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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
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Author | Topic: Motley Flood Thread (formerly Historical Science Mystification of Public) | |||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
This suggests the region was once crisscrossed by a braided river.
Actually, it would be dendritic pattern. That is a pattern similar to the veins in a leaf. Those 'islands' were probably never islands at all except for the ones that occurred after a meander loop was abandoned. The rough pattern of minor peaks and saddles occurred when minor tributaries and fractures intersected to make a bunch of random culminations. There is also some evidence of a trellis type of pattern caused by fractures and faults. The Bright Angel Canyon is one of them. It follows a nice straight fault line. Wikipedia gives a bit of an incomplete treatment here:
https://en.wikipedia.org/wiki/Drainage_system_(geomorphology) Edited by Adminnemooseus, : Fix link. The system doesn't seem to like having ( in URLs.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
Orogeny (mountain building) is not thought to occur through erosion, so I'm still seeking to understand what Edge meant.
Just a bit of geophilosophy. I figure that I'm old enough to stir the pot a little bit with some outlandish remarks. But think of it this way... Is the Colorado Plateau a mountain? Is the Kaibab Uplift a mountain? Well, you have to stretch the definition a bit... Will they become mountains over time? Most certainly. And why?
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined:
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And since this is going on just at the beginning of the draining of the Flood waters, it seems logical that the water, soon laden with chunks of strata, would have widened and deepened the cracks until they became a channel for the recedeing water that eventually became the Grand Canyon.
The canyon's sinuous shape is not dictated by fractures or any other rock structure. Period.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
I didn't say anything about fractures, just cracks in the strata high over it that became the channel for the flood water to cut the canyon when it got down to that level..
AFAIK, cracks are fractures.
I would like your answer to the post about the layered mountain though.
I responded. Those are eroded continental lakebeds composed mostly of volcanic ash. They are not laterally extensive and are not mountains, they are badlands.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
I said the uppermost strata were cracked, not the canyon.
The Colorado River's sinuous course has no relationship to cracks in any strata. That is practically the definition of a meandering stream. And why are these rocks cracked anyway. I thought they were sort'a, kind'a soft, but not so much soft. Please describe the process of cracks forming in these rocks.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
And would you say also material from the Shinumo Hills, some of which survived?
Exactly.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
Talking still about this whatever it is: If it's not a mountain I want to call it a formation but that word is used for something else so what should it be called?
It doesn't really matter what it is called. It could be a minor ridgeline or a low hill or a small mountain. By itself, it is an insignificant feature.
Anyway, you interpret the layers in this whatever-it-is as lakebeds: ...
Yes, I do; but not all "flat" layering occurs in lakes. And remember seeing a picture is not like being there. I'm not sure what to make of the rest of your post. In general, it doesn't make sense and is loaded with insinuations and misunderstandings. It seems like you haven't even read my posts or many of the others offered here. It is a rambling manifesto. Try to focus a little bit more.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined:
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My understanding of geology isn't to the point where I'm able to perform analogs to jazz improvisations.
Mea culpa.
Will they become mountains over time? Most certainly. And why?
Okay, the Colorado Plateau has some mountain ranges in it but much of it is a large, 'flat' surface of relatively low relief. As you drive down the south edge, the Mogollon Rim, you get into a very mountainous and irregular terrain. Why is that so? Simple: it's erosion of the plateau at its edges. What do you think will happen to the region in the next 60 million years? My contention is that it will become more and more irregular as rivers cut more deeply into the plateau.I can imagine buttes but not mountains. There seems nothing in the underlying strata that would contribute to erosive formations that resemble mountains in shape. I could be wrong. Think of it this way. If you didn't have erosion, you would just get flat highlands. What if there were no erosion of the modern Front Range in Colorado after its most recent uplift? There would be no Pikes Peak, no Mt. Evans, etc. Just a big wall of rock. And there are other such things than the CP in other parts of the world. This topic is pertinent to most of our discussions because erosion is the forgotten process in geology and yet is so important as this discussion with Faith shows. And yet this particular point is kind of esoteric. I only bring it up to emphasize the point of erosion being so important.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
I took a look at that Wikipedia article. So you mean the dendritic endpoints represent streams and creaks flowing in from the surrounding landscape? Why dendritic and not braids? Is there something about the pattern of the "islands" that says one rather than the other?
