|
Register | Sign In |
|
QuickSearch
EvC Forum active members: 65 (9162 total) |
| |
popoi | |
Total: 915,806 Year: 3,063/9,624 Month: 908/1,588 Week: 91/223 Day: 2/17 Hour: 0/0 |
Thread ▼ Details |
|
Thread Info
|
|
|
Author | Topic: Earth science curriculum tailored to fit wavering fundamentalists | |||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined:
|
The column has many local versions but the Geo Time Scale incorporates them all. Which are you all talking about? I'm surprised anybody would say the complete Geo Time Scale can't exist in any one place. I've never said that, and I've seen many cases where the whole range of time periods is represented.
I think of the Geological Time Scale as an immense tape that records geological events. There are many tracks on this tape, one for each location on earth, blindly painting a picture of what was happening at any given time. At any given time, there are hundreds of processes being recorded on various tracks and nothing at all on others. On some tracks there are gaps in the record, processes occur for a while and then, seemingly stop, only to begin again. In fact, it appears that some parts of the record are deleted, but at no time are all of the tracks silent. Somewhere, there is activity. If we are lucky, we can find a track where there is continuous information recorded on very long stretches of the tape, but that is not the rule. We live on an active planet and there are also pesky processes that erase the record on one track or more. Often we see trends of ancient life in the record, that we describe such as 'no life', 'early life', 'old life', 'middle life', etc.; that appear to span all of the tracks at once. This is the record of life on earth. Each of those tracks is a 'geological column', each unique to its location with its sedimentation, igneous activity, mountain building and erosional gaps showing what has happened at that very spot. This will continue until the tape (time) stops or all processes stop. While we have an idea when it began, and we can observe the present record forming, we cannot see the end. The record lies in the past.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined: |
Feel free. The analogy can be carried out to almost any level on any subject. Emphasize that erosion 'erases' parts of the recording. That's how we know that it happens, regardless of what some YECs seem to think about the non-existence of unconformities.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined: |
That's an impressive description of how a geologist thinks. It's really amazing how the human mind has such organizing power that even a random ink blot, or the random depositions of sediments and dead things by a worldwide Flood, can be perceived as a coherent meaningful story.
As usual, it's a little more complicated than that. Both the distribution of rocks and the distribution of fossils are hardly 'random'. They are formed by processes which leave behind evidence in the form of patterns that tell us something about the rocks themselves. This is something that YECs need to understand. Geology is not random. If randomness were the case, then predictive tools such as basin analysis and palynology (paleontology) would not be possible. And yet, there you are drilling into formations that might not exist in the case of random geology. I'm not sure how to get this across to YECs. Maybe more exposure to the field, or some practical examples. TAD, I might recommend, The Map that Changed the World for a presentation on how geology started moving from a 'natural philosophy' to an actual science, although someone must have already recommended it to you somewhere in this thread. It's all about patterns and processes.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined:
|
Those cases are not used to date the underlying layers are they? They could be used to date overlying layers, right
The issue would be the presence of significant unconformities beneath or above the lava flows. I would be very careful about either unless I was in a fairly continuous sequence of sediments briefly interrupted by a volcanic event. In the case of a sill, the only relationship would be intrusive younger than sediments on either side. ETA: One thing to remember, in partial answer to TAD's question, is that usually volcanic ages are used more to bracket the sedimentary rocks rather than date them directly. In other words, rocks or sediments below a dateable volcanic layer would be considered older and above such a layer as younger. Now if the layers were all continuous and interlayered, you could be pretty certain of the absolute date. This is the case with the KBS tuff situation, IIRC. Edited by edge, : No reason given. Edited by edge, : No reason given.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined: |
So they fell out of suspension, they dropped out of the water anyway. But limestones may precipitate out as petro said, and that would be the Tapeats and the Muav.
I don't think you intend to mention the Tapeats here. I've seen the Muav described as precipitated, but I'm not sure that's entirely accurate since few limestones are 'pure' and usually have a fine siliciclastic component. Indeed, 'precipitate' would be a nonstandard usage in the rocks we are discussing, but it is also kind of vague. Often, I try to use the phrase 'chemical sediment' to avoid ambiguity. I think that, for a layman, the confusion is understandable. ETA: I have no problem with making the clarification, however. Edited by edge, : No reason given.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined:
|
So how do you explain the layering of the diatomite and tuff? The layers look like all the other layers which were deposited from water.
There are two distinct types of alternating layers (I'm not going to say 'sediments' even though the environment is sedimentary and I could do that. I'd like to keep the distinction between sedimentary and volcanic deposition if possible, even though they overlap). Based on past experience, I'd say it was playa lake without a lot of clastic (sand, etc.) input, but a constant rain of diatom tests and intermittent volcanic eruptions. Disclaimer: I am not on site nor familiar with this location. Just going by what's been said here. Edited by edge, : No reason given.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined: |
You call this even layering?
