🚀 go-pugleaf

In article <531@weitek.UUCP> mae@weitek.UUCP (Mike Ekberg) writes:
>About ten years ago, while I was in college, I read a book that presented
>a theory to explain many of the phenomenon used to back up the theory of
>plate tectonics.
>
>The theory went something like this...
>
>The earth consists of a large gob of semi-liquid stuff(mantle) that is coated
>with an extremly thin shell of hardened goop, ie crust. Occasionally,
>for unknown reasons, the thin shell 'slips' over the surface of the
>semi-liquid stuff. After a while, the shell movement reaches some sort
>of equilibrium(sort of like Punctuated Revolution? :-} ).
>
>This theory 'explains' the following phenomenon:
>
>1. magnetic reversals          - since the magnetic pole is in the mantle,
>                                 when the crust shifts relative to the
>                                 mantle, the apparent direction of the
>                                 earths magnetic field shifts.

It doesn't explain why the field shifts direction 180 degrees. Not unless
you really believe that the entire crust rotates exactly 180 degrees
around some equatorial pole. I find that incredibly hard to believe.

>2. sea floor expansion         - since the earth is not a perfect sphere,
>                                 when the crust shifts, cracks open as the
>                                 crust gets stretched of the bulgy parts.
>                                 Stuff leakes out from the interior.

All right, I guess you need some explaination of plate tectonics (and the
evidence for it.) Okay, Seafloor spreading:  Around the world there are
ridges in the ocean, called mid-ocean ridges. There is a lot of volcanism
there. On both sides of these ridges you can find magnetic reversal
patterns (symmetric) which correspond to the dated patterns of magnetic
reversal on the continents. Now, these patterns had to be imprinted in
the rock when it was very hot, above a temperature called the curie
temperature (can't remember off hand how hot that is, but it's a lot
hotter than is normally found.) Basically it was laid in when the rock
solidified. These are fairly continuous patterns dating back over 170
million years, with reversals every million years or so (sometimes
much more often). The spreading is at a relatively continuous rate,
at least at this time scale. Any theory must account for this.
Somehow I find it much easier to believe slow continuous spreading
than occaisional massive shifts of the entire crust, which simulate
slow spreading sooo well.

>3. weird fossil records                - the author sited examples of fossils of
>                                 tropical plants in Siberia. Siberia used
>                                 to be on the equator.

According to plate tectonics, the continents are drifting. They move
slowly, but they do move. Siberia was tropical once, according to plate
tectonics.

>Is there anything to this theory or is it totally from left field?

I haven't even mentioned that seismic evidence supports this stuff,
and that spreading is occuring today (measurably). To say nothing
of subduction zones (ocean trenches, where ocean crust goes back
down into the mantle to be recycled).

>BTW, according to the Grab Bag column in the S. F. Examiner, the crust is
>much thinner relative to the inside then an egg shell is to the egg.

Well, I don't know how thin an eggshell is, but that's definitely
true.  The oceanic crust is about 7km thick, and the continental
crust is about 35km thick. The Earth is 6370km in radius, so using
continental crust, the crust is 0.55% of the Earth's radius.
If an egg is 3cm in radius (a pretty large egg), the equivalent thickness
of the crust is 0.16mm. That's a pretty thin shell.


			Bob Myers

A slightly better alternative than the previous one is the
Expanding Earth hypothesis. This explains seafloor spreading by
expansion of the Earth's interior, causing the crust to stretch.

Not that I believe it....

In any case, I did a literature review of this idea a couple
years ago. It would be easy to e-mail a copy to anyone who requests
it.

			Bob Myers

> A slightly better alternative than the previous one is the
> Expanding Earth hypothesis. This explains seafloor spreading by
> expansion of the Earth's interior, causing the crust to stretch.

Unfortunately, the Expanding Earth hypothesis ignores several decades of
research involving hot spots, subduction zones, active margins, 
island arcs, and passive margins.

The critical evidence which lead to the clear identification of the deep
oceanic trenches (or, more precisely the "Benioff zones" associated with
them) with sinking tongues of oceanic lithosphere came from work done on
the Tonga Trench in the mid 1960s using the World-Wide Standardized
Seismograph Network.  Subduction was clearly shown.  Since then, the same
essential picture has been seen at the other major trenches.

