Devils Tower erosion issue
and...@my-deja.com
(1) its sides eroded more in the mid-section than near the top;
(2) one side eroded more than the opposite side;
(3) its top is remarkably flat; and
(4) there is "no evidence of volcanic activity anywhere in the area. No
volcanic ash, no lava flows, no debris...nada," as one poster observed.
You can view some pictures at
http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/devils_tow
er.html
In another thread, I doubted there were any other structures comparable
to Devils Tower. I sorted through numerous responses but only found
Beacon Rock to be analogous. In contrast, however, Beacon Rock "rises
to a very sharp point," in the words of explorer Lewis. Nor are there
any signs of similarity between Beacon Rock and Devils Tower on the
other three observations above.
http://lewisandclarktrail.com/section4/wacities/vancouver/scenicgorge/
Erosion by water would explain observations 1-4 above. Water would
flatten the top, and as the water level dropped the erosion would be
greater in the mid-section than near the top. Directional current
would make the erosion greater on one side than the other. The water
would remove the volcanic ash, lava, debris, etc.
No one has yet suggested any other specific explanations for points 1-4
above. Perhaps because Devils Tower rises to a mile above sea level,
some simply refuse to accept water erosion as a possibility. But what
other explanation could resolve 1-4 above?
Andy
Sent via Deja.com
http://www.deja.com/
Gyudon Z
I know you don't like to actually read responses, but it is intellectually
dishonest to pretend that they don't exist.
Of course, we've come to expect no better.
"Between true science and erroneous doctrines, ignorance is in the middle."
Thomas Hobbes, Leviathan
David C. Fritzinger
I'll let the geologists answer your specific points (though it seems
to me that you 've already had your clock cleaned), but I couldn't
resist this one. If I'm in Denver, CO, and have a 1 inch pile of dirt, it
rises to one mile above sea level. How would you explain that?
Answer: Denver is the "Mile-High City".
l.
> some simply refuse to accept water erosion as a possibility. But
what
> other explanation could resolve 1-4 above?
Many have said that there is water erosion. What they also said is
that it couldn't have been caused by the infamous WWF (world
wide flood, not world wrestling federation-actually, it couldn't have
been caused by that wwf either 8^) ). You've really got to learn to
read for content some day.
Dave Fritzinger
and...@my-deja.com
gyu...@aol.com (Gyudon Z) wrote:
> Andrew Macrae et al. have explained Devil's Tower quite clearly.
>
> I know you don't like to actually read responses, but it is
intellectually
> dishonest to pretend that they don't exist.
Ah, you think you're a mindreader too ("I know you don't like ...")?
Evolved trait?
I looked again at Andrew Macrae's responses. They don't address the
four erosion points of this thread.
> Of course, we've come to expect no better.
I didn't expect you to be persuaded, but I thought you might present a
substantive argument.
ghos...@my-deja.com
Too bad you had to start a new thread especially since your comments
have already been addressed and shredded in that thread.
> The erosion pattern of Devils Tower is particularly prominent:
>
> (1) its sides eroded more in the mid-section than near the top;
>
> (2) one side eroded more than the opposite side;
>
> (3) its top is remarkably flat; and
>
> (4) there is "no evidence of volcanic activity anywhere in the area.
No
> volcanic ash, no lava flows, no debris...nada," as one poster
observed.
>
It was not a volcano
...
> Erosion by water would explain observations 1-4 above. Water would
> flatten the top, and as the water level dropped the erosion would be
> greater in the mid-section than near the top. Directional current
> would make the erosion greater on one side than the other. The water
> would remove the volcanic ash, lava, debris, etc.
Cool.
> No one has yet suggested any other specific explanations for points
1-4
> above. Perhaps because Devils Tower rises to a mile above sea level,
> some simply refuse to accept water erosion as a possibility. But what
> other explanation could resolve 1-4 above?
I am glad you seem to have given up on the idea that this shows evidence
of a global flood.
But then little evidence of such a flood exists and many contrary data.
Roger Schlafly
> No one has yet suggested any other specific explanations for points 1-4
> above. Perhaps because Devils Tower rises to a mile above sea level,
> some simply refuse to accept water erosion as a possibility. But what
> other explanation could resolve 1-4 above?
Wasn't that the UFO meeting place at the end of the movie Close
Encounters?
and...@my-deja.com
"David C. Fritzinger" <dfri...@my-deja.com> wrote:
> In article <933apk$gcp$1...@nnrp1.deja.com>,
> and...@my-deja.com wrote:
> > The erosion pattern of Devils Tower is particularly prominent:
> >
> > (1) its sides eroded more in the mid-section than near the top;
> >
> > (2) one side eroded more than the opposite side;
> >
> > (3) its top is remarkably flat; and
> >
> > (4) there is "no evidence of volcanic activity anywhere in the area.
> No
> > volcanic ash, no lava flows, no debris...nada," as one poster
> > No one has yet suggested any other specific explanations for
> points 1-4
> > above. Perhaps because Devils Tower rises to a mile above
> sea level,
>
> I'll let the geologists answer your specific points (though it seems
> to me that you 've already had your clock cleaned), but I couldn't
> resist this one.
If you can't address the specific points, then you can't judge who is
correct. Do you think a judge cares how many people in the courtroom
side with one party over the other?
> If I'm in Denver, CO, and have a 1 inch pile of dirt, it
> rises to one mile above sea level. How would you explain that?
>
> Answer: Denver is the "Mile-High City".
Right. It's only those emotionally opposed to enormous flood who would
automatically reject a flood rising as high as Denver.
> l.
> > some simply refuse to accept water erosion as a possibility. But
> what
> > other explanation could resolve 1-4 above?
> Many have said that there is water erosion. What they also said is
> that it couldn't have been caused by the infamous WWF (world
> wide flood, not world wrestling federation-actually, it couldn't have
> been caused by that wwf either 8^) ). You've really got to learn to
> read for content some day.
Demonstrate that you found any content on the erosion issue. Some
claimed that rainfall caused the erosion, but the pattern noted above
disproves that. Do you think any evolutionist admitted that Devils
Tower, which is a mile above sea level, could have been flooded?
Gyudon Z
Very well; we try this again.
(1) its sides eroded more in the mid-section than near the top;
A: Do you have a citation for that, and B: So what?
(2) one side eroded more than the opposite side;
A: Do you have a citation for that?, B: The glaciers retreated in one
direction. That means that meltwater flows, or C: Unless the ground is
perfectly level, it is to be expected that water will flow in one direction.
(3) its top is remarkably flat; and
A: So?, and B: If the top of the tower was under the last glacial advance,
along with the softer soil surrounding it, the area would have been scoured
pretty much flat.
I don't know the effect of glacial advancing on the area, but it is quite
possible, and certainly more likely than the flood tales.
(4) there is "no evidence of volcanic activity anywhere in the area. No
volcanic ash, no lava flows, no debris...nada," as one poster observed.
Possibly because the thing is millions of years old.
Gyudon Z
>In article <933d3f$i8u$1...@nnrp1.deja.com>,
> "David C. Fritzinger" <dfri...@my-deja.com> wrote:
>> In article <933apk$gcp$1...@nnrp1.deja.com>,
>> and...@my-deja.com wrote:
>> > The erosion pattern of Devils Tower is particularly prominent:
>> >
>> > (1) its sides eroded more in the mid-section than near the top;
>> >
>> > (2) one side eroded more than the opposite side;
>> >
>> > (3) its top is remarkably flat; and
>> >
>> > (4) there is "no evidence of volcanic activity anywhere in the area.
>> No
>> > volcanic ash, no lava flows, no debris...nada," as one poster
>> observed. ...
>> > No one has yet suggested any other specific explanations for
>> points 1-4
>> > above. Perhaps because Devils Tower rises to a mile above
>> sea level,
>>
>> I'll let the geologists answer your specific points (though it seems
>> to me that you 've already had your clock cleaned), but I couldn't
>> resist this one.
>If you can't address the specific points, then you can't judge who is
>correct. Do you think a judge cares how many people in the courtroom
>side with one party over the other?
The answer to the four specific points is generally "So what?". Why must we
conclude that miles of rushing water carved this tower out of the land (and
left no other signs of its existence)?
>> If I'm in Denver, CO, and have a 1 inch pile of dirt, it
>> rises to one mile above sea level. How would you explain that?
>>
>> Answer: Denver is the "Mile-High City".
>
>Right. It's only those emotionally opposed to enormous flood who would
>automatically reject a flood rising as high as Denver.
Actually, it's those geologists who know that the world's oceans haven't been
that shallow in the forty million years since the extrusion.
>> l.
>> > some simply refuse to accept water erosion as a possibility. But
>> what
>> > other explanation could resolve 1-4 above?
>> Many have said that there is water erosion. What they also said is
>> that it couldn't have been caused by the infamous WWF (world
>> wide flood, not world wrestling federation-actually, it couldn't have
>> been caused by that wwf either 8^) ). You've really got to learn to
>> read for content some day.
>Demonstrate that you found any content on the erosion issue. Some
>claimed that rainfall caused the erosion, but the pattern noted above
>disproves that.
How so?
>Do you think any evolutionist admitted that Devils
>Tower, which is a mile above sea level, could have been flooded?
No, because the seas have been deep enough in the last forty million years that
floodwater doesn't get that high.
and...@my-deja.com
ghos...@my-deja.com wrote:
> In article <933apk$gcp$1...@nnrp1.deja.com>,
> and...@my-deja.com wrote:
>
> Too bad you had to start a new thread especially since your comments
> have already been addressed and shredded in that thread.
We'll see how substantive you can be in addressing the specific
points. So far in this thread, the naysayers are batting .000 with
substance.
> > The erosion pattern of Devils Tower is particularly prominent:
> >
> > (1) its sides eroded more in the mid-section than near the top;
> >
> > (2) one side eroded more than the opposite side;
> >
> > (3) its top is remarkably flat; and
> >
> > (4) there is "no evidence of volcanic activity anywhere in the area.
> No
> > volcanic ash, no lava flows, no debris...nada," as one poster
> observed.
> >
>
> It was not a volcano
Partial answer to point #4 here. It was volcanic rock, but you claim
not a volcano. Can you explain that?
> ...
>
> > Erosion by water would explain observations 1-4 above. Water would
> > flatten the top, and as the water level dropped the erosion would be
> > greater in the mid-section than near the top. Directional current
> > would make the erosion greater on one side than the other. The
water
> > would remove the volcanic ash, lava, debris, etc.
>
> Cool.
Nothing substantive here.
>
> > No one has yet suggested any other specific explanations for points
> 1-4
> > above. Perhaps because Devils Tower rises to a mile above sea
level,
> > some simply refuse to accept water erosion as a possibility. But
what
> > other explanation could resolve 1-4 above?
>
> I am glad you seem to have given up on the idea that this shows
evidence
> of a global flood.
Non sequitur here.
> But then little evidence of such a flood exists and many contrary
data.
Conclusory allegation here.
3 points not addressed at all, and the 4th point only partially
addressed without any explanation.
Andy
Gyudon Z
>In article <933e5p$itk$1...@nnrp1.deja.com>,
> ghos...@my-deja.com wrote:
>> In article <933apk$gcp$1...@nnrp1.deja.com>,
>> and...@my-deja.com wrote:
>>
>> Too bad you had to start a new thread especially since your comments
>> have already been addressed and shredded in that thread.
>
>We'll see how substantive you can be in addressing the specific
>points. So far in this thread, the naysayers are batting .000 with
>substance.
>
>> > The erosion pattern of Devils Tower is particularly prominent:
>> >
>> > (1) its sides eroded more in the mid-section than near the top;
>> >
>> > (2) one side eroded more than the opposite side;
>> >
>> > (3) its top is remarkably flat; and
>> >
>> > (4) there is "no evidence of volcanic activity anywhere in the area.
>> No
>> > volcanic ash, no lava flows, no debris...nada," as one poster
>> observed.
>> >
>>
>> It was not a volcano
>Partial answer to point #4 here. It was volcanic rock, but you claim
>not a volcano. Can you explain that?
There is a difference between "volcano" and "igneous rock".
>> > Erosion by water would explain observations 1-4 above. Water would
>> > flatten the top, and as the water level dropped the erosion would be
>> > greater in the mid-section than near the top. Directional current
>> > would make the erosion greater on one side than the other. The
>water
>> > would remove the volcanic ash, lava, debris, etc.
>> Cool.
>Nothing substantive here.
Nothing substantive in your arguments either. To wit: Why would a flood produce
effects 1-3?
>> > No one has yet suggested any other specific explanations for points
>> 1-4
>> > above. Perhaps because Devils Tower rises to a mile above sea
>level,
>> > some simply refuse to accept water erosion as a possibility. But
>what
>> > other explanation could resolve 1-4 above?
>> I am glad you seem to have given up on the idea that this shows
>evidence
>> of a global flood.
>Non sequitur here.
You said: What other explanation [than erosion] could produce 1-4 above?
Since water erosion did produce 1-4 above, we're glad you agree.
>> But then little evidence of such a flood exists and many contrary
>data.
>
>Conclusory allegation here.
>
>3 points not addressed at all, and the 4th point only partially
>addressed without any explanation.
The standard explanation has been expounded on the first time you tried this
thread, and your only response was hand-waving.
ghos...@my-deja.com
and...@my-deja.com wrote:
...
> > I'll let the geologists answer your specific points (though it
seems
> > to me that you 've already had your clock cleaned), but I couldn't
> > resist this one.
>
> If you can't address the specific points, then you can't judge who is
> correct. Do you think a judge cares how many people in the courtroom
> side with one party over the other?
Others have already addressed the specific points. That's what he says
quite clearly.
>
> > If I'm in Denver, CO, and have a 1 inch pile of dirt, it
> > rises to one mile above sea level. How would you explain that?
> >
> > Answer: Denver is the "Mile-High City".
>
> Right. It's only those emotionally opposed to enormous flood who
would
> automatically reject a flood rising as high as Denver.
More unsupported assertions I notice. You have been told several times
now that geologists have no problems with floods, even massive floods,
but in case of the earth there is just no credible data supporting a
global flood of biblical proportions. You seem to be the one who has
emotions invested in this unsupportable notion.
> > l.
> > > some simply refuse to accept water erosion as a possibility. But
> > what
> > > other explanation could resolve 1-4 above?
> > Many have said that there is water erosion. What they also said is
> > that it couldn't have been caused by the infamous WWF (world
> > wide flood, not world wrestling federation-actually, it couldn't
have
> > been caused by that wwf either 8^) ). You've really got to learn to
> > read for content some day.
>
> Demonstrate that you found any content on the erosion issue. Some
> claimed that rainfall caused the erosion, but the pattern noted above
> disproves that.
Why ? And it was not just rain but also the river as well as the
heating/cooling, wind and other common erosion causes.
> Do you think any evolutionist admitted that Devils
> Tower, which is a mile above sea level, could have been flooded?
If there were any credible evidence then indeed evolutionists would
admit such but absence such data, why should they?
I understand your emotions, it's not easy to find out that your belief
in a global flood is somehow not supported by evidence. But that's what
happens when one enforces a literal reading of the bible.
ghos...@my-deja.com
and...@my-deja.com wrote:
> In article <933e5p$itk$1...@nnrp1.deja.com>,
> ghos...@my-deja.com wrote:
> > In article <933apk$gcp$1...@nnrp1.deja.com>,
> > and...@my-deja.com wrote:
> >
> > Too bad you had to start a new thread especially since your comments
> > have already been addressed and shredded in that thread.
>
> We'll see how substantive you can be in addressing the specific
> points. So far in this thread, the naysayers are batting .000 with
> substance.
Is this why you switched threads then? Several people have given some
quite detailed explanations of what took place and why your scenario
does not make sense.
> > It was not a volcano
>
> Partial answer to point #4 here. It was volcanic rock, but you claim
> not a volcano. Can you explain that?
Yep. Have you read the references. Several people have described the
process but here we go again:
"Devils Tower consists of two general types of rocks; igneous and
sedimentary. About sixty million years ago in the early Tertiary
times a mass of magma intruded and forced its way upwards into the
layers of red, yellow, green, and gray Jurassic sedimentary
rocks. This mass did not protrude through the surface but cooled into a
hard igneous rock called phonolite porphyry. As millions of
years went by the soft sedimentary rock eroded, exposing the top of
Devils Tower. As the erosion continued it exposed more and
more of the igneous rock plug. It has been concluded that when the
magma cooled underground, the rock contracted and
fractured into columns of 4, 5, 6, or more sides. Thus, giving the
outside of Devils Tower the impression it has deep scratches
(National Park Service, 1981). "
http://www.bhc.edu/academics/science/harwoodr/Geol102/projects/Lackey/
> > ...
