Re: RATE Vol. II

In a message dated 5/19/2006 5:11:07 PM Eastern Daylight Time,
alexanian@uncw.edu writes:
Why is plate tectonics necessary for a planet to
sustain life?
I think the idea behind this is that sooner or later many of the necessary
resources for life wash completely into the oceans and so there could be no way
to have life on the land (or in some cases extensive life in the oceans,
either) if these were not recycled and re-surfaced through plate tectonics.

Example: carbon in the form of carbon dioxide gets bound up into carbonates
by little ocean critters, and these sink to the bottom when the critters die
forming massive carbonate banks like Florida and the Bahamas. Eventually the
carbonates get subducted due to plate tectonics and released back into the
atmosphere through volcanism. Then new life forms have access to the carbon
through carbon dioxide. You and I depend on this because we get the carbon by
eating the plants that got them out of the atmosphere (which in turn got them from
the volcanoes...) This part of the carbon cycle makes life possible on Earth
over long periods of time.

Not being an expert on this, I can't personally vouch for these arguments,
but they seem reasonable to me. I know that some planetary scientists
(Kastings?) have argued that this aspect of the carbon cycle helps maintain global
temperatures over long-aged wavelengths, because temperatures regulate life and
life regulates carbonate deposition which feeds back into greenhouse gases
released through volcanism. Hence, it forms a self-regulating closed-loop. But
without plate tectonics the loop would not be closed.

Phil Metzger
Orlando, FL
Received on Fri May 19 17:21:57 2006