Evidence that the Great Unconformity did not Form Before the Strata above it

It is well-established, but there are exceptions.As you have been shown...And you do understand that principles are not necessarily laws, do you not? Actually, I don't see a definition of 'strata' here. Please explain. I thought we had gone over this definition before and it showed that you were wrong, and that the term strata also includes things like soil and gravel, etc.Did you miss that post? Quite wrong. For instance, the principle of cross-cutting relationships also refers to faults, folds, dikes, unconformities, etc. Actually, the definition includes rocks, soil and sediments. We've been over this previously.

I'm not sure what you're getting at. The way the strata to the sides and at the top are bent and broken is indication enough that the carbonate is an intruder into them. But the base is also far from undisturbed. The strata you think it's "sitting on" are bowed outward toward the front. I marked that bowing along with the fragments of strata that have collected around the object at its base, and two fractures in that forward-bowed base, showing that it underwent strain as the object pushed through. But again there is so much strain in the bent and broken strata above that I don't see any way you could explain it as sediment accumulating around it after it was there. As for how much the strata were bent, those that were pushed the most bent the most. OK I've marked my own copy to show the path I see it having taken from behind the upper strata, a curved path dragging some of the wet sediment with it. I've also outlined the many edges that show space behind the strata in front. Some kind of disturbance went on behind the scenes as it were, if only that rock's plunging through. The area you say looks like splash to you looks like stretched soft sediment to me where the rock broke through, leaving a large crack off to the right -- it stretched down to where the rock finally rested, in a hammock-shape it created in the strata. The piece on top of it also looks like it was dragged along with it. Sure, objects fall straight down but if they meet an obstacle on the way they can be deflected in another direction.[Please ignore camera which I outlined as if it were a hole in the rock.]Edited by Faith, : No reason given.

No, I think it's an insult to Steno, who was addressing strata, rock already formed.Just because you "show" me something doesn't mean I accept it. To include loose or unconsolidated gravel etc is wrong in this context. It's not as if Steno had not seen such things, but they aren't strata so he doesn't address them with his principles. When he said "initial horizontality" he clearly implied that strata are found in many conditions of nonhorizontality, caused by faults, folds, dikes and "unconformities" and so on. They aren't exceptions to the principles, they show the reason for the principles.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.

Was the camera intrusive also? Actually, there is one other little problem here.This is a volcanic rock, known as a surge deposit found at the base of an ash flow...Sorry folks.Edited by edge, : No reason given.

That's funny. I saw it as a camera and then when I was drawing the outlines I saw it as a space. Oh well. My eyes ARE bad.

And your point is?

Well, it's all moot anyway since the deposit is a pyroclastic surge and not even a sedimentary rock. I thought there was something funny about it when I first saw the picture, but my impression was that it was just a finely bedded lake deposit. This is the problem with just looking at photos. GigaPanning Kilbourne Hole - Mountain Beltway - AGU Blogosphere

But what does that change about how the rock dropped into it?

Thank you for the question.This deposit is a fine grained ash that was deposited at the base of a pyroclastic flow (a 'glowing avalanche') that would carry rocks of many sizes. I'm not sure of the mechanics, but they are documented. I think it has something to do with gases escaping the lava and forming a lubricating cushion for the larger fragments to flow on. They move very rapidly. Do not even try to outdrive them in your Landrover.At any rate this is not a sedimentary deposit.

Well, for one thing the whole thing is a flow. It was moving left or right, and may have even slumped further after it stopped flowing if it was hot enough.Again, this is one aspect of volcanoes that I have not really studied. But look at page 7 of this lecture to see how large blocks are entrained in a pyroclastic flow. It really does not conform to hydraulic principles and really has little to do with this discussion. The block obviously came from up above, but it's exact path could be anything.http://www.geo.umass.edu/.../volcanology/Pyroclastic%202.pdf

Here's your marked picture: You say: Nothing of the sort is in that picture. So I added my own marks to it, indicating how I see the direction of the gravel:

Actually the foreset beds are present. As I thought I mentioned, the topsets are eroded away, this often happens. The bottom set beds are usually not well developed and would be covered by scree in the picture.The point is that foreset beds are deposited in a non-horizontal fashion.

Reading back through recent posts I see everybody's very involved in these dropstones, and thinking something about them is "obscure" to me, etc. I haven't really been paying a lot of attention to it although I discussed how a few should be interpreted. I've been thinking more about edge's gravelly hill and how it has nothing to do with strata and what the definition of strata is and so on. So if I'm missing the point of the dropstone discussion somebody needs to clue me in. Thanks.

Hi Faith,I'd like to help the discussion get past the issue of horizontality to focus more immediately on the topic, so I think it might make sense now to spend a little time on horizontality so that we may soon put it behind us.I'm not taking sides in this discussion. When I don't understand something I'll say so, but that doesn't mean I think it's is wrong. So let me ask about what I don't understand concerning your position on horizontality: How horizontal does a surface have to be before it can no longer be considered horizontal and collect sediments?Obviously the answer can't be that a surface must be 100% horizontal before it will collect sediments. If a surface is 99.99% horizontal it will collect sediments just as well as one that is 100% horizontal. Where is the transition from horizontal enough to collect sediments to not horizontal enough? How far off from horizontal can a surface be and still collect sediments? Will a surface that is 99% horizontal still collect sediments? 98% horizontal? 97%? 95%? 90%? 80%?

But he was not defining strata. He was addressing the most common way in which strata are deposited. OK, that's cool. No gravel strata, at least for the purpose of argument. But...I don't recall anyone presenting "loose or unconsolidated gravel" as a stratum, I do, however, recall many examples of solid rock strata that obviously were deposited with big bumps in 'em. We know there are other (atypical) non-horizontal ways in which strata are deposited and do not follow the principle of horizontality and we've produced many examples.That's probably why no modern definition of stratum requires horizontality. Steno was not a prophet producing unchangeable commandments graven in stone. (Fundmentalists see so much as graven in stone). He did produce guidelines which fit most but not all situations. The modern definitions are not any kind of insult or travesty; they are more accurate modifications to Steno's versions. Remember your reference at Principle of original horizontality?

quote:

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"As one of Steno's Laws, the Principle of Original Horizontality served well in the nascent days of geological science. However, it is now known that not all sedimentary layers are deposited purely horizontally.

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Please stop flogging the loose gravel strawman, drop your personal and incorrect definiton of srtatum, and address the solid rock strata examples.