> >
> > > Erosion by water would explain observations 1-4 above. Water
would
> > > flatten the top, and as the water level dropped the erosion would
be
> > > greater in the mid-section than near the top. Directional current
> > > would make the erosion greater on one side than the other. The
> water
> > > would remove the volcanic ash, lava, debris, etc.
> >
> > Cool.
>
> Nothing substantive here.
Not needed. Your claim that water could have caused this is well within
the common explanation for the erosion.
http://www.nps.gov/deto/geo_slides/geology.htm
"Until erosion began its relentless work, Devils Tower was not visible
above the overlying sedimentary rocks. But the forces of erosion -
particularly that of water - began to wear away the sandstones and
shales. The much harder igneous rock survived the onslaught of erosional
forces, and the gray columns of Devils Tower began to appear above the
surrounding landscape.
As rain and snow continue to erode the sedimentary rocks surrounding
the Tower's base, and the Belle Fourche River carries away the debris,
more of Devils Tower will be exposed. But at the same time, the Tower
itself is slowly being eroded. Rocks are continually breaking off and
falling from the steep walls. Rarely do entire columns fall, but on
remote occasions, they do. Piles of rubble - broken columns, boulders,
small rocks, and stones - lie at the base of the Tower, indicating that
it was, at some time in the past, larger than it is today."
> >
> > > No one has yet suggested any other specific explanations for
points
> > 1-4
> > > above. Perhaps because Devils Tower rises to a mile above sea
> level,
> > > some simply refuse to accept water erosion as a possibility. But
> what
> > > other explanation could resolve 1-4 above?
> >
> > I am glad you seem to have given up on the idea that this shows
> evidence
> > of a global flood.
>
> Non sequitur here.
Not really since this was what you seemed to be arguing in your previous
thread on this topic.
> > But then little evidence of such a flood exists and many contrary
> data.
>
> Conclusory allegation here.
Notice the absence of supporting evidence of a global flood. Are you
interested in the data that disproves a global flood? For instance ask
the creationist researcher of last century who set out to prove the
global flood only to conclude that it was unsupported by the data.
> 3 points not addressed at all, and the 4th point only partially
> addressed without any explanation.
Then I am doing not worse than you are but now that I have added
explanations, it's your turn to show evidence of a global flood as found
in the devil's tower.
Alan Barclay
>above. Perhaps because Devils Tower rises to a mile above sea level,
>some simply refuse to accept water erosion as a possibility. But what
>other explanation could resolve 1-4 above?
I've just realized a major flaw in your argument. Lets say that you're
right, and Devil's Tower was eroded by a flood. However, you claim that
Devil's Tower is unique. How can this be if it was a world wide flood?
If a feature is demonstrative of a particular geological history, then
I'd expect it to be repeated whenever that geological history is
repeated. There is not just one fjord in Norwary, there are thousands
of them, wherever the glaciars met the sea. A world wide flood carving
a Devils Tower should mean that we've hundreds, thousands, or millions
of them.
Which one of your misconceptions would you like to give up first?
Mark VandeWettering
1. At least as a possibility, it may be that the underlying igneous
intrusion in fact may have been broader near the top, and the underlying
erosion processes preserve that original geometry.
2. Tell me, the eroded side wouldn't per chance be the south side?
3. The intrusion occurs in sedimentary rock. The intrusion could have
hit a particular layer which was more resistent to intrusion, and instead
spread out along the sediment line rather than penetrating it. This is
also in line with the answer to 1.
4. It wasn't a volcano, in the sense that magma never reached the
surface to become a lava flow. Hence, one wouldn't expect to find
lava fields, flows, ash, etc.
Mark
>Andy
--
/* __ __ __ ____ __*/float m,a,r,k,v;main(i){for(;r<4;r+=.1){for(a=0;
/*| \/ |\ \ / /\ \ / /*/a<4;a+=.06){k=v=0;for(i=99;--i&&k*k+v*v<4;)m=k*k
/*| |\/| | \ V / \ \/\/ / */-v*v+a-2,v=2*k*v+r-2,k=m;putchar("X =."[i&3]);}
/*|_| |_ark\_/ande\_/\_/ettering <ma...@telescopemaking.org> */puts("");}}
Adam Marczyk
Other people have offered better answers to these points than I could, so I
won't bother. Nevertheless, I'm driven to ask: Just what kind of water
currents do you think would produce those remarkably tall, straight vertical
columnar formations that the merest glimpse of photos of Devil's Tower
shows?
> Andy
>
>
> Sent via Deja.com
> http://www.deja.com/
>
--
When I am dreaming,
I don't know if I'm truly asleep, or if I'm awake.
When I get up,
I don't know if I'm truly awake, or if I'm still dreaming...
--Forest for the Trees, "Dream"
To send e-mail, change "excite" to "hotmail"
Lowell Ross
>
so, why aren't there a lot of such structures? If Devil's Tower was caused
by a worldwide flood, such structures should be common. If it is rare or
unique, it was more likely caused by conditions or phenomena unique to the
area.
Mark VandeWettering
The "pattern" does nothing of the sort. It may suggest that to you,
but frankly, calling you a cretin would be an insult to cretins. If
you've got a problem with geologists who seemingly don't come to the
conclusion that you do, why unfairly involve evolutionists in the
discussion anyway? When you don't get a good hamburger at McDonalds
do you go to the local hardware store and complain there?
Bobby D. Bryant
> The erosion pattern of Devils Tower is particularly prominent:
So. When you lose an argument, you start a new thread on it and hope for
better results?
Bobby Bryant
Austin, Texas
Nell P. Wright
Starting a new thread isn't going to change the information you were
given in the last one. All your so-called points were fully addressed
there. However...
>
> (1) its sides eroded more in the mid-section than near the top;
Wind, rain, sun, water, water freezing expanding and melting, streams,
glaciers...
>
> (2) one side eroded more than the opposite side;
See above.
>
> (3) its top is remarkably flat; and
Glacier.
>
> (4) there is "no evidence of volcanic activity anywhere in the area.
No
> volcanic ash, no lava flows, no debris...nada," as one poster
observed.
That is because it is not a volcano. It never was a volcano. It never
will be a volcano.
Now it's YOUR turn. Please document the evidence for such a flood in
this particular area (certainly if there *was* a flood, there would be
more evidence than one geological formation, so let's hear the rest of
it), and why there is only one formation of this kind there; if it was
caused by floodwaters, there should be more of 'em, right? I'm going to
cut you some slack; I'm not even requiring you to document a global
flood here, just "an enormous flood".
>
> You can view some pictures at
>
http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/devils_tow
> er.html
>
> In another thread, I doubted there were any other structures
comparable
> to Devils Tower. I sorted through numerous responses but only found
> Beacon Rock to be analogous. In contrast, however, Beacon Rock "rises
> to a very sharp point," in the words of explorer Lewis. Nor are there
> any signs of similarity between Beacon Rock and Devils Tower on the
> other three observations above.
> http://lewisandclarktrail.com/section4/wacities/vancouver/scenicgorge/
Not comparable for your purposes, you mean.
>
> Erosion by water would explain observations 1-4 above.
Yes, indeed. *Water*.
> Water would
> flatten the top, and as the water level dropped the erosion would be
> greater in the mid-section than near the top. Directional current
> would make the erosion greater on one side than the other. The water
> would remove the volcanic ash, lava, debris, etc.
>
> No one has yet suggested any other specific explanations for points
1-4
> above. Perhaps because Devils Tower rises to a mile above sea level,
> some simply refuse to accept water erosion as a possibility. But what
> other explanation could resolve 1-4 above?
See above. Re-read the responses to your other thread. Read what
geologists have to say about it. I don't think you'll find a flood
mentioned anywhere. Them's the facts. I know you don't like facts...but
then I'm sure you'll have no problem ignoring these...
Nell P. Wright
Matt Silberstein
[snip]
> If you can't address the specific points, then you can't judge who is
> correct. Do you think a judge cares how many people in the courtroom
> side with one party over the other?
No, I think that a judge allows expert testimony from recognized
experts in the field. I think that a judge would not allow testimony on
a topic from someone who did not have knowledge of the topic. Andrew is
a geologist, you are not. So, given the above what point do you have at
all? You don't know geology and you can't explain the tower. Andrew
does know geology and can explain the tower.
[snip]
> Right. It's only those emotionally opposed to enormous flood who
> would automatically reject a flood rising as high as Denver.
Those and those who know something about geology.
[snip]
--
Matt Silberstein
Unhappy the country that needs heroes. B. Brecht
Derek Stevenson
> The erosion pattern of Devils Tower is particularly prominent:
>
> (1) its sides eroded more in the mid-section than near the top;
>
> (2) one side eroded more than the opposite side;
>
> (3) its top is remarkably flat; and
>
> (4) there is "no evidence of volcanic activity anywhere in the area.
> No volcanic ash, no lava flows, no debris...nada," as one poster
> observed.
[snip]
> Erosion by water would explain observations 1-4 above. Water would
> flatten the top, and as the water level dropped the erosion would be
> greater in the mid-section than near the top. Directional current
> would make the erosion greater on one side than the other. The water
> would remove the volcanic ash, lava, debris, etc.
>
> No one has yet suggested any other specific explanations for points
> 1-4 above. Perhaps because Devils Tower rises to a mile above sea
> level, some simply refuse to accept water erosion as a possibility.
> But what other explanation could resolve 1-4 above?
Then you should be able to provide examples of similar structures that
have clearly been formed -- or better still, are in the process of being
formed -- by erosion.
The Flood may have been a unique, one-time occurrence, but running water
and rock still exist in abundance.
R. Tang
>In article <20010104213226...@ng-cn1.aol.com>,
> gyu...@aol.com (Gyudon Z) wrote:
>> Andrew Macrae et al. have explained Devil's Tower quite clearly.
>>
>> I know you don't like to actually read responses, but it is
>intellectually
>> dishonest to pretend that they don't exist.
>
>Ah, you think you're a mindreader too ("I know you don't like ...")?
>Evolved trait?
>
>I looked again at Andrew Macrae's responses. They don't address the
>four erosion points of this thread.
Yes, they do.
Now, stop lying and go back and REALLY read them. You may have to
do a year or two of remedial geology work, but they address quite well.
--
-Roger Tang, gwan...@u.washington.edu, Artistic Director PC Theatre
- Editor, Asian American Theatre Revue [NEW URL]
- http://www.abcflash.com/a&e/r_tang/AATR.html
-Declared 4-F in the War Between the Sexes
R. Tang
>> No
>> > volcanic ash, no lava flows, no debris...nada," as one poster
>> observed.
>> >
>>
>> It was not a volcano
>
>Partial answer to point #4 here. It was volcanic rock, but you claim
>not a volcano. Can you explain that?
Idiot.
Take some geology. Intrusive dike. Common in geologic areas.
Stop being so sloppy with your terminology; it would help if you
actually studied geology like some of us have.
Bill Hudson
also because it wasn't a volcano, but rather a magma intrusion. It
never breached the surface. Which, by the way, could also explain #3
above, although I'd bet it was more likely glacial grading.
Devils Postpile was also exposed and graded flat on top by glaciers. In
some areas there are these beautiful polished tops of the columns, and
you can also see straight grooves crossing several yards of column-tops.
Then along comes river erosion and eats away at one side, exposing the
collonade flank. Its really impressive.
--
Bill Hudson
Andrew MacRae
|In article <933e5p$itk$1...@nnrp1.deja.com>,
| ghos...@my-deja.com wrote:
|> In article <933apk$gcp$1...@nnrp1.deja.com>,
|> and...@my-deja.com wrote:
|>
|> Too bad you had to start a new thread especially since your comments
|> have already been addressed and shredded in that thread.
|
|We'll see how substantive you can be in addressing the specific
|points. So far in this thread, the naysayers are batting .000 with
|substance.
It is convienent that you initiated a new thread, then.
|> > The erosion pattern of Devils Tower is particularly prominent:
|> >
|> > (1) its sides eroded more in the mid-section than near the top;
|> >
|> > (2) one side eroded more than the opposite side;
|> >
|> > (3) its top is remarkably flat; and
Do the words "laccolith", "columnar jointing", "mass wasting", and
"gravitational slump" help? If not, you should look them up, in a
geological textbook.
|> > (4) there is "no evidence of volcanic activity anywhere in the area.
|> No
|> > volcanic ash, no lava flows, no debris...nada," as one poster
|> observed.
If it was ever there, it would likely be eroded off the top. It
is more likely it not did breach the surface, and, coincidentally, the
shape of such an intrusive body could easily account for a flat or nearly
flat top (e.g., if it were a sill or the thickest, central part of a
laccolith). Also note that the size and shape of the columns changes in
the upper part -- very characeristic of approaching the edges of a cooling
intrusive body, or the top of a thick lava flow.
Oh yeah. #4 is also wrong, in a way. There isn't evidence of
*volcanic* (i.e. extrusive) activity in the area (well, unless you include
distant Yellowstone), but there is ample evidence of other igneous
intrusive activity. For example, only 4km to the NW of Devils Tower are
the "Missouri Buttes". They are not as spectacular as Devils Tower (not
as thick/tall), but they are rather similar.
|>
|> It was not a volcano
|
|Partial answer to point #4 here. It was volcanic rock, but you claim
|not a volcano. Can you explain that?
Igneous rocks are rocks derived from a melt. Volcanic rocks are
melts that are extruded onto the surface, like lava flows, volcanic ash,
or pyroclastic flows. Intrusive rocks are melts that were produced
beneath the surface, but solidified there, without ever breaching the
surface. Examples are large, blob-shaped plutons or batholiths (often
composed of coarsely-crystalline granite or gabbro), dykes (sheets of rock
that cross-cut the enclosing stratigraphy), sills (sheets of rock that are
parallel to the enclosing stratigraphy), laccoliths (bulging,
pillow-shaped sills), and pipes (like the column of magma beneath some
types of volcanoes).
The rock at Devils Tower is apparently a phonolite -- a particular
type of moderately silicic, heterogeneously-cystalline, igneous rock. It
is clear from its shape and contacts with surrounding rocks at the base
that the portion currently exposed was at one time buried, and was not
erupted onto the surface at this level, therefore, it is an intrusive
structure. An open question worthy of debate is whether this intrusive
structure also reached the surface higher up, and erupted like a volcanic
pipe, or whether it was only ever sub-surface until being exposed by
erosion. Apparently evidence favours the latter interpretation, based
upon what published authors have said. Although significant to the
broader question of the origin of the structure, the answer does not
change what the appropriate term would be for the part that is present
today -- this part is clearly intrusive, not volcanic, even if the
now-eroded upper part once breached the surface. Note that it could still
be correct to call it the remnants of a volcano if it did breach the
surface, like similar volcanic necks in other parts of the world. It is
normal (if not inevitable) for volcanoes to have both extrusive rocks on
the surface, and intrusive rocks at depth. This is probably the source of
confusion.
An intrusive situation raises an interesting question: what, if
anything, could the nature of this structure have to do with a global
flood, other than its subsequent erosion? An intrusion beneath the
Earth's surface under water is much the same as one beneath land, unless
it is very close to the surface (e.g., like an invasive sill -- more
details upon request). If it is just a matter of erosion providing
supposed evidence of a global flood, then why is this structure special in
that respect? Most of what I see is evidence of mass wasting -- i.e.
splitting along the pre-existing columnar joints and falling as rubble
around the structure. There are large fans of debris present around the
base. Rivers may be responsible for carrying away that rubble from the
base, but they are not resonsible for the shape of the sides, slumping is.
There are plenty of other examples of erosion in the area, and the
geomorphology bears little resemblance to the very distinctive structures
seen in areas of known gigantic floods, such as the Channeled Scablands.
All I see is evidence of the activity of ordinary rivers and mass wasting.
So, what do you think is especially flood-like here, Andy?
..
-Andrew
mac...@agc.bio._NOSPAM_.ns.ca
Vincent Maycock
"Nell P. Wright" <wrigh...@my-deja.com> wrote in message
news:934ktc$gd0$1...@nnrp1.deja.com...
> In article <933apk$gcp$1...@nnrp1.deja.com>,
> and...@my-deja.com wrote:
> > The erosion pattern of Devils Tower is particularly prominent:
>
> Starting a new thread isn't going to change the information you were
> given in the last one. All your so-called points were fully addressed
> there. However...
>
> >
> > (1) its sides eroded more in the mid-section than near the top;
>
> Wind, rain, sun, water, water freezing expanding and melting, streams,
> glaciers...
That sounds about right, Nell, except for the glaciers part. I doubt that
glaciers were involved with the formation of this Tower, although I would be
rather interested if you have geological data which suggest otherwise.
