The greatest mass extinction in Earth's history was caused by a gigantic eruption of methane gas from deep in the oceans, 250 million years ago.

That is the theory of a Northwestern University scientist, who says similar, if smaller, disasters have occurred regularly throughout history.

In his view, methane produced by microbes collects under pressure at the bottom of the ocean and blows outwards in a similar fashion to a bottle of soda after it has been shaken. The eruption could cause destructive tsunamis at the coasts and a continent-sized conflagration as the clouds of methane gas ignite, sending firestorms around the world.

Using state of the art computer animation, the story of this mega methane disaster is shown in unbelievable realism.