects of a reduction in the relative amount of oxygen rather than direct toxicity of CO2.]

And when the CO2 hits about 7% to 10% of your ambient air, you DO die. Even if the rest is O2. It's CO2 narcosis, and it shuts you down.

posted by Kirth Gerson at 11:31 AM on June 11, 2010 [1 favorite]

could this happen in iceland? in the pacific northwest (where we have many volcanoes as well)?
posted by seawallrunner at 12:37 PM on June 11, 2010

Also, Valley of Death.

The circle-of-death aspect is pretty creepy:

As soon as the snow melts at the Valley, a great number of mice rush there and die after inhaling the poisonous substance. Dead mice attract foxes that also die poisoned by hydrogen sulfide. The smell of dead foxes like a magnet attracts bears and gluttons - the fate of these animals is easy to predict. However, that is not all: Steller`s sea eagles notice dead bear bodies descent to the Valley in search of food and stay there forever.

posted by odinsdream at 12:42 PM on June 11, 2010 [1 favorite]

I remember reading about this in a "How Stuff Works" article sometime ago. I found it striking that local villages built up a mythos around this event involving evil spirits that live in Lake Nyos and Lake Monoun that periodically emerge to massacre people in the surrounding areas. There's more information in this article.
posted by superquail at 1:00 PM on June 11, 2010

Interestingly (at least to me) is this fire suppression gas mixture which lowers the 02 in a space so it does not support combustion. What makes people survive in this gas mixture is INCREASED carbon dioxide.

I have been a demonstration subject in which I was placed in a plastic chamber, with an 02 monitor, and this gas was pumped in and the oxygen content went down to the extent that I should have lost consciousness, but I didn't.

"The normal atmosphere in a room contains approximately 21% oxygen and less than 1% carbon dioxide. If the oxygen content is reduced below 15%, most ordinary combustibles will not burn. INERGEN agent will reduce the oxygen content to approximately 12.5% while increasing the carbon dioxide content to about 4%. The increase in the carbon dioxide content increases a person's respiration rate the body's ability to absorb oxygen. Simply stated, the human body is stimulated by the carbon dioxide to breathe more deeply and rapidly to compensate for the lower oxygen content of the atmosphere."

A very weird experience.
posted by Danf at 1:19 PM on June 11, 2010

CO₂ is dangerous stuff, there's a good reason why winemakers used to carry a candle with them every time they went down into the fermenting cellars even after electric lights became commonplace; an electric light won't go out and warn you if there are elevated levels of carbon dioxide in the air.
posted by PontifexPrimus at 1:38 PM on June 11, 2010

This is completely wrong. If CO2 reaches 9% of your atmosphere, you will die even if the other 91% is pure oxygen

Acknowledged.

But if you consider odinsdream's earlier comment, do you entertain the possibility that the CO2 poisoning was comorbid with blood toxicity of another compound? Hydrogen sulfide/chloride, perhaps? Once again, I'm not sure if the symptoms described in the article indicate Hypercapnia, unless the lack of oxygen produced hysterical hyperventilation causing secondary physical effects.

I condede, I'm going on what I recall from the safety documentation we had to read before my 200 level chemical engineering courses, so it in no way reflects any actual medical knowledge. I'm just curious if I think I know more than I do.
posted by Bathtub Bobsled at 1:47 PM on June 11, 2010

"could this happen in iceland? in the pacific northwest (where we have many volcanoes as well)?"

Crater Lake in Oregon would be a pretty good candidate if the magma beneath it starts to rise again. The lake has to be deep (high pressure) for the CO² to dissolve and concentrate. Something similar but without the lake water to store and release the CO² catastrophically as at Lake Nyos has been happening in Mammoth Mountain CA where some of the vegetation and small animals have died.
posted by vapidave at 1:53 PM on June 11, 2010 [1 favorite]

Hydrogen sulfide (aka sour gas) is extremely poisonous. 200-300 ppm are dangerous and roughly twice that is deadly.
posted by warbaby at 1:56 PM on June 11, 2010

Here's a very good summary with pictures
posted by warbaby at 2:08 PM on June 11, 2010

I was thinking monkey knife fights with villagers through stampedes in steaming water

...no, this is good too. The whole volcano thing. S'pretty violent. N'stuff.
*looks off wistfully*

Nobody witnessed the event, but...

Ah, yeah. Journalism. No one witnessed the silent, invisible, lethal cloud of gas that came out of nowhere in the middle of the night and killed anyone nearby. Hn. Weird.
posted by Smedleyman at 4:32 PM on June 11, 2010

In a weird way this reminds me of seeing victims of Pompeii in National Geographic when I was a kid.

Give the term "caught out" some real weight.
posted by bwg at 4:38 PM on June 11, 2010

Volcanic CO2-seeps aren't only beneath African lakes. When nearly pure CO2 pools itself in a spot near your village, it's called a Mazuku. This vid shows the pool in eerie 3D via a smoke marker. Lake Nyos also appears in a Nat Geo Special.
posted by billb at 6:28 PM on June 11, 2010

But if you consider odinsdream's earlier comment, do you entertain the possibility that the CO2 poisoning was comorbid with blood toxicity of another compound?

Yes, certainly.

I was responding to delmoi's assertion that CO2 is non-toxic, which is both common knowledge and wrong. I see that assertion all over the Internet, whenever the subject of CO2 comes up, and it's always stated as incontrovertible fact. I think this is the third time I've tried to correct it here on MetaFilter.
posted by Kirth Gerson at 6:33 PM on June 11, 2010

Well Kirth that happens. I have been lying about how fixed wings generate lift for about 20 years. In my defense though the plane flew despite the moving runway and I still hold the gender of the first child has nothing to do with the gender of the subsequent child.
If you're really feeling quixotic you can join me in my endeavor to make every wikianswer at least sniff the toes of veracity.
posted by vapidave at 8:18 PM on June 11, 2010 [1 favorite]