There are media reports coming out that, in addition to oozing a few bazillion gallons of oil into the Gulf of Mexico, the Deepwater Horizon site is on the verge of unleashing a massive methane bubble that will cause global warming on an inconceivable scale, leading to the planet heating up to where we will all be immolated and life as we know it will end. These reports claim that the same thing happened 250 million years ago at the end of the Permian period when there was a mass extinction, allegedly caused by a methane bubble of indeterminate origin, that wiped out 90 percent of the species then living.
This is absolute and shameless douchery on the part of anyone who is propagating these reports. There was, indeed, a mass extinction at the end of the Permian period. It was so massive that life on Earth came very close to being wiped out and it took the biosphere something like 75 million years to recover. To put this 75 million number in perspective, homo sapiens has been dragging its knuckles around the planet for about 20 thousand years. Whatever happened at the end of the Permian period was some powerful bad juju, but the fact of the matter is that no one has a clue what happened.
The problem is that the geological record from 250 million years ago is very sparse. The boundary between the Permian and the Triassic period, where the extinction event occurred, has been preserved in only three places in the world; South Africa, central Russia, and reportedly, in a section of China. That limited geological record tells us that at the end of the Permian period, there was an abundance of life and, at the beginning of the Triassic period, bupkus, nada, zilch. The boundary between the Permian and the Triassic, where it has been preserved, is characterized by a thick layer of black, carbonaceous gunk...the remnants of trillions of tons of animal and plant life that checked out. Oxygen isotope samples indicate a substantial increase in temperatures at this boundary (maybe 10 degrees Celsius). This is what is known about the Permian mass extinction. Truth.
So, what caused this catastrophe? -- and this was a catastrophe. No one knows. The extinction at the end of the Cretaceous period that wiped out the dinosaurs was recent enough that the geological record is mostly preserved and it is, at this point, unambiguously clear that it was caused by a big honking meteorite/comet slamming into the Earth at cosmic speeds off-shore from the Yucatan Peninsula. Buh-bye dinosaurs.
The Permian extinction is much more mysterious. The temperature increase suggested by oxygen isotope samples led some geologists to speculate that extreme global warming caused it...and indeed, there is evidence of massive volcanic eruptions in India at about that time period (India being far to the south and not part of Asia at the end of the Permian period). However, estimates of the carbon dioxide released by those eruptions showed that the warming associated with that release was far short of what would be required to cause the indicated temperature rise. It was then speculated -- and let me stress the word "speculated" -- that the temperature rise attributable to the volcanic emissions was enough to cause sufficient warming at the poles to stimulate the release of massive methane bubbles that were enough to account for the indicated temperature rise.
However, other geologists have looked at the record and claimed that the temperature rise is an expected consequence of the death and decay of virtually every living thing on the planet, which releases methane on a massive scale. These geologists would claim that the origin of the Permian extinction is unknowable based on presently available information, but it is not inconsistent with a massive meteor impact or a massive solar fluctuation. Other geologists have rejected the idea that the Permian extinction was the result of a single catastrophic event and have argued that the assembly of the supercontinent, Pangea, at the beginning of the Permian period radically altered ocean and air circulation around the globe, which set in motion climatic changes that most species then living were unable to adapt to and became extinct. Keep in mind that the geologic record from that time period is so incomplete that it is impossible to determine whether the Permian extinction occurred suddenly or over the course of several hundred thousand years.
The moral of this story, kids, is that any "science" you read in the mainstream media has nothing to do with science. It is junk science being used to push an agenda.
A very accessible book on the Permian extinction is Michael J. Benton's "When Life Nearly Died". An even more entertaining and readable discussion of the Cretaceous (buh-bye dinosaurs) extinction is Walter Alvarez' "T-Rex and the Crater of Doom". References to alternate explanations for the Permian extinction can be found in Frank Decourten's "The Broken Land" and Scott Baldridge's "Geology of the American Southwest'.