I might generalize them as 'thinly bedded', but then, I'm not sure what Faith means by 'even layering'. You will notice that she never does answer your question. I wonder what she thinks of varves.
If so, I have to wonder what you would call uneven layering?
Again, not answered.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined:
|
I apologize in advance for this question because i know I've seen it answered multiple times on this forum but I just can't think of a search term that would return what I need.
If the lab knows nothing about the rock, they cannot tell if the sample is beyond the useful range or not by radiomtric analysis. All they can tell is that it is near the upper or lower detection limit.Let's suppose the viable dating range of a given RID method is 1 million years to 1 billion years. Let's suppose I send in a rock #1 that is a half a million years old. Let's suppose I also send in a rock #2 that is 2 billion years old. My recollection is that the lab will NOT send you a results saying that the first rock is 1 million years old (even though that may be what their equipment returned) but rather a return saying something like "Less than a million"? Same with the other rock ... "More than a billion". Would it be something like Rock 1: =< 1,000,000Rock 2: => 1,000,000,000 Is there some additional language a lab would put with this to note that the date range is outside the normal range return of their equipment/method. Thanks so much. Personally, I've never had this happen, so I can't say, but this is one of the flags for an inappropriate application of technique. I'm thinking that you'd end up with erratic results due to measurement of very small quantities of parent and daughter isotopes. Then you get into the statistics of very small numbers and the effects of background quantities. I'm also guessing that the result will be reported with a larger than usual error estimate. Someone here else might have more experience with that.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined: |
I said : "The diatomite was caused by the deposition of diatoms and the volcanic tuff was caused by the eruption of a volcano."
I doubt that you will get an answer here. Faith is simply trying to ask questions until she finds one that you can't answer (or give up due to boredom). What did you expect it to look like? How does it fall short of your expectations? By the way, for those who dig a little more deeply into sources, one of the sources for this picture misidentifies the material being imaged. It says: "Diatomite and volcanic tufa layers.jpg" The actual material is 'tuff' which has nothing to do with 'tufa'. Be careful of geological jargon... Category - Wikimedia Commonsiatomite?uselang=itWikimedia
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined:
|
This is true. However it is not completely unjustified.
The Tapeats Sandstone, the Potsdam Sandstone, the Saint Peter's Sandstone, and the Sawatch Quartzsite, among otbers are all time-equivalent units. These are all basal Sandstone units related to the first major Paleozoic marine transgression. What Snelling fails to tell you is that there are discontinuities due to non-deposition (which would mean contemporary land masses) and/or later erosion. He also fails to tell you why this scenario indicates rapid deposition. That is simply another baseless assertion. Edited by edge, : No reason given.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined: |
Still, rapid deposition does not mean old ages. One could have rapid deposition of one layer ... hundreds of millions of years ago.
This is deception on the part of Snelling.. Also, note that he is switching from the Tapeats to the Coconino in the same paragraph. This is more deception. The Tapeats is a beach sandstone and the Coconino is an eolian sand deposit. And yes, we can tell the difference.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined: |
More nonsense.
The White Cliffs of Dover were deposited at about the same time as the Cretaceous Seaway in North America. At that time, the oceans were at a higher level covering large amounts of the continents.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined:
|
More nonsense.
The White Cliffs of Dover were deposited at about the same time as the Cretaceous Seaway in North America. At that time, the oceans were at a higher level covering large amounts of the continents. This resulted in large areas shallow seas covering the continental shelves with little input from continental sediments. In Europe and into the Middle East the sediments were starved of terrigenous sediments and developed carbonate banks. In North America, formations such as the Niobrara limestone are the equivalent of the White Cliffs of Dover. However, there were land masses to the west in North America. It all makes sense if you understand the distribution of rocks in a global conrext.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined: |
Well, considering that YECS do not recognize that these time periods exist, it is no wonder that it is a mystery to them. However, there is little doubt that they exist and that they are associated with major geological changes.
|
|||||||||||||||||||||||||||||||||||||||||||||||
edge Member (Idle past 1705 days) Posts: 4696 From: Colorado, USA Joined:
|
All of them. Every single boundary that marks off both a sedimentary deposit and a time period.
Actually, the rock types fit within a time period. And those 'rock types' are not pure. For instance the Supai group is a sequence of thin beds of mudstone, sandstone and limestone in no particular order nor purity. In general, the contacts are not as sharp as you think. Yes, from a great distance, they are distinct, but upon viewing in detail, most contacts are gradational. Have you actually visited the GC? My impression is that you have not.
But what I'm hoping is that someone else will come along who simply gets what I'm talking about from what I've already said. I've explained it as well as I'm able. There's no point in trying harder to convince somebody who is determined not to be convinced, even if I had more I could say about it.
The reality is not what you make of it. Consequently, you will never have any support.
|
|
|
Do Nothing Button
Copyright 2001-2023 by EvC Forum, All Rights Reserved
Version 4.2
Innovative software from Qwixotic © 2024