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Author Topic:   Was there a worldwide flood?
edge
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Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 59 of 372 (411434)
07-20-2007 4:29 PM
Reply to: Message 57 by Percy
07-20-2007 2:57 PM


Re: Please Explain the Following Evidence From Geology
A single immense erosive event such as a gigantic flow of water would not cut in this tiered way but would quickly cut straight down, and if only 6000 years ago the slopes would have had barely any time to retreat. Plus such a flow would be far too violent to meander.

I find no evidence of mulitple uplifts of the CRBs. The stair-stepped topography in this picture looks more like successive lava flows; with interflow deposits being the ledge-formers and flows being the cliff-formers.
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edge
Member
Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 73 of 372 (411487)
07-20-2007 9:07 PM
Reply to: Message 70 by Percy
07-20-2007 6:56 PM


Re: Please Explain the Following Evidence From Geology
Looking at the three tiered vertical cliff faces on the left of the picture, what is it about the green portions in between that indicates they are not terraces.

I would call them ledges. They have loose material on them that sits at the angle of repose (more or less). They represent more easily erodable material.

The roughly 45 degree angle of these terraces would be caused by till ...

Well, talus...

...from the rock face above covered with a thin layer of gradually accumulated soil on which some low growing greenery has found purchase.

Correct.

I understand that differential erosion rates cause different angles of slope retreat, but vertical slopes indicate rapid erosion, possibly even a series of waterfalls moving gradually upstream by a few inches per year.

Actually, the other way around. Quickly eroding shales form things like Badlands or the Tonto platform. Resistant rocks form cliffs like the Palisades.

Is the type of layer, basalt versus sedimentary, apparent to you from the photo?

You will notice that I carefully called them 'interflow deposits' in my original post. They may be sediments, they may be breccias, they may be simply porous flow-tops. The added feature they would have is that water would reach daylight along these porous horizons so that plants could live there.

If so, what features in the photograph are you looking at to identify them?

All of the above: gentler slopes, vegetation, and a lot of field experience...

Or, given that "the Columbia plateau it could be all lava with different degrees of resistance to erosion", how do you tell that's the case versus differential uplift rates from the photo?

I've been there. I have worked in volcanic rocks most of my career. These CR Basalts were highly fluid lavas that spread out quickly from linear vents, possibly at some great distance from these outcrops.

Or is the conclusion based on knowledge that uplift rates, once begun, tend to stay roughly constant or only change very slowly?

No, but I looked up a reference at the USGS website looking for uplift of the Columbia River plateau and it was pretty clear. The only real uplift here has been to the north in the Okanogan area that has resulted in a gentle regional dip to the south. These are really quite young rocks.
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edge
Member
Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 74 of 372 (411489)
07-20-2007 9:18 PM
Reply to: Message 71 by Percy
07-20-2007 7:43 PM


Re: Please Explain the Following Evidence From Geology
So if there was a constant rate of uplift and a constant rate of river cutting down through basalt layers, then what must have happened to cause the tiered appearance.

There is no evidence of major uplift here. In fact, a positive gravity anomaly over the CR Plateau suggests the opposite at present. These are very dense tholeiitic basalts erupted over a about 1.5 ma starting at 16 ma. Not a lot has gone on there since then.

Let's just consider the top most stretch of vertical cliff face on the left and the greenery covered layers just below it. The rate of slope retreat is tiny compared to the rate of downcutting, so this cliff face is vertical or nearly vertical. The we reach some softer layers, now hidden behind the green covering, and given that they're softer the river cuts through them much more quickly. This should still yield a vertical cliff face, so I'm guessing that's what's hiding behind the green covering. But beneath the green covering is what? I'm guessing talus on a flat ledge. (Did I call it till before?)

So if there's a flat ledge covered with talus underneath the greenery, what caused the ledge? Seems to me only a pause in uplift, during which the exposed cliffs of the downcut continue retreating, could do this.


What actually happens is the same thing as the Grand Canyon. Weaker layers erode, thereby undermining the stronger layers. The stronger layers, with their vertical joint systems simply collaps along those joints. So, when erosion happens it is quite fast. The problem is that it happens episodically and, in the long run, is slow. This is part of the confusion regarding the Grand Canyon as well. That is why the erosion looks catastrophic, but still takes a long time to form the overall landform.
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edge
Member
Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
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Message 81 of 372 (411576)
07-21-2007 12:01 PM
Reply to: Message 79 by Percy
07-21-2007 10:43 AM


Re: Basalts
Except that this:

Doesn't resemble the upper left cliff face, the one I've been focusing on, at all:

There do not appear to be any vertical faults, only horizontal stratification between layers.


