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Author | Topic: YECs, how do you explain meandering canyons? | |||||||||||||||||||||||||||
edge Member (Idle past 1732 days) Posts: 4696 From: Colorado, USA Joined: |
Walt Brown: "Release of Grand Lake’s vast waters first eroded hundreds of meters of relatively soft Mesozoic sediments off northern Arizona. Once surface erosion was completed, downcutting through the harder Kaibab limestone began." Nonsense. There is no evidence for this except that the Mz rocks happen to not be present at the GC. However, if there were such erosion of the Mz rocks, there should be some kind of channeling and sheet runoff features all over the Kaibab Uplift. There aren't.
Walt: "As erosion cut deeper beneath the water table, more water, under greater pressure, was released from the water-saturated sediments flanking the canyon." Fortunately, for us, Walt does not practice hydrogeology. Ground water cannot be regionally under excessive pressure when exposed to surface waters. Also, he has no idea what releasing such pressure would do or the evidence it would leave. This only makes the cliffs of the GC MORE unlikely.
Walt: "This escaping water cut dozens of side canyons entering the Grand Canyonlarge canyons previously unexplained because they have no significant surface flow entering them. Subsurface flow and landslides were extreme." There is no evidence of such jetting of water from the canyon walls. The side canyons form normal dendritic patterns, sometimes controled by preexisting brittle-rock structue. I'm not sure what he means by 'subsurface flow', but extreme landslides may be actually correct. We know that this is the modern method of forming the canyon and probably the side canyons: landslide dams and breeching of dams.
Walt: "The weight of material removed from northern Arizona produced isostatic uplifts that account for the uplift of the Kaibab Plateau. This produced much faulting and volcanism, the barbed canyons, and layered strata that dip down and away from Marble Canyon and Grand Canyon." It is true that erosion results in isostatic uplift. However, I would love to see Walt's actual calculations on this.
L: Actually, it is not even MY knowledge of the subject; it is Walt Brown's...I know pretty much nothing about geology. Well, then, you have something in common with Walt...
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Harlequin Inactive Member |
Walt Brown is just plain wrong. It does not matter what the alleged catastophic flood is the Noachian Deluge or a dam burst, it will not create a meander.
And if such a catastophic flood caused the Grand Canyon than how come it failed to do anything to the land immediate outside of it. One of the things that is so striking about visiting Grand Canyon is until one actually sites the canyon itself, there is no sign (well other than "Grand Canyon x miles" etc) that anything geologically unusual is in the area. How can a catastophic flood be so precise?
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Buzsaw Inactive Member |
It does not matter what the alleged catastophic flood is the Noachian Deluge or a dam burst, it will not create a meander. Have you considered my message 14 possibility?
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Harlequin Inactive Member |
Have you considered my message 14 possibility? It is NOT a possiblity. Meanders will ONLY appear on a relatively level river course. A flood capable of digging out something as large as a canyon is not going to follow such a shallow meanders. Unless you are willing to invoke a miracle, the Grand Canyon was formed by a river, and not a flood. Edited by AdminJar to fix formatting This message has been edited by AdminJar, 12-19-2004 09:17 PM
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TheLiteralist Inactive Member |
Edge,
I was mainly providing Roxrkool with a map of Walt Brown's proposed Grand Lake location and pointing out that many (probably most) creationists consider Grand Canyon to post date the Flood at least by several centuries. The albert/kaiabab squirrel populations (very similar squirrel populations separated by the canyon) seem to require this conclusion. The reason I included Walt Brown's ideas about relatively soft Mz sediments versus harder limestone sediments wasn't because I thought it was undeniable truth (I have no way of knowing), but I just wanted to point out that Walt Brown is using the words "soft sediments" in comparison between Mz sediments and limestone sediments--as opposed to "soft sediments" left behind by a recently retreated Flood. I was just emphasizing the idea that many creationists propose the canyon to have formed some centuries AFTER the Flood; that's all.
