Are Volcanic Lakes Dangerous?

Volcanic lakes can be very dangerous, especially when there is volcanic activity. “Nature” posted an article online that discusses the hazards with a focus on Lake Kivu in Africa.

A lakeful of trouble: Africa’s Lake Kivu contains vast quantities of gas, which makes it both dangerous and valuable. … Lake in an old volcanic crater or caldera, Iceland

In late 2001, Mount Nyiragongo in the Democratic Republic of the Congo (DRC) was growing restless. Plumes of smoke issued from the central crater, alarming volcanologists in the nearby city of Goma. Then, on 17 January 2002, lava fountained from a fracture on Nyiragongo’s southern flank. The molten rock snaked down the sides of the volcano and razed the centre of Goma… the lava streamed into nearby Lake Kivu, generating a plume of water vapour that clouded the area for days1.

More than 100 people were killed and nearly 300,000 people fled their homes. The only obvious refuge for the displaced people was along the shores of the lake. But Kivu poses its own threats. Beneath its placid surface, the lake contains 300 cubic kilometres of carbon dioxide and 60 cubic kilometres of methane. A disruption to the lake — such as a bigger, closer eruption — could cause a gas burst, with potentially deadly consequences for the roughly 2 million people who live along Kivu’s shores…

Lake Kivu lies in the Great Rift Valley, where tectonic forces are slowly ripping Africa apart. That movement brings up molten rock, which releases carbon dioxide that seeps into the bottom of Lake Kivu. Bacteria convert some of the carbon dioxide into methane, and other bacteria produce methane by breaking down organic matter in the deep waters …

Residents around the lake have known about the dissolved gases for many decades, but it wasn’t generally thought to be a hazard. Then, in 1984, carbon dioxide erupted from Lake Monoun in Cameroon, killing 37 people. Two years later, another Cameroonian lake, Lake Nyos, spat up 0.3–1 cubic kilometres of carbon dioxide, asphyxiating more than 1,700 people…

Carbon dioxide is denser than air so, when it emerged, it hugged the ground, smothering everything as it spread up to 26 kilometres from the lake…

Latent threat

There are no historic records of …eruptions in Lake Kivu. But gaps in layers of plankton fossils at the bottom of the lake suggest that such paroxysms have struck several times in the past 5,000 years4. If Kivu were to undergo a(n) eruption soon, it would dwarf the Nyos disaster. Kivu is more than 3,000 times larger and contains more than 350 times as much gas as was released by Lake Nyos. Kivu’s shores are also densely populated…

Ever seen a volcanic lake?  No? If you’ve been to Yellowstone National Park, you’ve visited one, Yellowstone Lake. And Yellowstone National Park is  a volcano is edging it’s way to an eruption. You can send me your comments below. I’d like to hear what you think!

 

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