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Author Topic:   Dating methodology for the Vishnu Schist
Centrus
Inactive Member


Message 1 of 17 (360641)
11-02-2006 4:59 AM


Before I begin, I would just like to point out that, whilst I am a devout Roman Catholic, I am having many troubles as to which creation theory (Creation or Evolution) I believe. Suffice to say I have seen much evidence for and against both, but I am certainly open to more evidence either way.

I have a particular question about carbon dating...

Many supporters of the 'Young Earth' theory accuse carbon dating techniques to be flawed. I myself have seen evidence for it, but fear it to be the rampant criticism of some of my fellow close-minded Christians. And so, I was hoping that a discussion may help me with my conclusion...

A very simple thing that a mate of mine (not the birghtest fellow in the world, but certainly logical) exposed to me, was this:

This 'evidence' concerns the Grand Canyon (as many of you Americans would be familiar with).

The Vishnu Schist, lying at the bottom of Inner Gorge, is said to be up to 2 billion years old. Now, the deepest point of the Grand Canyon is approximately 6,000ft or 1800m. Now, according to my limited understanding of geology, greater depth implies greater age, no? But, doing the math (and this is also assuming the Vishnu Schist is at the bottom of the Grand Canyon, as it may very well not be), this essentially means that every 1.8 micro metres is a year!

Now, a simple dust storm could cover centimetres of the top (at this point), no? And of course, a dust storm does not happen over 20 millenia! I know this is putting it extremely simply, but it was just an example I was given by a 15 year old fellow, and it makes sense.

Once again I am no geologist, so of course, I am not convinced. I am well open and prepared for complete and utter destruction of this example; just be aware that I'm eager to read it. I started this topic to learn

Which forum? Origin of Life I guess...

Edited by Centrus, : No reason given.


Replies to this message:
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AdminWounded
Inactive Member


Message 2 of 17 (360643)
11-02-2006 5:18 AM


Thread moved here from the Proposed New Topics forum.

  
AdminWounded
Inactive Member


Message 3 of 17 (360647)
11-02-2006 5:29 AM
Reply to: Message 1 by Centrus
11-02-2006 4:59 AM


Doh!
Hi Centrus,

I should have vetted this more carefully. Your OP and the subject seem fine but once I promoted it I noticed that the title is 'carbon dating'.

While you mention carbon dating in your post carbon dating has nothing to do with the methods used in dating geologic structures such as the Vishnu schist.

If you actually have a concern about carbon dating per se you might add a post centred on that to this thread. If your are specifically interested in the Grand Canyon example then perhaps you could click on the 'edit' button in your first post and change the thread title to something more appropriate, i.e. 'Dating methodology for the Vishnu schist'.

TTFN,

AW

Edited by AdminWounded, : No reason given.


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riVeRraT
Member (Idle past 856 days)
Posts: 5746
From: NY USA
Joined: 05-09-2004


Message 4 of 17 (360656)
11-02-2006 6:12 AM
Reply to: Message 1 by Centrus
11-02-2006 4:59 AM


The Vishnu Schist, lying at the bottom of Inner Gorge, is said to be up to 2 billion years old. Now, the deepest point of the Grand Canyon is approximately 6,000ft or 1800m. Now, according to my limited understanding of geology, greater depth implies greater age, no? But, doing the math (and this is also assuming the Vishnu Schist is at the bottom of the Grand Canyon, as it may very well not be), this essentially means that every 1.8 micro metres is a year!

Not being a scientist, and not qualified to really answer this but, doesn't this assume that the Grand Canyon has been flowing for 2 billion years? Wouldn't that be a mistake?

Actually I just looked it up.
http://en.wikipedia.org/wiki/Geology_of_the_Grand_Canyon_area

But the canyon did not start to form until 5.3 million years ago when the Gulf of California opened up and thus lowered the river's base level (its lowest point) from that of large inland lakes to sea level.

You are associating two different things in your statement. The depth of the Grand Canyon is not relevent to carbon dating.

{ABE} Also the age of the rocks at the bottom of the canyon have nothing to do with the age of the canyon itself.

Edited by riVeRraT, : No reason given.


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PaulK
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Posts: 16881
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Member Rating: 2.9


Message 5 of 17 (360659)
11-02-2006 6:20 AM
Reply to: Message 1 by Centrus
11-02-2006 4:59 AM


The answer is quite simple - your calculations deal with the average rate taking into account all additive and subtractive processes and in terms of rock, not sediment,

One lesser point is that sedimentary rock is compressed, so that it occupies less volume than the equivalent loose sediment.

But more importantly there have been times where there was erosion - quite considerable erosion. The base of the Grand Canyon - including the Vishnu Schist represents the roots of mountains that were raised - and destroyed by erosion. The boundary between these rocks and the higher, later rocks is known as the "Great Unconformity"

See the picture at the bottom of this page

There are more - if less impressive - examples of erosion between strata further up the canyon.