Walt: As erosion cut deeper beneath the water table, more water, under greater pressure, was released from the water-saturated sediments flanking the canyon. {snip} This escaping water cut dozens of side canyons entering the Grand Canyonlarge canyons previously unexplained because they have no significant surface flow entering them. Subsurface flow and landslides were extreme. Edge: Fortunately, for us, Walt does not practice hydrogeology. Ground water cannot be regionally under excessive pressure when exposed to surface waters. Also, he has no idea what releasing such pressure would do or the evidence it would leave. This only makes the cliffs of the GC MORE unlikely. {snip} There is no evidence of such jetting of water from the canyon walls. The side canyons form normal dendritic patterns, sometimes controled by preexisting brittle-rock structue. I'm not sure what he means by 'subsurface flow', but extreme landslides may be actually correct. We know that this is the modern method of forming the canyon and probably the side canyons: landslide dams and breeching of dams. -- emphasis is mine If I understand Walt Brown correctly, he is attempting to explain the barbed canyons, of course, which apparently run in the OPPOSITE direction of the flow of the Colorado river. Your last two sentences (in the quote above) seem to offer SOME support to his ideas. Is it possible for his overall Grand Canyon theory to have merit while some details are incorrect? I think his reference to "subsurface flow" is an attempt to describe water from the water table running into the canyons formed by the breached dam (probably not two completely separate and independant events). If I'm getting the picture in my mind correct, the land has a slight tilt counter to the flow of the river (above the river, apparently). So, I *think* that Walt Brown is proposing the dam broke and Grand Lake emptied. The backwards tilt of the land wasn't enough to overcome the general flow of the water from the breached dam. The Grand Lake waters made their own canyon system flowing away from Grand Lake, but this canyon system cut beneath the water table. The water in the water table (influenced by the backwards tilt of the land) made the canyons that run in the opposite direction of the Colorado River flow. Of course, this whole scenario would probably make a different water table level; so it could happen only once. (This is addressed really to everybody, not just Edge.) Now, here I go out on a limb. How much merit would there be to the idea of (assuming a breached dam scenario) the breached dam waters creating meanders due to the backwards tilt of the land? Seems that the proposed Grand Lake waters would have a general downhill flow (due to it being a breached dam), but the backwards tilt might have been a somewhat countering force to the general flow of the Grand Lake waters. {Added by edit}I find the idea that the Flood laid down the sediments in the rising stages and then cut the canyon in the receding stages a bit unrealistic. The idea about the cliffs not being able to support themselves at this stage pretty much refutes such reasoning. That's why I keep emphasizing that many creationists do not take this view. This message has been edited by TheLiteralist, 12-20-2004 09:22 AM
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JonF Member (Idle past 194 days) Posts: 6174 Joined: |
Now, here I go out on a limb. How much merit would there be to the idea of (assuming a breached dam scenario) the breached dam waters creating meanders due to the backwards tilt of the land? Seems that the proposed Grand Lake waters would have a general downhill flow (due to it being a breached dam), but the backwards tilt might have been a somewhat countering force to the general flow of the Grand Lake waters. Not much merit. Water flows downhill. Slow moving water on a near-flat plain produces meanders. A "backwards tilt" and fast-moving water might produce changes in direction (which would be accompanied by severe undercuts and erosion, which we don't see, on the outside of the direction changes) but it wouldn't produce the back-and-forth pattern of meanders, nor would it produce 180o changes in direction in a short distance
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TheLiteralist Inactive Member |
Rats! I thought I really had it, too.
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Buzsaw Inactive Member |
It is NOT a possiblity. Meanders will ONLY appear on a relatively level river course. A flood capable of digging out something as large as a canyon is not going to follow such a shallow meanders. Unless you are willing to invoke a miracle, the Grand Canyon was formed by a river, and not a flood. I said I didn't want to get into a debate on this, but it's frigid out here in the NE and have a little time to discuss this. You seem to have ignored the specifics of my post. I would apprecieate if you would copy and paste them and address these specific points I've made?
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roxrkool Member (Idle past 1015 days) Posts: 1497 From: Nevada Joined: |
buzsaw writes:
Sort of like a beach environment? You get small-scale meanders on a beach after most of the water had drained off. Or at the end of a flood - a normal flood! Yes, this is possible.
If there were a big rush bringing down a huge quantity of soft sediment, the meandering possibly could occur subsequently as a fairly strong but not rushing amount of water continued down the now relatively, I say relatively, level sediment which would be deep but still quite soft. We see this sometimes on a small scale where erosion occurs in soft sediment of fairly gradual slopes. After the meandering is shaped, though yet fairly shallow, surging water from a succession of other small outbreaks or pockets of water upstream could cut the now shaped meandering much deeper rather quickly.