Also, very careful measurements of plate movements have been made, using
not only paleological and magnetic analyses, but also using careful
surveying techniques, including measurements using satellite navigation
techniques.  Turns out that the plates are definitely moving around at
relatively rapid speeds (well, rapidly geologically speaking) of the order
of centimeters per year.  One of the problems has been trying to determine
what to use as a global reference that could be considered relatively
static (sort of a geological version of "relativity" :-).  The current
popular static reference is the means of the global "hot spots" which don't
seem to move too much relative to each other.

To see the effects of a plate (the Pacific plate) moving over a "hot spot",
get out your favorite globe or world map and look at the Hawaiian islands.
The youngest island is Hawaii at the southern end of the chain (actually,
it's the undersea volcano Loihi just southeast of Hawaii).  The rest of the
chain of islands are progressively older as they trend northwest for
1,000 miles or so.  If you have a map or chart which details undersea
features, you can follow the remains of even older islands that are known
as the "Emperor Seamounts" for considerably further towards the northwest.
[Congratulations if you see a change of direction, the Pacific plate hasn't
always been moving in exactly the same way.]

-- 
Bob Cunningham
bob@hig.hawaii.edu

In article <1273@cit-vax.Caltech.Edu> myers@hobiecat.UUCP (Bob Myers) writes:
>A slightly better alternative than the previous one is the
>Expanding Earth hypothesis. This explains seafloor spreading by
>expansion of the Earth's interior, causing the crust to stretch.

Using very long baseline interferometry, one can actually measure the
continents' motion (it amounts to an inch or so a year in most
cases).  The results support plate tectonics, not an expanding earth
(some continents are getting closer together).  I have a friend at
NASA-Goddard who is involved in this work.  
-- 
- Joe Buck 	{hplabs,ihnp4,sun}!oliveb!epimass!jbuck		HASA (A,S)
  Entropic Processing, Inc., Cupertino, California

For a description of some of the VLB interferometry work, see the Carter &
Robertson article in the Nov 1986 Scientific American.
-- 
Bob Cunningham
bob@hig.hawaii.edu

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.

This is a well documented objection, and has led to the foundation of the "Stop
Continental Drift Society" (of which I hasten to add I am not a member). If
there is enough demand I can dig out the references to papers that discuss this
theory.

J.P. Bennett
University of Bath
England BA2 7AY
+44 225 826826

>About ten years ago, while I was in college, I read a book that presented
>a theory to explain many of the phenomenon used to back up the theory of
>plate tectonics.
>The theory went something like this...
>
>The earth consists of a large gob of semi-liquid stuff(mantle) that is coated
     
     The mantle is very much solid, in fact it is more dense than
     most any of the rocks seen on the surface.  The core of the
     earth is partial molten (the center part is not however).

>with an extremely thin shell of hardened goop, ie crust. Occasionally, 

       Basically correct.

>for unknown reasons, the thin shell 'slips' over the surface of the 
>semi-liquid stuff. After a while, the shell movement reaches some sort
>of equilibrium(sort of like Punctuated Revolution? :-} ).
>
     This 'thin shell' is constantly moving at a slow rate, on what
     is known as the mid-atlantic ridge about 2 cm per year.  Now
     this may not seem like a lot but for geology this is very rapid
     movement.

>This theory 'explains' the following phenomenon:
 
>1. magnetic reversals		- since the magnetic pole is in the mantle,
>				  when the crust shifts relative to the
>				  mantle, the apparent direction of the 
>				  earths magnetic field shifts.

     Magnetic reversals are believed to be caused by convection
     currents in the core of the earth, which acts as kind of a 
     magnet.  Some directional changes are caused by the movement
     of the crust over the mantle also, but only in the crust, not
     the rest of the earth.

>2. sea floor expansion		- since the earth is not a perfect sphere,
>				  when the crust shifts, cracks open as the
>				  crust gets stretched of the bulgy parts. 
>				  Stuff leakes out from the interior.

     This happens in that were places like the mid-atlantic ridge
     occur the drop in pressure caused by the crust being stretched
     causes the rock in the mantle to melt, and because this melted
     rock is lighter than what surrounds it, it works its way to the
     surface and creates the 'stuff that leaks out'.  This stuff 
     (melt) also hardens to form new crustal material because not 
     near all of it reaches the surface.  The distance that this
     melt must travel is about 10 km.

>3. weird fossil records	- the author sited examples of fossils of 
>				  tropical plants in Siberia. Siberia used
>				  to be on the equator. 

