This creates a dangerous cloud of gas that can be fatal to those around the lake. This phenomenon was unheard of until 1984, when a lake in Cameroon exploded and produced a cloud of gas that killed 37 people. Another Cameroonian lake exploded in 1986, killing about 1,700.
In this video, you can see huge amounts of flammable methane gas spewing from various frozen lakes around the world. Not only does this demonstrate how dangerous the lake would be if it thawed, but relieving the lake of its methane and burning it allows it to enter into the atmosphere as CO2.