Ok now I’ve read it and I can tell you the writer is an idiot.
First, the biggest mass extinction in the history of the planet was the meteor that killed the dinosaurs.
Second, theres no “bubble” of methane in the depths of the ocean or the planet thats waiting to erupt. Its not a volcano. The methane extinctions of the past were caused by a series of chemical reactions that produce methane, that were self supplying and starting. The theory of the methane kill thing basically says that the mass amounts of chemicals we are putting into our ATMOSPHERE and to some degree our oceans, is having chemical reactions with compounds in the ocean and creating methane. Those reactions create more of the compounds that restart the reaction, and it grows exponentially, until it goes out of control and makes a massive excess of methane that floods the atmosphere and the oceans and kills everything.
It is set off by a tipping point of pollution, NOT by a drilling accident. The oil being poured into the ocean could help in this problem…. But you have to keep in mind that ALL of the oil thats been spilled into the ocean as of yet by the spill, is less than 100,000 barrels (assuming the numbers provided are true) worth… and we use what, 3 or 4 million barrels a day in gas?
There is no methane “bubble” for you to worry about. The methane theory is a real one, but I (and I am a chemist) doubt THIS will be the lone thing to set it off, and if it is then we were close already. The natural impact you should worry about is all the dead sea life from the oil, and things like that.