     Using the fact that the crustal 'plates' have moved in the past
     as well as they are currently moving also produces changing 
     environments.  Indiana, for example, during one period in 
     geologic time also was near the equator.  Coral reefs, abundant
     limestone (Indiana University and many of the buildings in
     Washington D.C. were made of one very pure type of limestone,)
     and coal were all formed under tropical conditions.  The
     northward movement of the North American plate has brought
     cooler weather to this once Bahama-type environment.  Traces
     of glaciers can be found in very dry areas of Africa.



>BTW, according to the Grab Bag column in the S. F. Examiner, the crust is
>much thinner relative to the inside then an egg shell is to the egg.

     It is.  That is why it is so difficult to study the mantle and
     core, because the crust, even though it is relatively thin, is
     on land up to 30 km thick, and in the oceans about 6-10 km
     thick.  A project known as the Deep Sea Drilling Project has
     drilled a hole 1.5 km deep, barely scratching the surface.
     The mantle and core are studied using siesmic procedures 
     using such things as earthquakes and planned and controlled
     explosions.  This subject of plate tectonics touches all
     areas of geology to some degree.   I am a geology under-
     graduate here at Purdue University and am currently taking
     a course about this very subject.  All the current literature
     I am familier with is very technical.  This theory has been
     greatly refined since it was first proposed.  Perhaps another
     geologist out there can come up with a good non-technical
     book on the subject.  Any protests or other questions can
     be sent to this account. 

				    Ellen Meadows

Disclaimer :
    The views stated herein are the views of the author and in
    no way should be connected to the organization to which I
    or to me for that matter.
-- 

In Real Life:           Jerry L. Bloomfield  

USENET:   {seismo, decvax, ucbvax, ihnp4}!pur-ee!h.cc!ahv
BITNET:   BLOO@PURCCVM

In article <648@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.

BULLSHIT BULLSHIT BULLSHIT

If I push a cart with my hand, does it get all its energy from
the kinetic energy of my hand???

It gets its energy from what drives the motion of my hand.

Same for plates. I have seen a couple of proposals for driving energy for
plate motion.

Ex.: Potential energy as the plate moves down from the
mid-ocean ridge crest (where it is formed) and then gets subducted into
the mantle. It has been proposed that the subducting end falling into
the mantle (it is heavier, mostly because it's colder) creates the
plate motion by pulling the plate down.

Ex.: Mantle convection. Upwelling at ridge crests, downwelling near
subduction zones, energy driven by internal heat of the Earth.

    ridge
    crest         subduction
      ->>>>>>>>>>>>   zone
     ^            \/
     ^            \/
     ^            \/
     ^            \/
     <<<<<<<<<<<<<<

			Bob Myers

Just recently on Public TV, there was a show that mentioned plate tectonics,
sea-floor spreading and the like.  They made one very interesting statement
that I'm having a lot of trouble verifying.  According to Wegner's hypothesis,
there was once a large super-continent (Pan-gaea) that split up to form the
later continents.  MUCH evidence supports this.  Also supported is the fact
that the current continent shapes (plus or minus a few buldges) are very
similar to what the were when Pan-gaea broke up.

Now the show I saw contended that for North America, at least, the continent
was built up from deposition on an originally smaller continent based in
southern Canada.  They called it the Canadian shelf or something like that.
They also noted that this rock PRE-DATED the formation of Pan-Gaea!

Try as I might, I can't find any books or other sources that either confirm or
deny this.  Most go back to Pan-gaea and talk about the break up and the sea-
floor spreading and subduction that has taken place since then, but nothing
that would indicate shapes of continents prior to the formation of Pan-gaea.

Was this just a flight of fancy of the author of the show?  Are there any
theories on continents prior to Pan-gaea?  Where can one find this stuff??

-----Larry

-- 
-----Lawrence F. Strickland (larry@jc3b21)      Dept. of Engineering Technology
                                                St. Petersburg Jr. College
     Phone:  +1 813 341 4705                    P.O. Box 13489
     UUCP:  ...akgua!usfvax2!jc3b21!larry       St. Petersburg, FL 33733

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

In article <777@jc3b21.UUCP> larry@jc3b21.UUCP (Lawrence F. Strickland) writes:
>
>Now the show I saw contended that for North America, at least, the continent
>was built up from deposition on an originally smaller continent based in
>southern Canada.  They called it the Canadian shelf or something like that.
>They also noted that this rock PRE-DATED the formation of Pan-Gaea!

That's Canadian Shield. It is the core of the present North American continent.
Yes, it does predate Pangaea, by quite a bit. On the order of 1.5 billion
years old, while Pangaea was only about 2-400 million years ago. Plate
tectonics as a process is older than Pangaea. The Appalachians were formed
by the collision of Proto-North America and Proto-Europe about 4-500 million
years ago. Can't remember exact times, but that's about right.
The Atlantic reopened about 180 million years ago, splitting North America
and Europe along nearly the same boundry (but not quite).