--
Vince
David Kellogg
[snip answer to Andy Schlafly]
I just wanted to say that I continue to be impressed by Andrew MacRae and
other serious t.o. regulars. Sometimes it seems like a futile exercise to
give Andy S. such a comprehensive geology lesson, as he has avoided
learning much from his previous trips to the woodshed. However, _I_
learned a few things, as I imagine several other sideline observers did as
well. Andrew M., you explain geology almost as well as my sister. :-)
So your effort is not completely futile.
Hey Andy S.: At this point the responsible thing would be for you to say,
"Thanks for the information, Andrew. I guess I was wrong; the standard
geological explanations _are_ better than a single large flood.
Apologies for my stubbornness." Are you up to that?
Cheers,
David
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
David Kellogg Assistant Director
kel...@acpub.duke.edu University Writing Program
(919) 660-4357 Duke University
FAX (919) 660-4372 http://www.duke.edu/~kellogg/
R. Tang
David Kellogg <kel...@duke.edu> wrote:
>Andrew MacRae <mac...@agc.bio_nospam_.ns.ca> wrote:
>
>[snip answer to Andy Schlafly]
>
>I just wanted to say that I continue to be impressed by Andrew MacRae and
>other serious t.o. regulars.
That's why he is known (justifiably) as St. Andrew....
>Sometimes it seems like a futile exercise to
>give Andy S. such a comprehensive geology lesson, as he has avoided
>learning much from his previous trips to the woodshed. However, _I_
>learned a few things, as I imagine several other sideline observers did as
>well. Andrew M., you explain geology almost as well as my sister. :-)
>So your effort is not completely futile.
>
>Hey Andy S.: At this point the responsible thing would be for you to say,
>"Thanks for the information, Andrew. I guess I was wrong; the standard
>geological explanations _are_ better than a single large flood.
>Apologies for my stubbornness." Are you up to that?
Nah...Andy isn't "man enough" to do that.
Bobby D. Bryant
> Right. It's only those emotionally opposed to enormous flood who would
> automatically reject a flood rising as high as Denver.
Last week you were arguing that the world was "flat" before the flood, so
that the water wouldn't have to rise that high at all.
You throw hypotheses out and then retract them at the drop of a hat --
whatever you think will help in the current thread of argument.
Bobby Bryant
Austin, Texas
Howard Hershey
"R. Tang" wrote:
>
> In article <934vqo$sdj$1...@news.duke.edu>,
> David Kellogg <kel...@duke.edu> wrote:
> >Andrew MacRae <mac...@agc.bio_nospam_.ns.ca> wrote:
> >
> >[snip answer to Andy Schlafly]
> >
> >I just wanted to say that I continue to be impressed by Andrew MacRae and
> >other serious t.o. regulars.
>
> That's why he is known (justifiably) as St. Andrew....
It's tough to be called a golf course. We should stop these ad
hominem attacks.
[snip]
Howard Hershey
>
> and...@my-deja.com wrote:
>
> > Right. It's only those emotionally opposed to enormous flood who would
> > automatically reject a flood rising as high as Denver.
>
[snip]
There certainly can be *local* floods a mile high (or anywhere where
the volume of input by rain overwhelms the rate of drainage to the
oceans in the local drainage area), but I think most people who have
any common sense (and understanding of the water cycle) would be quite
skeptical about the mechanics of a model involving waters rising from
current sea level to reach a mile higher than they currently do in
order and thus flood everything at this elevation by a
from-the-ocean-up mechanism.
marcof...@my-deja.com
R. Tang
Ad hominen??? St. Andrew is to be worshipped as a holy shrine!!
You, sir, are no golfer....you are a duffer!
>
>[snip]
Bill Hudson
I have to admire the persistence, if nothing else.
>
> The erosion pattern of Devils Tower is particularly prominent:
>
>
Agreed.
> (2) one side eroded more than the opposite side;
>
Agreed
> (3) its top is remarkably flat; and
>
Agreed
> (4) there is "no evidence of volcanic activity anywhere in the area. No
> volcanic ash, no lava flows, no debris...nada," as one poster observed.
>
Agreed, with the caveat that the tower itself is 'volcanic' (in laymans
terms) because of the type of rock it is. Other volcanic activity is
apparently non-existant in the area. I'll stipulate to this point due
to lack of contrary evidence.
> You can view some pictures at
> http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/devils_tow
> er.html
>
> In another thread, I doubted there were any other structures comparable
> to Devils Tower.
There are *lots* of structures comparable to Devils Tower in one way or
another. I seriously doubt you'll find any structure that has *all* of
the features of Devil's Tower. But then the question becomes "so
what"?
I seriously doubt you'll find any structure that has all of the features
of half-dome in Yosemite, or Ayers Rock in Australia, or Gibralter.
Absolute uniqueness exists in lots of places. However, each of the
structures I mention has 'comparable structures' elsewhere, as does
Devil's Tower.
>... I sorted through numerous responses but only found
> Beacon Rock to be analogous. In contrast, however, Beacon Rock "rises
> to a very sharp point," in the words of explorer Lewis. Nor are there
> any signs of similarity between Beacon Rock and Devils Tower on the
> other three observations above.
> http://lewisandclarktrail.com/section4/wacities/vancouver/scenicgorge/
>
> Erosion by water would explain observations 1-4 above.
Disagreed. 'Erosion by water' would explain *some* of the observations
above.
>... Water would
> flatten the top,
By what mechanism? If you say 'wave action' then you'd better be
prepared to claim that there are not any higher geographical elements in
the close vicinity, and there are.
>... and as the water level dropped the erosion would be
> greater in the mid-section than near the top. Directional current
> would make the erosion greater on one side than the other. The water
> would remove the volcanic ash, lava, debris, etc.
>
> No one has yet suggested any other specific explanations for points 1-4
> above. Perhaps because Devils Tower rises to a mile above sea level,
> some simply refuse to accept water erosion as a possibility. But what
> other explanation could resolve 1-4 above?
Water erosion is not a problem. In fact, water erosion is an
explanation for some of the features. <gasp> BUT it is not "flood
water" erosion.
Specific explanations *have* been presented for all of your points. You
obviously missed them.
> (1) its sides eroded more in the mid-section than near the top;
The erosion appears to follow the existing fracture patterns in the
collonades. The fracture patterns apparently form perpendicular to
lines of isotherms (areas of uniform temperature) as the rock cools. In
the case of Devil's Tower, the fracture patterns tend to form a slight
'neck'. Other similar collonade structures show similar waves, curves,
and straight areas. (cf. Devil's Postpile, Giant's Causeway, many
others). Wave action would have left more evidence of shelving, or
even carved caves as it did at Finegan's Cave. It certainly causes
those nice sharp corners of the columns to erode. cf. The Giant's
Causeway.
It seems clear to me that the columns fell away because the surrounding
rock was removed by erosion at a faster pace than the tower itself.
> (2) one side eroded more than the opposite side;
See my reply to #1.
> (3) its top is remarkably flat; and
Two possibilities occur to my teeny layperson's mind: a) the magma
intrusion 'topped out' on a layer of rock it couldn't easily penetrate,
or b) the whole thing, as well as surrounding rock, was sliced off flat
by glaciation. I favor 'b'.
> (4) there is "no evidence of volcanic activity anywhere in the area. No
> volcanic ash, no lava flows, no debris...nada," as one poster observed.
Two points here. a) the magma intrusion is known to have cooled
underground due to it's structure. b) the area apparently shows
evidence of glacial activity. Now, given these two things, why *would*
you expect to find volcanic ash, a 'lava flow' or debris?
To recap: the Devil's Tower apparently formed by the following:
1) sedimentary deposits laid down
2) magma intrusion into the sedimentary rock.
2.1) the magma cooled slowly, fracturing into columns along lines
perpendicular to areas of uniform temperature (isotherms).
3) glacial scouring removed the overburden of sedimentary rock, exposing
and scouring the top of the tower.
4) differential rates of erosion removed surrounding sedimentary rock
faster than the harder rock of the tower.
5) As the surrounding rock was gradually removed, the columns were
subjected to erosion, tending to break along the lines of fracture and
fall away from the tower, forming the scree slopes below the main tower.
Doubtless some geologist in the group will correct me on the areas I've
got wrong, but the point is; I don't see how Devil's Tower requires a
massive flood to form. It seems to be easily explained by known and
documented geologic processes in the area.
--
Bill Hudson
Al Petterson
>
Everyone seems to have let you get away with this. It's untrue. The top
third of the tower shows far more weathering -- and even to an untrained
eye has clearly been exposed to the elements for far longer -- than the
bottom two-thirds. Take a look more closely at the picture
http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/columns.jp
g
(my apologies if dejanews makes the URL hard to decipher.)
>
> (2) one side eroded more than the opposite side;
This is typical for rock formations. Water flows downhill; winds often
come from one direction (the "prevailing" one). Nothing unusual about
one side of an object being eroded more than another.
> (3) its top is remarkably flat;
Which makes it unusual, but geologic extrusions make all sorts of odd
shapes; the flat top seems likely to have been scraped that way by
glaciers (though I'm not a geologist and I don't actually know).
> and
>
> (4) there is "no evidence of volcanic activity anywhere in the area.
> No volcanic ash, no lava flows, no debris...nada," as one poster
> observed.
This is untrue. The 'one poster' was mistaken, and many other posters in
the previous thread pointed this out to you. There may be no *current*
geologic activity in the area, but Devil's Tower is 40 million years
old.
> Erosion by water would explain observations 1-4 above. Water would
> flatten the top,
Water erosion doesn't explain the greater weathering on the top third.
The more likely explanation by far is that some mechanism initially
exposed the top third, then stopped for several million years
(permitting the exposed portion to weather) and the remaining
surrounding sedimentary rock was exposed sometime more recently.
> The water
> would remove the volcanic ash, lava, debris, etc.
Um, Devil's Tower is cooled volcanic lava (that's what "igneous" means
in the url). If we gave the water sufficient force and time to clear
away other lava it would have cleared away Devil's Tower as well.
> Perhaps because Devils Tower rises to a mile above sea level,
> some simply refuse to accept water erosion as a possibility.
That's preposterous. The ground next to Devil's Tower is three-quarters
of a mile above sea level, and a river runs along next to the tower.
Why would you claim that anyone would doubt that water erosion occurs a
mile above sea level? Having spent last weekend in Lake Tahoe, I can
testify that there's plenty of water at five thousand feet. Mountains
are known for getting snowed on; snow melts; water runs downhill, QED.
There's also higher ground near Devil's Tower, if I recall correctly,
which easily provides a source for lots of running water (given a
different climate, and climates do change over time).
Not to mention that places that are a mile above sea level now were not
necessarily a mile above sea level forty million years ago -- we have
plenty of examples of that as well.
Not being a geologist or expert on this particular area, I don't know
the exact history. I'm sure there are people here who do. But it's not
that difficult to explain. It *is* a beautiful, impressive, and unique
formation; I've been there. The geologic explanation is surprising, I
admit -- it looks much more like it extruded up from the surface than
that it formed underground amid sedimentary rock and the rock eroded
away from around it. But then again geology is frequently surprising,
and one's initial assumptions are often wrong.
Ken Cox
> "R. Tang" wrote:
> > That's why he is known (justifiably) as St. Andrew....
> It's tough to be called a golf course. We should stop these ad
> hominem attacks.
In one of those odd loops that arise from time to time, there is
a joke calendar published every year called "World's Toughest
Golf Holes". They take pictures of geological features, like the
Grand Canyon or Victoria Falls, and digitally add a tiny little
tee area and green. Devil's Tower was featured in a recent year.
--
Ken Cox k...@research.bell-labs.com
Ken Cox
> "Bobby D. Bryant" <bdbr...@mail.utexas.edu> wrote:
> > You throw hypotheses out and then retract them at the drop of a hat --
> > whatever you think will help in the current thread of argument.
> Retraction? Where?
Good point. "Later ignore" would be a better phrase.
--
Ken Cox k...@research.bell-labs.com
Andrew MacRae
|In article <933d3f$i8u$1...@nnrp1.deja.com>,
| "David C. Fritzinger" <dfri...@my-deja.com> wrote:
|> and...@my-deja.com wrote:
|> > The erosion pattern of Devils Tower is particularly prominent:
|> >
|> > (1) its sides eroded more in the mid-section than near the top;
|> >
|> >
|> >
|> > (4) there is "no evidence of volcanic activity anywhere in the area.
|> No
|> > volcanic ash, no lava flows, no debris...nada," as one poster
|> > No one has yet suggested any other specific explanations for
|> points 1-4
|> sea level,
|>
|> I'll let the geologists answer your specific points (though it seems
|> to me that you 've already had your clock cleaned), but I couldn't
|> resist this one.
|
|correct. Do you think a judge cares how many people in the courtroom
|side with one party over the other?
No, but, because you haven't really put together a plausible
scientific case (e.g., elsewhere you say there is evidence for the
direction of water flow -- where and what is it?), it is a bit of a moot
point, Andy. Your comments are rife with fundamental misunderstandings
about what you are seeing in the picture. Your case probably wouldn't get
to trial in the first place, because you haven't adequately researched the
issue. A judge would probably tell you to come back in a month or two,
after you were prepared. You could start by reading some of the
references listed on the web page you previously cited, so that you
understand the conventional explanation you are rejecting.
|> If I'm in Denver, CO, and have a 1 inch pile of dirt, it
|> rises to one mile above sea level. How would you explain that?
|>
|> Answer: Denver is the "Mile-High City".
|
|Right. It's only those emotionally opposed to enormous flood who would
|automatically reject a flood rising as high as Denver.
Nonsense.
Denver: 5280ft
Spokane: ~2100ft
Salt Lake City: >4330-5200ft (depending upon location in the city)
Spokane is a bit less than half as high, but parts of western
Montana near Missoula are higher (these are relevant to the Spokane area
for interesting reasons), and Salt Lake City is almost the same altitude
as Denver. Why does this matter? Because all of these other areas are
thought to have been immersed in lake water or had gigantic floods rage
through them -- the Missoula and Bonneville floods. Most of modern Salt
Lake City used to be under water. Some of the suburbs up on the sides of
the local mountains are built on top of the old beaches, as are many of
the local gravel pits.
Altitude, therefore, is not the problem for conventional
geologists. The lack of specific geological evidence left by that
quantity of water, and the presence of other types of evidence, is the
problem. In the other areas I mentioned, the evidence for flooding is in
the form of stranded beaches and abandoned Gilbert-type deltas, varved
lake sediments, megadunes with huge foreset structures, streamlined hills,
and a variety of other features. Where is any of that in the Devils Tower
area? What is there are a great number of rather ordinary-looking
dendritic and meandering river valleys, starting with the Belle Fourche.
|> l.
|> > some simply refuse to accept water erosion as a possibility. But
|> what
|> > other explanation could resolve 1-4 above?
|> Many have said that there is water erosion. What they also said is
|> that it couldn't have been caused by the infamous WWF (world
|> wide flood, not world wrestling federation-actually, it couldn't have
|> been caused by that wwf either 8^) ). You've really got to learn to
|> read for content some day.
|
|Demonstrate that you found any content on the erosion issue. Some
|claimed that rainfall caused the erosion, but the pattern noted above
|disproves that. Do you think any evolutionist admitted that Devils
|Tower, which is a mile above sea level, could have been flooded?
Why would someone admit something for which there isn't any
supporting evidence, and for which there is plenty of contradictory
evidence? And what does any of this have to do with evolution? Most
geologists, even the creaionist ones, rejected global flood models decades
prior to the proposal of evolutionary theory, back in the early 1800s.
You are not proposing a new alternative, you are trying to resurrect an
alternative about 200 years after it was falsified in the opinion of most
geologists. People are understandably skeptical about your
interpretation.
-Andrew
mac...@agc.bio._NOSPAM_.ns.ca
Bill Hudson
>
> In article <933apk$gcp$1...@nnrp1.deja.com>,
> and...@my-deja.com wrote:
> > The erosion pattern of Devils Tower is particularly prominent:
> >
> > (1) its sides eroded more in the mid-section than near the top;
>
> Everyone seems to have let you get away with this. It's untrue. The top
> third of the tower shows far more weathering -- and even to an untrained
> eye has clearly been exposed to the elements for far longer -- than the
> bottom two-thirds. Take a look more closely at the picture
>
> http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/columns.jp
> g
>
Ah! Yes I see that very clearly now. I withdraw my 'agreed' to Andy's
point #1 in my prior posting.
--
Bill Hudson
Andrew MacRae
<roger...@my-dejanews.com> writes:
|and...@my-deja.com wrote:
|> No one has yet suggested any other specific explanations for points 1-4
|> above. Perhaps because Devils Tower rises to a mile above sea level,
|> other explanation could resolve 1-4 above?
|
|Encounters?
