From: Smigrodzki, Rafal (SmigrodzkiR@msx.upmc.edu)
Date: Wed Mar 27 2002 - 11:32:11 MST
Mike Lorrey [mailto:mlorrey@datamann.com]
wrote:
Rafal's comments about volcanic outgassing are a bit
overdone. There is
nowhere near enough volcanic activity around subduction
zones to allow
for outgassing of all CO2 (especially since there isn't
enough O2 for
all the carbon)
### Thermal carbonate dissociation does not need oxygen. The
amount of elemental carbon in sediments is minuscule compared to the mass of
carbonate.
, although there is a greater proportion than at one
time. Note that as the Moon orbits further and further from
the Earth as
it drains radial momentum from Earth's rotation, its tidal
influence
decreases and thus tectonic activities slow down.
### Do you know precisely how much volcanic activity is
there, and how much CO2 is being released, in relationship to the amount
sequestered in sediments? Can you point me to any authoritative text
implying that there is a long-term imbalance between the two processes,
impacting on Earth's ability to sustain life (in the time until the Sun
becomes a red giant)?
Also, lunar tides are not the only source of energy for
tectonic activity - please remember heat from radioactivity.
Nor does subduction do anything about carbonates deposited
outside of
subduction areas. The Great Barrier Reef, for one, is not
subducting and
is one of the great modern carbon sequestration areas, as is
the
Carribean basin. Another sequestration area is the Southern
Sea around
Antarctica, which produces a huge amount of phytoplankton
that
sequesters billions of tons of carbon each year that settles
to the
bottom of the ocean to become hydrates in non-subduction
areas.
### As I mentioned above, the amount of carbon sequestered
in the elemental form or in organic molecules is insignificant compared to
the mass of carbonate. It is only a matter of geological time before any
part ocean floor will reach a subduction zone, or, conversely, will be
elevated and weathered.
Rafal
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