Continents have been drifting around the world for about the last 1.5
billion years, sometimes joining, sometimes breaking up.

It is, however, real difficult to figure out the geography older than
200 million years ago. This is because we don't have any seafloor
records older than that. All the oceanic crust is less than 200 million
years old!

There have been some attempts at reconstruction, despite the difficulties.
Let's see, references....
Best I can do is geological journals for stuff that technical. Maybe
you can find some of these journals in a University Geology library.

Scotese, C. R., et al. 1979. Paleozoic base maps. Journal of Geology.
	    87: 217--277.
Smith, A.G., et al. 1973. Phanerozoic world maps. Special Papers in
	    Palaeontology. 12: 1-42.
Whittington, H. B., et al. 1972. Ordovician geography and faunal provinces
	    deduced from trilobite distribution. Philosophical
	    Transactions of the Royal Society of London, Series B.
	    263: 235--278.

These should provide a start. I don't know where to find much in the
way of popular material dealing with this subject, though.

New continental crust has been added, as well. Sometimes pieces
of oceanic crust get jammed onto the continents. The volcanism near
subduction zones will create island arcs that also often are
accreted onto the continents. The Shield areas are the continental
cores, generally the areas of low geologic activity older
than 1 billion years.

You should be able to find some relatively simple geology texts that
can explain these aspects of plate tectonics.
Example of one I like:

Press, Frank, and Siever, Raymond. 1982. Earth. W.H. Freeman and Company,
	San Francisco.

I just took a look at it and there is a Middle Ordovician (475-490 Million
years ago) world map in there, p. 457.

Have fun!

--------------------------------------------------------------

		 Don't Should on yourself.

Bob Myers                       myers@hobiecat.Caltech.Edu

In article <648@bath63.ux63.bath.ac.uk> ma_jpb@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.


Consider the following thought experiment:

	Take 2 identical cars and place them nose to nose.  Rig the 
	accelerators of both so that you can give equal acceleration
	to each.  Now slowly increase the accelerations of the two
	cars.  Assuming that there is no slippage of the wheels, the
	cars will remain motionless.  That is until the bumpers start
	to crumple.

	If I remember my freshman physics, this state is called
	static equilibrium.  The velocity of the cars (except
	for that allowed by the crumpling bumpers) is zero.  Thus,
	their kinetic energy is also zero (or very close to it,
	the bumpers again).  However, the force produced by each
	car is not zero.  This is what is producing the crumpled
	bumpers (and the crumpled landscape i.e. Himalayas).

So, what does kinetic energy have to do with it?

>This is a well documented objection, and has led to the foundation of the "Stop
>Continental Drift Society".

Have the members of this Society taken freshman physics?


 Dan Tilque				dant@tekla.tek.com

Hey! Who left my Cosmic Holographic Recorder on replay?

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.... 

True, but do we know the velocity of the Indian Plate 10 or
20 million years ago?  Remember that once most of the kinetic
energy of an object has been turned into potential energy, the
object tends to be moving slowly, in comparison.  Has anyone
investigated this line?

Doug Murphy
AT&T-Bell Laboratories
Liberty Corner, NJ
{lcuxlm!dmu}

>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... Although the
> Indian plate is large it moves exceedingly slowly...
> Calculation would suggest that within an order of magnitude the
> Himalayas should be one millimetre high.... 

This would indeed be a serious problem if the proposed mechanism
causing continental drift was that the plates have leftover momentum
from some past disaster and are bouncing off each other like billiard
balls.  It becomes evident with only a little thought that that would
be a silly assertion, since the mantle is much thicker than lemon
custard, and would slow them to a stop in no time (geologically
speaking).