Yes, it was over to one side. They probably reforested the runway
in the ensuing years, though, to cover up the event :-) :-)
-Andrew
mac...@agc.bio._NOSPAM_.ns.ca
Bill Hudson
--
Bill Hudson
Bill Hudson
>
> and...@my-deja.com wrote:
>
> I have to admire the persistence, if nothing else.
>
> >
> > The erosion pattern of Devils Tower is particularly prominent:
> >
>
> >
>
> Agreed.
>
I seem to have flubbed the quoting in this section. It should have
read:
> (1) its sides eroded more in the mid-section than near the top;
>
To which I initially agreed. Based on Al Petterson's posting in this
thread, I now disagree. The top third of Devil's Tower clearly shows
more erosion than the bottom, or the midsection.
cf.
http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/columns.jpg
Someone else has disagreed with the glacial hypothesis, and since I'm
not a geologist, I can't address the issue.
[snipped]
> To recap: the Devil's Tower apparently formed by the following:
>
> 1) sedimentary deposits laid down
> 2) magma intrusion into the sedimentary rock.
> 2.1) the magma cooled slowly, fracturing into columns along lines
> perpendicular to areas of uniform temperature (isotherms).
> 3) glacial scouring removed the overburden of sedimentary rock, exposing
> and scouring the top of the tower.
I hereby revise #3 to read "Glacial scouring or some other geologic
process removed..."
> 4) differential rates of erosion removed surrounding sedimentary rock
> faster than the harder rock of the tower.
> 5) As the surrounding rock was gradually removed, the columns were
> subjected to erosion, tending to break along the lines of fracture and
> fall away from the tower, forming the scree slopes below the main tower.
>
> Doubtless some geologist in the group will correct me on the areas I've
> got wrong, but the point is; I don't see how Devil's Tower requires a
> massive flood to form. It seems to be easily explained by known and
> documented geologic processes in the area.
>
... and I stand by my conclusion.
--
Bill Hudson
Andrew MacRae
|In article <20010104213226...@ng-cn1.aol.com>,
| gyu...@aol.com (Gyudon Z) wrote:
|> Andrew Macrae et al. have explained Devil's Tower quite clearly.
|>
|> I know you don't like to actually read responses, but it is
|> intellectually dishonest to pretend that they don't exist.
|
|Ah, you think you're a mindreader too ("I know you don't like ...")?
|Evolved trait?
Well, I'm glad you read them. I thought I might be speaking to
the wind.
|I looked again at Andrew Macrae's responses. They don't address the
|four erosion points of this thread.
Yes. Obviously. Because you had not stated them yet in this new
thread. You still haven't stated them very well here, or why a Flood
model supposedly accounts for them effectively. For example, the
relatively flat top (#3) -- huh? Wouldn't flood waters round the top off
rather well? For that matter, wouldn't they tend to round off the entire
structure much more than its present shape would suggest? The top of the
structure would have experienced *much* stronger forces due to faster flow
than the bottom part would have, presuming it was some sort of
unidirectional current, which you seemed to imply by the claim that you
could tell which way it was flowing.
|> Of course, we've come to expect no better.
|
|I didn't expect you to be persuaded, but I thought you might present a
|substantive argument.
Why would you expect that? There are substantive arguments
presented in the references on the web page you cited. Did you look those
up yourself first, to familiarize yourself with what conventional
geologists interpret, or do you expect other people to do the work for
you? It is fine to expect other people to put forth a substantive
argument if they are going to disagree with you, but it is a bit redundant
to do so when other sources are available, and when your interpretation
isn't exactly detailed in the first place.
For example, why do you think one side is "more eroded" than the
opposite side (#2)? Be specific. There are two pictures on the web page
you cited. Describe which picture and side you mean -- the one facing the
viewer, or the silhouetted ones on left and right? You also mentioned
that you could somehow tell which way the flood currents had moved. How?
And which direction?
-Andrew
mac...@agc.bio._NOSPAM_.ns.ca
Boikat
>
> and...@my-deja.com wrote:
> > No one has yet suggested any other specific explanations for points 1-4
> > above. Perhaps because Devils Tower rises to a mile above sea level,
> > some simply refuse to accept water erosion as a possibility. But what
> > other explanation could resolve 1-4 above?
>
> Encounters?
Non sequitur, but yes.
Boikat
Andrew MacRae
writes:
|In article <933apk$gcp$1...@nnrp1.deja.com>,
| and...@my-deja.com wrote:
|> The erosion pattern of Devils Tower is particularly prominent:
|>
|> (1) its sides eroded more in the mid-section than near the top;
|
|Everyone seems to have let you get away with this. It's untrue.
By sloppiness or design, Andy is pretty vague about what he meant.
In some interpretations of his vague statement, he could be correct. I
guessed that he was referring to the way the shape of the tower "bows in"
on the sides very steeply, and is relatively flat and sharp-edged at the
top. Using crude ASCII graphics, the tower is shape like this:
_________
| |
| |
| |
/ \
/ \
---------------
Rather than the anticipated, more rounded shape to an ordinary
hill of similar height:
_____________
_/ | | \_ <--- less erosion here at the top
__/ | | \__
___/ | | \___ <---than here
/ / \ \
/ / \ \
-----------------------------------
Compared to an ordinary, rounded hill, Devils Tower looks like
erosion has occurred "more in the mid-section" to make it so steep. Is
this what Andy means? I don't know. It would be nice if he explained
himself better.
Anyway, the explanation for this shape is not difficult, in the
conventional model, once it is realized that the strucure is penetrated
with nearly vertical fractures (i.e. the columnar jointing), which
preferentially causes the cliff face to peel off, en masse, and pile up as
rubble at the bottom. If it were a homogeneous mass of rock, Andy's
question would be the makings of a genuine puzzle, but with an
understanding of the nature of the rock at this location, it is no
surprise at all. If you look at any other type of slope with columnar
jointing developed, it tends to form a steep cliff because of the way the
rock fails along the vertical fractures. In the case of Devils Tower,
because the columns fan out towards the base, and because the igneous mass
is not a continuous layer but more of a cylindrical plug, the shape is a
little more exotic than just a vertical cliff. The spreading column
geometry has an explanation too (although it has nothing to do with
erosion, but with cooling).
|The top
|third of the tower shows far more weathering -- and even to an untrained
|eye has clearly been exposed to the elements for far longer -- than the
|bottom two-thirds. Take a look more closely at the picture
It is more rubbly-looking, isn't it? But it isn't a random
arrangement. If you look even more closely, especially at the picture
towards the bottom, you will see that the geometry and size of the columns
changes towards the top of the rock mass -- they become bigger, and the
sides of the columns become more irregular. This is not a feature of
erosion, but of the column development itself. Look carefully, and you
will see a few spots where multiple columns merge upwards into one big,
uglier, bumpier one. This (or similar geometries) is a common feature in
basaltic lava flows, either towards the top or towards the bottom.
|http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/columns.jpg
|
|(my apologies if dejanews makes the URL hard to decipher.)
|
|>
|> (2) one side eroded more than the opposite side;
|
|This is typical for rock formations. Water flows downhill; winds often
|come from one direction (the "prevailing" one). Nothing unusual about
|one side of an object being eroded more than another.
You are right, but, frankly, it is not clear to me what "side"
Andy is referring to (Face on? Left? Right?), and until he specifies,
trying to explain it is futile. However, potential explanations are
numerous, and range from differences in erosion (e.g., the south side
receives more sun, and therefore more temperature extremes, than the
shaded side on the north, so fracturing due to ice or thermal expansion
and contraction will be different on either side), which side of the
structure has had a big slump most recently, to merely differences in
shape in the original intrusive rock mass (i.e. *nothing* to do with
erosion).
|> (3) its top is remarkably flat;
|
|Which makes it unusual, but geologic extrusions make all sorts of odd
|shapes; the flat top seems likely to have been scraped that way by
|glaciers (though I'm not a geologist and I don't actually know).
I think it is more likely in this case that the relatively flat
top (it isn't perfectly flat, just flatt*er*) is close to or parallel to
some kind of original geological boundary -- like the top of the
intrusion, butted up against a more resistant layer of rock that was once
on top. This proximity could account for the change in the column
geometry too. Alternatively, if this is a volcanic neck that did breach
the surface, it could simply be as far up as the pipe went to reach a
relatively flat surface, plus or minus a hundred metres or so of erosion
of the weakest material at the top (e.g., if there was an especially
bubbly and soft layer in the top part, it could have been removed by
ordinary erosion processes, while leaving the underlying, more resistant
layers of solid igneous rock virtually intact).
Regardless, because of the preferential fracturing of the columns
at the edges, any topography on the top of the original structure would
tend to be preserved, even as much of the edges were falling away. There
are plenty of analogues. It is *very* common for columnar-jointed basalt
flows to be quite flat on top, and not develop streams incised into the
top, even if they have been eroded away until they only consist of a small
mesa bounded by steep cliffs on all sides. The process is especially
effective if there is a weak layer below the resistant basalt flow.
|> and
|>
|> (4) there is "no evidence of volcanic activity anywhere in the area.
|> No volcanic ash, no lava flows, no debris...nada," as one poster
|> observed.
|
|This is untrue. The 'one poster' was mistaken, and many other posters in
|the previous thread pointed this out to you. There may be no *current*
|geologic activity in the area, but Devil's Tower is 40 million years
|old.
Yes. And, furthermore, it is almost the northwesternmost example
of a whole field of igneous structures in the area. This is explained in
one of the references on the page that Andy cited (the one in the GSA
Centenial Field Guide). The "Missouri Buttes" are just 4 kilometres or so
to the northwest, for example. They aren't as tall, but they are similar
composition and age, and they show that the igneous activity represented
by Devils Tower was not a solitary event.
|> Erosion by water would explain observations 1-4 above. Water would
|> flatten the top,
|
|Water erosion doesn't explain the greater weathering on the top third.
I have no idea how water would produce a flat top. It just isn't
characteristic of any kind of water flow I can think of. Rounding of an
obstacle to flow, to produce a shape more like a dome, is normal.
|The more likely explanation by far is that some mechanism initially
|exposed the top third, then stopped for several million years
|(permitting the exposed portion to weather) and the remaining
|surrounding sedimentary rock was exposed sometime more recently.
No, I think it is probably reflecting something about the shape of
the original structure, perhaps an overlying, bounding layer of the
country rock that has since been eroded away.
|> The water
|> would remove the volcanic ash, lava, debris, etc.
|
|Um, Devil's Tower is cooled volcanic lava (that's what "igneous" means
|in the url).
It is igneous, but I don't think it is extrusive. Not at this
level, anyway.
|If we gave the water sufficient force and time to clear
|away other lava it would have cleared away Devil's Tower as well.
|
|> Perhaps because Devils Tower rises to a mile above sea level,
|> some simply refuse to accept water erosion as a possibility.
|
|That's preposterous. The ground next to Devil's Tower is three-quarters
|of a mile above sea level, and a river runs along next to the tower.
|Why would you claim that anyone would doubt that water erosion occurs a
|mile above sea level? Having spent last weekend in Lake Tahoe, I can
|testify that there's plenty of water at five thousand feet.
Yes. In fact, the effectiveness of water erosion by streams and
rivers generally increases with altitude, because of the steeper
gradients. This is quite different from an immersive flow, where the flow
velocity is slow near the bottom (due to drag), and faster higher up.
|Mountains
|are known for getting snowed on; snow melts; water runs downhill, QED.
|There's also higher ground near Devil's Tower, if I recall correctly,
To the west, yes.
|which easily provides a source for lots of running water (given a
|different climate, and climates do change over time).
|
|Not to mention that places that are a mile above sea level now were not
|necessarily a mile above sea level forty million years ago -- we have
|plenty of examples of that as well.
Yes.
More problematic, though, for Andy's scenario, is not simply the
altitude, or the evidence for water deposition in rocks now found at that
altitude (e.g., like fossil corals and other marine fossils), but how such
fossils became intercalated with sediments that are clearly terrestrial
(e.g., soil horizons, river channels, and fossil trees in growth
position), in alternating successions, in those mountains. It isn't as
simple as Flood goes up, Flood goes down.
|Not being a geologist or expert on this particular area, I don't know
|the exact history. I'm sure there are people here who do.
I'm no expert either, but I can go to the library and read some of
the references listed on the web page where Andy got his information, and
find out how other geologists have interpreted the features found there.
|But it's not
|that difficult to explain.
Certainly not "impossible", even if it were difficult, which it
isn't.
|It *is* a beautiful, impressive, and unique
|formation; I've been there. The geologic explanation is surprising, I
|admit -- it looks much more like it extruded up from the surface than
|that it formed underground amid sedimentary rock and the rock eroded
|away from around it. But then again geology is frequently surprising,
|and one's initial assumptions are often wrong.
Yes. That has been true all through its history of study. I'm
sure plenty of suprises are left. But Andy has not identified any, as
near as I can tell.
-Andrew
mac...@agc.bio._NOSPAM_.ns.ca
Karel Plisek
Way back,
I came cross a similar mountain in Queensland, Australia.
I found it in hundreds of miles, floods ridden, flat lands.
It sticking out of a horizon like only a one tooth in a mouth.
It is obviously extremely old and half way covered in its
own rubble. The interesting thing about it is, that it is not
a solid rock but it is made out of long, straight hexagonal columns,
which appears to grow out of the ground. All of them are a similar size.
The locals call it a "musical mountain" as the rock columns,
when hit with a hammer, they sound like church bells.
An extremely hard rock.
I do not pretend to know its origins but it is very unlikely
that it is of volcanic origin. It has all characteristic of a
crystalline growth. The original size of the musical mountain
may have been some hundred of meters height. Perhaps such
crystalline growth of such proportions may be possible only
if it happened under water with help of some capable bacteria.
KP
John Harshman
mac...@agc.bio_NOSPAM_.ns.ca wrote:
> In article <933dpi$ioi$1...@nnrp1.deja.com> and...@my-deja.com writes:
> |In article <20010104213226...@ng-cn1.aol.com>,
> | gyu...@aol.com (Gyudon Z) wrote:
> |> Andrew Macrae et al. have explained Devil's Tower quite clearly.
> |>
> |> I know you don't like to actually read responses, but it is
> |> intellectually dishonest to pretend that they don't exist.
> |
> |Ah, you think you're a mindreader too ("I know you don't like ...")?
> |Evolved trait?
>
> Well, I'm glad you read them. I thought I might be speaking to
> the wind.
>
> |I looked again at Andrew Macrae's responses. They don't address the
> |four erosion points of this thread.
>
> Yes. Obviously. Because you had not stated them yet in this new
> thread. You still haven't stated them very well here, or why a Flood
> model supposedly accounts for them effectively. For example, the
> relatively flat top (#3) -- huh? Wouldn't flood waters round the top off
> rather well? For that matter, wouldn't they tend to round off the entire
> structure much more than its present shape would suggest? The top of the
> structure would have experienced *much* stronger forces due to faster flow
> than the bottom part would have, presuming it was some sort of
> unidirectional current, which you seemed to imply by the claim that you
> could tell which way it was flowing.
Is it possible he's suggesting something like a guyot? The gross shape is
rather guyot-like. Of course the timescale for guyot formation would
require the flood wave-base to remain constant for rather longer than a
year, but is Andy interested in details like that?
--
*Note the obvious spam-defeating modification
to my address if you reply by email.
Boikat
>
> Way back,
> I came cross a similar mountain in Queensland, Australia.
> I found it in hundreds of miles, floods ridden, flat lands.
> It sticking out of a horizon like only a one tooth in a mouth.
> It is obviously extremely old and half way covered in its
> own rubble. The interesting thing about it is, that it is not
> a solid rock but it is made out of long, straight hexagonal columns,
> which appears to grow out of the ground. All of them are a similar size.
> The locals call it a "musical mountain" as the rock columns,
> when hit with a hammer, they sound like church bells.
> An extremely hard rock.
> I do not pretend to know its origins but it is very unlikely
> that it is of volcanic origin.
Sounds like hexagonal basalt. Why would volcanism
(in this case, meaning any igneous rock generating
process that would produce lave or magma flow
close to the surface) not be the very likely
origin of the formation. (Please do not descend
into the "because scientists say so!" level)
> It has all characteristic of a
> crystalline growth.
The uniform columnar jointing is characteristic of
many basalt formations. What other physical
characteristics did the formation have that was
crystalline?
> The original size of the musical mountain
> may have been some hundred of meters height. Perhaps such
> crystalline growth of such proportions may be possible only
> if it happened under water with help of some capable bacteria.
The only example that comes to mind would be
stromatolites, however, they would usually display
a fine horizontal layering effect, alternating
between dark carbon rich bands and lighter
limestone or dolomite bands with significantly
less carbon present, and not really likely to form
close jointing like columnar basalt.
