It was a peaceful summer evening in the rainforest of Cameroon in Africa, the date was August
21st, 1986, and it was 9:30 pm.
All of a sudden, loud rumbling was heard, causing confused people to awake and venture
outside.
Less than a minute later, these people who went to investigate fell to the ground, lifeless.
As a 50 meter or 164 foot tall cloud of lethal carbon dioxide advanced across the landscape,
it killed all humans and animals in its path.
This killed almost everyone in a 10 kilometer or 6.2 mile radius with fatalities among people
and livestock occurring up to 25 kilometers or 15.5 miles distant of Lake Nyos, totaling
more than 1,700 people.
What had just occurred was a catastrophic release of 1.6 million metric tons of carbon
dioxide gas in a short timespan from Lake Nyos in a rare natural disaster known as a
limnic eruption.
For many years, it was assumed that limnic eruptions could only occur within Cameroon
at specific crater lakes at certain volcanoes in the country, as since 1900 both limnic
eruptions on the planet which were observed occurred within the country.
Yet, one recent study showed evidence that a much larger limnic eruption occurred in
sections of modern day Rwanda and the Democratic Republic of Congo arouns 2000 BCE at a section
of Lake Kivu.
However, this type of natural disaster does not merely occur or have the potential to
occur in a narrow strip of Africa, as in recent years it was discovered that another volcanic
lake can and has historically also produced limnic eruptions.
And yet, many people who live adjacent to this lake in a separate part of the world
are completely unaware that a similar hazard exists.
What I am referring to is the caldera lake of the Quilotoa volcano in Ecuador which is
known as Laguna de Quilotoa.
This lake was the site of 4 limnic eruptions during the 18th century, the last of which
occurred on February 4th, 1797.
Of course, the previous and following statements are based on a scientific paper which could
be wrong but in my opinion is likely but not certainly accurate.
Per a direct quote from a scientific paper which is referenced on screen, this event
"originated due to an earthquake under the Tungurahua volcano, generated flames and suffocating
gases in the lake, and destroyed the cattle on the slopes of Quilotoa".
If such a repeat event were to occur today, it could in my opinion result during a worst
case scenario in hundreds or thousands of casualties.
Before I describe why limnic eruptions occur, let me first describe where they occur, as
four factors are needed.
All known limnic eruptions mentioned in this video occurred in a narrow range of latitudes
between 8 north and 8 south.
Specifically, it has occurred in parts of the world which essentially stay the same
temperature yearround.
With this being said, it is not unreasonable to assume that limnic eruptions could theoretically
occur in a larger range of latitudes.
The second factor is that a limnic eruption can only occur at a lake which is meromictic,
meaning that it has two or more layers which do not intermix.
Third, a persistent carbon dioxide source is needed which emits large volumes of gas
into the body of water which dissolves, and so far this has only been known to occur at
certain lakes at specific volcanoes.
Lastly, although limnic eruptions could originate at shallower lakes, all known lakes which
have produced limnic eruptions are quite deep, being at least 91 meters or 300 feet deep
at their deepest point.
Limnic eruptions can occur when large volumes of carbon dioxide are dissolved in a lake
which at some depth overlies a body of magma which produces the gas.
This gas largely remains at depth in the lower section of a lake, not interacting with higher
carbon dioxide poor layers.
Eventually, if enough dissolved carbon dioxide is located in the lake, a limnic eruption
might be triggered, whether it be through a volcanic eruption, an earthquake, or another
possible reason such as a landslide.
This causes the carbon dioxide dissolved in the bottom of the lake to rapidly rise to
the surface, causing a runaway reaction where much of the carbon dioxide in the lake escapes
in a short period of time.
It thereafter advances downslope since carbon dioxide is denser than air, killing all animals
and people the invisible cloud of gas encounters.
Although a known limnic eruption has not occurred from Laguna de Quilotoa since February 4th
1797, recent measurements suggest that an underlying magma chamber or perhaps cooling
body of magma releases approximately 330 tons of carbon dioxide every day.
Additionally, I want to note that limnic eruptions do not literally involve a lake exploding,
as this has instead been a phrase popularized by the media to describe this natural disaster.
Since this video might cause a commotion of sorts, I am including the following sentences
in a rapid fire Q&A format so this video's statements are NOT taken out of context.
Am I telling people who live nearby or tourists to avoid Quilotoa and its surrounding area
or evacuate right now?
No.
The area in question is my opinion is currently safe to visit and/or live in.
Is a limnic eruption of Quilotoa imminent?
Is a limnic eruption going to occur this year?
Do we know when its next limnic eruption will occur?
The answer to these three questions is no, we don't know, and we don't know.
This video was not made to scare tourists or people off as the area is quite beautiful
and interesting as instead this video was made to make people who live in the region
or tourists who plan to visit aware of an ever present hazard which has always existed
for the last several hundred years that they might have otherwise been unaware of.
Thanks for watching!
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