   In fact, I believe the theory goes that the plates are moved by
convection currents in the chewy liquid center of the Earth, these
currents being caused by heat generated by the decay of radioactive
elements.  There's a _lot_ more energy than just the momentum of the
crustal plates involved.
-- 
  /'C`\	 TWALG ASHALC RITMOHF.			Andre Guirard
 ( o_o )					Botoj de timeco
 )) _ (( AWSWG SWVVG BWSWBSWH!			ihnp4!mmm!cipher
///   \\\

In article <777@jc3b21.UUCP> larry@jc3b21.UUCP (Lawrence F. Strickland) writes:
>
>Just recently on Public TV, there was a show that mentioned plate tectonics,
>sea-floor spreading and the like.  They made one very interesting statement
>that I'm having a lot of trouble verifying.  According to Wegner's hypothesis,
>there was once a large super-continent (Pan-gaea) that split up to form the
>later continents.  MUCH evidence supports this.  Also supported is the fact
>that the current continent shapes (plus or minus a few buldges) are very
>similar to what the were when Pan-gaea broke up.
>
>Now the show I saw contended that for North America, at least, the continent
>was built up from deposition on an originally smaller continent based in
>southern Canada.  They called it the Canadian shelf or something like that.
>They also noted that this rock PRE-DATED the formation of Pan-Gaea!
>
>Try as I might, I can't find any books or other sources that either confirm or
>deny this.  Most go back to Pan-gaea and talk about the break up and the sea-
>floor spreading and subduction that has taken place since then, but nothing
>that would indicate shapes of continents prior to the formation of Pan-gaea.
>
>Was this just a flight of fancy of the author of the show?  Are there any
>theories on continents prior to Pan-gaea?  Where can one find this stuff??
>

No, it wasn't a flight of fancy. What was being discussed was the
theories of micro-plate accreation. This is work that has come out
of the NW US and Western Canada studies back around 1978-1983. Most
of the discussions have been going on in the geology technical journals.
I don't have the references here at work, but I know that Dr.Charles A.
Ross did some work in paleontology that discussed this theory and gave
some supporting evidence. Other authors to look up are Zvi Ben-Avraham,
Alan Cox, Amos Nur, and especially Davey Jones,Norman Silberling, and
John Hillhouse (USGS). You would probably want to look up information
on Wrangellia and allochthonous terranes.

I do have one popular article on the subject.

Overbye,Dennis, 1983, The Jigsaw Earth,Discover,april,n.4v.4,p.86-91.

This gives a good description of what was covered in the tv show.

Hope this helps.

Pam Pincha-Wagener

In article <648@bath63.ux63.bath.ac.uk> ma_jpb@ux63.bath.ac.uk (Bennett) writes:
>[...]
>                                           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.

There seems to be a limit to the height of the mountains.  If I remember 
correctly from freshman physics,  Everest is close to the theoretical height
of a mountain.  This is because the intense pressure sustained by the rock 
supporting the mountain has brought it to nearly melting temperatures.         
Obviously this is only applicable to the rock deep inside the base region of
the mountain, upon which most of the stress falls.  

I'm lead to wonder whether a molten inner base of a mountain (due to stress)
would cause the mountain to collapse, or if the molten portion could be
successfully contained by the less-strained base of the mountain?

-charles
 
-- 
All that we may see or seem     | Snail : Box 1662 Bloomington, In. 47402-1662
Is but a dream within a dream   | ATT   : (812) 339-7354
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 (can anyone help me?)          | BITNET: BCHC901@INDYCMS

> There seems to be a limit to the height of the mountains...

The principle is correct, but the details get a little complicated...

Under pressure and high temperatures, most minerals undergo phase changes
---effectively becoming different minerals---that increase their ability to
withstand pressure and temperature.  Although obviously rare,
carbon-to-diamond is one almost everybody knows about.  Less well known are
minerals like perovskite that the various high-pressure labs around the
world have only recently been able to produce by duplicating
the extreme pressures and temperatures deep in the earth.

That Mt. Everest isn't near the theoretical limits of height for a mountain
should be obvious.  There are other mountains that---from their base to
peak---are higher (and there are mountain peaks further from the earth's
center as well).  Everest is just the mountain with the most elevation
above the earth's geoid (or, if you prefer a less precise term: above sea
level).

-- 
Bob Cunningham
bob@hig.hawaii.edu

In article <153@uhmanoa.UUCP>, bob@uhmanoa.UUCP (Bob Cunningham) writes:
> There are other mountains  that---from their base to peak---are higher
> [than Everest] (and there are mountain peaks further from the earth's
> center as well).  Everest is just the mountain with the most elevation
> above ...sea level).

> Bob Cunningham
> bob@hig.hawaii.edu
          ^^^^^^

Given his location, I'm not surprised that Bob is aware that Everest is not 
the tallest mountain from base to summit.  Anyone else catch this? :-)

And 
you 
thought
the 
line
eater
was 
bad. :-(
-- 
			   Mike Sellers
     UUCP: {...your spinal column here...}!tektronix!tekecs!mikes

	 	       Otium cum Dignitatum