>
> KP
Boikat
marcof...@my-deja.com
and...@my-deja.com wrote:
> The erosion pattern of Devils Tower is particularly prominent:
>
> (1) its sides eroded more in the mid-section than near the top;
>
>
>
> (4) there is "no evidence of volcanic activity anywhere in the area.
> No volcanic ash, no lava flows, no debris...nada," as one poster
> observed.
>
>
http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/devils_tow
> er.html
>
Incompetent, irrelevant, and immaterial.
You need some context. Step back and look at the bigger picture.
Stitch this together for the Devil's Tower area:
http://terraserver.microsoft.com/image.asp?
S=14&T=1&X=163&Y=1542&Z=13&W=2
Likewise, stitch this for a view of a small part of the Channeled
Scablands near Coulee City, WA (includes the aptly named Dry Falls):
http://terraserver.microsoft.com/image.asp?
S=14&T=1&X=101&Y=1647&Z=11&W=2
The images are at the same scale. Both areas have comparable annual
precipitation. Exposed rock type in this part of the Scablands is
basalt (CRB); the rock comprising the Tower is a bit more silicic
(phonolite?) but the physical properties are similar. The exposed
basalt in the second photo is part of a series of flows; as others have
pointed out, the Tower is likely to be a shallow intrusive. FYI,
basaltic composition melts also form columnar joints upon cooling if
emplaced as sills.
The Channeled Scablands are acknowledged by geologists to be a classic
example of "catastrophic" flood geomorphology. Prominent flood-related
features in the Coulee City photo are potholes and scour channels, the
latter trending from ENE to WSW (upper right to lower left). Zoom in
for a closer look.
The Tower area physiography isn't flood-related; exposure of the Tower
is considered to result from common fluvial and mass wasting processes
typically occurring in the semi-arid parts of the U.S., and the fine-
scale features of the Tower (i.e., columnar jointing) and geometry are
consistent with known emplacement and solidification mechanisms of
intermediate to silicic magmas.
jmonrad
Adam Marczyk
news:3A56760C...@bellsouth.net...
Not to mention, how could bacteria possibly be responsible for depositing an
igneous formation? I've heard of extremophiles that can live in boiling
water, but this is ridiculous.
> >
> > KP
>
> Boikat
>
--
When I am dreaming,
I don't know if I'm truly asleep, or if I'm awake.
When I get up,
I don't know if I'm truly awake, or if I'm still dreaming...
--Forest for the Trees, "Dream"
To send e-mail, change "excite" to "hotmail"
Roger Schlafly
> > Yes. Obviously. Because you had not stated them yet in this new
> > thread. You still haven't stated them very well here, or why a Flood
> > model supposedly accounts for them effectively. For example, the
> > relatively flat top (#3) -- huh? Wouldn't flood waters round the top off
> > rather well? For that matter, wouldn't they tend to round off the entire
> > structure much more than its present shape would suggest? The top of the
> > structure would have experienced *much* stronger forces due to faster flow
> > than the bottom part would have, presuming it was some sort of
> > unidirectional current, which you seemed to imply by the claim that you
> > could tell which way it was flowing.
> Is it possible he's suggesting something like a guyot? The gross shape is
> rather guyot-like. Of course the timescale for guyot formation would
> require the flood wave-base to remain constant for rather longer than a
> year, but is Andy interested in details like that?
I think Andy is talking about a flood that might have happened
millions of years ago, and maybe lasted 1000s or millions of
years. (But all I know is what I read here.)
Boikat
True, however, Keral's description did not go into
deep enough of detail. I was giving KP the
benefit of the doubt, in case more info was
forthcoming.
Boikat
and...@my-deja.com
mac...@agc.bio_NOSPAM_.ns.ca wrote:
> In article <933fun$kci$1...@nnrp1.deja.com> and...@my-deja.com writes:
> |In article <933e5p$itk$1...@nnrp1.deja.com>,
> | ghos...@my-deja.com wrote:
> |> In article <933apk$gcp$1...@nnrp1.deja.com>,
> |> and...@my-deja.com wrote:
> |>
comments
> |> have already been addressed and shredded in that thread.
> |
> |We'll see how substantive you can be in addressing the specific
> |points. So far in this thread, the naysayers are batting .000 with
> |substance.
>
> It is convienent that you initiated a new thread, then.
I'll look through all of your postings in this thread to see if you
address the 4 points in a substantive manner and, if you do, I'll
respond. I'll even agree with you if the substance requires it.
> |> > The erosion pattern of Devils Tower is particularly prominent:
> |> >
> |> > (1) its sides eroded more in the mid-section than near the top;
> |> >
> |> > (2) one side eroded more than the opposite side;
> |> >
> |> > (3) its top is remarkably flat; and
>
> Do the words "laccolith", "columnar jointing", "mass wasting",
and
> "gravitational slump" help? If not, you should look them up, in a
> geological textbook.
None of this explains or even addresses points 1-3 above.
> |> > (4) there is "no evidence of volcanic activity anywhere in the
area.
> |> No
> |> > volcanic ash, no lava flows, no debris...nada," as one poster
> |> observed.
>
> If it was ever there, it would likely be eroded off the top.
Evidence of volcanic activity would not just be at the top. It would
be at the base as well. Something eroded it from there, and it could
not have been wind.
> It
> is more likely it not did breach the surface, and, coincidentally,
the
> shape of such an intrusive body could easily account for a flat or
nearly
> flat top (e.g., if it were a sill or the thickest, central part of a
> laccolith).
Are you referring to Devils Tower as the "intrusive body"? If that's
what you mean, then one would expect a point at the top, as in Beacon
Rock.
> Also note that the size and shape of the columns changes in
> the upper part -- very characeristic of approaching the edges of a
cooling
> intrusive body, or the top of a thick lava flow.
That's fine, but irrelevant to points 1-4 above.
> Oh yeah. #4 is also wrong, in a way. There isn't evidence of
> *volcanic* (i.e. extrusive) activity in the area (well, unless you
include
> distant Yellowstone), but there is ample evidence of other igneous
> intrusive activity. For example, only 4km to the NW of Devils Tower
are
> the "Missouri Buttes". They are not as spectacular as Devils Tower
(not
> as thick/tall), but they are rather similar.
Again, that's fine, but irrelevant to points 1-4 above. I don't
dispute that Devils Tower is igneous intrusive activity. The issue is
the erosion.
> |>
> |> It was not a volcano
> |
> |Partial answer to point #4 here. It was volcanic rock, but you claim
> |not a volcano. Can you explain that?
>
> Igneous rocks are rocks derived from a melt. Volcanic rocks
are
> melts that are extruded onto the surface, like lava flows, volcanic
ash,
> or pyroclastic flows. Intrusive rocks are melts that were produced
> beneath the surface, but solidified there, without ever breaching
the
> surface. Examples are large, blob-shaped plutons or batholiths
(often
> composed of coarsely-crystalline granite or gabbro), dykes (sheets of
rock
> that cross-cut the enclosing stratigraphy), sills (sheets of rock
that are
> parallel to the enclosing stratigraphy), laccoliths (bulging,
> pillow-shaped sills), and pipes (like the column of magma beneath
some
> types of volcanoes).
>
> The rock at Devils Tower is apparently a phonolite -- a
particular
> type of moderately silicic, heterogeneously-cystalline, igneous
rock. It
> is clear from its shape and contacts with surrounding rocks at the
base
> that the portion currently exposed was at one time buried, and was
not
> erupted onto the surface at this level, therefore, it is an
intrusive
> structure. An open question worthy of debate is whether this
intrusive
> structure also reached the surface higher up, and erupted like a
volcanic
> pipe, or whether it was only ever sub-surface until being exposed by
> erosion. Apparently evidence favours the latter interpretation,
based
> upon what published authors have said. Although significant to the
> broader question of the origin of the structure, the answer does not
> change what the appropriate term would be for the part that is
present
> today -- this part is clearly intrusive, not volcanic, even if the
> now-eroded upper part once breached the surface. Note that it could
still
> be correct to call it the remnants of a volcano if it did breach the
> surface, like similar volcanic necks in other parts of the world. It
is
> normal (if not inevitable) for volcanoes to have both extrusive rocks
on
> the surface, and intrusive rocks at depth. This is probably the
source of
> confusion.
This is all fine and interesting, but doesn't address the erosion issue
of this thread.
> An intrusive situation raises an interesting question: what,
if
> anything, could the nature of this structure have to do with a
global
> flood, other than its subsequent erosion? An intrusion beneath the
> Earth's surface under water is much the same as one beneath land,
unless
> it is very close to the surface (e.g., like an invasive sill -- more
> details upon request).
You say "other than its subsequent erosion." That's the title of this
thread -- "erosion issue."
> If it is just a matter of erosion providing
> supposed evidence of a global flood, then why is this structure
special in
> that respect? Most of what I see is evidence of mass wasting --
i.e.
> splitting along the pre-existing columnar joints and falling as
rubble
> around the structure. There are large fans of debris present around
the
> base. Rivers may be responsible for carrying away that rubble from
the
> base, but they are not resonsible for the shape of the sides,
slumping is.
Water carrying away the rubble at the base is part of 4 above. Points
1-3 suggest a flood as well -- but remain unaddressed.
> There are plenty of other examples of erosion in the area, and the
> geomorphology bears little resemblance to the very distinctive
structures
> seen in areas of known gigantic floods, such as the Channeled
Scablands.
Again, the issue is what caused the erosion at Devils Tower. Do you
see other signs of water erosion in the area at such high elevation?
> All I see is evidence of the activity of ordinary rivers and mass
wasting.
> So, what do you think is especially flood-like here, Andy?
Points 1-4 set forth at the top of the thread and cited again above.
Andy
and...@my-deja.com
mac...@agc.bio_NOSPAM_.ns.ca wrote:
> In article <9355df$2o$1...@nnrp1.deja.com> Al Petterson <aamp@my-
deja.com>
> writes:
> |In article <933apk$gcp$1...@nnrp1.deja.com>,
> | and...@my-deja.com wrote:
> |> The erosion pattern of Devils Tower is particularly prominent:
> |>
> |> (1) its sides eroded more in the mid-section than near the top;
> |
> |Everyone seems to have let you get away with this. It's untrue.
>
> By sloppiness or design, Andy is pretty vague about what he
meant.
I found this posting after I responded to your other one. This posting
at least mentions the erosion issue of this thread, and I respond below.
Yes, and also that more surface material appears to have eroded from
the middle than near the top.
> Anyway, the explanation for this shape is not difficult, in
the
> conventional model, once it is realized that the strucure is
penetrated
> with nearly vertical fractures (i.e. the columnar jointing), which
> preferentially causes the cliff face to peel off, en masse, and pile
up as
> rubble at the bottom. If it were a homogeneous mass of rock, Andy's
> question would be the makings of a genuine puzzle, but with an
> understanding of the nature of the rock at this location, it is no
> surprise at all. If you look at any other type of slope with
columnar
> jointing developed, it tends to form a steep cliff because of the way
the
> rock fails along the vertical fractures. In the case of Devils
Tower,
> because the columns fan out towards the base, and because the igneous
mass
> is not a continuous layer but more of a cylindrical plug, the shape
is a
> little more exotic than just a vertical cliff. The spreading column
> geometry has an explanation too (although it has nothing to do with
> erosion, but with cooling).
Look again at
http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/devils_tow
er.html
It's clear from the bottom picture that more surface material has
eroded from the middle of Devils Tower than near the top.
If you dispute this, then please so state. Otherwise, let's address
the erosion of the surface material at issue in this thread.
> |The top
> |third of the tower shows far more weathering -- and even to an
untrained
> |eye has clearly been exposed to the elements for far longer -- than
the
> |bottom two-thirds. Take a look more closely at the picture
Right. Explaining that difference is the issue here. It appears to
represent a water line around the Tower.
> It is more rubbly-looking, isn't it? But it isn't a random
> arrangement. If you look even more closely, especially at the
picture
> towards the bottom, you will see that the geometry and size of the
columns
> changes towards the top of the rock mass -- they become bigger, and
the
> sides of the columns become more irregular. This is not a feature
of
> erosion, but of the column development itself. Look carefully, and
you
> will see a few spots where multiple columns merge upwards into one
big,
> uglier, bumpier one. This (or similar geometries) is a common
feature in
> basaltic lava flows, either towards the top or towards the bottom.
I looked at the picture again. The top third plainly has surface
material that has eroded from the middle third. It's not just columns
merging together. That may occur as well, but there far is more than
that.
Are you saying that there is no difference in erosion of the surface
material as discribed above? If that's your argument, then please be
precise. If that's not your argument, then please address the
difference in erosion.
>
|http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/columns.j
pg
> |
> |(my apologies if dejanews makes the URL hard to decipher.)
> |
> |>
> |> (2) one side eroded more than the opposite side;
> |
> |This is typical for rock formations. Water flows downhill; winds
often
> |come from one direction (the "prevailing" one). Nothing unusual
about
> |one side of an object being eroded more than another.
>
> You are right, but, frankly, it is not clear to me what "side"
> Andy is referring to (Face on? Left? Right?), and until he
specifies,
> trying to explain it is futile. However, potential explanations are
> numerous, and range from differences in erosion (e.g., the south
side
> receives more sun, and therefore more temperature extremes, than the
> shaded side on the north, so fracturing due to ice or thermal
expansion
> and contraction will be different on either side), which side of the
> structure has had a big slump most recently, to merely differences
in
> shape in the original intrusive rock mass (i.e. *nothing* to do with
> erosion).
Compare the right side to the left side on the top picture at the site
I provided, as well as the depression in the front side. The erosion
is directional, suggesting that it was caused by water flow.
> |> (3) its top is remarkably flat;
> |
> |Which makes it unusual, but geologic extrusions make all sorts of odd
> |shapes; the flat top seems likely to have been scraped that way by
> |glaciers (though I'm not a geologist and I don't actually know).
The trouble with that explanation is that Devils Tower is so high up.
Also, if glaciers scraped it, then it was likely flooded as well.
Other posters have noted that large lakes can occur at high elevations,
but only if trapped by mountains. No trapping of water around Devils
Tower.
> I think it is more likely in this case that the relatively
flat
> top (it isn't perfectly flat, just flatt*er*) is close to or parallel
to
> some kind of original geological boundary -- like the top of the
> intrusion, butted up against a more resistant layer of rock that was
once
> on top. This proximity could account for the change in the column
> geometry too. Alternatively, if this is a volcanic neck that did
breach
> the surface, it could simply be as far up as the pipe went to reach
a
> relatively flat surface, plus or minus a hundred metres or so of
erosion
> of the weakest material at the top (e.g., if there was an especially
> bubbly and soft layer in the top part, it could have been removed by
> ordinary erosion processes, while leaving the underlying, more
resistant
> layers of solid igneous rock virtually intact).
If Devils Tower pierced a crust, then one would expect a point-like
top. As the crust broke, the Tower would form a point at the place of
breakage. See, e.g., Beacon Rock. Moreover, gravity would work
against a flat top for such a large structure.
> Regardless, because of the preferential fracturing of the
columns
> at the edges, any topography on the top of the original structure
would
> tend to be preserved, even as much of the edges were falling away.
There
> are plenty of analogues. It is *very* common for columnar-jointed
basalt
> flows to be quite flat on top, and not develop streams incised into
the
> top, even if they have been eroded away until they only consist of a
small
> mesa bounded by steep cliffs on all sides. The process is
especially
> effective if there is a weak layer below the resistant basalt flow.
Feel free to provide a structure analogous to Devils Tower with its
size and flat top, and we can look at them. I doubt other real
examples exist -- unless they were flooded too! :-)
>
> |> and
> |>
> |> (4) there is "no evidence of volcanic activity anywhere in the
area.
> |> No volcanic ash, no lava flows, no debris...nada," as one poster
> |> observed.
> |
> |This is untrue. The 'one poster' was mistaken, and many other
posters in
> |the previous thread pointed this out to you. There may be no
*current*
> |geologic activity in the area, but Devil's Tower is 40 million years
> |old.
Then that only reinforces my point. What eroded the debris?
> Yes. And, furthermore, it is almost the northwesternmost
example
> of a whole field of igneous structures in the area. This is
explained in
> one of the references on the page that Andy cited (the one in the
GSA
> Centenial Field Guide). The "Missouri Buttes" are just 4 kilometres
or so
> to the northwest, for example. They aren't as tall, but they are
similar
> composition and age, and they show that the igneous activity
represented
> by Devils Tower was not a solitary event.
OK, fine. What eroded the debris?
> |> Erosion by water would explain observations 1-4 above. Water would
> |> flatten the top,
> |
> |Water erosion doesn't explain the greater weathering on the top
third.
It looks like a water line dividing the top third from the middle third.
> I have no idea how water would produce a flat top. It just
isn't
> characteristic of any kind of water flow I can think of. Rounding of
an
> obstacle to flow, to produce a shape more like a dome, is normal.
