Methane
is a gas at room temperature and pressure and a major fraction of natural gas.
It forms underwater as a by-product of bacterial decomposition of organic
sediments. Under high pressure and
low temperature it reacts with water to form a solid called a
gas
hydrate. Thousands of tons
of this material lie trapped in sediments spread out over enormous areas.
It can be detected by acoustic reflection and has been “observed” on
most of the world’s continental margins. It is also found in shallow deposits
below permafrost in polar regions.
Estimates
on how much methane is locked up in this form are highly speculative but go as
high as 10,000 gigatons of carbon, double the amount of all known fossil fuel
sources. This has interested
Congress who have appropriated money to study it as a fuel for the future.
However, to date no significant concentrations of it have been located.
Japan
will be the first nation to actually
explore the potential for recovering methane from the sea and has recently
started a drilling project off their shores to try and recover it in commercial
quantities. They are trying to find
out is if sedimentary strata bearing gas hydrates can be induced to collect in a
well.
What
interests climatologists is the potential for sudden releases through a slight
warming up of the sea. Methane is a
greenhouse gas. They speculate that
a slight warming near the end of the last glacial period, 18,000 years ago, and
the release of the gas, may have sped up the whole process.
For
more, check the November 1999 issue of Scientific American and an article titled
“Flammable Ice," or
here for a US Geological Survey site on the subject.
01/08/04 19:13