With Speed and Violence Fred Pearce - Global Commons Institute

ut even so, they could not have delivered the amount of carbon-12 required.
Only one last source—big enough and accessible enough to unleash a
climatic eruption—was left. That, Dickens suggested, had to be the vast
stores of methane that geologists have recently been discovering frozen in
sediment beneath the oceans: methane clathrates.
Methane clathrates are an enigma. They have until recently escaped the
attention of oil and gas prospectors, because they don't turn up in the kind of
deep and confined geological formations where prospectors traditionally
look for fossil fuels. Nor are they the product of current ecosystems, such as
tropical and Arctic bogs. They are generally close to the surface of the ocean
floor but frozen—confined not by physical barriers but by high pressures and
low temperatures, in a lattice of ice crystals rather like a honeycomb.
Scientists still debate exactly how and when they were formed, but they seem
to arise when cold ocean water meets methane created by microbes living
beneath the seabed. Seismic surveys have revealed these structures in the
top few hundred yards of sediments beneath thousands of square miles of
ocean. They exist unseen, usually just beyond the edge of continental shelves.
Many of these frozen clathrate structures trap even larger stores of gaseous
methane beneath, where heat from Earth's core keeps them from freezing.
Dickens estimates that between i and 10 trillion tons of methane is tied up
today in or beneath clathrates. But its confinement may not be permanent.
Release the pressure or raise the temperature, and the lattices will shatter,
pouring methane up through the sediment into the ocean and finally into the
atmosphere. It seems that some such event must have happened 55 million
years ago. Moreover, if this was the source of the great release of carbon-12,
it would also explain why the extinctions appeared to be most serious in the