For several days, bloggers and journalists have been passing around a news story about how the BP oil disaster will unleash a "giant methane bubble" and initiate a mass extinction. Yes, it's a myth. And we've busted it.
In this article, called "Doomsday: How BP Gulf disaster may have triggered a 'world-killing' event," a guy named Terrence Aym takes some information he got from a "Mega Disasters" TV special on undersea methane bubbles and mixes it with comments about how there are "giant rifts" beneath the sea and an "information blackout." He proposes that a "twenty mile methane bubble" dislodged by the BP oil disaster will erupt from the ocean floor, causing tidal waves and giant explosions. The sad part about all this is that news organizations and blogs took the story seriously.
While it's true that there are methane bubbles (and methane ice) beneath the ocean floor, they are not about to erupt from Gulf and destroy all life on Earth. This morning I spoke with two Earth scientists, Dave Valentine of UC Santa Barbara and Chris Reddy of the Woods Hole Oceanographic Institute, who study methane and oil seeps from the sea floor. Valentine has just been out to the Gulf to study the methane levels there, and told io9:
During our recent cruise to the Gulf we observed significantly elevated levels of methane at water depth greater than 2500 feet, in the vicinity of the Deepwater Horizon spill site. While the total quantity of methane and other hydrocarbons is enough to cause problems with the regional ecosystem, there is no plausible scenario by which this event alone will cause global-scale extinctions.
So yes, there is a methane seep. No, it will not cause tidal waves or explode.
Another fishy fact in the methane bubble doomsday story is Aym's description of how methane bubbles are what caused the End Permian mass extinction event 250 million years ago - a mass extinction that I wrote about recently, here. Many scientists do believe that atmospheric changes and ocean anoxia (de-oxygenization) were to blame for that extinction - but even Gregory Ryskin, the scientist whose highly speculative work is cited in the article, doesn't try to claim this as the sole cause, nor does he believe that one bubble of methane could bring down the biosphere instantly. The End Permian extinction took millennia to happen.