Silent but deadly. Literally.
Nobody knows what triggered it, but on August 21st, 1986, the lake exploded -- actually exploded. A column of water over 300 feet high erupted into the air, and with it, enough gas to cause a small genocide. Hundreds of thousands of tons of carbon dioxide shat out at 60 miles an hour, while a mini-tsunami of water cascaded down at the same time. When the air cleared, 1,746 people were dead. The nearby town of Nyos had 800 residents, and only six survived the lakesplosion.
In 2001, French scientists finally figured out a way to make sure Lake Nyos would never kill again. The bottom of the lake now hosts pipes that carry a constant stream of gas far away. Plus, an alarm system has also been installed to warn the lakeside villages in case the silent killer returns, giving them some time to sprint 15 miles to avoid being lake-farted to death.