http://www.nature.com/nsu/030818/030818-16.html
Boiling
seas linked to mass extinction
Methane belches may have catastrophic consequences
22 August 2003
TOM CLARKE
CAPTION:
"Exploding ocean methane could have had the force of 100
million
megatons of TNT. © Alamy.com"
QUOTE:
"All the fountains of the great deep burst forth and the
floodgates
of the heavens were opened", Genesis 7:11
A massive methane explosion frothing out of the world's oceans
250 million years ago caused the Earth's worst mass extinction,
claims a US geologist.
Similar, smaller-scale
events could have happened since, which
might explain the Biblical flood, for example, suggests Gregory
Ryskin of Northwestern University in Evanston, Illinois1.
And they could happen again: "It's a very conjectural idea
but it's too important to ignore," says Ryskin.
Up to 95% of Earth's
marine species disapeared at the end
of the Permian period. Some 70% of land species, including
plants, insects and vertebrates, also perished. "It's arguably
the single most important event in biology but there's
no consensus as to what happened," says palaeontologist
Andrew Knoll of Harvard University in Cambridge, Massacheusetts.
Ryskin contends that
methane from bacterial decay or from
frozen methane hydrates in deep oceans began to be released.
Under the enormous pressure from water above, the gas dissolved
in the water at the bottom of the ocean and was trapped there
as its concentration grew.
Just one disturbance
- a small meteorite impact or even a
fast moving mammal - could then have brought the gas-saturated
water closer to the surface. Here it would have bubbled out of
solution under the reduced pressure. Thereafter the process
would have been unstoppable: a huge overturning of the water
layers would have released a vast belch of methane.
The oceans could easily
have contained enough methane to explode
with a force about 10,000 times greater than the world's entire
nuclear-weapons stockpile, Ryskin argues. "There would be
mortality
on a massive scale," he says.
"It's a wacky
idea," says geologist Paul Wignall of the University
of Leeds, UK, "but not so wild that it shouldn't be taken
seriously."
There is evidence that the oceans stagnated at the end of the
Permian period. And the chemical signature in fossils of the
time hints there was a massive change in the amount of atmospheric
carbon dioxide. Carbon dioxide would have been produced as methane
broke down or exploded in the atmosphere.
After all, belches
of trapped methane from lakes and oceans
are "a rare but well-known maritime hazard", Wignall
adds.
Flood warning
The same phenomenon
could explain more recent events, such
as the Biblical flood, Ryskin also argues. An eruption from
Europe's stagnant Black Sea would fit the bill. There is even
some geological evidence that such an event took place
7,000-8,000 years ago.
Other sluggish seas
might still be accumulating methane
at their depths and could represent a future hazard,
Ryskin adds. "Even if there's only a small probability
that I am right, we should start looking for areas of the
ocean where this might be happening," he argues.
References
1. Ryskin, G. Methane driven oceanic eruptions and mass
extinctions. Geology, 31, 737 - 740, (2003)