Flattened rock formations are fairly common in the oceans, I think. If
Devils Tower originally had a point at top, water pressure could easily
break it and then smooth out the broken surface.
> |The more likely explanation by far is that some mechanism initially
> |exposed the top third, then stopped for several million years
> |(permitting the exposed portion to weather) and the remaining
> |surrounding sedimentary rock was exposed sometime more recently.
That's tough to formulate. Everyone seems to agree that the Tower rose
in one step, not two.
> No, I think it is probably reflecting something about the shape
of
> the original structure, perhaps an overlying, bounding layer of the
> country rock that has since been eroded away.
Ah, yes, the erosion issue. What eroded it? It must explain the
pattern of erosion.
> |> The water
> |> would remove the volcanic ash, lava, debris, etc.
> |
> |Um, Devil's Tower is cooled volcanic lava (that's what "igneous"
means
> |in the url).
>
> It is igneous, but I don't think it is extrusive. Not at this
> level, anyway.
OK, fine.
> |If we gave the water sufficient force and time to clear
> |away other lava it would have cleared away Devil's Tower as well.
Not necessarily. Lots of rock formations still exist in the oceans.
> |
> |> Perhaps because Devils Tower rises to a mile above sea level,
> |> some simply refuse to accept water erosion as a possibility.
> |
> |That's preposterous. The ground next to Devil's Tower is three-
quarters
> |of a mile above sea level, and a river runs along next to the tower.
> |Why would you claim that anyone would doubt that water erosion
occurs a
> |mile above sea level? Having spent last weekend in Lake Tahoe, I can
> |testify that there's plenty of water at five thousand feet.
Because Lake Tahoe has mountains all around to trap the water.
[snip]
> |Not to mention that places that are a mile above sea level now were
not
> |necessarily a mile above sea level forty million years ago -- we have
> |plenty of examples of that as well.
>
> Yes.
Yes, indeed. Do you agree that Devils Tower may have been much closer
to sea level years ago? Likewise, do you agree that the depth of
oceans may have been less years ago?
> More problematic, though, for Andy's scenario, is not simply
the
> altitude, or the evidence for water deposition in rocks now found at
that
> altitude (e.g., like fossil corals and other marine fossils), but how
such
> fossils became intercalated with sediments that are clearly
terrestrial
> (e.g., soil horizons, river channels, and fossil trees in growth
> position), in alternating successions, in those mountains. It isn't
as
> simple as Flood goes up, Flood goes down.
This thread is not devoted to discussing general Biblical Flood
issues. But to answer your question, I think Biblical Flood advocates
cite the likely violence of a flood as the reason for intercalated
sediments.
[snip]
> |It *is* a beautiful, impressive, and unique
> |formation; I've been there. The geologic explanation is surprising,
I
> |admit -- it looks much more like it extruded up from the surface than
> |that it formed underground amid sedimentary rock and the rock eroded
> |away from around it. But then again geology is frequently
surprising,
> |and one's initial assumptions are often wrong.
>
> Yes. That has been true all through its history of study.
I'm
> sure plenty of suprises are left. But Andy has not identified any,
as
> near as I can tell.
Whew! I got through all this, but still cannot find a clear statement
and substance on:
1) whether you think there are differences in erosion at Devils Tower,
and
2) whether you think a flood could have caused those differences (and
if not, what did cause the specific erosion pattern observed).
Once again, I note the thread title: "Devils Tower erosion issue".
Andy
Gyudon Z
He has just told you why it appears that the column has eroded more in the
middle than near the top, and explained why this is the case. If you dispute
this explanation, please do so.
<snip>
>> You are right, but, frankly, it is not clear to me what "side"
>> Andy is referring to (Face on? Left? Right?), and until he
>specifies,
>> trying to explain it is futile. However, potential explanations are
>> numerous, and range from differences in erosion (e.g., the south
>side
>> receives more sun, and therefore more temperature extremes, than the
>> shaded side on the north, so fracturing due to ice or thermal
>expansion
>> and contraction will be different on either side), which side of the
>> structure has had a big slump most recently, to merely differences
>in
>> shape in the original intrusive rock mass (i.e. *nothing* to do with
>> erosion).
>
>Compare the right side to the left side on the top picture at the site
>I provided, as well as the depression in the front side. The erosion
>is directional, suggesting that it was caused by water flow.
Or sun exposure causing temperature extrema, or any number of other
explanations.
<snip>
>> I think it is more likely in this case that the relatively
>flat
>> top (it isn't perfectly flat, just flatt*er*) is close to or parallel
>to
>> some kind of original geological boundary -- like the top of the
>> intrusion, butted up against a more resistant layer of rock that was
>once
>> on top. This proximity could account for the change in the column
>> geometry too. Alternatively, if this is a volcanic neck that did
>breach
>> the surface, it could simply be as far up as the pipe went to reach
>a
>> relatively flat surface, plus or minus a hundred metres or so of
>erosion
>> of the weakest material at the top (e.g., if there was an especially
>> bubbly and soft layer in the top part, it could have been removed by
>> ordinary erosion processes, while leaving the underlying, more
>resistant
>> layers of solid igneous rock virtually intact).
>
>If Devils Tower pierced a crust, then one would expect a point-like
>top. As the crust broke, the Tower would form a point at the place of
>breakage.
And forty million years of erosion would probably deal with those points pretty
easily.
>See, e.g., Beacon Rock. Moreover, gravity would work
>against a flat top for such a large structure.
Why? If, for example, it is as far up as the pipe went, then the semiliquid
stone coming up the pipe would "seek its own level", that is, form a plane
perpendicular to the local radius of the earth.
>> Regardless, because of the preferential fracturing of the
>columns
>> at the edges, any topography on the top of the original structure
>would
>> tend to be preserved, even as much of the edges were falling away.
>There
>> are plenty of analogues. It is *very* common for columnar-jointed
>basalt
>> flows to be quite flat on top, and not develop streams incised into
>the
>> top, even if they have been eroded away until they only consist of a
>small
>> mesa bounded by steep cliffs on all sides. The process is
>especially
>> effective if there is a weak layer below the resistant basalt flow.
>
>Feel free to provide a structure analogous to Devils Tower with its
>size and flat top, and we can look at them. I doubt other real
>examples exist -- unless they were flooded too! :-)
It's been done in both threads. In fact, it was done in the post you've
responded to.
<snip>
>> Yes. And, furthermore, it is almost the northwesternmost
>example
>> of a whole field of igneous structures in the area. This is
>explained in
>> one of the references on the page that Andy cited (the one in the
>GSA
>> Centenial Field Guide). The "Missouri Buttes" are just 4 kilometres
>or so
>> to the northwest, for example. They aren't as tall, but they are
>similar
>> composition and age, and they show that the igneous activity
>represented
>> by Devils Tower was not a solitary event.
>OK, fine. What eroded the debris?
I believe rainwater was the prevailing explanation.
>> |> Erosion by water would explain observations 1-4 above. Water would
>> |> flatten the top,
>> |
>> |Water erosion doesn't explain the greater weathering on the top
>third.
>
>It looks like a water line dividing the top third from the middle third.
I'm afraid I don't see that, apart from what Macrae already explained about the
distinctive shape of the tower. I'm sure Macrae would have held forth on it if
there were some other difference in erosion.
>> I have no idea how water would produce a flat top. It just
>isn't
>> characteristic of any kind of water flow I can think of. Rounding of
>an
>> obstacle to flow, to produce a shape more like a dome, is normal.
>Flattened rock formations are fairly common in the oceans, I think.
Do you have a citation for that?
>If
>Devils Tower originally had a point at top, water pressure could easily
>break it and then smooth out the broken surface.
Except that when you press down on something with even pressure, you tend to
spread out the bottom, not break the top. You see, the bottom not only has all
the external pressure to deal with, but the weight of whatever is above it, so
it is what is going to "feel" the pressure first.
<snip>
>> No, I think it is probably reflecting something about the shape
>of
>> the original structure, perhaps an overlying, bounding layer of the
>> country rock that has since been eroded away.
>Ah, yes, the erosion issue. What eroded it? It must explain the
>pattern of erosion.
I think rainwater (and possibly the expansion of ice) is the prevailing
explanation.
<snip>
>> |Not to mention that places that are a mile above sea level now were
>not
>> |necessarily a mile above sea level forty million years ago -- we have
>> |plenty of examples of that as well.
>>
>> Yes.
>
>Yes, indeed. Do you agree that Devils Tower may have been much closer
>to sea level years ago? Likewise, do you agree that the depth of
>oceans may have been less years ago?
I think he agrees that it is possible, but forty million years ago Pangaea had
already broken up and the continent was quite comparable to the configuration
you'll find it in now.
>> More problematic, though, for Andy's scenario, is not simply
>the
>> altitude, or the evidence for water deposition in rocks now found at
>that
>> altitude (e.g., like fossil corals and other marine fossils), but how
>such
>> fossils became intercalated with sediments that are clearly
>terrestrial
>> (e.g., soil horizons, river channels, and fossil trees in growth
>> position), in alternating successions, in those mountains. It isn't
>as
>> simple as Flood goes up, Flood goes down.
>
>This thread is not devoted to discussing general Biblical Flood
>issues. But to answer your question, I think Biblical Flood advocates
>cite the likely violence of a flood as the reason for intercalated
>sediments.
No, that would explain it if they were all mixed together. Layering that
precise can't be done over one year in turbulent waters.
>[snip]
>> |It *is* a beautiful, impressive, and unique
>> |formation; I've been there. The geologic explanation is surprising,
>I
>> |admit -- it looks much more like it extruded up from the surface than
>> |that it formed underground amid sedimentary rock and the rock eroded
>> |away from around it. But then again geology is frequently
>surprising,
>> |and one's initial assumptions are often wrong.
>>
>> Yes. That has been true all through its history of study.
>I'm
>> sure plenty of suprises are left. But Andy has not identified any,
>as
>> near as I can tell.
>
>Whew! I got through all this, but still cannot find a clear statement
>and substance on:
>
>1) whether you think there are differences in erosion at Devils Tower,
>and
He explained why there appears to be a difference in erosion between the
columnar bit of the tower and the conical spreading at the base.
>2) whether you think a flood could have caused those differences
Since he has explained what *really* caused those differences, I think not.
>(and
>if not, what did cause the specific erosion pattern observed).
Rainwater, thermal expansion, water expanding when it freezes...
>Once again, I note the thread title: "Devils Tower erosion issue".
I notice you seem to have conceded your other three points. That's nice...
"Between true science and erroneous doctrines, ignorance is in the middle."
Thomas Hobbes, Leviathan
Gyudon Z
>In article <934sj6$htk$1...@darwin.ediacara.org>,
> mac...@agc.bio_NOSPAM_.ns.ca wrote:
>> In article <933fun$kci$1...@nnrp1.deja.com> and...@my-deja.com writes:
>> |In article <933e5p$itk$1...@nnrp1.deja.com>,
>> | ghos...@my-deja.com wrote:
>> |> In article <933apk$gcp$1...@nnrp1.deja.com>,
>> |> and...@my-deja.com wrote:
<snip>
>> |> > The erosion pattern of Devils Tower is particularly prominent:
>> |> >
>> |> > (1) its sides eroded more in the mid-section than near the top;
>> |> >
>> |> > (2) one side eroded more than the opposite side;
>> |> >
>> |> > (3) its top is remarkably flat; and
>>
>> Do the words "laccolith", "columnar jointing", "mass wasting",
>and
>> "gravitational slump" help? If not, you should look them up, in a
>> geological textbook.
>None of this explains or even addresses points 1-3 above.
They would if you would actually look them up. Learning is so important, Andy;
why don't you try it sometime?
>> |> > (4) there is "no evidence of volcanic activity anywhere in the
>area.
>> |> No
>> |> > volcanic ash, no lava flows, no debris...nada," as one poster
>> |> observed.
>> If it was ever there, it would likely be eroded off the top.
>Evidence of volcanic activity would not just be at the top. It would
>be at the base as well. Something eroded it from there, and it could
>not have been wind.
He means that it would overlay whatever preexisting structure was there. Erode
the overlaying away and the preexisting structure will be what's left over. It
wouldn't be at the top of the tower, it would be at the top of the surrounding
area.
>> It
>> is more likely it not did breach the surface, and, coincidentally,
>the
>> shape of such an intrusive body could easily account for a flat or
>nearly
>> flat top (e.g., if it were a sill or the thickest, central part of a
>> laccolith).
>Are you referring to Devils Tower as the "intrusive body"? If that's
>what you mean, then one would expect a point at the top, as in Beacon
>Rock.
He seems to be saying that it intruded into one layer (which would have given
it a pointy top), but then hit a layer too dense for it to intrude into. The
magma piled up against that layer, producing a flat top.
>> Also note that the size and shape of the columns changes in
>> the upper part -- very characeristic of approaching the edges of a
>cooling
>> intrusive body, or the top of a thick lava flow.
>That's fine, but irrelevant to points 1-4 above.
But it does explain the shape of a tower much better than a cataclysmic flood
would.
>> Oh yeah. #4 is also wrong, in a way. There isn't evidence of
>> *volcanic* (i.e. extrusive) activity in the area (well, unless you
>include
>> distant Yellowstone), but there is ample evidence of other igneous
>> intrusive activity. For example, only 4km to the NW of Devils Tower
>are
>> the "Missouri Buttes". They are not as spectacular as Devils Tower
>(not
>> as thick/tall), but they are rather similar.
>
>Again, that's fine, but irrelevant to points 1-4 above.
He said that point 4 is wrong. It seems quite relevant to points 1-4 above.
>I don't
>dispute that Devils Tower is igneous intrusive activity. The issue is
>the erosion.
Point 4 doesn't even have the word "erosion" in it.
Neither did the comment about how volcanic rock is not accompanied by a
volcano, but you insterted that yourself.
<snip>
>> If it is just a matter of erosion providing
>> supposed evidence of a global flood, then why is this structure
>special in
>> that respect? Most of what I see is evidence of mass wasting --
>i.e.
>> splitting along the pre-existing columnar joints and falling as
>rubble
>> around the structure. There are large fans of debris present around
>the
>> base. Rivers may be responsible for carrying away that rubble from
>the
>> base, but they are not resonsible for the shape of the sides,
>slumping is.
>
>Water carrying away the rubble at the base is part of 4 above. Points
>1-3 suggest a flood as well -- but remain unaddressed.
He addressed them in a separate post, as I recall.
>> There are plenty of other examples of erosion in the area, and the
>> geomorphology bears little resemblance to the very distinctive
>structures
>> seen in areas of known gigantic floods, such as the Channeled
>Scablands.
>
>Again, the issue is what caused the erosion at Devils Tower. Do you
>see other signs of water erosion in the area at such high elevation?
Most people do. It's called rain (and the set of causes of erosion that is
accompanied by rain, i.e. water working into cracks and then freezing).
>> All I see is evidence of the activity of ordinary rivers and mass
>wasting.
>> So, what do you think is especially flood-like here, Andy?
>Points 1-4 set forth at the top of the thread and cited again above.
But why are they especially flood-like?
John Harshman
>
> Flattened rock formations are fairly common in the oceans, I think. If
> Devils Tower originally had a point at top, water pressure could easily
> break it and then smooth out the broken surface.
>
Aha! I was right in my conjecture. Andy thinks that Devil's Tower is a
sort of land-bound guyot.
Bobby D. Bryant
> In article <934sj6$htk$1...@darwin.ediacara.org>,
> mac...@agc.bio_NOSPAM_.ns.ca wrote:
> > In article <933fun$kci$1...@nnrp1.deja.com> and...@my-deja.com writes:
>
> > |We'll see how substantive you can be in addressing the specific
> > |points. So far in this thread, the naysayers are batting .000 with
> > |substance.
> >
> > It is convienent that you initiated a new thread, then.
>
> I'll look through all of your postings in this thread to see if you
> address the 4 points in a substantive manner and, if you do, I'll
> respond. I'll even agree with you if the substance requires it.
Why don't you go back and read the other thread, instead of making everyone
post their responses to your lame argments again? Do you think geology has
changed since the last thread? Or do you think it makes you "right" if you
just keep posting the same nonsense over and over until everyone gets tired
of correcting you?
Go back and read the other thread, and respond to people's posts there --
if you have anything worth saying.
Bobby Bryant
Austin, Texas
Ken Cox
> Aha! I was right in my conjecture. Andy thinks that Devil's Tower is a
> sort of land-bound guyot.
And, given the time required to produce a guyot, that there
was a period of a half-million years or so, at some time in
the past, when sea level in the area corresponded to the top
of Devil's Tower.
--
Ken Cox k...@research.bell-labs.com
Paul Blake
It sounds like you are talking about Mount Scoria outside of Biloela.