Yes, I believe this is also true, at least the first part, as long as you keep the water surges small enough so that they do not flow over and across the meanders, which would wipe them out. However, I don't think it would necessarily be very quick. The only time you could increase the amount of water and erode quickly would be after rather deep incision of the meanders into hard rock - not soft sediment or even weakly lithified rock. Before you can deepen the meanders, the rock must lithify completely. Otherwise all you'll be doing is causing slope and bank failure and widening the channel in the unlithified sediment.
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roxrkool Member (Idle past 1015 days) Posts: 1497 From: Nevada Joined: |
No comments, Buz???
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edge Member (Idle past 1732 days) Posts: 4696 From: Colorado, USA Joined: |
quote: Perhaps you could give us an example of such 'barbed canyons'. I don't suppose you or Walt would consider that such canyons are controlled by rock structure formed in competent rocks? Nah, that would make too much sense since we see it everywhere else in the world...
quote: In this case, no. There is no evidence of the break out of a large flood-stranded lake. We know that thousands, if not millions of small dams have formed in the GC and this may have contributed to the erosion of hard rocks.
quote: There is no need to explain this.
quote: In the scenario you are talking about, the 'tilt of the land' has nothing to do with it. There is no evidence of a dam breach to form the GC.
quote: Or never... I can make no sense of your story. Basically, Walt has no clue about erosion or erosional processes.
quote: You are going out on a limb for Walt? Sorry, but this makes no sense at all: completely different flow regimes. By the way just where is your dam?
quote: The backward tilt has nothing to do with it. On the downstream side, the tilt is in the direction of flow.
quote: You are being too reasonable to be a YEC.
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ohnhai Member (Idle past 5188 days) Posts: 649 From: Melbourne, Australia Joined: |
Nope, you all got it wrong.
It’s Slartybartfast doing a spot of moonlighting on the rivers, during the weekend to help break up the monotony of doing fiords all the time.
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AdminNosy Administrator Posts: 4754 From: Vancouver, BC, Canada Joined: |
Hello Ohnhai,
By the way, welcome to EvC. Could you (most of the time) use ther reply button at the bottom of the post you are replying to. This allows others to follow the thread of discussion and lets the system send email for those asking for it.
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ohnhai Member (Idle past 5188 days) Posts: 649 From: Melbourne, Australia Joined: |
normally do. but as this was a rebuttal of the entire thread (in jest) and not a reply to a specific post or chain of posts I thought the general reply was warranted.
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TrueCreation Inactive Member |
Well, if there is a feasible explanation, Walt Brown, of all people will probably not be able to give it to you.
quote:--I agree with your reasoning, but im not so sure about your last sentence (if we are dealing with majorities). The majority of creationists do not understand the relevant geological processes and data that refute their simplistic hypotheses (a problem Walt Brown seems to have--or at least he just isn't that concerned with potentially falsifiable scientific accuracy). However I would be happy to see revolution in this instance. I certainly hope that the majority of YEC's can at least grasp the fact that the grand canyon problem(s) aren't as simple as Kent Hovind would convey. --As per the question of whether grand canyon walls would slump or not after catastrophic fluvial(?) erosion; the only way to address the problem would be to find a balance between the rate of lithification and of erosion. I do not think that catastrophic erosion is feasible because the rate of erosion is far too high. --YEC's should attempt to model the rate of lithification of a large column of sediment vs. the rate of fluvial erosion. I think that required conditions would be: [a] - complete dessication and cementation of the sediments making up the grand canyon area should not occur for the majority of the time involved. This is because the rate of erosion would decrease to about current rates. This applies to the strata directly under the fluvial system(not the sediments which makeup walls).
[b] - the rate of erosion should not exceed some ideal rate of lithification that would enduce slumping of the canyon walls. [c] - basically, as the river continues to erode underlying sediment, the sediment constituting the GC walls should lithify sufficiently to support superposing sediment. [d] - the initial or overall regime of erosion should be sufficient to compensate for meandering. Im not sure about the plausibility of a coherent young earth situation, but I would like to see Austin, et al. look into this rationally. Then again my recent time away from the geological literature may be showing. This message has been edited by TrueCreation, 01-03-2005 20:06 AM This message has been edited by TrueCreation, 01-03-2005 20:15 AM This message has been edited by TrueCreation, 01-03-2005 20:17 AM
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