Re: Is shrinkage more important for mountain-building than mantle convection?

There is no viable evidence for shrinking of the earth that I am aware of. 
 This sounds like work based on a variant of a creationist argument about 
the age of the moon.  There tidal friction usually is taken to be too fast, 
however any analysis that extrapolates current values is wrong because the 
amount of tidal friction depends on the shape and depth of earth's oceans 
and is therefore a changing quantity over time.  For a detailed discussion 
see:
 http://www.talkorigins.org/faqs/moonrec.html

Which includes citations to current (1994, 1997, 1999) papers discussing 
this issue.

In addition, there is a rapidly growing body of evidence from geodetic 
surveys that constrain the size of the earth and the rate of change of that 
size.  I have not seen any evidence that would support a significant change 
in earth's size over time.

The processes involved in building mountains are best explained by standard 
models involving lateral motions of the lithosphere (plate tectonics). 
There is a very close correlation between mountain building and motions and 
very good evidence that surface motions match mantle dynamics.  Other 
influences are not needed to explain the existing evidence. This, in 
addition to the lack of evidence supporting shrinkage or other such changes 
makes the shrinkage hypothesis less likely than others.

Thanks for your question.  I knew the earth wasn't shrinking, but I learned 
some new things about tides tidal friction as I researched my answer.

David Smith, Ph.D.
Geology and Environmental Science 
La Salle University