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From: ethan@utastro.UUCP (Ethan Vishniac)
Newsgroups: sci.misc
Subject: Re: alternative to plate tectonics
Message-ID: <1444@utastro.UUCP>
Date: Mon, 8-Dec-86 18:38:49 EST
Article-I.D.: utastro.1444
Posted: Mon Dec  8 18:38:49 1986
Date-Received: Mon, 8-Dec-86 22:34:19 EST
References: <531@weitek.UUCP> <1272@cit-vax.Caltech.Edu> <648@bath63.ux63.bath.ac.uk>
Organization: U. Texas, Astronomy, Austin, TX
Lines: 37
Keywords: plate tectonics, continental drift
Summary: Inappropriate comparison

In article <648@bath63.ux63.bath.ac.uk>, ma_jpb@bath63.ux63.bath.ac.uk (Bennett) writes:
> 
> There is a problem with tectonic plate theory and continental drift due to the
> conservation of energy. Consider the theory that the Himalayas are caused by
> the Indian plate hitting the Asiatic plate. A substantial amount of potential
> energy is generated in raising the Himalayas, which has presumably come from
> the kinetic energy of the Indian plate. Given we can work out the kinetic
> energy of the plate, we can calculate the height of the mountains this would
> raise if converted to potential energy with 100% efficiency. Although the
> Indian plate is large it moves exceedingly slowly (a few centimetres a year at
> most).  Calculation would suggest that within an order of magnitude the
> Himalayas should be one millimetre high. Observation refutes this. At least in
> this case continental drift is not a good model.
> 
I am *not* a geologist.  Perhaps that is why I can't understand this
argument.  I always thought that continental drift was supposed to be
driven by the interaction between the crust and convective currents
from deep within the Earth.  If this were not so then continental motion
would never have started and if started would stop quickly.  After all
the motions of the plates are highly dissipative.

The energetics must work like this:

radioactive decay of heavy atoms - > thermal energy of core -> convective
currents -> deformations of crust and other dissipative effects.

Mr. Bennett's argument can allow us to calculate the rate at which
energy is being transferred from internal convective currents into
the kinetic energy of the Indian subcontinent.  Unless I'm completely
mistaken (rarely out of the question :-) ) it tells us nothing
about the validity of plate tectonics.
-- 
"More Astronomy                Ethan Vishniac
 Less Sodomy"                  {charm,ut-sally,ut-ngp,noao}!utastro!ethan
  - from a poster seen         ethan@astro.AS.UTEXAS.EDU
    at an airport              Department of Astronomy
                               University of Texas