Disasters

These Exploding Lakes Killed Thousands of People in an Instant

People who live near fault lines just have to know that an earthquake could uplift their entire life at any moment. Just like people who live near volcanoes have to be ready for an eruption, and like people who live near lakes need to be aware that the water could blow up at any time. Wait, what was that last one?

Lake Nyos, shortly after a limnic eruption

Death in a Heartbeat

Yes, sometimes lakes explode to disastrous effect. The two most recent of these natural disasters occurred in short succession, in 1984 and 1986. The first was Lake Monoun. On August 15, 1984, a giant bubble of CO2 rose up from the bottom of the lake, creating a massive tsunami. In the aftermath, rescuers discovered that plant life had been flattened on the eastern shore of the lake, forced to the ground by the giant wave. In a low-lying area further to the east, the effects were much worse: 37 people were suffocated by the bubble of toxic gas. And that was only the beginning.

Two years later, disaster struck again, and this time it was much worse. When nearby Lake Nyos exploded, it did so with horrible force. On August 21, 1986, the people living in the highlands heard a distant boom in the night. When they woke up, they discovered a scene out of a horror movie. Because CO2 is heavier than air, it had rolled down the mountains, through the low-lying villages, and into people's homes. By the morning, more than 1,700 people and 3,000 animals were dead.

The Deadliest Soda

These explosions of deadly gas are called limnic eruptions, and they happen because carbon dioxide has dissolved into the water, just like in a carbonated beverage. If you look at the liquid in an unopened bottle, it appears perfectly still, but when you remove the cap the bubbles appear out of nowhere. The pressure held in by the cap prevented the bubbles from escaping.

Now imagine that region of dormant bubbles is massive, and lies deep at the bottom of a lake. The "cap" is the pressure of the water above, perhaps assisted by an outcropping of rock. But if something happens to shift that water, crumble that rock, or just disturb the carbon dioxide enough, the bubbles will erupt, sending a massive wave and a giant cloud of carbon dioxide out over the land.

Defusing the Bomb

The good news is that these kinds of eruptions can only happen in places where carbon dioxide has seeped into a lake. There are only three known lakes in the world that have such a feature. Lake Nyos and Lake Monoun are nearby neighbors in Cameroon, and Lake Kivu in Rwanda, approximately 1,400 miles (2,250 kilometers) away, is the third.

Lake Nyos, the greater of the two '80s disasters, is about 1 square mile (1.5 square kilometers). Lake Kivu is about 1,680 square miles (2,700 square kilometers). Its shores are also home to approximately two million people, so if disaster strikes here, the loss could be enormous. Fortunately, the tragedies of decades past gave us insight into how to prevent such a disaster from happening again. By using vent pipes to bring the deep, CO2-enriched water to the surface, modern methods allow for controlled releases of the gas.

Limnic Eruptions: When Lakes Explode

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Key Facts In This Video

  1. The 1986 limnic eruption of Lake Nyos suffocated everything within a 25 km radius, killing more than 1,700 people. 00:11

  2. Most lakes don't experience limnic eruptions because their water circulates with yearly changes in temperature. 01:28

  3. Pipes were installed in Lake Nyos and Lake Monoun to allow the escape of carbon dioxide. 02:27

Written by Reuben Westmaas March 8, 2018

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