Many of the locals call it a musical mountain. It is a volcanic plug
that has intruded through an Early Tertiary oil-shale basin. The
Tertiary basins around Queensland alway produce flat topography.
I have been geologically mapping the area for the last couple of year
and Mount Scoria is certainly a columnar jointed basalt. It does have a
nice ring to it when you hit it with a hammer but there is nothing
exceptional about it.
--
Regards
Paul Blake
pbl...@dme.qld.gov.au
--------------------------------------
Ignorance more frequently begets confidence than does knowledge: it is
those who know little, and not those who know much, who so positively
assert that this or that problem will never be solved by science. -
Charles Darwin
--------------------------------------
John Harshman
<k...@lucent.com> wrote:
> John Harshman wrote:
> > Aha! I was right in my conjecture. Andy thinks that Devil's Tower is a
> > sort of land-bound guyot.
>
> And, given the time required to produce a guyot, that there
> was a period of a half-million years or so, at some time in
> the past, when sea level in the area corresponded to the top
> of Devil's Tower.
Yup. Give or take a couple hundred thousand years. Or maybe the top was
planed off before the sediments that make up Devil's Tower (I know, but
work with me here) had consolidated, and so a period of only a year was
needed..
Andrew MacRae
Thank you. You could have saved considerable confusion if you had
explained it yourself. You can't expect effective criticism that is
directly relevant to your area of interest (the erosion issue you keep
emphasizing) if your presentation is vague in the first place.
|and also that more surface material appears to have eroded from
|the middle than near the top.
What do you mean by "surface material"? What distinguishes its
appearance? I'm guessing you mean the top portion which has been
fractured in a different way.
|> Anyway, the explanation for this shape is not difficult, in
|> the conventional model, once it is realized that the strucure is
|> penetrated with nearly vertical fractures (i.e. the columnar jointing),
|> which preferentially causes the cliff face to peel off, en masse, and
|> pile up as rubble at the bottom. If it were a homogeneous mass of
|> rock, Andy's question would be the makings of a genuine puzzle, but
|> with an understanding of the nature of the rock at this location, it is
|> no surprise at all. If you look at any other type of slope with
|> columnar jointing developed, it tends to form a steep cliff because of
|> the way the rock fails along the vertical fractures. In the case of
|> Devils Tower, because the columns fan out towards the base, and because
|> the igneous mass is not a continuous layer but more of a cylindrical
|> plug, the shape is a
|> little more exotic than just a vertical cliff. The spreading column
|> geometry has an explanation too (although it has nothing to do with
|> erosion, but with cooling).
|
|Look again at
|http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/devils_towe
r.html
|
|It's clear from the bottom picture that more surface material has
|eroded from the middle of Devils Tower than near the top.
|
|If you dispute this, then please so state.
Andy, how can I effectively dispute it? You have not explained
yourself adequately enough for me to really understand what you mean by
"surficial material", but I think I know what you mean, and if I am right,
I did discuss it previously, but attributed it to another process.
I can see that there is an obvious difference in the irregularity
of the exposed surface on the middle portion of the Devils Tower versus on
the top portion, but I think this is expressed by a difference in the
density and orientation of fractures. This *could* be due to differences
in weathering, yes, such as the top portion experiencing more weathering
than the lower portions (e.g., such as if the upper portion was exposed to
the elements earlier and longer, as the other rock originally surrounding
the tower was being eroded away). It could also be due to original
differences in the cooling joints (i.e. columnar jointing) that have
nothing to do with erosion, but with events that occurred long before
(that is what I first suggested in the quoted part further below). If a
difference in fracture pattern and density during cooling was established,
or even a difference in composition or vesicle (bubble) density, that
would yield a difference in the subsequent erosion, but the difference is
not present primarily because erosive forces are acting in a greatly
different way, but because the rock is responding to the same forces in a
different manner -- i.e. it is an example what is known as differential
erosion, such as between a hard versus a soft or chemically less-resistant
rock layer. This is why the pre-existing structure of the rock is so
important to the subsequent erosion. As I mentioned, if the rock were a
homogeneous mass, then neglecting these issues might be okay, but here,
there is an extremely distinct fabric (i.e. preferential orientation) to
the fracture pattern, and big differences in its density. The walls of
the Grand Canyon have a stair-step-like shape not because rivers and rain
like to move in steps, but because the rock layers have different
strengths and responses to erosion. Likewise here, the erosion is being
strongly controlled by the nature and orientation of structures
established in the original rock, *before* it was exposed to erosion. You
should not neglect it as an essential issue when trying to understand the
erosion.
But, for argument's sake, I'll throw away the possibility that the
difference in appearance between top and bottom reflects something about
the original composition or fractures in this igneous unit, and adopt your
interpretation by assuming it is all due to erosion. The most plausible
explanation to me is the one I mentioned above -- i.e. during its
incremental erosion out of the surrounding, softer rocks, the top was
exposed first and longer, and experienced more chemical alteration at the
surface. This meant that when the bottom portion was eventually exposed
too, it would appear to be a "fresher" outcrop.
The big problem I see with such a "erosion difference" scenario
within a Flood model is the need for a relatively slow exposure of the
entire structure, so that there would be a significant difference in
erosional effects between the long-exposed top versus the more
recently-exposed/fresher middle. It is perfectly consistent with the
conventional model, though. I realize that you suggest below that the
difference has something to do with a "waterline", but this is not very
consistent with the evidence, for reasons explained below.
|Otherwise, let's address
|the erosion of the surface material at issue in this thread.
|
|> |The top
|> |third of the tower shows far more weathering -- and even to an
|> |untrained eye has clearly been exposed to the elements for far longer
|> |-- than the
|> |bottom two-thirds. Take a look more closely at the picture
|
|Right. Explaining that difference is the issue here.
Fine. In my opinion, it creates more problems than solutions for
the Flood model.
|It appears to represent a water line around the Tower.
You mean the uppermost portion was exposed to the air, while the
mid portion was under water, thus accounting for greater erosion of the
air-exposed part? How long was this supposed to have taken? For a
significant difference to develop would take an awful lot longer than 40
days, a year, or even many decades. Dense igneous rocks like these do not
usually erode quickly. Also, a waterline -- i.e. a shoreline -- lapping
up against a cliff is often expressed by a notch, where waves have
preferentially eroded the part of the cliff subjected to their pounding,
while leaving upper and lower portions comparably intact. Often, an
overhang develops, if the rock is strong enough. On a slope (rather than
a sheer cliff), a shoreline is usually expressed by a bench-like level at
the height of the shoreline. These are commonly seen along the edges of
former Lake Bonneville, centered on Great Salt Lake in Utah. In profile,
it would look a bit like this:
/
/
__/ <- bench at former lake level
/ <- beach sediments often preserved here
/
/
/
I don't see anything like that on the upper part of Devils Tower.
One would also expect to see comparable shoreline indicators at about the
same level elsewhere in the nearby hills. I don't think any have been
reported (although the Lake Bonneville ones are further to the west, on
the other side of much of the Rocky Mountains. I suppose you could appeal
to those).
|> It is more rubbly-looking, isn't it? But it isn't a random
|> arrangement. If you look even more closely, especially at the
|> picture towards the bottom, you will see that the geometry and size of
|> the columns changes towards the top of the rock mass -- they become
|> bigger, and the sides of the columns become more irregular. This is
|> not a feature of erosion, but of the column development itself. Look
|> carefully, and you will see a few spots where multiple columns merge
|> upwards into one big, uglier, bumpier one. This (or similar
|> geometries) is a common feature in
|> basaltic lava flows, either towards the top or towards the bottom.
|
|I looked at the picture again. The top third plainly has surface
|material that has eroded from the middle third.
This is confusing phraseology. I do not think you mean to imply
that material has eroded from the middle third and somehow been deposited
on top. You mean that there is some kind of "surface material" that has
been eroded from the middle that has not yet been eroded from the top,
right? Specifically, you are referring to the zone in the upper, oh,
1/5th or so of the lower picture that has a more rubbly, irregular
jointing pattern to it, right? I do see the difference. I tried to
explain it before. What I dispute is the necessity that this difference
is due to differences in erosion processes, rather than the same erosion
process having different effects due to the rock itself being different --
specifically, the jointing pattern being different. I honestly don't know
whether my interpretation along those lines is right. The pictures are
not quite detailed enough (and certainly not detailed enough to see if
compositional changes, such as vesicles or mineralogy, are changing), but
I think I see a change in columnar jointing geometry that is not
accountable by erosion alone. You do realize that the shape of the
columns is not something that is established by erosional processes,
right? Erosion is just peeling apart pre-existing fractures that are
there for other reasons.
|It's not just columns
|merging together. That may occur as well, but there far is more than
|that.
|
|Are you saying that there is no difference in erosion of the surface
|material as discribed above?
There is a difference, yes, but I was attributing it do a
different process -- differences in the original composition or in the
fracture geometry within the igneous body.
|If that's your argument, then please be
|precise. If that's not your argument, then please address the
|difference in erosion.
I have, the first time by appealing to erosion of rock with
different pre-existing fracture patterns, and, this time, by also adopting
your weathering interpretation for the differences, and suggesting it
could reflect different exposure times as the igneous body was being
exhumed. A combination of the two may even be possible. Either way, I
don't see how this difference can be easily accounted for by a Flood of
global scale. There aren't the expected features if the difference
represents a "waterline".
||http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/columns.jp
g
|> |
|> |(my apologies if dejanews makes the URL hard to decipher.)
|> |
|> |>
|> |> (2) one side eroded more than the opposite side;
|> |
|> |This is typical for rock formations. Water flows downhill; winds
|> |often
|> |come from one direction (the "prevailing" one). Nothing unusual
|> |about one side of an object being eroded more than another.
|>
|> You are right, but, frankly, it is not clear to me what "side"
|> Andy is referring to (Face on? Left? Right?), and until he
|> specifies, trying to explain it is futile. However, potential
|> explanations are numerous, and range from differences in erosion (e.g.,
|> the south side
|> receives more sun, and therefore more temperature extremes, than the
|> shaded side on the north, so fracturing due to ice or thermal
|> expansion and contraction will be different on either side), which side
|> of the structure has had a big slump most recently, to merely
|> differences in
|> shape in the original intrusive rock mass (i.e. *nothing* to do with
|> erosion).
|
|Compare the right side to the left side on the top picture at the site
|I provided, as well as the depression in the front side.
Okay. That is much more specific. Thank you.
|The erosion
|is directional, suggesting that it was caused by water flow.
"Directional" erosion is not that simple to attribute. It can
also reflect pre-existing weakness in the rock structure in question, such
as (here we go again) differences in composition and pre-existing fracture
density and orientation. It could simply be a difference in the shape of
the original intrusion (they aren't usually perfectly circular). What you
see is far from what I would expect of a water-worn structure, which
should be streamlined in some way if it were indicating direction.
Ironically, the bench-like shape of the profile on the left side, towards
the bottom, looks more (superficially) like the mark of a "waterline" than
anything in the top portion that you were trying to explain as such
earlier on. Unfortunately, the bench/notch geometry does not persist
around the structure, and it also happens to coincide with about the level
where the columnar jointing starts flaring outwards. It is highly likely
the shape is due to that change in fracture geometry.
The depression in the front side looks much like the scoop-shape
typical of a slump scarp -- i.e. when rock slides, en masse, downslope due
to gravity. The uphill edge of the slump very commonly develops as a
fault plane that rotates down on the back edge before the material slides
(often breaking up in the process). I could try to draw the typical shape
using ASCII graphics, but it isn't well-suited to curved surfaces. Look
on the web for terms like "slump scarp", or look it up in a geology text.
If the depression on the front in the upper picture is a slump
scarp, one would expect a lobate, fan-shaped heap of rock debris to be
tossed out in front of it. Uncoincidentally, there are several such
"debris aprons" distributed in a few lobes around Devils Tower, but I'm
not sure exactly what orientation they have with respect to that
scoop-shaped depression on its steep face in that picture. It is pretty
normal for steep cliffs to have that kind of scoop shape all along them,
though, because of the common occurrence of slumps.
|> |> (3) its top is remarkably flat;
|> |
|> |Which makes it unusual, but geologic extrusions make all sorts of odd
|> |shapes; the flat top seems likely to have been scraped that way by
|> |glaciers (though I'm not a geologist and I don't actually know).
|
|The trouble with that explanation is that Devils Tower is so high up.
Glaciers are common in alpine areas. But, if it is any
consolation, I doubt glaciation is involved here.
|Also, if glaciers scraped it, then it was likely flooded as well.
There isn't much evidence of glaciation in the area, actually. It
is mostly further to the west and north.
|Other posters have noted that large lakes can occur at high elevations,
|but only if trapped by mountains.
Not *only* (e.g., glacial ice can do it too), but commonly, yes.
The topography does not have to be mountainous, though. A shallow basin
is perfectly adequate.
|No trapping of water around Devils Tower.
I agree, other than comparably tiny, normal-sized lakes, of
course.
|> I think it is more likely in this case that the relatively
|> flat top (it isn't perfectly flat, just flatt*er*) is close to or
|> parallel to some kind of original geological boundary -- like the top
|> of the intrusion, butted up against a more resistant layer of rock that
|> was once on top. This proximity could account for the change in the
|> column geometry too. Alternatively, if this is a volcanic neck that
|> did breach the surface, it could simply be as far up as the pipe went
|> to reach a relatively flat surface, plus or minus a hundred metres or
|> so of erosion
|> of the weakest material at the top (e.g., if there was an especially
|> bubbly and soft layer in the top part, it could have been removed by
|> ordinary erosion processes, while leaving the underlying, more
|> resistant layers of solid igneous rock virtually intact).
|
|If Devils Tower pierced a crust,
I don't know if it reached the surface, but I think you can pretty
much take it as a given that it was pushed into pre-existing rock, at
least at the level presently exposed.
|then one would expect a point-like top.
No, not necessarily. Igneous intrusive bodies take the form of
all sorts of shapes, including ones whose geometry could best be described
as "pancake flat" (i.e. sills), over lateral distances of kilometres.
When sills are intruded into a layered succession of rocks, they very
commonly split apart the layers, flow along approximately horizontal
cracks, and solidify. Their top and bottom surfaces look almost parallel
(if not perfectly at the scale that people look at a typical outcrop).
They are so flat that they may be mistaken for lava flows (i.e. extrusive)
rather than intrusive rocks, unless people pay close attention to
associated structures (such as dykes, which cut across the stratigraphy
and often feed into sills, baking of the rocks below *and* above, and the
pattern of crystallization and columnar jointing in the igneous unit).
Devils Tower is not a sill, but there are a great many precidents for an
igneous body to have a relatively flat top. Piercing a crust has nothing
to do with it.
|As the crust broke, the Tower would form a point at the place of
|breakage.
Potentially. It would then be a volcanic structure -- i.e. one
that breaches the surface. However, I thought it was fairly well accepted
that, Flood or not, we are not looking at the part that was not at the
surface, but at a deeper, sub-surface portion that has been exposed due to
erosion and removal of the surrounding rock. Do you dispute this
interpretation? If you think the exposed portion was actually at the
surface at the time of eruption, then the problems for your Flood scenario
become much more severe, because as I and others have noted in other
posts, the products of subaqueous eruption are usually very distinctive,
and are not present at Devils Tower, as far as I can tell from the
descriptions and morphology.
|See, e.g., Beacon Rock. Moreover, gravity would work
|against a flat top for such a large structure.
Just the opposite. Gravity flattens material that is fluid, and
if there are any gas phases within the liquid, those will tend to float to
the top, forming a layer of foam like the head on a glass of beer. Upon
solidification, the subsequent erosion of the weaker, frothier igneous
rock would be much more rapid than the underlying, more massive layer, and
could produce a relatively flat top to the resulting structure even if the
overall shape of the igneous rock did not start out that way. As another
example, the lava lake in the crater at Kilauea in Hawaii is flat as a
pancake. If it cooled and solidified, and the surrounding volcanic rock
were eroded away from that conduit, the top of it would be relatively flat
(it wouldn't happen in the case of Kilauea -- the surrounding volcanic
rocks are too hard).
All of this depends upon the exact nature of the portion of the
igneous body that was closer to the surface, if it did indeed breach the
surface, and the style of eruption if it did. Regardless, whether the
upper portion was still intrusive or breached the surfacce, it is
certainly not "impossible to explain" a relatively flat top, as you have
asserted previously. There are plausible explanations in either
circumstance (although additional evidence at the site would be required
to test them out -- maybe they do not apply after all). The top is
apparently not especially flat anyway, although it looks fairly flat from
the ground.
|> Regardless, because of the preferential fracturing of the
|> columns at the edges, any topography on the top of the original
|> structure would tend to be preserved, even as much of the edges were
|> falling away. There are plenty of analogues. It is *very* common for
|> columnar-jointed basalt flows to be quite flat on top, and not develop
|> streams incised into the top, even if they have been eroded away until
|> they only consist of a small mesa bounded by steep cliffs on all sides.
|> The process is especially
|> effective if there is a weak layer below the resistant basalt flow.
|
|Feel free to provide a structure analogous to Devils Tower with its
|size and flat top, and we can look at them.