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anglagard
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Posts: 2309
From: Socorro, New Mexico USA
Joined: 03-18-2006
Member Rating: 4.8


Message 6 of 17 (360660)
11-02-2006 6:24 AM
Reply to: Message 1 by Centrus
11-02-2006 4:59 AM


Deposition and Erosion
Welcome to EvC Centrus,

The answer to this concern:

The Vishnu Schist, lying at the bottom of Inner Gorge, is said to be up to 2 billion years old. Now, the deepest point of the Grand Canyon is approximately 6,000ft or 1800m. Now, according to my limited understanding of geology, greater depth implies greater age, no? But, doing the math (and this is also assuming the Vishnu Schist is at the bottom of the Grand Canyon, as it may very well not be), this essentially means that every 1.8 micro metres is a year!

Now, a simple dust storm could cover centimetres of the top (at this point), no? And of course, a dust storm does not happen over 20 millenia! I know this is putting it extremely simply, but it was just an example I was given by a 15 year old fellow, and it makes sense.

The sequence of events in any given geologic column, such as the Grand Canyon, almost always consists of both deposition, where rock is added, and erosion, where rock already added is subtracted. Therefore depth is not a measure of time as rock layers were not always added.

Some places on Earth have been continuously eroding for quite some time, such as Australia and the Appalachian mountains, which have been since the Permian, some 250 million years ago.

At this site http://www.kaibab.org/geology/gc_geol.htm is a summary of the depositional and erosional events at the Grand Canyon. As you can see, there were two times where the layers are not present in the column due to erosion that cover a significant period of time. One right above the Vishnu schist of 450 million years duration, and one of 250 million years duration between the Chuar Group and the Tapeats Sandstone. Also,

quote:
Rock layers younger than 250 million years have been eroded away and no longer exist in the immediate vicinity of the Grand Canyon.

Also, the layers of sandstone, limestone, shale, basalt, etc. that make up the Grand Canyon deposit at different rates and from different causes.

Hope that helps.


This message is a reply to:
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Replies to this message:
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RAZD
Member (Idle past 341 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 7 of 17 (360695)
11-02-2006 8:08 AM
Reply to: Message 1 by Centrus
11-02-2006 4:59 AM


Welcome to the fray Centrus.

Carbon Dating

Is based on the radioactive decay of 14C, which has a half life of ~5700 years, and the limit of any object being dated by 14C methods is ~50,000 years. Further 14C can only date organic samples, as it is dependent on the organic accumulation of atmospheric 14C to provide the base level from which the decay is calculated.

I have a particular question about carbon dating...

If you are interested in the validity of dates, I can suggest a review of Age Correlations and an Old Earth: Version 1 No 3 (formerly Part III) and Correlation Among Various Radiometric Ages (see Message 5)

For a good review of the geology of the Grand Canyon, I recommend Exploring the Grand Canyon, from the bottom up.

I am having many troubles as to which creation theory (Creation or Evolution) I believe. Suffice to say I have seen much evidence for and against both, but I am certainly open to more evidence either way.

The big issue, imho, is whether you will consider all evidence on the table or deny that some is valid. The different concepts have different filters for "truth" and many YEC (young earth creationist) models rely on ignoring ample corroborated evidence for an old earth.

This still leaves OEC (old earth creationist) models and theistic models.

We no longer see claims of earth being at the center of the universe, because there is just too much evidence that the earth orbits the sun in an outer arm of a rather common type of galaxy in a universe with many different and varied galaxies.

The biblical interpretation that led to this geocentric claim is no longer in vogue because of this overwhelming evidence that refutes it.

The evidence for an old earth is similar. I believe the effect of this reality on the various world religions will also be similar.

Once we've dealt with the age issues then we can proceed to the evolution issues eh?

Enjoy.


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CACTUSJACKmankin
Member (Idle past 5210 days)
Posts: 48
Joined: 04-22-2006


Message 8 of 17 (360698)
11-02-2006 8:11 AM
Reply to: Message 6 by anglagard
11-02-2006 6:24 AM


Re: Deposition and Erosion
To address the issue of carbon dating, the reason why carbon dating is not relevant in this discussion of the grand canyon is that the half-life of carbon 14 (5,730 years) is much too short to measure anything as old as most rocks. Carbon 14 is only good for about 50,000 years before there's too little of it present in the material to reliably measure. The other reason why you wouldn't use carbon to date rocks is that rocks usually don't contain all that much carbon, carbon dating is used for dead things like pieces of paper or paint or wood from archaeological sites.
The most common decays used are potassium-argon (HL of 1.3 billion years) and uranium-lead (the two isotopes of uranium (238 and 235) decay to different isotopes of lead (207 and 206) with HLs of 700 million and 4.5 billion).

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Matt P
Member (Idle past 3711 days)
Posts: 106
From: Tampa FL
Joined: 03-18-2005


Message 9 of 17 (360839)
11-02-2006 2:07 PM
Reply to: Message 1 by Centrus
11-02-2006 4:59 AM


The grand canyon
Hi Centrus!
I am also a devout Catholic and I went through a similar period of questioning science and faith about 10 years ago. I'm currently at the University of Arizona doing origins of life research, and have been in contact with several Jesuits who are active researchers in astronomy and planetary science here at the U of A. They are faithful Catholics and good researchers, and many criticize creation science.

