Lake Abraham, in Canada, is filled with beautiful bubbles that, if they pop, will ruin your day on the ice at least two different ways. First, they'll displace oxygen. Second, if they pop anywhere near sparks or fire, they'll explode.
Most of us believe that, once we've weighted down a body and chucked it in a lake, it's the end of the matter. On the contrary! Our misdeeds may have consequences generations later. When the murdered body of someone who was rude to us in the street - or any other type of organic matter - sinks to the bottom of a lake, it is set upon by bacteria. The bacteria digest the matter, and produce gases. Sometimes those gases are just carbon dioxide. Other times, they're something a little stronger, like methane.
The methane rises to the surface in great bubbles. In the case of Lake Abraham, methane's trip to the surface often hindered by ice. The lake, when frozen, is filled with beautiful frozen bubbles. If one of those bubbles is pierced, or the lake thaws, the methane gets out. Unless methane is escaping in such quantities that it displaces all the oxygen in an area, little harm is done. But if someone were to have a fire, or even wave a lighter around as a bubble was pierced, the whole area above the bubble would erupt in flame. Guess what the scientists studying the bubbles immediately did. Guess whether or not they filmed it.
It's a fun thing to watch, but like many fun things to watch it comes with some bad news. Methane is a greenhouse gas. It, along with carbon dioxide and other greenhouse gases, are trapped below permafrost that may not be so permanent anymore. If people keep heating the planet, we might not just have to deal with our own gas, but the gas of generations past.