Originally Posted by TheDoc

Having a localized release of methane is very bad.

The East Siberian Arctic Shelf, which covers 2 million square kilometers of sea floor is across a large enough area that it doesn't shut life down. And it's the largest releaser of methane on the planet, more than the rest of the oceans combined together. The oceans are the number one releaser of methane, however the water filters it and it happens across the entire globe.

If the methane was to build in an area, spewing out and can't be filtered - strong enough to kill life. It means it's strong enough to ignite. All it takes is cloud lightening, and you have a monster fire ball.