WEBVTT - What Makes Some Lakes Explode?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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<v Speaker 1>Lauren Vogelbam. Here today we're talking about a rare but

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<v Speaker 1>incredibly deadly natural phenomenon, exploding lakes a k A. Limnic eruptions.

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<v Speaker 1>A limnic eruption is what happens when deadly gases like

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<v Speaker 1>carbon dioxide explode out of volcanic lakes. Sometimes the carnage

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<v Speaker 1>unfolds on multiple fronts. Just as lethal clouds suffocate humans

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<v Speaker 1>and animals, the abrupt displacement of water is liable to

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<v Speaker 1>create tsunamis. That exact combination of events killed more than

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<v Speaker 1>seventeen hundred people one grim summer day in nine six

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<v Speaker 1>in the West African country of Cameroon. And now scientists

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<v Speaker 1>wonder if an even bigger limnic eruption is in the making.

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<v Speaker 1>But how does such an explosion happen? Let's start with

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<v Speaker 1>water pressure. Water pressure increases with depth. That's why scuba

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<v Speaker 1>divers can't venture too far below the surface without the

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<v Speaker 1>right equipment. The force that's exerted upon a submerged object

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<v Speaker 1>by the weight of all the liquid above it is

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<v Speaker 1>called hydrostatic pressure. Normally, this pressure intensifies by fourteen point

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<v Speaker 1>five pounds per square inch or one kilo pascals or

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<v Speaker 1>one bar for every ten meters of water depth. That's

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<v Speaker 1>about thirty three ft. But the key to limnic eruptions

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<v Speaker 1>lies in temperature. The gases dissolve more easily in cold,

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<v Speaker 1>high pressure water. Limnic eruptions can only occur in deep

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<v Speaker 1>bodies of water with a lot of hydrostatic pressure at

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<v Speaker 1>the bottom. There must also be a significant difference in

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<v Speaker 1>both the pressure and temperature between the surface water and

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<v Speaker 1>the lower depths, With the lower depths being much chillier.

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<v Speaker 1>Stratification will act like a barrier, keeping that dissolved gas

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<v Speaker 1>confined to the lake bottom, where it can't depressurize and

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<v Speaker 1>escape out into the atmosphere. Because it's trapped, the dissolved

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<v Speaker 1>gas accumulates in massive and potentially deadly quantities. Explosions are

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<v Speaker 1>impossible in lakes whose lower and upper water levels intermingle

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<v Speaker 1>on the regular For build up to occur, the water

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<v Speaker 1>also needs a continuous supply of some highly soluble gas,

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<v Speaker 1>like carbon dioxide or methane, and that's where volcanism comes in.

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<v Speaker 1>At localities with active volcanoes, buried magma is liable to

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<v Speaker 1>send methane, CO two and other gases seeping up through

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<v Speaker 1>thin sections of Earth's crust. If a lake is overhead,

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<v Speaker 1>the gas may pass right into the water, traveling by

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<v Speaker 1>volcanic fence and other roots that brings us back to

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<v Speaker 1>Cameroon and to its lakes. NEOs and Monoun both are

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<v Speaker 1>located in a volcanic field, and both lake bottoms are

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<v Speaker 1>oversaturated with carbon dioxide, which underlying magma sends their way.

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<v Speaker 1>On August fifteenth, some of the deep water in Monoun

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<v Speaker 1>that had been loaded up with the dissolved gas ascended

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<v Speaker 1>to the surface. No one knows why this happened. It's

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<v Speaker 1>possible that heavy rainfall and an earthquake or landslide displaced

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<v Speaker 1>some of the lake bottom water. Regardless, as the water rose,

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<v Speaker 1>the dissolved carbon dioxide lurking inside it became depressurized and

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<v Speaker 1>formed bubbles. Those bubbles drove even more of the water

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<v Speaker 1>up to the top of the lake, resulting in a massive,

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<v Speaker 1>foul smelling cloud of carbon dioxide gas. Under the wrong

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<v Speaker 1>set of circumstances, this gas is extremely dangerous to people.

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<v Speaker 1>Large quantities of CEO to cling to the ground and

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<v Speaker 1>displace oxygen, which can lead to death by suffocation. The

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<v Speaker 1>eruption killed at least thirty seven people, and two years later,

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<v Speaker 1>on August twenty one, six, Lake Neo's experienced a limnic

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<v Speaker 1>eruption of its own. Once again, there was a sudden,

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<v Speaker 1>mysterious upheaval of carbon dioxide laden water from its frigid,

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<v Speaker 1>high pressure depths, but this time the body count was

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<v Speaker 1>much higher. Carbon dioxide from the Lake Neo's disaster killed

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<v Speaker 1>approximately one thousand, seven hundred forty six people and more

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<v Speaker 1>than three thousand, five hundred domestic animals. Somewhere from three

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<v Speaker 1>hundred thousand to one point six million metric tons of

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<v Speaker 1>c O two gas burst out of the water with

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<v Speaker 1>enough force to set off a twentys tsunami that's about

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<v Speaker 1>sixty six ft tall. That was the last recorded limnic eruption.

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<v Speaker 1>If you're worried about a killer limnic eruption coming to

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<v Speaker 1>a lake near you, University of Michigan geoscience professor yolks

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<v Speaker 1>Jung says you probably shouldn't be. Lake NEOs and Lake

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<v Speaker 1>Monoon are located just above the equator, where it tends

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<v Speaker 1>to be warm all year round, and there's just no

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<v Speaker 1>way for a limnic eruption to happen in a temperate

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<v Speaker 1>body of water. In places where seasonal temperatures vary widely,

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<v Speaker 1>like in the Great Lakes, lake surfaces often cool down,

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<v Speaker 1>causing the water at that level to sink and swap

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<v Speaker 1>places with the layers of water beneath it. Any gas

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<v Speaker 1>is dissolved in there don't stay trapped. They're released as

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<v Speaker 1>they depressurized nearer to the surface. No gas accumulation, no eruptions. However,

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<v Speaker 1>Young and many of his colleagues have taken a healthy

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<v Speaker 1>interest in Lake Kivu, an up and coming vacation destination

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<v Speaker 1>on the border of Rwanda and the Democratic Republic of

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<v Speaker 1>the Congo. Why because it seems to have all the

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<v Speaker 1>necessary criteria for a truly colossal limnic eruption. The lake

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<v Speaker 1>contains about ten point five billion cubic feet of carbon

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<v Speaker 1>dioxide that's about three billion cubic meters, and two billion

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<v Speaker 1>cubic feet of methane about up sixty billion cubic meters,

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<v Speaker 1>all lurking near the bottom. Were those gases to explode

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<v Speaker 1>from the lake's surface, the two million people who live

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<v Speaker 1>around Kivu might find themselves in jeopardy. One possible solution though,

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<v Speaker 1>harvest those very gases as a possible energy source by

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<v Speaker 1>an extraction barge. Kivu Wat is a one of a kind,

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<v Speaker 1>two million dollar facility that uses an offshore barge to

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<v Speaker 1>draw up water from the lake. It then siphons off

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<v Speaker 1>the methane and sends it to a power plant, generating

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<v Speaker 1>electricity for the area. When life gives you lemons, turn

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<v Speaker 1>it into electricity. Today's episode was written by Mark Mancini

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<v Speaker 1>and produced by Tyler Clang. For more on this and

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<v Speaker 1>lots of other powerful topics lurking in the depths, visit

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<v Speaker 1>our home planet has Stuff works dot com.