I have seen a great many isolated mesas of columnar-jointed basalt
flows and sills. Unfortunately, most of them don't have names, are in
rather remote locations, and I would have to scan and send you a picture.
Flat-topped volcanic mesas are not the sort of thing that would receive a
great deal of attention in publications, because they are so common and
easily explained. I suppose there might be pictures of some in that
"Volcanic Landforms" book by Green and Short that is listed on the web
page you cited. You could check there. There are several
directly-comparable, but smaller structures like Devils Tower only 4 or 5
km to the northwest of its location, but I don't know if any pictures are
available (they are called "Missouri Buttes").
You have seen pictures of mesas and buttes of other types, haven't
you? It really isn't much different for resistant igneous rocks rather
than other types of rock, and the columnar jointing enhances the tendancy
for vertical fracture-related slump failures and cliff formation around
the edges even more.
Here is an example of another volcanic neck with a similar gross
morphology and origin to Devils Tower:
http://volcano.und.nodak.edu/vwdocs/volc_images/img_fumarole.html
You have to realize something: Devils Tower is distinctive because
it is one of the biggest, and nicest examples of this type of structure.
There has to be a "biggest" of everything, somewhere in the world. That
does not mean it is without close analogues, other than in its sheer size
and visual impressiveness.
Profound topographic relief due to strong differential resistance
to erosion is also not uncommon. For example, check out these dykes:
http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/gray_butte.h
tml
(Look at the picture down at the bottom)
If it is possible for differential erosion of weak rocks from
around resistant igneous intrusive rocks to produce sheer walls like that,
then why is it so strange for it to do a similar thing for Devils Tower?
I suppose these dykes bear the hallmarks of erosion by the Flood too,
right?
|I doubt other real
|examples exist -- unless they were flooded too! :-)
I thought everywhere in the world was, so how could I ever find a
negative example? :-) Seriously, though, it isn't hard to find
*positive* examples, by looking at such places as the Channeled Scablands.
I highly recommend doing so.
|> |> and
|> |>
|> |> (4) there is "no evidence of volcanic activity anywhere in the
|> |> area. No volcanic ash, no lava flows, no debris...nada," as one
|> |> poster observed.
|> |
|> |This is untrue. The 'one poster' was mistaken, and many other
|> |posters in the previous thread pointed this out to you. There may be
|> |no *current* geologic activity in the area, but Devil's Tower is 40
|> |million years old.
|
|Then that only reinforces my point. What eroded the debris?
Rivers, just like run past the Devils Tower today -- the Belle
Fourche River. What is not seen is evidence for erosion by spectacular,
huge flows, such as those that scoured the Channeled Scablands of
Washington. They produce a different type of channel geometry and other
types of fairly unique features versus the rather ordinary-looking rivers
around Devils Tower today.
If you want to understand just how grand the erosion in that area
really is, then look more broadly at the geology, and consider the Black
Hills, to the east, where a substantial amount of stratigraphy, amounting
to a good kilometre or so, has been eroded off the top of a broad domal
structure. Devils Tower is sitting on one flank. The erosion in the
immediate area around Devils Tower is miniscule compared to this greater
problem, and that is just the modern erosion. It does not account for the
ample evidence for older periods of erosion that were at least as
extensive. Compared to that, you are talking about a rather small erosion
problem, in terms of its scale.
You can appeal to the Flood to account for all of that, sure, but
I will again remind you that the products of gigantic floods, as
geologists know them from such places as the Channeled Scablands, are very
distinctive and look substantially different. The products of ordinary
riverine erosion are rather distinctive too, and are all over the area.
|> Yes. And, furthermore, it is almost the northwesternmost
|> example of a whole field of igneous structures in the area. This is
|> explained in one of the references on the page that Andy cited (the one
|> in the GSA Centenial Field Guide). The "Missouri Buttes" are just 4
|> kilometres or so to the northwest, for example. They aren't as tall,
|> but they are similar composition and age, and they show that the
|> igneous activity represented by Devils Tower was not a solitary event.
|
|OK, fine. What eroded the debris?
The same thing that is eroding the region today -- mostly mass
wasting (gravity) processes and rivers, plus a bit of wind erosion.
|> |> Erosion by water would explain observations 1-4 above. Water would
|> |> flatten the top,
|> |
|> |Water erosion doesn't explain the greater weathering on the top
|third.
|
|It looks like a water line dividing the top third from the middle third.
I disagree. See above.
|> I have no idea how water would produce a flat top. It just
|> isn't characteristic of any kind of water flow I can think of.
|> Rounding of an obstacle to flow, to produce a shape more like a dome,
|> is normal.
|
|Flattened rock formations are fairly common in the oceans, I think.
If you are thinking of guyots, those are flat-topped because of
both wave erosion on the top, and because of original depositional
processes, which often involved submarine volcanism that did not quite
breach the sea surface. The submarine volcanism often produced
hyaloclastites and other types of fragmental igneous rocks that were
easily redistributed by the waves. The wave activity also breaks up and
rounds the rocks in very distinctive ways. Speaking of that, Devils Tower
isn't composed primarily of extrusive igneous rocks, and it is a different
composition from a guyot. It is primarily massive phonolite.
|If
|Devils Tower originally had a point at top, water pressure could easily
|break it and then smooth out the broken surface.
"Water pressure"? What is that? You mean waves? And if the
Flood did that, then what accounts for the apparent difference in
weathering appearance on the top portion versus the middle? If it was
worn off more on top, due to waves or whatever "water pressure" is, then
the top should have experienced more erosion than the sides, contrary to
your earlier claims.
|> |The more likely explanation by far is that some mechanism initially
|> |exposed the top third, then stopped for several million years
|> |(permitting the exposed portion to weather) and the remaining
|> |surrounding sedimentary rock was exposed sometime more recently.
|
|That's tough to formulate.
No, it is easy. If the surrounding rock also had variations in
resistance to weathering, such as layers of sandstone that were more
resistant than layers of soft shale, it could easily have slowed the
exhumation of the structure, and then resume its prior rate once the more
resistant layer was entirely removed. Coincidentally, the stratigraphy of
the area does have such variations.
|Everyone seems to agree that the Tower rose
|in one step, not two.
It was intruded in one step, yes, but its exposure need not have
been continuous in rate.
|> No, I think it is probably reflecting something about the shape
|> of the original structure, perhaps an overlying, bounding layer of the
|> country rock that has since been eroded away.
|
|Ah, yes, the erosion issue. What eroded it? It must explain the
|pattern of erosion.
It does, potentially -- better than your "waterline" scenario
does.
|> |> The water
|> |> would remove the volcanic ash, lava, debris, etc.
|> |
|> |Um, Devil's Tower is cooled volcanic lava (that's what "igneous"
|> |means in the url).
|>
|> It is igneous, but I don't think it is extrusive. Not at this
|> level, anyway.
|
|OK, fine.
|
|> |If we gave the water sufficient force and time to clear
|> |away other lava it would have cleared away Devil's Tower as well.
|
|Not necessarily. Lots of rock formations still exist in the oceans.
Yes. However, 1) in anything less than about 100 metres of water,
wave action has a large effect during storms, especially in the last few
tens of metres. This would be even stronger in a "violent" event such as
the Flood supposedly was, or even the ordinary waves in a much larger
global ocean; 2) one must consider the geological context in this area
too -- nearby, there are much thicker, continous successions of
sedimentary rocks that have apparently been stripped away at the immediate
location of Devils Tower. These include Jurassic and Cretaceous-aged
sediments that are widespread in a ring around the Black Hills and further
to the west, in the Rocky Mountains. It is pretty obvious that this
structure was once encased in sedimentary rock, rather than something that
piled up as an isolated, volcanic seamount in the middle of a Flood ocean.
|> |> Perhaps because Devils Tower rises to a mile above sea level,
|> |> some simply refuse to accept water erosion as a possibility.
|> |
|> |That's preposterous. The ground next to Devil's Tower is three-
|> |quarters of a mile above sea level, and a river runs along next to the
|> |tower. Why would you claim that anyone would doubt that water erosion
|> |occurs a
|> |mile above sea level? Having spent last weekend in Lake Tahoe, I can
|> |testify that there's plenty of water at five thousand feet.
|
|Because Lake Tahoe has mountains all around to trap the water.
It does not take mountains. Look at the Great Lakes. There is
relief trapping the water, sure, but the area isn't especially
mountainous. Mind you, it is at significantly lower elevation, but given
appropriate topography, it does not take mountains to trap water in a
basin.
As for the question of water's involvement in the erosion of the
structure, a significant river flows right past Devils Tower. There are
smaller streamlets all around it. It rains there. Why would someone
discount the possibility of water erosion as a possibility? I think it
was probably the major reason for the eventual removal of the sedimentary
rock from around it, but I don't see any indication of the extremely
rapid, gigantic flood effects that are typical of other areas that
experienced such unusual processes. It looks more like mundane rivers
have been active for quite some time, judging by the drainage pattern in
the area. As for the shape of the exposure of Devils Tower and most of
the features you have identified upon it, most of that appears to be the
result of gravity-related processes, like slumping, rather than the
abrasion of flowing water.
|[snip]
|> |Not to mention that places that are a mile above sea level now were
|> |not
|> |necessarily a mile above sea level forty million years ago -- we have
|> |plenty of examples of that as well.
|>
|> Yes.
|
|Yes, indeed. Do you agree that Devils Tower may have been much closer
|to sea level years ago?
Yes, although probably not by as much as you might think, because
by the Eocene (the time the igneous rock is thought to have been
intruded), the Rocky Mountains and Great Plains had probably attained a
good portion of their present altitude. There isn't much evidence for
marine sediments in the area by that time, except for some fairly limited
areas (much less extensive than sedimentary rocks back in, say, the
Cretaceous). Most of the deposition from the Eocene in that area is from
terrestrial lakes and rivers.
|Likewise, do you agree that the depth of
|oceans may have been less years ago?
Yes. During the last glaciation, for example, sea level is
thought to have been a little over 100 metres lower, and over the entire
Phanerozoic, there have been sea level fluctuations estimated at about
+-200metres.
I fail to see your point in any of this. Evidence for limited,
global sea level fluctuations has been known several decades, at least.
This poses a significant problem for a global flood model, because one has
to wonder why geologists are able to find evidence for some smaller-scale
sea level fluctuations, but still have not found comparable evidence for
something more grand. What they have found is a great deal of evidence
inconsistent with a global flood, such as the occurrence of terrestrial
sediments throughout most of the rock record.
|> More problematic, though, for Andy's scenario, is not simply
|> the altitude, or the evidence for water deposition in rocks now found
|> at that altitude (e.g., like fossil corals and other marine fossils),
|> but how such fossils became intercalated with sediments that are
|> clearly terrestrial (e.g., soil horizons, river channels, and fossil
|> trees in growth position), in alternating successions, in those
|> mountains. It isn't as simple as Flood goes up, Flood goes down.
|
|This thread is not devoted to discussing general Biblical Flood issues.
I understand that, but you do have to consider the geological
context for Devils Tower if you want to understand its formation, and if
you want to really test out whether a Flood model is a plausible
explanation.
|But to answer your question, I think Biblical Flood advocates
|cite the likely violence of a flood as the reason for intercalated
|sediments.
I don't see how soil horizon deposits, in layer after layer, or
how terrestrial, wind-deposited dunes could be the result of the "violence
of a flood".
|[snip]
|> |It *is* a beautiful, impressive, and unique
|> |formation; I've been there. The geologic explanation is surprising,
|> |I admit -- it looks much more like it extruded up from the surface
|> |than that it formed underground amid sedimentary rock and the rock
|> |eroded away from around it. But then again geology is frequently
|> |surprising, and one's initial assumptions are often wrong.
|>
|> Yes. That has been true all through its history of study.
|> I'm sure plenty of suprises are left. But Andy has not identified any,
|> as near as I can tell.
|
|Whew! I got through all this, but still cannot find a clear statement
|and substance on:
|
|1) whether you think there are differences in erosion at Devils Tower,
|and
There are. But we differ in their intepretation, and whether they
are a product of different erosive processes, or different effects of the
same erosive processes because the rock itself it different.
|2) whether you think a flood could have caused those differences
That depends upon what you mean by "flood". If you mean river
floods like those that probably occur on the nearby Belle Fourche River
from time to time, yes, they probably were involved. If you mean "flood"
on the scale of immersing the entire or most of the structure and currents
that operated at vast scales comparable or greater than those seen in the
Channeled Scablands of Washington State, no, there is no evidence for
anything remotely like that. I don't think you have adequately considered
what sort of products such a process would create, and I think you have
misunderstood some of the features you are seeing in the pictures of
Devils Tower. Regardless of what I think about a global flood scenario,
you clearly have not met your bold claim that Devils Tower is "impossible
to explain" in the context of the conventional model. What you have
mostly demonstrated is unfamiliarity with that model.
|(and if not, what did cause the specific erosion pattern observed).
See above. I think it is a product of differential erosion,
primarily by mass wasting processes and ordinary rivers much like those
found in the area today.
|Once again, I note the thread title: "Devils Tower erosion issue".
Yes. But there is more to the products of erosion than just the
erosive process itself. You have to carefully consider the pre-existing
features of the rock being eroded, because those can have a profound
effect on how the erosion is expressed. In the case of Devils Tower, for
example, any explanation that neglects the effects of the columnar
jointing will be severely deficient. Likewise, if you approach the
question of erosion without an understanding of the appearance of the
products of particular erosive processes (e.g., like what a
"waterline"/shoreline often looks like), then you are not likely to reach
a reliable interpretation.
If you find there are deficiencies in my attempt at explanation, I
again recommend that you look up some of the references cited on that web
page. They may help.
-Andrew
mac...@agc.bio._NOSPAM_.ns.ca
Al Petterson
> | [ a mixture of truth and misinterpretation ]
> [corrections]
I'm happy to be corrected; most of my knowledge (such as it is) of
Devil's Tower comes from visiting it nearly twenty years ago, and trying
to remember what the park rangers said in their exhibit. Not the most
authoritative of sources. :) As with almost any subject, had I bothered
to follow the links and do a little reading, I could have learned more.
Thanks for setting me straight!
Andrew MacRae
writes:
That's okay. I'm not an expert either, I just dug a little
further into some of the literature, and perhaps know a little more about
the broader geological context (e.g., setting on the Black Hills dome and
beside the Powder River Basin). Some questions about Devils Tower are
genuinely challenging, such as whether or not the currently-exposed
intrusive portion was once attached to a vent at the surface, or if it was
completely sub-surface. There is some evidence that could be interpreted
either way, and it is a genuinely hard question when much of the most
obvious evidence (e.g., the actual vent, if there was one) has been
subsequently eroded away. Some clues can be obtained from similar
structures and igneous masses in the area (like the Missouri Buttes and
others), some of which have clearer indications they were at one time
attached to vents at the surface, but there is no guarantee that those
nearby analogues experienced exactly the same history as Devils Tower.
Each one is unique in its own subtle ways, and many igneous provinces
include both intrusive and extrusive phases and units, even if the magma
that was produced for all of them was fairly similar. As for the erosion
itself, I still can't decide whether the differences Andy is seeing
between the mid portion and top portion are primarily due to some kind of
differential erosion, because the column geometry really is different, or
(as is often the case for these sort of questions) a combination. I have
not found enough information to tell for sure.
So, don't feel apologetic if you suggested an interpretation, mine
differs in some way, and mine *sounds* more authoritative. I could be
wrong, and so could the references I have relied upon for information.
I am fairly sure about one thing, though: all the explanations I
have read about, and the suggestions you made, are clearly more plausible
than Andy's are, and his earlier "impossible to explain" claim is
spectacularly bogus. I'm sure he would disagree, but that is what makes
scientific investigation interesting. If everybody agreed, then it would
get boring. Ideally, once the disagreements are expressed in a fair
amount of detail, and specific predictions are made for the different
interpretations, it would be time for everybody to go out in the field
again and see things for ourselves to test the ideas out. Unfortunately,
that is not practical in this case, but you do have the advantage of
having visited the site and seeing it for yourself. Don't ever sell
yourself short on the value of that experience versus whatever Andy or
myself might come up with from secondary sources (unless he has been there
too, in which case you are both ahead of me). In my experience, park
rangers usually do a pretty good job too, but their explanations are short
and simplified, for understandable reasons of communication.
-Andrew
mac...@agc.bio._NOSPAM_.ns.ca