Re: RATE Vol. II

> 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.

Yes. As previously stated plate tectonics is a integral part of the
global carbon cycle. Plate tectonics is also critical to the global
recycling of a wide range of other elements. Gas release by
volcanism and the removal of atmospheric gases by biological activity
and weathering is critical for determining the elemental composition
of the atmosphere and thus climate. Weathering products in solution
are carried to the oceans and atmospheric gasses are dissolved at the
ocean/atmosphere interface. These dissolved compounds are removed
from the oceans by both organic and inorganic processes to form
chemical precipitates or react with ocean sediments. These ocean
sediments are ultimately subducted and recycled in the Earth's mantle
to be returned via volcanism. This global scale cycling is necessary
to maintain the availability of elements necessary for life both on
land and in the oceans.

Also, without the uplift associated with plate boundaries weathering
would reduced the land to a nearly flat plane near sealevel (like the
coastal plane) within a matter of a few 10s of millions of years.
Deep weathering would also leach out vital elements leaving nutrient-
poor soils.

Keith

Keith B. Miller
Research Assistant Professor
Dept of Geology, Kansas State University
Manhattan, KS 66506-3201
785-532-2250
http://www-personal.ksu.edu/~kbmill/
Received on Fri May 19 19:06:38 2006