In regards to your Grand Canyon question, consider an analogy: let's say you wanted to dig a hole in your backyard. You grab your shovel and start digging. An hour into it, you've gone down three feet and want to take a break. You take an hour break, then start back up for another hour, digging another three feet. Then you get tired and go to bed, sleeping for 8 hours. You dig another three feet as soon as you wake up over the next two hours, then you get bored. You don't dig your hole any more for two months (61 days), during which time a foot of the soil you dug out falls back in. You then dig the hole for another hour, getting four feet of soil removed this time.

What was your average digging rate over this time? Doing a calculation analogous to your grand canyon calculation, you'd get:
(3+3+3-1+4)/(62 days * 24 hours/day) = 0.008 feet per hour. Is that a realistic digging rate?

A more reasonable digging rate would be (3+3+3+4)/4 hours = 3.25 feet/hour. That's the average amount of dirt you were able to remove per hour. These calculations are more accurate overall for what you're actually interested in.

Analogously, the Grand Canyon records several different episodes of deposition, times where no rock was deposited, and times where rock were eroded away (like the dirt falling back into the hole you dug). The rock types of the Grand Canyon were deposited in different environments, from solidified sand dunes, to marine deposits, to lava flows to mudslides. These were formed in different environments and frequently are from very different times. I agree with some of the posts here and encourage you to look at some of the topics on the Grand Canyon and Carbon Dating.

Good luck!


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Centrus
Inactive Member


Message 10 of 17 (361037)
11-03-2006 3:00 AM


Thankyou everyone for such explanatory replies, they were extremely helpful.

I apologise for my misunderstanding... it obviously shows how little I know of geology. I was interested in both subjects; that of carbon dating and that of the explanation of the Vishnu Schist. As for this particular thread, I juts thought it easier to concentrate on my example supplied. Your explanations were wonderful, but they still leave me with a question...

If the accumulation is indeed an average, taking into account the additions and subtractions made (which makes perfect sense), how is it possible for us to age? How do we know when these particular additions/subtractions occurred? Or how much rock/sand was added/subtracted? Or how long the gaps of time in between were?


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PaulK
Member
Posts: 16881
Joined: 01-10-2003
Member Rating: 2.9


Message 11 of 17 (361039)
11-03-2006 3:15 AM
Reply to: Message 10 by Centrus
11-03-2006 3:00 AM


That is where radiometric methods come in very handy. Methods using longer-lived radioactive substances do give an absolute age - although most methods only work on igneous rocks (there are other things to beware of, too - for instance periods of heating can reset the "clock").

It is possible to make rough estimates based on depth and the early geologists did. It is possible to find evidence that erosion has occurred - and, at least sometimes, the eroded strata can be still found in other locations. For all I know it may still be used to fill in the gaps between more solid dates.


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jar
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Posts: 33343
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.9


Message 12 of 17 (361092)
11-03-2006 10:18 AM
Reply to: Message 10 by Centrus
11-03-2006 3:00 AM


how is it possible for us to age rocks?
One of the purposes of the thread Grand Canyon from the bottom up was to show that even without specific dating methods, the ONLY possible conclusion is that very long time periods were involved.

One such example is that the Vishnu Schist was once sandstone. Now to get sandstone you fist need to wear another stone down into very small pieces and transport those pieces to a new location where they are then compacted and eventually metamorphosed into schist. To even get the Vishnu Schist, mountains had to be made, worn down, the sand transported and accumulated and compressed. We can look at mountains and we can get an idea of just how long it takes to wear them down.

There simply was no other possible explanation for the existence of the Vishnu Schist (and just about every other feature that the geologists saw) then long periods of time.


Aslan is not a Tame Lion

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Replies to this message:
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Casey Powell 
Inactive Suspended Member


Message 13 of 17 (374494)
01-04-2007 4:26 PM
Reply to: Message 12 by jar
11-03-2006 10:18 AM


Re: how is it possible for us to age rocks?
Begging the question fallacy.

The ages dated in the Grand Canyon are not even close to each other. To use this Radioisotope example is almost an embarassment to your cause.

The Radioisotopic evidence actually suggests that the rocks are young when we properly investigate them.

Edited by Casey Powell, : No reason given.

Edited by Casey Powell, : No reason given.


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AdminModulous
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Message 14 of 17 (374497)
01-04-2007 4:31 PM
Reply to: Message 13 by Casey Powell
01-04-2007 4:26 PM


Not productive
This post does not advance the topic, indeed it doesn't do anything. I think you need to take 24 hours time out, if you return and continue in this vein it will be for longer. As it stands you are simply spamming debates with unproductive interjections and copy/pastes.


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iceage 
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Posts: 1024
From: Pacific Northwest
Joined: 09-08-2003


Message 15 of 17 (374498)
01-04-2007 4:34 PM
Reply to: Message 13 by Casey Powell
01-04-2007 4:26 PM


Re: how is it possible for us to age rocks?
casey writes:

The Radioisotopic evidence actually suggests that the rocks are young when we properly investigate them.

You have a reference that dates the Vishnu schist as young?

Forget the whole radiometric dating question and find a young earth explanation for the angular unconformity of which the Vishnu Schist is a component.


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