Sometimes the columnar jointing is not well developed in lava flows and the one pictured is obviously a textbook example. Few things in geology are straightforward becasue of the enormous number of variables present. I agree there is some horizontal banding in the flows pictured, along with the obvious stratification, but if you look at the right side of the canyon the upper flows do have a columnar appearance. I can virtually guarantee that there is some kind of vertical cooling joint in these rocks.
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edge
Member
Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 82 of 372 (411579)
07-21-2007 12:15 PM
Reply to: Message 80 by iceage
07-21-2007 11:34 AM


Re: Please Explain the Following Evidence From Geology
The ledges probably formed because the various layers are distinct with a contact zone that often consists of ash (probably from a preruption activity), sediments, palagonite (result of the meeting of lava and water).

As an example, just look at the tops of flows in Hawaii. They are a jumbled terrane of blocks, bombs, ash, soils and even vegetation. This is what the 'interflow' material is commonly made up of. It is very uncommon to get a sequence of volcanic rocks that does not have strong vertical variability. That is why the rate of downcutting relative to widening of the canyon is oversimplified for this example: there are multiple rock types.

As the river or floods cut through basalt they would erode differentially between the layers due to this discontinuity and form ledges? Just a guess.

Correct. Rapid erosion of the weaker layers will undermine the stronger one, which in this case, just happen to have vertical planes of weakness (cooling fractures).
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edge
Member
Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 87 of 372 (411683)
07-21-2007 8:55 PM
Reply to: Message 85 by Percy
07-21-2007 5:39 PM


Re: Please Explain the Following Evidence From Geology
And this is in Utah and was caused by uplift?

The theory, and I see no alternative, is that the meanders existed before the uplift. Otherwise, there would not be such well developed meanders.

Thank you and iceage for clarifying this. The critical part of Angalard's statement was the 'meanders' part. Otherwise the logic falls apart.


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edge
Member
Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 88 of 372 (411685)
07-21-2007 9:06 PM
Reply to: Message 86 by RAZD
07-21-2007 6:07 PM


Re: Basalts
Maybe I'm wrong, but I read the wiki article to say that the basalt in the tops (ie flow-tops) would be porous and mixed:

Well, remembering that a flow top here could also be a flow bottom...

Basalt in the tops of subaerial lava flows and cinder cones will often be highly vesiculated, imparting a lightweight "frothy" texture to the rock.

vesicle - n
3. A small cavity formed in volcanic rock by entrapment of a gas bubble during solidification.

If these sections are porous (frothy bubbles) compared to the lower basalt layers then aquifers could flow along them, but I would think the vertical fissures of the basalt would work against this.


From personal experience this is not always the case. On the Modoc Plateau a few years ago we considered the vertical permeability to be high, but direct observation of lakes showed that this was not so. I imagine that the cooling fractures (columnar joints) are quite tight until they are weathered, or else they plug up easily with silt or oxidation products.

It could be that the groundwater is flowing down inside AND horizontally along the interface between the different layers.

This is almost certainly true as observed in outcrops and in mines. In intact sections, lateral permeabilities are almost always higher than vertical. There are exceptions and they can be discussed if you wish.
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edge
Member
Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 92 of 372 (411698)
07-21-2007 10:59 PM
Reply to: Message 89 by Repzion
07-21-2007 9:11 PM


Re: Here's more Stuff.
I see evidence for a worldwide flood in these links.

Of course you do, that is what they are telling you to think. Rep, if I seriously read the entirety of these two links, my brain would implode under all of the ignorance displayed there. And you would be responsible. If you have a favorite piece of evidence, please discuss it.

ETA: Rep, one note of caution. These guys are basically relying upon your ignorance of the topic to make outlandish arguments. My advice is to ignore it.

Edited by edge, : No reason given.


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edge
Member
Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 98 of 372 (411708)
07-22-2007 12:55 AM
Reply to: Message 96 by Repzion
07-22-2007 12:19 AM


Well, near as I can tell, all you've done is refer us to a bunch of websites that recycle all of the old YEC arguments we've refuted before. Why not find one you like and we can actually discuss it.
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edge
Member
Posts: 4578
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.5


Message 108 of 372 (411795)
07-22-2007 3:43 PM
Reply to: Message 106 by Dr Adequate
07-22-2007 1:10 PM


Re: Here's more Stuff.
Why he thinks a flood would cause thousands of animals to get trapped in a tar pit is beyond me.

Ah, then you haven't heard of the oil-water flood theory. It is a corollary of the wet-dry flood theory which also includes other YEC notions such as the hot-cold, rapid-slow, turbulent-gentle, long-short, deep-shallow, turbid-clear and fresh-saline hypotheses.

It's all very simple, and everything is explained, you see...

Anyway, it's obvious that the flood included hydrocarbons, some of which were restricted to the same biomes as what we call Cenozoic creatures. Due to weathering and oxidation during a year at sea, these hydrocarbons turned into floating mats of tar. These just happened to wash up (gently in this case) at Rancho La Brea in California, so that later humans could make movies about prehistoric mammals that escaped the flood. Unfortunately, the creatures did not survive because the tar sank into the late flood sediments, creating steep-walled pits from which the creatures could not escape. This is an example of "good" design.


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