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![A Landsat image of Lake Nyos](http://www.scienceiq.com/Images/FactsImages/nyos_web.jpg)
But if something happens to disturb the layers (like shaking the soda can!), the dissolved gas can come rushing to the surface and form a deadly cloud that spreads around the shores of the lake. A landslide, an earthquake, or even a big storm can set it off.
Carbon dioxide is a normal part of the air we breathe, but only a tiny part (0.3%). A cloud of carbon dioxide gas contains no oxygen, so we would suffocate if we breathed it. Carbon dioxide is heavier than air, so when the lakes 'burped,' the cloud stayed close to the ground, killing the people and animals near the lake shore. Last year, scientists stuck a vent pipe down to the bottom of both lakes. They hope this will let the trapped gas escape slowly and not build up to dangerous levels.