In geometry, braids conform more nearly to the course of the stream. They are nearly parallel.
Don't rivers on level landscapes change often between braided and meander paths?
There can be braided geometries within the dendritic pattern, but mainly braided streams indicate high sediment loads that overload the stream. Water must continually find routes through and around the sediments that it is trying to move.
I need help with this one. The definition of "culmination" I found was "The highest antiformal point (see antiform) of a *crest line along all non-*cylindroidal folds."
Okay, perhaps I misused the term. What I mean is a high point or the collection of high points after a pattern of erosion has removed material from the sedimentary deposit. I did not intend for it to mean anything actually rising due to a fold.
So would it be correct to say that this widest part of the Grand Canyon was once a level area where a great deal of water flowed in from streams and rivers from the surrounding area, but that the flow was very slow and created occasional meanders that were influenced somewhat by a pre-existing fracture pattern.
In a sense. However, for Faith to say that the stream was 18 miles wide and then decreased in width as the water source depleted is ridiculous. The width of the canyon is dictated by its ease of bank erosion. In the case of the GC, there are enough weak layers that the average slope is not steep even though there are precipitous cliffs. There a numerous canyons on earth that are very deep but not so wide because the rocks are more competent. So yes, the area was quite flat when the meanders formed. But the river was not that wide. Meanders usually form where this is no structural influence on the stream geometry. You will notice that I carefully stated the "main course of the river" is not due to any kind of fractures or faults. As its tributaries cut more deeply into the rock they will encounter some features such as the Bright Angel fault and exploit that weakness. Added by edit by Adminnemooseus - Braided river at wikipedia: Braided river - Wikipedia Edited by Adminnemooseus, : Added by edit by Adminnemooseus
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
Does that mean the Coconino Plateau is not Coconino sandstone as I'd thought?
Correct. Both the Coconino Plateau and the Coconino Sandstone are named after Coconino County which is probably named after something else.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
Here is a good, brief explanation of braided streams:
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
What about salt flats, like in Utah?
Heh, heh ... I've heard that the maximum depth of the Great Salt Lake is 30 feet. I guess Faith never heard of playa lakes.
The average depth of Hudson Bay is only about 100 meters. And I wonder where Faith thinks all of those perfectly flat areas of the midwest (US) came from. Edited by edge, : No reason given.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
Yes, your evidence is lacking - completely lacking. And again, I very much doubt there are any complete stratigraphic columns.
There is no (meaning "none-zero-nada") trained geologist who expects to find an absolutely continuous record of the earth in a stratigraphic column. Only YECs say that such a thing should exist. This is an egregious strawman argument and only proves someone's ignorance of the topic. And, just to tie in our previous subthread, erosion is the main culprit in chopping up the global stratigraphy. I suppose that is why YECs must ignore the process of erosion.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
But the Kaibab Plateau is limestone, correct? Is the Coconino plateau also Kaibab limestone?
The top layer is mostly Kaibab in both places.
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edge Member (Idle past 1736 days) Posts: 4696 From: Colorado, USA Joined: |
Even salt flats aren't that flat, Mod, they have low and high points over distances (a few yards?) that would show up in such a contact line, and they have cracks in them when dry that would also show at the contact line. Please, this is so clear, so obvious. You could take a yardstick to those strata in the picture and the contact line would be just about as straight. OK, even that can't be perfect but NOTHING I can think of in geological nature is that nearly-ruler-straight, that nearly-tabletop-flat EXCEPT water-deposited strata. abe: Well, for that matter even volcano-deposited strata since those at Mt. St. Helens are awfully straight.
Nevertheless, these are lake bottoms and they wouldn't have dessication cracks if the water was still present.
ABE: Up close of salt flat: I think the next one indicates some surface waviness but I'm not sure: In any case most strata are not salt. .
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