"The evacuation order comes on the heels of a warning by the Goma Volcano Observatory (OVG), which monitors the pulse of Nyiragongo and the Nyamuragira volcano, 13 kilometres (nine miles) away.... In the first two scenarios, Nyiragongo would erupt again, sending renewed lava flows southwards towards Goma and Gisenyi, destroying buildings in their path before reaching Lake Kivu.... But in the worst-case scenario, lava flows from Nyiragongo would combine with volcanic activity under the floor of the lake... In this scenario, 'a limnic eruption would take place and dissolved gas in the lake's deep water would rise to the surface, especially CO2, asphyxiating all living beings around Lake Kivu on the Congolese and Rwandan side.'"
From "'Limnic eruption': DR Congo's volcano nightmare" (France 24).
"The phenomenon first came to the world's attention in August 1984, when 37 people mysteriously died at Lake Monoun in western Cameroon. Scientists found that dissolved carbon dioxide (CO2) gas in the depths of the lake had erupted, creating invisible clouds at the surface that were borne by winds into homes and fields, snuffing out life.Two years later, more than 1,700 people and thousands of cattle died in Lake Nyos, also in Cameroon, strengthening the belief that earthquakes and volcanic activity can trigger these unusual events."AND: Here's a BBC article from last October, "In central Africa is a deep lake that has a dangerous propensity to explode – but tapping it as a source of energy could help avert disaster":
Scientists have found what may be evidence of at least one previous limnic eruption at Kivu that likely occurred between 3,500 and 5,000 years ago, and possibly several more recent ones....
If the water becomes completely saturated with dissolved gases, any additional CO2 or methane injected into the lake will be forced to bubble out of solution, rise and be released into the air. Eruptions can also be caused when something forces the deep water with its dissolved gases to mix with the layers above, reducing the pressure on the gases and allowing them to quickly come out of solution and escape, similar to the effect of shaking a can of soda and then opening it....
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1 comment:
Bart writes:
One problem with CO2 is that it is heavier than air, so it settles into low spots, But it gets worse, in that CO2 does not kill by suffocating, but instead is fairly toxic in its own right. Concentrations >10,000 ppm [= 1%] will kill, even at normal oxygen levels.
That's why on brewery tours they typically do not allow anyone in a wheelchair, or under 5 feet tall to participate. The low areas could be a fatal risk. Greenhouse operators, and basement marijuana growers have died when their CO2 supplementation systems -- plants prefer 1500 ppm -- have not stopped injecting CO2 because the sensor system failed.
Similarly, the CO2 scrubbers [Lithium Hydroxide] on crewed spacecraft are an absolutely essential element of life-support systems. In low-Earth orbit they can be replaced easily if they fail, which they do. Trips to the Moon were of short duration, and they carried enough spares.
CO2 scrubbing will be one of the really big challenges for what is a 7 month trip to Mars, one way, and with no possible resupply. It's nasty stuff, and it doesn't require much to kill things. In fact, it's commonly used by growers of "organic" grain to kill all the bugs in rail cars full of grain, because once it's purged there's no trace of possible residue.
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